Steam Guide by Armstrong

Handbook N-101

SteamConservation

Guidelines forCondensate

DrainageSteam Trap Sizing

and Selection.

© 1997 Armstrong International, Inc.

Table of ContentsIntroduction Gatefold A

Recommendation Chartsand Instructions for Use Gatefold B

Steam Tables 2

Flash Steam 3

Steam...Basic Concepts 4-7

The Inverted Bucket Steam Trap 8-9

The Float & Thermostatic Steam Trap 10-11

The Controlled Disc Steam Trap 11

The Thermostatic Steam Trap 12

The Automatic DifferentialCondensate Controller 13

Steam Trap Selection 14-15

HOW TO TRAP:Steam Distribution Systems 16-19

Steam Tracer Lines 20-21

Space Heating Equipment 22-24

Process Air Heaters 25

Shell and Tube Heat Exchangers 26-27

Evaporators 28-29

Jacketed Kettles 30-31

Closed Stationary SteamChamber Equipment 32-33

Rotating DryersRequiring Syphon Drainage 34-35

Flash Tanks 36-37

Steam Absorption Machines 38

Trap Selection and Safety Factors 39

Installation and Testing 40-43

Troubleshooting 44

Pipe Sizing Steam Supplyand Condensate Return Lines 45-47

Useful Engineering Tables 48

Conversion Factors 49

Specific Gravity-Specific Heat 50

Complete Index Inside Back Cover

Bringing Energy Down to EarthSay energy. Think environment.And vice versa.Any company that is energy conscious is also environ-mentally conscious. Less energy consumed means lesswaste, fewer emissions and a healthier environment.

In short, bringing energy and environment togetherlowers the cost industry must pay for both. By helpingcompanies manage energy, Armstrong products andservices are also helping to protect the environment.

Armstrong has been sharing know-how since weinvented the energy-efficient inverted bucket steam trapin 1911. In the years since, customers’ savings haveproven again and again that knowledge not shared isenergy wasted.

Armstrong’s developments and improvements in steamtrap design and function have led to countless savingsin energy, time and money. This Handbook has grownout of our decades of sharing and expanding what we’velearned. It deals with the operating principles of steamtraps and outlines their specific applications to a widevariety of products and industries. You’ll find it a usefulcomplement to other Armstrong literature and theArmstrong Software Program 1 for Steam Trap Sizingand Selection.

The Handbook also includes Recommendation Chartswhich summarize our findings on which type of trap willgive optimum performance in a given situation and why.

GatefoldA

IMPORTANT: This Handbook is intended to summarize generalprinciples of installation and operation of steam traps, asoutlined above. Actual installation and operation of steamtrapping equipment should be performed only by experiencedpersonnel. Selection or installation should always beaccompanied by competent technical assistance or advice.This Handbook should never be used as a substitute for suchtechnical advice or assistance. We encourage you to contactArmstrong or its local representative for further details.

Instructions for Using the Recommendation Charts

GatefoldB

A quick reference RecommendationChart appears throughout the “HOWTO TRAP” sections of this Handbook,pages 16-38.

A feature code system (rangingfrom A to Q) supplies you with“at-a-glance” information.

The chart covers the type of steamtraps and the major advantages thatArmstrong feels are superior for eachparticular application.

For example, assume you are lookingfor information concerning the propertrap to use on a gravity drainedjacketed kettle. You would:

1 Turn to the “How to Trap JacketedKettles” section, pages 30-31, and

1. Drainage of condensate is continuous.Discharge is intermittent.

2. Can be continuous on low load.3. Excellent when “secondary steam”

is utilized.

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

CharacteristicFeatureCode

Method of Operation

Energy Conservation (Time in Serv

Resistance to Wear

Corrosion Resistance

Resistance to Hydraulic Shock

Vents Air and CO2 at Steam Temp

Ability to Vent Air at Very Low Press

Ability to Handle Start-up Air Loads

Operation Against Back Pressure

Resistance to Damage from Freezi

Ability to Purge System

Performance on Very Light Loads

Responsiveness to Slugs of Conde

Ability to Handle Dirt

Comparative Physical Size

Ability to Handle “Flash Steam”

Mechanical Failure (Open—Closed

A

How Various Types of Steam Traps Meet

look in the lower left-hand cornerof page 30. (The RecommendationChart for each section is on the firstpage of that particular section.)

2 Find “Jacketed Kettles, GravityDrained” in the first column under“Equipment Being Trapped” and readto the right for Armstrong’s “1st Choiceand Feature Code.” In this case, thefirst choice is an IBLV and the featurecode letters B, C, E, K, N are listed.

3 Now refer to the chart below, titled“How Various Types of Steam Traps MeetSpecific Operating Requirements” andread down the extreme left-handcolumn to each of the letters B, C, E,K, N. The letter “B,” for example,refers to the trap’s ability to provideenergy conserving operation.

4. Bimetallic and wafer traps—good.5. Not recommended for low pressure

operations.6. Cast iron traps not recommended.

InvertedBucket F&T

(1) Intermittent Continuous

ice) Excellent Good

Excellent Good

Excellent Good

Excellent Poor

erature Yes No

ure (• psig) Poor Excellent

Fair Excellent

Excellent Excellent

ng (6) Good Poor

Excellent Fair

Excellent Excellent

nsate Immediate Immediate

Excellent Poor

(7) Large Large

Fair Poor

) Open Closed

JackeKettleGravi

JackeKettleSyph

EquiB

Tra

Specific Operating Requirements

Recommendation Chart References.)

4 Follow the line for “B” to the rightuntil you reach the column whichcorresponds to our first choice, in thiscase the inverted bucket. Based ontests and actual operating conditions,the energy conserving performanceof the inverted bucket steam trap hasbeen rated “Excellent.” Follow thissame procedure for the remainingletters.

AbbreviationsIB Inverted Bucket TrapIBLV Inverted Bucket Large VentF&T Float and Thermostatic TrapCD Controlled Disc TrapDC Automatic Differential

Condensate ControllerCV Check ValveT Thermic BucketPRV Pressure Relief Valve

7. In welded stainless steel construction—medium.

8. Can fail closed due to dirt.9. Can fail either open or closed depending

upon the design of the bellows.

Disc Thermostatic Differential Controller

(2) Intermittent

Fair

Fair

Good

(4) Poor

No

Good

Excellent

Excellent

Good

Good

Excellent

Delayed

Fair

Small

Poor

(9)

Intermittent

Poor

Poor

Excellent

Excellent

No

(5) NR

Poor

Poor

Good

Excellent

Poor

Delayed

Poor

Small

Poor

(8) Open

Continuous

(3) Excellent

Excellent

Excellent

Excellent

Yes

Excellent

Excellent

Excellent

Good

Excellent

Excellent

Immediate

Excellent

Large

Excellent

Open

ted s ty Drain

ted s

on Drain

IBLVB, C, E, K, N

F&T or Thermostatic

DCB, C, E, G, H,

K, N, PIBLV

1st Choice and

Feature Code

Alternate Choice

pment eing pped

(See Chart on Gatefold B for “FEATURE CODE”

2

Steam Tables…What They Are…How to Use ThemThe heat quantities and temperature/pressure relationships referred to in thisHandbook are taken from the Propertiesof Saturated Steam table.

Definitions of Terms UsedSaturated Steam is pure steam at thetemperature that corresponds to theboiling temperature of water at the existingpressure.

Absolute and Gauge PressuresAbsolute pressure is pressure in poundsper square inch (psia) above a perfectvacuum. Gauge pressure is pressure inpounds per square inch above atmo-spheric pressure which is 14.7 pounds persquare inch absolute. Gauge pressure(psig) plus 14.7 equals absolute pressure.Or, absolute pressure minus 14.7 equalsgauge pressure.

Pressure/Temperature Relationship(Columns 1, 2 and 3). For every pressureof pure steam there is a correspondingtemperature. Example: The temperatureof 250 psig pure steam is always 406°F.

Heat of Saturated Liquid (Column 4).This is the amount of heat required to raisethe temperature of a pound of water from32°F to the boiling point at the pressureand temperature shown. It is expressedin British thermal units (Btu).

Latent Heat or Heat of Vaporization(Column 5). The amount of heat (ex-pressed in Btu) required to change apound of boiling water to a pound ofsteam. This same amount of heat isreleased when a pound of steam iscondensed back into a pound of water.This heat quantity is different for everypressure/temperature combination, asshown in the steam table.

How the Table is UsedIn addition to determining pressure/temperature relationships, you cancompute the amount of steam which willbe condensed by any heating unit ofknown Btu output. Conversely, the tablecan be used to determine Btu output ifsteam condensing rate is known. In theapplication section of this Handbook, thereare several references to the use of thesteam table.

Total Heat of Steam (Column 6). The sumof the Heat of the Liquid (Column 4) andLatent Heat (Column 5) in Btu. It is the totalheat in steam above 32°F.

Specific Volume of Liquid (Column 7).The volume per unit of mass in cubic feetper pound.

Specific Volume of Steam (Column 8).The volume per unit of mass in cubic feetper pound.

Properties of Saturated Steam(Abstracted from Keenan and Keyes, THERMODYNAMIC PROPERTIES OFSTEAM, by permission of John Wiley & Sons, Inc.)

Col. 1 Gauge

Pressure

Col. 2 Absolute Pressure

(psia)

Col. 3SteamTemp. (°F)

Col. 4Heat of

Sat. Liquid(Btu/lb)

Col. 5Latent Heat

(Btu/lb)

Col. 6Total Heat of Steam(Btu/lb)

Col. 7Specific

Volume of Sat. Liquid (cu ft/lb)

Col. 8Specific

Volume of Sat. Steam(cu ft/lb)

Inch

es o

f Vac

uum

PSIG

3306.001526.00333.6073.5238.4235.1432.4030.0628.0426.8024.7523.3920.0916.3013.7511.9010.509.407.796.665.825.174.654.233.883.593.333.223.112.922.752.602.342.131.921.741.541.161.030.930.770.500.360.280.240.190.130.110.05

0.0960220.0160270.0161360.0164070.0165900.0166200.0166470.0166740.0166990.0167150.0167460.0167680.0168300.0169220.0170040.0170780.0171460.0172090.0173250.0174290.0175240.0176130.0176960.0177750.0178500.0179220.0179910.0180240.0180570.0181210.0181830.0182440.0183600.0184700.0186020.0187280.0188960.0193400.0195470.0197480.020130.021230.022320.023460.024280.025650.028600.030270.05053

1075.81085.01106.01131.1143.31145.01146.61148.11149.51150.41152.01153.11156.31160.61164.11167.11169.71172.01175.91179.11181.91184.21186.21188.11188.81191.11192.41193.01193.51194.61195.61196.51198.01199.31200.61201.71202.81204.51204.61204.41203.21195.41183.41167.91155.91135.11091.11068.3902.7

0.0021.2169.70

130.13161.17165.73169.96173.91177.61180.07184.42187.56196.16208.42218.82227.91236.03243.36256.30267.50277.43286.39294.56302.10308.80315.68321.85324.82327.70333.24338.53343.57353.10361.91372.12381.60393.84424.00437.20449.40471.60526.60571.70611.60636.30671.70730.60756.20902.70

32.0053.14

101.74162.24193.21197.75201.96205.88209.56212.00216.32219.44227.96240.07250.33259.28267.25274.44287.07297.97307.60316.25324.12331.36337.90344.33350.21353.02355.76360.50365.99370.75379.67387.89397.37406.11417.33444.59456.28467.01486.21531.98567.22596.23613.15635.82668.13679.55705.40

0.088540.21.05.0

10.011.012.013.014.014.69616.017.020.025.030.035.040.045.055.065.075.085.095.0

105.0114.7125.0135.0140.0145.0155.0165.0175.0195.0215.0240.0

300.0400.0450.0500.0600.0900.0

265.0

0.01.32.35.3

10.315.320.325.330.340.350.360.370.380.390.3

100.0110.3120.3125.3130.3140.3150.3160.3180.3200.3225.3250.3

29.74329.51527.88619.7429.5627.5365.4903.4541.418

1200.01500.01700.02000.02500.02700.03206.2

1075.81063.81036.31001.0982.1979.3976.6974.2971.9970.3967.6965.5960.1952.1945.3939.2933.7928.6919.6911.6904.5897.8891.7886.0880.0875.4870.6868.2865.8861.3857.1852.8844.9837.4828.5820.1809.0780.5767.4755.0731.6668.8611.7556.3519.6463.4360.5312.1

0.0

3

Condensate at steam temperature andunder 100 psig pressure has a heatcontent of 308.8 Btu per pound. (SeeColumn 4 in Steam Table.) If this conden-sate is discharged to atmosphericpressure (0 psig), its heat content instantlydrops to 180 Btu per pound. The surplusof 128.8 Btu re-evaporates or flashes aportion of the condensate. The percentagethat will flash to steam can be computedusing the formula:

% flash steam = x 100

SH = Sensible heat in the condensate atthe higher pressure beforedischarge.

SL = Sensible heat in the condensate atthe lower pressure to whichdischarge takes place.

H = Latent heat in the steam at thelower pressure to which thecondensate has been discharged.

% flash steam = x 100 = 13.3%

For convenience Chart 3-1 shows theamount of secondary steam which will beformed when discharging condensate todifferent pressures. Other useful tableswill be found on page 48.

The heat absorbed by the water in raisingits temperature to boiling point is called“sensible heat” or heat of saturated liquid.The heat required to convert water atboiling point to steam at the sametemperature is called “latent heat.” Theunit of heat in common use is the Btuwhich is the amount of heat required toraise the temperature of one pound ofwater 1°F at atmospheric pressure.

If water is heated under pressure,however, the boiling point is higher than212°F, so the sensible heat required isgreater. The higher the pressure, thehigher the boiling temperature and thehigher the heat content. If pressure isreduced, a certain amount of sensibleheat is released. This excess heat willbe absorbed in the form of latent heat,causing part of the water to “flash” intosteam.

Flash Steam (Secondary)What is flash steam? When hot conden-sate or boiler water, under pressure, isreleased to a lower pressure, part of it isre-evaporated, becoming what is knownas flash steam.

Why is it important? This flash steam isimportant because it contains heat unitswhich can be used for economical plantoperation—and which are otherwisewasted.

How is it formed? When water is heatedat atmospheric pressure, its temperaturerises until it reaches 212°F, the highesttemperature at which water can exist atthis pressure. Additional heat does notraise the temperature, but converts thewater to steam.

308.8 - 180 970.3

400

300

200

100

0 100 200 300 400

PRESSURE AT WHICH CONDENSATEIS FORMED – LBS/SQ IN

CU

FT

FL

AS

H S

TE

AM

PE

R C

U F

T O

F C

ON

DE

NS

AT

E

Chart 3-2.Volume of flash steam formed when one cubic footof condensate is discharged to atmospheric pressure

30

0

5

10

15

20

25

– 20 300250200150100500

PE

RC

EN

TAG

E O

F F

LA

SH

ST

EA

M

PSI FROM WHICH CONDENSATE IS DISCHARGED

CURVEBACK PRESS.

LBS/SQ IN

ABCDEFG

105010203040

––

B

C

DEF

A

G

Chart 3-1.Percentage of flash steam formed when discharging condensateto reduced pressure

SH - SL H

4

Steam…Basic Concepts

Steam is an invisible gas generated byadding heat energy to water in a boiler.Enough energy must be added to raisethe temperature of the water to theboiling point. Then additional energy—without any further increase in tempera-ture—changes the water to steam.

Steam is a very efficient and easilycontrolled heat transfer medium. It ismost often used for transporting energyfrom a central location (the boiler) toany number of locations in the plantwhere it is used to heat air, water orprocess applications.

As noted, additional Btu are required tomake boiling water change to steam.These Btu are not lost but stored in thesteam ready to be released to heat air,cook tomatoes, press pants or dry a rollof paper.

The heat required to change boilingwater into steam is called the heat ofvaporization or latent heat. The quantityis different for every pressure/tempera-ture combination, as shown in thesteam tables.

Figure 4-1. These drawings show how muchheat is required to generate one pound ofsteam at atmospheric pressure. Note that ittakes1 Btu for every 1° increase in temperatureup to the boiling point, but that it takes moreBtu to change water at 212°F to steam at 212°F.

+ 142 Btu =

+ 970 Btu =

1 lb steamat 212°F

1 lb waterat 212°F

1 lb waterat 70°F

Steam at Work…How the Heat of Steam is UtilizedHeat flows from a higher temperaturelevel to a lower temperature level in aprocess known as heat transfer. Startingin the combustion chamber of the boiler,heat flows through the boiler tubes to thewater. When the higher pressure in theboiler pushes steam out, it heats thepipes of the distribution system. Heatflows from the steam through the walls ofthe pipes into the cooler surrounding air.This heat transfer changes some of thesteam back into water. That’s whydistribution lines are usually insulated tominimize this wasteful and undesirableheat transfer.

When steam reaches the heat exchang-ers in the system, the story is different.Here the transfer of heat from the steamis desirable. Heat flows to the air in an airheater, to the water in a water heater orto food in a cooking kettle. Nothingshould interfere with this heat transfer.

Definitions■ The Btu. A Btu—British thermal unit—is

raise the temperature of one pound of coheat energy given off by one pound of wa

■ Temperature. The degree of hotness witenergy available.

■ Heat. A measure of energy available withillustrate, the one Btu which raises one pcome from the surrounding air at a tempetemperature of 1,000°F.

Figure 4-2. These drawings show how much heaat 100 pounds per square inch pressure. Note themake water boil at 100 pounds pressure than at aamount of heat required to change water to steam

1 lb waterat 70°F,0 psig

1 lb waterat 338°F,100 psig

+ 270 Btu =

Condensate Steam

Condensate Drainage…Why It’s NecessaryCondensate is the by-product of heattransfer in a steam system. It forms inthe distribution system due to unavoid-able radiation. It also forms in heatingand process equipment as a result ofdesirable heat transfer from the steam tothe substance heated. Once the steamhas condensed and given up its valuablelatent heat, the hot condensate must beremoved immediately. Although theavailable heat in a pound of condensateis negligible as compared to a pound ofsteam, condensate is still valuable hotwater and should be returned to the boiler.

the amount of heat energy required told water by 1°F. Or, a Btu is the amount ofter in cooling, say, from 70°F to 69°F.h no implication of the amount of heat

no implication of temperature. Toound of water from 39°F to 40°F couldrature of 70°F or from a flame at a

t is required to generate one pound of steam extra heat and higher temperature required totmospheric pressure. Note, too, the lesser at the higher temperature.

1 lb steamat 338°F,100 psig

+ 880 Btu =

The need to drain the distributionsystem. Condensate lying in the bottomof steam lines can be the cause of onekind of water hammer. Steam traveling atup to 100 miles per hour makes “waves”as it passes over this condensate(Fig. 5-2). If enough condensate forms,high-speed steam pushes it along,creating a dangerous slug which growslarger and larger as it picks up liquid infront of it. Anything which changes thedirection—pipe fittings, regulating valves,tees, elbows, blind flanges—can bedestroyed. In addition to damage fromthis “battering ram,” high-velocity watermay erode fittings by chipping away atmetal surfaces.

Figure 5-4. Note that heat radiation from the dispoints or ahead of control valves. In the heat excto heat transfer. Hot condensate is returned thro

Vent

Trap

100 psig337.9°F

A B

FLUID TO BE

METAL

SCALE

DIRTWATER

NON-CONDEGASES

STEAM

The need to drain the heat transferunit. When steam comes in contact withcondensate cooled below the tempera-ture of steam, it can produce anotherkind of water hammer known as thermalshock. Steam occupies a much greatervolume than condensate, and when itcollapses suddenly, it can send shockwaves throughout the system. This formof water hammer can damage equip-ment, and it signals that condensate isnot being drained from the system.

Obviously, condensate in the heattransfer unit takes up space and reducesthe physical size and capacity of theequipment. Removing it quickly keepsthe unit full of steam (Fig. 5-3). As steamcondenses, it forms a film of water onthe inside of the heat exchanger.

tribution system causes condensate to form and,hangers, traps perform the vital function of remough the traps to the boiler for reuse.

Trap

Trap

PRV

Figure 5-2. Condensate allowed to collect inpipes or tubes is blown into waves by steampassing over it until it blocks steam flow atpoint A. Condensate in area B causes apressure differential that allows steampressure to push the slug of condensate alonglike a battering ram.

��

yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy

HEATED

NSABLE

COIL PIPE CUTAWAY

Figure 5-1.Potential barriers toheat transfer: steamheat and temperaturemust penetrate thesepotential barriers todo their work.

Condensate Steam Vapor

Non-condensable gases do not changeinto a liquid and flow away by gravity.Instead, they accumulate as a thin filmon the surface of the heat exchanger—along with dirt and scale. All are potentialbarriers to heat transfer (Fig. 5-1).

The need to remove air and CO 2.Air is always present during equipmentstart-up and in the boiler feedwater.Feedwater may also contain dissolvedcarbonates which release carbon dioxidegas. The steam velocity pushes thegases to the walls of the heat exchang-ers where they may block heat transfer.This compounds the condensate drainageproblem because these gases must beremoved along with the condensate.

5

therefore, requires steam traps at natural lowving the condensate before it becomes a barrier

TrapTrap

Trap

50.3 psig297.97°F

Figure 5-3. Coil half full of condensate can’twork at full capacity.

6

Steam…Basic Concepts

Effect of Air on SteamTemperatureWhen air and other gases enter the steamsystem, they consume part of the volumethat steam would otherwise occupy. Thetemperature of the air/steam mixture fallsbelow that of pure steam. Figure 6-1explains the effect of air in steam lines.Table 6-1 and Chart 6-1 show the varioustemperature reductions caused by air atvarious percentages and pressures.

Temp. of Steam Mixed with Various Percentages of Air

(by Volume) (°F)

10% 20% 30%

Pressure(psig)

Temp. of Steam, No Air

Present (°F)

10.3

25.3

50.3

75.3

100.3

240.1

267.3

298.0

320.3

338.1

234.3

261.0

291.0

312.9

330.3

228.0

254.1

283.5

304.8

321.8

220.9

246.4

275.1

295.9

312.4

Steam chamber 100% steamTotal pressure 100 psia

Steam pressure 100 psiaSteam temperature 327.8°F

Figure 6-1. Chamber containing air andsteam delivers only the heat of the partialpressure of the steam, not the total pressure.

Steam chamber 90% steam and 10% airTotal pressure 100 psiaSteam pressure 90 psia

Steam temperature 320.3°F

Table 6-1. Temperature Reduction Caused by Air

Effect of Air on Heat TransferThe normal flow of steam toward the heatexchanger surface carries air and othergases with it. Since they do not condenseand drain by gravity, these non-condens-able gases set up a barrier between thesteam and the heat exchanger surface.The excellent insulating properties of airreduce heat transfer. In fact, under certainconditions as little as ^ of 1% by volumeof air in steam can reduce heat transferefficiency by 50% (Fig. 7-1).

When non-condensable gases (primarilyair) continue to accumulate and are notremoved, they may gradually fill the heatexchanger with gases and stop the flowof steam altogether. The unit is then“air bound.”

CorrosionTwo primary causes of scale and corrosionare carbon dioxide (CO

2) and oxygen.

CO2 enters the system as carbonates

dissolved in feedwater and when mixedwith cooled condensate creates carbonic

Chart 6-1. Air Steam MixtureTemperature reduction caused by variouspercentages of air at differing pressures.This chart determines the percentage of airwith known pressure and temperature bydetermining the point of intersection betweenpressure, temperature and percentage of air

acid. Extremely corrosive, carbonicacid can eat through piping and heatexchangers (Fig. 7-2). Oxygen entersthe system as gas dissolved in the coldfeedwater. It aggravates the action ofcarbonic acid, speeding corrosion andpitting iron and steel surfaces (Fig. 7-3).

bphdt

Eliminating the UndesirablesTo summarize, traps must drain conden-sate because it can reduce heat transferand cause water hammer. Traps shouldevacuate air and other non-condensablegases because they can reduce heattransfer by reducing steam temperatureand insulating the system. They can alsofoster destructive corrosion. It’s essentialto remove condensate, air and CO

2 as

quickly and completely as possible.A steam trap, which is simply an auto-matic valve which opens for condensate,air and CO

2 and closes for steam, does

this job. For economic reasons, thesteam trap should do its work for longperiods with minimum attention.

y volume. As an example, assume systemressure of 250 psig with a temperature at theeat exchanger of 375°F. From the chart, it isetermined that there is 30% air by volume inhe steam.

What the Steam Trap Must DoThe job of the steam trap is to get conden-sate, air and CO

2 out of the system as

quickly as they accumulate. In addition,for overall efficiency and economy, thetrap must also provide:

1. Minimal steam loss. Table 7-1 showshow costly unattended steam leakscan be.

2. Long life and dependable service.Rapid wear of parts quickly brings a trapto the point of undependability. An efficienttrap saves money by minimizing traptesting, repair, cleaning, downtime andassociated losses.

3. Corrosion resistance. Working trapparts should be corrosion resistant inorder to combat the damaging effectsof acidic or oxygen-laden condensate.

4. Air venting. Air can be present in

Figure 7-1. Steam condensing in a heattransfer unit moves air to the heat transfersurface where it collects or “plates out” toform effective insulation.

Condensate Steam

steam at any time and especially onstart-up. Air must be vented for efficientheat transfer and to prevent systembinding.

5. CO2 venting. Venting CO2 at steamtemperature will prevent the formation ofcarbonic acid. Therefore, the steam trapmust function at or near steam tempera-ture since CO

2 dissolves in condensate

which has cooled below steamtemperature.

6. Operation against back pressure.Pressurized return lines can occur bothby design and unintentionally. A steamtrap should be able to operate against theactual back pressure in its return system.

7. Freedom from dirt problems. Dirt isan ever-present concern since traps arelocated at low points in the steam system.Condensate picks up dirt and scale inthe piping, and solids may carry overfrom the boiler. Even particles passingthrough strainer screens are erosive and,

Figure 7-2. CO2 gas combines withcondensate allowed to cool below steamtemperature to form carbonic acid whichcorrodes pipes and heat transfer units. Notegroove eaten away in the pipe illustrated.

Size of Orifice(in)

Lbs Steam WastedPer Month

835,000

637,000

470,000

325,000

210,000

117,000

52,500

1/2

7/16

3/8

5/16

1/4

3/16

1/8

Table 7-1. Cost of Various Sized Steam Leaks at

The steam loss values assume clean, dry steam floatmospheric pressure with no condensate presenlosses due to the flashing effect when a pressur

therefore, the steam trap must be able tooperate in the presence of dirt.

A trap delivering anything less thanall these desirable operating/designfeatures will reduce the efficiency of thesystem and increase costs. Whena trap delivers all these features thesystem can achieve:

1. Fast heat-up of heat transferequipment

2. Maximum equipment temperaturefor enhanced steam heat transfer

3. Maximum equipment capacity4. Maximum fuel economy5. Reduced labor per unit of output6. Minimum maintenance and a long

trouble-free service life

Sometimes an application may demand atrap without these design features, but inthe vast majority of applications the trapwhich meets all the requirements willdeliver the best results.

7

Figure. 7-3. Oxygen in the system speedscorrosion (oxidation) of pipes, causing pittingsuch as shown here.Figs. 7-2 and 7-3 courtesy of DearbornChemical Company.

Total Cost Per Month Total Cost Per Year

$4,175.00

3,185.00

2,350.00

1,625.00

1,050.00

585.00

262.50

$50,100.00

38,220.00

28,200.00

19,500.00

12,600.00

7,020.00

3,150.00

100 psi (assuming steam costs $5.00/1,000 lbs)

wing through a sharp-edged orifice tot. Condensate would normally reduce these

e drop is experienced.

8

The Inverted Bucket Steam Trap

The Armstrong inverted submerged bucketsteam trap is a mechanical trap whichoperates on the difference in densitybetween steam and water. See Fig. 8-1.Steam entering the inverted submergedbucket causes the bucket to float andclose the discharge valve. Condensateentering the trap changes the bucket to aweight which sinks and opens the trapvalve to discharge the condensate. Unlikeother mechanical traps, the invertedbucket also vents air and carbon dioxidecontinuously at steam temperature.

This simple principle of condensateremoval was introduced by Armstrong in1911. Years of improvement in materialsand manufacturing have made today’sArmstrong inverted bucket traps virtuallyunmatched in operating efficiency,dependability and long life.

Long, Energy-Efficient Service LifeAt the heart of the Armstrong invertedbucket trap is a unique leverage systemthat multiplies the force provided by the

1. Steam trap is installed in drain line between stecondensate return header. On start-up, bucket is dopen. As initial flood of condensate enters the trabottom of bucket, it fills trap body and completelyCondensate then discharges through wide open v

FlowHere

Picks UpDirt

ValveWide Open

Figure 8-1. Operatio

St

bucket to open the valve against pressure.There are no fixed pivots to wear or createfriction. It is designed to open the dischargeorifice for maximum capacity. Since thebucket is open at the bottom, it is resistantto damage from water hammer. Wearingpoints are heavily reinforced for long life.

An Armstrong inverted bucket trap cancontinue to conserve energy even in thepresence of wear. Gradual wear slightlyincreases the diameter of the seat andalters the shape and diameter of the ballvalve. But as this occurs, the ball merelyseats itself deeper—preserving a tight seal.

p

a

e

Reliable OperationThe Armstrong inverted bucket trap owesmuch of its reliability to a design thatmakes it virtually free of dirt problems.Note that the valve and seat are at thetop of the trap. The larger particles of dirtfall to the bottom where they are pulver-ized under the up-and-down action of thebucket. Since the valve of an invertedbucket is either closed or fully open, thereis free passage of dirt particles. Inaddition, the swift flow of condensatefrom under the bucket’s edge creates aunique self-scrubbing action that sweeps

am-heated unit andown and valve is wide and flows under submerges bucket.lve to return header.

2. Steam also enters tracollects at top, impartintoward its seat until valvdioxide continually passAny steam passing thro

n of the Inverted Bucket Steam Trap (at pressure

am Condensate Air Flashing Con

123123123123

dirt out of the trap. The inverted buckethas only two moving parts—the valvelever assembly and the bucket. Thatmeans no fixed points, no complicatedlinkages—nothing to stick, bind or clog.

pg

u

Corrosion-Resistant PartsThe valve and seat of Armstrong invertedbucket traps are high chrome stainlesssteel, ground and lapped. All otherworking parts are wear- and corrosion-resistant stainless steel.

Operation Against Back PressureHigh pressure in the discharge linesimply reduces the differential across thevalve. As back pressure approaches thatof inlet pressure, discharge becomescontinuous just as it does on the very lowpressure differentials.

Back pressure has no adverse effect ininverted bucket trap operation other thancapacity reduction caused by the lowdifferential. There is simply less forcerequired by the bucket to pull the valveopen, cycling the trap.

under bottom of bucket, where it rises and buoyancy. Bucket then rises and lifts valvee is snapped tightly shut. Air and carbonthrough bucket vent and collect at top of trap.gh vent is condensed by radiation from trap.

s close to maximum)

ValveClosed

densate

Types of Armstrong InvertedBucket Traps Available to MeetSpecific RequirementsThe availability of inverted bucket trapsin different body materials, piping configu-rations and other variables permitflexibility in applying the right trap tomeet specific needs. See Table 9-1.

3. As the entering condensate starts to fill the bbegins to exert a pull on the lever. As the condemore force is exerted until there is enough to othe differential pressure.

ValveClosed

Type Connections

Operating Pressure(psig)

Capacity(lbs/hr)

Cast Iron

Connections

Screwed

0 thru 250

To 20,000

1/2" thru 21/2"

Table 9-1. Typical Design Parameters for Inv

1. All-Stainless Steel Traps.Sealed, tamper-proof stainless steelbodies enable these traps to withstandfreeze-ups without damage. They may beinstalled on tracer lines, outdoor dripsand other services subject to freezing.For pressures to 650 psig and tempera-tures to 800°F.

2. Cast Iron Traps.Standard inverted bucket traps forgeneral service at pressures to 250 psigand temperatures to 450°F. Offered withside connections, side connections withintegral strainers and bottom inlet—topoutlet connections.

ucket, the bucketnsate continues to rise,pen the valve against

4. As the valve starts tis reduced. The bucketAccumulated air is discflow under the bottom of the trap. Discharge cand the cycle repeats.

SelfScrubbing

Flow

DrawnStainless Steel Forged Steel

Screwed,Socketweld orCompression

Fitting

Screwed,Socketweld or

Flanged

0 thru 650 0 thru 2,700

To 4,400 To 19,000

3/8" thru 1" 1/2" thru 2"

erted Bucket Traps

3. Forged Steel Traps.Standard inverted bucket traps for highpressure, high temperature services(including superheated steam) to 2,700psig at 1,050°F.

4. Cast Stainless Steel Traps.Standard inverted bucket traps for highcapacity, corrosive service. Repairable.For pressures to 700 psig and tem-peratures to 506°F.

9

o open, the pressure force across the valve then sinks rapidly and fully opens the valve.harged first, followed by condensate. Theof the bucket picks up dirt and sweeps it outontinues until more steam floats the bucket,

��

��

��

��

��

ValveWide Open

Cast Steel Cast Stainless Steel

0 thru 600 0 thru 700

To 4,400 To 19,000

1/2" thru 1" 1/2" thru 2"


Flanged


Flanged

10

The Float and Thermostatic Steam Trap

The float and thermostatic trap is amechanical trap which operates on bothdensity and temperature principles. Thefloat valve operates on the density principle:A lever connects the ball float to the valveand seat. Once condensate reaches acertain level in the trap the float rises,opening the orifice and draining conden-sate. A water seal formed by the conden-sate prevents live steam loss.

Since the discharge valve is under water,it is not capable of venting air and non-condensables. When the accumulation ofair and non-condensable gases causes asignificant temperature drop, a thermostaticair vent in the top of the trap discharges it.The thermostatic vent opens at a tem-perature a few degrees below saturationso it’s able to handle a large volume ofair—through an entirely separate orifice—but at a slightly reduced temperature.

Armstrong F&T traps provide high air-venting capacity, respond immediatelyto condensate and are suitable for bothindustrial and HVAC applications.

NOTE: These operational schematics of the F&T

1. On start-up low system pressure forces airout through the thermostatic air vent. A highcondensate load normally follows air ventingand lifts the float which opens the main valve.The remaining air continues to dischargethrough the open vent.

Figure 10-1. Operation of the F&T Steam Trap

Reliable Operation on ModulatingSteam PressureModulating steam pressure means thatthe pressure in the heat exchange unitbeing drained can vary anywhere fromthe maximum steam supply pressuredown to vacuum under certain condi-tions. Thus, under conditions of zeropressure, only the force of gravity isavailable to push condensate through asteam trap. Substantial amounts of airmay also be liberated under theseconditions of low steam pressure. Theefficient operation of the F&T trap meetsall of these specialized requirements.

trap do not represent actual trap configuration.

2. When steam reaches the trap, thethermostatic air vent closes in response tohigher temperature. Condensate continues toflow through the main valve which is positionedby the float to discharge condensate at the samerate that it flows to the trap.

High Back Pressure OperationBack pressure has no adverse effect onfloat and thermostatic trap operationother than capacity reduction due to lowdifferential. The trap will not fail to closeand will not blow steam due to the highback pressure.

3. As air accumulates in the trap, thetemperature drops below that of saturatedsteam. The balanced pressure thermostaticair vent opens and discharges air.

Steam Condensate Air

Table 11-1. Typical Design Parameters forFloat and Thermostatic Traps

TypeConnections

OperatingPressure(psig)

Capacity(lbs/hr)

Cast Iron Cast Steel2" thru 3"Connections

Screwed orFlanged

Screwed,Socketweldor Flanged

0 thru 250 0 thru 450

To 208,000 To 280,000

1/2" thru 3"

F

1.tharinorto

SHEMA RatingsFloat and thermostatic traps for pressuresup to 15 psig may be selected by pipesize on the basis of ratings establishedby the Steam Heating EquipmentManufacturers Association (SHEMA).SHEMA ratings are the same for allmakes of F&T traps as they are anestablished measure of the capacityof a pipe flowing half full of condensateunder specific conditions of pressure,length of pipe, pitch, etc.

The Controlled D

igure 11-1. Design and Operation of Controlle

Heating Chamber

Control Chamber

Control Disc

Inlet Passage

Outlet Passages

On start-up, condensate and air enteringe trap pass through the heating chamberound the control chamber and through thelet orifice. This flow lifts the disc off the inletifice, and the condensate flows through the outlet passages.

Various specification writing authoritiesindicate different procedures for sizingtraps by SHEMA ratings, and their proce-dures must be followed to assure compli-ance with their specifications. However, asSHEMA ratings provide for continuous airelimination when the trap operates atmaximum condensate capacity rating andprovision is made for overload conditions,no trap safety factor is necessary.

isc Steam Trap

Table 11-2. Typical Design Parameters forControlled Disc Traps

TypeConnections

OperatingPressure (psig)

Capacity(lbs/hr)

Steel

ConnectionsScrewed,

Socketweld orFlanged

10 thru 600

To 2,850

3/8" thru 1"

The controlled disc steam trap is a timedelayed device that operates on thevelocity principle. It contains only onemoving part, the disc itself. Because it isvery lightweight and compact, the CDtrap meets the needs of many applica-tions where space is limited. In additionto the disc trap’s simplicity and smallsize, it also offers advantages such asresistance to hydraulic shock, thecomplete discharge of all condensatewhen open and intermittent operation fora steady purging action.

Operation of controlled disc trapsdepends on the changes in pressures inthe chamber where the disc operates.The Armstrong CD trap will be open aslong as cold condensate is flowing.When steam or flash steam reaches theinlet orifice, velocity of flow increases,

d

2. anveincth

pulling the disc toward the seat. Increas-ing pressure in the control chamber snapsthe disc closed. The subsequent pressurereduction, necessary for the trap to open,is controlled by the heating chamber inthe cap and a finite machined bleedgroove in the disc. Once the system is upto temperature, the bleed groove controlsthe trap cycle rate.

D

dl

e

Unique Heating ChamberThe unique heating chamber inArmstrong’s controlled disc traps sur-rounds the disc body and controlchamber. A controlled bleed from thechamber to the trap outlet controls thecycle rate. That means that the trapdesign—not ambient conditions—controls the cycle rate. Without thiscontrolling feature, rain, snow and coldambient conditions would upset the cyclerate of the trap.

11

isc Traps

High Velocity FlowSeat

Steam enters through the inlet passage flows under the control disc. The flow

ocity across the face of the control discreases, creating a low pressure that pulls disc toward the seat.

3. The disk closes against two concentric facesof the seat, closing off the inlet passage andalso trapping steam and condensate above thedisc. There is a controlled bleeding of steamfrom the control chamber; flashing condensatehelps maintain the pressure in the controlchamber. When the pressure above the discis reduced, the incoming pressure lifts the discoff the seat. If condensate is present, it will bedischarged, and the cycle repeats.

Steam Condensate Air Condensate and Steam Mixture

��@@@@��ÀÀÀÀ��@@@@��ÀÀÀÀ��@@@@��ÀÀÀÀ��yyyy

ControlChamber

Disc is heldagainst twoconcentricfaces of seat

12

The Thermostatic Steam Trap

Table 12-1. Design Parameters for Thermostatic Traps

TypeConnections

Operating Pressure(psig)

Operating Capacity(lbs/hr)

Balanced Pressure Bellows Balanced Pressure Wafer

Connections

0-400

To 70

Body and Cap Material CarbonSteel

0-65

StainlessSteel

Bronze

1/4" thru 3/4" 1/2", 3/4", 1"

Screwed,Socketweld

Screwed,Socketweld

NPT Straight,Angle

0-600

To 77 To 960

Screwed,Socketweld

0-300

To 3,450

1/2", 3/4"

StainlessSteel Bronze

0-50

NPT Straight,Angle

To 1,600Capacity (lbs/hr)

1/2", 3/4" 1/2",3/4"

Armstrong thermostatic steam traps areavailable with balanced pressure bellowsor wafer type elements and are constructedin a wide variety of materials, includingstainless steel, carbon steel and bronze.These traps are used on applications withvery light condensate loads.

Thermostatic OperationThermostatic steam traps operate on thedifference in temperature between steamand cooled condensate and air. Steamincreases the pressure inside the thermo-static element, causing the trap to close.As condensate and non-condensablegases back up in the cooling leg, thetemperature begins to drop and the ther-mostatic element contracts and opens thevalve. The amount of condensate backedup ahead of the trap depends on the load

1. On start-up, condensate and air arepushed ahead of the steam directly throughthe trap. The thermostatic bellows element isfully contracted and the valve remains wideopen until steam approaches the trap.

Figure 12-1. Operation of the

conditions, steam pressure and size ofthe piping. It is important to note that anaccumulation of non-condensable gasescan occur behind the condensate backup.

2. As the temperature inside the trapincreases, it quickly heats the chargedbellows element, increasing the vaporpressure inside. When pressure inside theelement becomes balanced with systempressure in the trap body, the spring effect ofthe bellows causes the element to expand,closing the valve. When temperature in thetrap drops a few degrees below saturatedsteam temperature, imbalanced pressurecontracts the bellows, opening the valve.

Stea

FigurThermostatic Steam Trap

NOTE: Thermostatic traps can also be usedfor venting air from a steam system. Whenair collects, the temperature drops and thethermostatic air vent automatically dischargesthe air at slightly below steam temperaturethroughout the entire operating pressurerange.

Balanced Pressure Thermostatic Waferoperation is very similar to balanced pressurebellows described in Fig. 12-1. The wafer ispartially filled with a liquid. As the temperatureinside the trap increases, it heats the chargedwafer, increasing the vapor pressure inside.When the pressure inside the wafer exceeds thesurrounding steam pressure, the wafermembrane is forced down on the valve seat andthe trap is closed. A temperature drop caused bycondensate or non-condensable gases coolsand reduces the pressure inside the wafer,allowing the wafer to uncover the seat.

Alcohol Vapor

Bulkhead

Alcohol Liquid

Alcohol Chamber

Wafer

m Condensate and Air Condensate

e 12-2. Operation of Thermostatic Wafer

The Automatic Differential Condensate Controller

Armstrong automatic differential conden-sate controllers (DC) are designed tofunction on applications where conden-sate must be lifted from a drain point orin gravity drainage applications whereincreased velocity will aid in drainage.

Lifting condensate from the drain point—often referred to as syphon drainage—reduces the pressure of condensate,causing a portion of it to flash into steam.Since ordinary steam traps are unable todistinguish flash steam and live steam,they close and impede drainage.

Increased velocity with gravity drainagewill aid in drawing the condensate and airto the DC. An internal steam by-passcontrolled by a manual metering valvecauses this increased velocity. Therefore,the condensate controller automaticallyvents the by-pass or secondary steam.

To Secondary Steam Header

Condensate Retu

For the most efficient use of steam energy, Armsrecommends the piping arrangement when seconis collected and reused in heat transfer equipmen

➨DC

Piping arrangement when flash steam and non-care to be removed and discharged directly to thereturn line.

Condensate Return

➨ ➨

➨

DC

Figure 13-1.

➨

➨

➨

This is then collected for use in otherheat exchangers or discharged to thecondensate return line.

Capacity considerations for drainingequipment vary greatly according tothe application. However, a singlecondensate controller provides sufficientcapacity for most applications.

Cast Iron

Screwed

0 thru 250

To 20,000

TypeConnections

OperatingPressure (psig)

Capacity (lbs/hr)

Connections 1/2" thru 2"

Table 13-1.Typical Design Parameters for theAutomatic Differential Condensate Controller

��

�

�

�

�

�

�

�

�

�

�

�

��

Secondary Steam

Bucket

Inlet

Manual Metering Valve

��

��

Condensate

Live and Flash Ste

Condensate and S

rn

trongdary steamt.

ondensables condensate

Figure 13-2.

��

��

Condensate Controller OperationCondensate, air and steam (live andflash) enter through the controller inlet.At this point flash steam and air areautomatically separated from thecondensate. Then they divert into theintegral by-pass at a controlled rate,forming secondary steam (See Fig. 13-2).

The valve is adjustable so it matchesthe amount of flash present under fullcapacity operation or to meet the velocityrequirements of the system. Thecondensate discharges through aseparate orifice controlled by theinverted bucket.

Because of the dual orifice design, thereis a preset controlled pressure differen-tial for the secondary steam systemwhile maximum pressure differential isavailable to discharge the condensate.

13

��

��

��

��

��

�

�

�

�

��

��

Condensate Discharge Valve

Outlet

am

econdary Steam�

�

��

�

��

Dotte

d Li

nes

Indi

cate

Fie

ld P

ipin

g

Condensate Controller Operation

14

Trap Selection

To obtain the full benefits from the trapsdescribed in the preceding section, it isessential to select traps of the correctsize and pressure for a given job and toinstall and maintain them properly. Oneof the purposes of this Handbook is tosupply the information to make thatpossible. Actual installation and operationof steam trapping equipment should beperformed only by experienced person-nel. Selection or instal-lation shouldalways be accompanied by competenttechnical assistance or advice. ThisHandbook should never be used as asubstitute for such technical advice orassist-ance. We encourage you to contactArmstrong or its local representative forfurther details.

Basic ConsiderationsUnit trapping is the use of a separatesteam trap on each steam-condensingunit including, whenever possible, eachseparate chest or coil of a single ma-chine. The discussion under the ShortCircuiting heading explains the “why” ofunit trapping versus group trapping.

Figure 14-3. Continuous coil, constant pressuregravity flow to trap. 500 lbs/hr of condensatefrom a single copper coil at 30 psig. Gravitydrainage to trap. Volume of steam space verysmall. 2:1 safety factor.

Steam Con

Identical Condens

WRONG

Figure 14-1. Two steam consuming unitsdrained by a single trap, referred to as grouptrapping, may result in short circuiting.

Rely on experience. Select traps withthe aid of past experience. Either yours,the know-how of your Armstrong Repre-sentative or what others have learned intrapping similar equipment.

Do-it-yourself sizing. Do-it-yourselfsizing is simple with the aid of ArmstrongSoftware Program I (Steam Trap Sizingand Selection). Even without this computerprogram, you can easily size steam trapswhen you know or can calculate:

1. Condensate loads in lbs/hr2. The safety factor to use3. Pressure differential4. Maximum allowable pressure

1. Condensate load. Each “How To”section of this Handbook contains formulasand useful information on steam condens-ing rates and proper sizing procedures.

Figure 14-4. Multiple pipes, modulated pressuregravity flow to trap. 500 lbs/hr of condensatefrom unit heater at 80 psig. Multiple tubescreate minor short circuiting hazard. Use 3:1safety factor at 40 psig.

densate

ing Rates, Identical Pressures with Differing Sa

RIGHT

Figure 14-2. Short circuiting is impossiblewhen each unit is drained by its own trap.Higher efficiency is assured.

2. Safety Factor or Experience Factorto Use. Users have found that they mustgenerally use a safety factor in sizingsteam traps. For example, a coil con-densing 500 lbs/hr might require a trapthat could handle up to 1,500 for bestoverall performance. This 3:1 safetyfactor takes care of varying condensaterates, occasional drops in pressuredifferential and system design factors.

Safety factors will vary from a low of1.5:1 to a high of 10:1. The safety factorsin this book are based on years of userexperience.

Configuration affects safety factor. Moreimportant than ordinary load and pres-sure changes is the design of the steamheated unit itself. Refer to Figs. 14-3, 14-4 and 14-5 showing three condensingunits each producing 500 pounds ofcondensate per hour, but with safetyfactors of 2:1, 3:1 and 8:1.

Short CircuitingIf a single trap connects more than onedrain point, condensate and air from oneor more of the units may fail to reach thetrap. Any difference in condensing rateswill result in a difference in the steampressure drop. A pressure drop differencetoo small to register on a pressure gaugeis enough to let steam from the higherpressure unit block the flow of air orcondensate from the lower pressure unit.The net result is reduced heating, outputand fuel waste (See Figs. 14-1 and 14-2).

➤

➤

➤

➤

10"-12"

6"

Figure 14-5. Large cylinder, syphon drained.500 lbs/hr from a 4' diameter 10' long cylinderdryer with 115 cu ft of space at 30 psig. Thesafety factor is 3:1 with a DC and 8:1 with an IB.

fety Factors

Economical steam trap/orifice selection.While an adequate safety factor is neededfor best performance, too large a factorcauses problems. In addition to highercosts for the trap and its installation, aneedlessly oversized trap wears out morequickly. And in the event of a trap failure,an oversized trap loses more steamwhich can cause water hammer and highback pressure in the return system.

3. Pressure differential. Maximumdifferential is the difference between boileror steam main pressure or the downstreampressure of a PRV and return line pressure.See Fig. 15-1. The trap must be able toopen against this pressure differential.

NOTE: Because of flashing condensate in thereturn lines, don’t assume a decrease in pressuredifferential due to static head when elevating.

Operating differential. When the plant isoperating at capacity, the steam pressureat the trap inlet may be lower than steammain pressure. And the pressure in thecondensate return header may go aboveatmospheric.

If the operating differential is at least 80%of the maximum differential, it is safe touse maximum differential in selectingtraps.

Differential Pressureor Maximum

Operating Pressure(MOP)

BackPressure or

Vacuum

Trap

A B

Figure 15-1. “A” minus “B” is PressureDifferential: If “B” is back pressure, subtractit from “A”. If “B” is vacuum, add it to “A”.

Inlet Pressureor Maximum

AllowablePressure (MAP)

Modulated control of the steam supplycauses wide changes in pressuredifferential. The pressure in the unitdrained may fall to atmospheric or evenlower (vacuum). This does not preventcondensate drainage if the installationpractices in this handbook are followed.

IMPORTANT: Be sure to read the discussionto the right which deals with less common butimportant reductions in pressure differential.

4. Maximum allowable pressure.The trap must be able to withstand themaximum allowable pressure of the systemor design pressure. It may not have tooperate at this pressure, but must be ableto contain it. As an example, themaximum inlet pressure is 350 psig andthe return line pressure is 150 psig. Thisresults in a differential pressure of 200 psi,however, the trap must be able towithstand 350 psig maximum allowablepressure. See Fig. 15-1.

Figure 15-2. Condensate from gravity drainpoint is lifted to trap by a syphon. Every twofeet of lift reduces pressure differential byone psi. Note seal at low point and the trap’sinternal check valve to prevent backflow.

Steam Condensate

9'

8'

7'

6'

5'

4'

3'

2'

1'

4psi

3psi

2psi

1psi

Steam Main

Water Seal

Trap

Lift in feet

Pressure dropover water sealto lift coldcondensate

Factors Affecting Pressure DifferentialExcept for failures of pressure controlvalves, differential pressure usually varieson the low side of the normal or designvalue. Variations in either the inlet ordischarge pressure can cause this.

Inlet pressure can be reduced below itsnormal value by:

1. A modulating control valve ortemperature regulator.

2. “Syphon drainage.” Every two feet of liftbetween the drainage point and the trapreduces the inlet pressure (and thedifferential) by one psi. See Fig. 15-2.

Discharge pressure can be increasedabove its normal value by:

1. Pipe friction.2. Other traps discharging into a return

system of limited capacity.3. Elevating condensate. Every two feet

of lift increases the discharge pressure(and the differential) by one psi whenthe discharge is only condensate.However, with flash present, the extraback pressure could be reduced tozero. See Fig. 15-3, noting the externalcheck valve.

15

ExternalCheckValve

Figure 15-3. When trap valve opens, steampressure will elevate condensate. Every twofeet of lift reduces pressure differential by one psi.

Trap

16

How to Trap Steam Distribution Systems

Steam distribution systems link boilersand the equipment actually using steam,transporting it to any location in the plantwhere its heat energy is needed.

The three primary components of steamdistribution systems are boiler headers,steam mains and branch lines. Each fulfillscertain requirements of the system and,together with steam separators andsteam traps, contributes to efficientsteam use.

Drip legs. Common to all steam distribu-tion systems is the need for drip legs atvarious intervals (Fig. 16-1). These areprovided to:

Drip leg same asup to 4". Above 4

never l

Trap

Figure 16-2.Boiler Headers

Figure 16-1.Drip Leg Sizing

*Provide internal check valve when pre**Use IBLV above F&T pressure/tempeNOTE: On superheated steam, use an IBand burnished valve and seat.

*On superheated steam never use an F&Always use an IB with internal check va

Steam Mains and Branch Lines Non-freezing Conditions

Steam Mains and Branch Lines Freezing Conditions

B, M, N, L, F,

Alternate

B, C, D, E, F, L

Alternate

1st Choice, Feand Alternate

Equipment Being Trapped

Boiler Header

1st Choice and

Feature Code

AlteCh

Equipment Being

Trapped

IBLVM, E, L, N,

B, Q*F

Recommendation Chart (See Chart o

The properly sized drip legwill capture condensate.Too small a drip leg canactually cause a venturi“piccolo” effect wherepressure drop pullscondensate out of the trap.See Table 18-1.

1. Let condensate escape by gravityfrom the fast-moving steam.

2. Store the condensate until thepressure differential can discharge itthrough the steam trap.

e

sr

E

C

,

C

ro

&

Boiler HeadersA boiler header is a specialized type ofsteam main which can receive steamfrom one or more boilers. It is most oftena horizontal line which is fed from the topand in turn feeds the steam mains.It is important to trap the boiler headerproperly to assure that any carryover(boiler water and solids) is removedbefore distribution into the system.

Trap

Boiler #1

Boiler #2

the header diameter", 1/2 header size, butss than 4".

Header Level

TypicalTakeoffs

to System

sures fluctuate.ature limitations. with internal check valve

T type trap.lve and burnished valve and seat.

0-30 psig

Above 30 psig

, C, D, Q

hoice

*IB

F&T

*IB

**F&T

M, N, Q, J

hoice

*IB

Thermostatic or CD

*IB

Thermostatic or CD

ature Code Choice(s)

nate ice

T

n Gatefold B for “FEATURE CODE” References.)

Steam traps which serve the headermust be capable of discharging large slugsof carryover as soon as they are present.Resistance to hydraulic shock is also aconsideration in the selection of traps.

Trap selection and safety factor forboiler headers (saturated steam only).A 1.5:1 safety factor is recommended forvirtually all boiler header applications.The required trap capacity can beobtained by using the following formula:Required Trap Capacity = Safety Factor xLoad Connected to Boiler(s) x AnticipatedCarryover (typically 10%).

EXAMPLE: What size steam trap will berequired on a connected load of 50,000 lbs/hrwith an anticipated carryover of 10%?Using the formula:Required Trap Capacity =1.5 x 50,000 x 0.10 = 7,500 lbs/hr.

The ability to respond immediately toslugs of condensate, excellent resistanceto hydraulic shock, dirt-handling abilityand efficient operation on very light loadsare features which make the invertedbucket the most suitable steam trap forthis application.

Installation. If steam flow through theheader is in one direction only, a singlesteam trap is sufficient at the downstreamend. With a midpoint feed to the header(Fig. 16-2), or a similar two-directionalsteam flow arrangement, each end of theboiler header should be trapped.

Steam MainsOne of the most common uses of steamtraps is the trapping of steam mains.These lines need to be kept free of airand condensate in order to keep steam-using equipment operating properly.Inadequate trapping on steam mainsoften leads to water hammer and slugsof condensate which can damage controlvalves and other equipment.

There are two methods used for the warm-up of steam mains—supervised andautomatic. Supervised warm-up is widelyused for initial heating of large diameterand/or long mains. The suggestedmethod is for drip valves to be openedwide for free blow to the atmospherebefore steam is admitted to the main.These drip valves are not closed until all ormost of the warm-up condensate hasbeen discharged. Then the traps takeover the job of removing condensate that

Table 17-2. The Warming-Up Load from 70°F,

Pipe Size(in)

sq ft perLineal ft

Pressure, psig 15 30 60 125 180

.12.10.07.06.05.3441

.14.12.09.07.06.43411/4

.16.14.10.08.07.49711/2

.20.17.13.10.08.6222

.24.20.15.12.10.75321/2

.28.24.18.14.12.9163

.32.27.20.16.131.04731/2

.36.30.22.18.151.1784

.44.37.27.22.181.4565

.51.44.32.25.201.7356

.66.55.41.32.272.2608

.80.68.51.39.322.81010

.92.80.58.46.383.340121.03.87.65.51.423.670141.19.99.74.57.474.200161.311.11.85.64.534.710181.451.23.91.71.585.250201.711.451.09.84.686.28024

Pounds of Condensate

Table 17-1. Condensation in Insulated Pipes Cin Quiet Air at 70°F (Insulation Assumed to be 7

2 15 30Pipe Size

(in)wt of Pipeper ft (lbs)

Steam Pressure, psig

Pounds of W

.043.037.0301.691

.057.050.0402.2711/4

.069.059.0482.7211/2

.092.080.0653.652

.146.126.1045.7921/2

.190.165.1337.573

.229.198.1629.1131/2

.271.234.19010.794

.406.352.25814.625

.476.413.33518.976

.720.620.50428.5581.020.880.71440.48101.3501.170.94553.60121.5801.3701.11063.00142.0801.8101.46083.00162.6302.2801.850105.00183.0802.6802.170123.00204.2903.7203.020171.0024

may form under operating conditions.Warm-up of principal piping in a powerplant will follow much the same procedure.

Automatic warm-up is when the boiler isfired, allowing the mains and some or allequipment to come up to pressure andtemperature without manual help orsupervision.

CAUTION: Regardless of warm-up method,allow sufficient time during the warm-upcycle to minimize thermal stress and preventany damage to the system.

Trap selection and safety factor forsteam mains (saturated steam only).Select trap to discharge condensateproduced by radiation losses at runningload. Sizing for start-up loads results inoversized traps which may wear prema-turely. Size drip legs to collect condensateduring low-pressure, warm-up conditions.

Table 17-3. PipSchedule 40 Pipe

250 450 600 900

.186.14 .221 .289

.231.17 .273 .359

.261.19 .310 .406

.320.23 .379 .498

.384.28 .454 .596

.460.33 .546 .714

.520.38 .617 .807

.578.43 .686 .897

.698.51 .826 1.078

.809.59 .959 1.2531.051.76 1.244 1.6281.301.94 1.542 2.0191.5391.11 1.821 2.3931.6881.21 1.999 2.6241.9271.38 2.281 2.9972.1511.53 2.550 3.3512.3871.70 2.830 3.7252.8332.03 3.364 4.434

Per Hour Per Lineal Foot

arrying Saturated Steam5% Efficient)

Chart 17-1.

111098

7

6

5

4.5

4.0

3.53.3

3.0

2.8

2.6

2.5

2.4

2.3

2.2

2.15

PSIG

5.3

10.3

15.3

PRE

BT

U P

ER

SQ

FT

PE

R H

OU

R P

ER

°F

TE

MP

ER

AT

UR

E D

IFF

ER

EN

CE

150° 160° 180° 2

1"

2"

3"

5"

2"

5"

6"

10"FLAT

60 125 180 250

ater Per Lineal Foot

.079.071.063.051

.106.095.085.068

.127.114.101.082

.171.153.136.110

.271.262.215.174

.354.316.282.227

.426.381.339.273

.505.451.400.323

.684.612.544.439

.882.795.705.5691.3401.1901.060.8601.8901.6901.5001.2102.5102.2402.0001.6102.9402.6402.3401.8903.8803.4703.0802.4904.9004.4003.9003.1505.7505.1504.5703.6908.0007.1506.3505.130

Pipe Size(in) Sched

111/411/22

21/23

31/214151628410512614816

101812201724

(See Table 18-1.) Condensate loads ofinsulated pipe can be found in Table17-1. All figures in the table assumethe insulation to be 75% effective. Forpres-sures or pipe sizes not includedin the table, use the following formula:

C =

Where:C = Condensate in lbs/hr-footA = External area of pipe in square feet

(Table 17-1, Col. 2)U = Btu/sq ft/degree temperature

difference/hr from Chart 17-1T1 = Steam temperature in °FT2 = Air temperature in °FE = 1 minus efficiency of insulation

(Example: 75% efficient insulation:1-.75 = .25 or E = .25)

H = Latent heat of steam(See Steam Table on page 2)

A x U x (t1-t2)E H

17

e Weights Per Foot in Pounds

Btu Heat Loss Curves

111098

7

6

5

4.5

4.0

3.53.3

3.0

2.8

2.6

2.5

2.4

2.3

2.2

2.15

2.10

25.3

50.3

75.3

100.

3

150.

3

250.

3

450.

360

0.3

900.

3

1500

.324

00.3

SSURE IN LBS PER SQUARE INCH

TEMPERATURE DIFFERENCE00° 240° 300° 400° 500° 700° 900° 1050°

SURFACES

ule 40 Schedule 80 Schedule 160 XX Strong

2.17 2.85 3.661.693.00 3.76 5.212.273.63 4.86 6.412.725.02 7.45 9.033.657.66 10.01 13.695.79

10.25 14.32 18.587.5712.51 — 22.859.1114.98 22.60 27.540.7920.78 32.96 38.554.6228.57 45.30 53.168.9743.39 74.70 72.428.5554.74 116.00 —0.4888.60 161.00 —3.60

107.00 190.00 —3.00137.00 245.00 —3.00171.00 309.00 —5.00209.00 379.00 —3.00297.00 542.00 —1.00

18

For traps installed between the boilerand the end of the steam main, apply a2:1 safety factor. Apply a 3:1 safetyfactor for traps installed at the end of themain or ahead of reducing and shutoffvalves which are closed part of the time.

Divide the warming-up load from Table17-2 by the number of minutes allowedto reach final steam temperature.Multiply by 60 to get pounds per hour.

For steam pressures and pipe schedulesnot covered by Table 17-2, the warming-up load can be calculated using thefollowing formula:

C =

Where:C = Amount of condensate in lbsW = Total weight of pipe in lbs

(See Table 17-3 for pipe weights)

W x (t1 - t2) x .114H

* DC is 1st choice wh90% or less.

Steam Separator

BE

1s

FEquipment

Being Trapped

Recommendation Chart (See Char

Figure 18-1. Trap draining strainer ahead ofPRV.

t1 = Final temperature of pipe in °Ft2 = Initial temperature of pipe in °F.114= Specific heat of steel pipe Btu/lb-°FH = Latent heat of steam at final tempera-

ture in Btu/lb (See Steam Tables)

A more conservative approach is asfollows: Determine the warming-up loadto reach 219°F or 2 psig. Divide by thenumber of minutes allowed to reach219°F and multiply by 60 to get poundsper hour. Size the trap on the basis of1 psi pressure differential for every 28"of head between the bottom of the mainand the top of the trap.

The inverted bucket trap is recommendedbecause it can handle dirt and slugs ofcondensate and resists hydraulic shock.In addition, should an inverted bucket fail,it usually does so in the open position.

ere steam quality is

IBLV, M, L, , F, N,

Q

*DC

t Choice and

eature Code

Alternate Choice

t on Gatefold B for “FEATURE CODE” References.)

S

FDf

Figure 18-2. Trap draining drip leg on main.

Steam Mains

TB

M

D

H

Installation. Both methods of warm-upuse drip legs and traps at all low spots ornatural drainage points such as:

Ahead of risersEnd of mainsAhead of expansion joints or bendsAhead of valves or regulators

Install drip legs and drain traps even wherethere are no natural drainage points (SeeFigs. 18-1, 18-2 and 18-3). These shouldnormally be installed at intervals of about300' and never longer than 500'.

On a supervised warm-up, make drip leglength at least 11/2 times the diameter ofthe main, but never less than 10". Makedrip legs on automatic warm-ups a minimumof 28" in length. For both methods, it is agood practice to use a drip leg the samediameter as the main up to 4" pipe sizeand at least 1/2 of the diameter of the mainabove that, but never less than 4".See Table 18-1.

team MainSize(in)

DM

Drip LegDiameter

(in)SupervisedWarm-Up

AutomaticWarm-Up

Drip Leg Length Min. (in)

282828282828282828282828283036

101010101010101215182124273036

1234446688101012

1/23/412346810121416182024

H

1/23/4

Drip leg same asthe header

diameter up to 4".

igure 18-3. Trap draining drip leg at riser.istance “H” in inches ÷ 28 = psi static head

or forcing water through the trap.

Above 4", 1/2 headersize, but never less

than 4".

able 18-1. Recommended Steam Main andranch Line Drip Leg Sizing

Branch LinesBranch lines are take-offs from the steammains supplying specific pieces of steam-using equipment. The entire system mustbe designed and hooked up to preventaccumulation of condensate at any point.

Trap selection and safety factor forbranch lines . The formula for computingcondensate load is the same as that usedfor steam mains. Branch lines also have arecommended safety factor of 3:1.

Installation. Recommended piping fromthe main to the control is shown in Fig. 19-1for runouts under 10' and Fig. 19-2 forrunouts over 10'. See Fig. 19-3 for pipingwhen control valve must be below the main.

Install a full pipe size strainer ahead of eachcontrol valve as well as ahead of the PRVif used. Provide blowdown valves, prefer-ably with IB traps. A few days afterstarting system, examine the strainerscreens to see if cleaning is necessary.

Figure 19-1. Piping for runout less than 10 ft.No trap required unless pitch back to supplyheader is less than ^" per ft.

Pitch 1/2" per 1 ft

Figure 19-2. Piping for runout greater than10'. Drip leg and trap required ahead of controlvalve. Strainer ahead of control valve can serveas drip leg if blowdown connection runs to aninverted bucket trap. This will also minimize thestrainer cleaning problem. Trap should beequipped with an internal check valve or aswing check installed ahead of the trap.

Morethan10'

Runout OversizedOne Pipe Size or

More

Pitch Down1/2" per 10 ft

Branch Lines

10' or Less

SeparatorsSteam separators are designed toremove any condensate that forms withinsteam distribution systems. They aremost often used ahead of equipmentwhere especially dry steam is essential.They are also common on secondarysteam lines, which by their very nature,have a large percentage of entrainedcondensate.

Important factors in trap selection forseparators are the ability to handle slugsof condensate, provide good resistanceto hydraulic shock and operate on lightloads.

Trap selection and safety factors forseparators. Apply a 3:1 safety factor inall cases, even though different types oftraps are recommended, depending oncondensate and pressure levels.

Use the following formula to obtain therequired trap capacity:

Figure 19-3. Regardless of the length of therunout, a drip leg and trap are required aheadof the control valve located below steamsupply. If coil is above control valve, a trapshould also be installed at downstream side ofcontrol valve.

Required trap capacity in lbs/hr = safetyfactor x steam flow rate in lbs/hr xanticipated percent of condensate (typically10% to 20%).

EXAMPLE: What size steam trap will berequired on a flow rate of 10,000 lbs/hr?Using the formula:

Required trap capacity =3 x 10,000 x 0.10 = 3,000 lbs/hr.

The inverted bucket trap with largevent is recommended for separators.When dirt and hydraulic shock are notsignificant problems, an F&T type trapis an acceptable alternative.

An automatic differential condensatecontroller may be preferred in manycases. It combines the best features ofboth of the above and is recommendedfor large condensate loads whichexceed the separating capability of theseparator.

InstallationConnect traps to the separator drainline 10" to 12" below the separatorwith the drain pipe running the full sizeof the drain connection down to thetrap take-off (Fig. 19-4). The drain pipeand dirt pocket should be the samesize as the drain connection.

19

Shutoff Valve 10"-12"

Figure 19-4. Drain downstream side ofseparator. Full size drip leg and dirt pocketare required to assure positive and fastflow of condensate to the trap.

Steam Separator

SteamSeparator

IBLVor DC

6"

20

How to Trap Steam Tracer Lines

Steam tracer lines are designed tomaintain the fluid in a primary pipe at acertain uniform temperature. In mostcases, these tracer lines are usedoutdoors which makes ambient weatherconditions a critical consideration.

The primary purpose of steam traps ontracer lines is to retain the steam until itslatent heat is fully utilized and thendischarge the condensate and non-condensable gases. As is true with anypiece of heat transfer equipment, eachtracer line should have its own trap. Eventhough multiple tracer lines may beinstalled on the same primary fluid line,unit trapping is required to prevent shortcircuiting. See page 14.

Figure 20-1.

FreezeProtection

Drain

*

*Select a ‹" steam traenergy and avoid plugg

Tracer Lines A, BJ, N

1st Ca

FeaC

Equipment Being

Trapped

Recommendation Chart (See Chart on

In selecting and sizing steam traps, it’simportant to consider their compatibilitywith the objectives of the system, astraps must:

1. Conserve energy by operating reliablyover a long period of time.

2. Provide abrupt periodic discharge inorder to purge the condensate and airfrom the line.

3. Operate under light load conditions.4. Resist damage from freezing if the

steam is shut off.

The cost of steam makes wasteful tracerlines an exorbitant overhead which noindustry can afford.

CheckValve

Typical Tracer Installation

p orifice to conserveing with dirt and scale.

IB, C, L, , I, K

Thermostatic or CD

hoice nd ture

ode

Alternate Choice

Gatefold B for “FEATURE CODE” References.)

Trap Selection for Steam Tracer Lines.The condensate load to be handled on asteam tracer line can be determined fromthe heat loss from the product pipe byusing this formula:

Q =

Where:Q = Condensate load, lbs/hrL = Length of product pipe between

tracer line traps in ftU = Heat transfer factor in Btu/sq ft/°F/hr

(from Chart 21-1)∆T = Temperature differential in °FE = 1 minus efficiency of insulation

(example: 75% efficient insulation or1 - .75 = .25 or E = .25)

S = Lineal feet of pipe line per sq ftof surface (from Table 48-1)

H = Latent heat of steam in Btu/lb(from Steam Tables, page 2)

L x U x ∆T x ES x H

Figure 20-2.

Iron Pipe Copper orBrass Pipe

Pipe Size(in)

1/2

3/4

1

11/4

11/2

2

21/2

3

4

4.55

3.64

2.90

2.30

2.01

1.61

1.33

1.09

.848

7.63

5.09

3.82

3.05

2.55

1.91

1.52

1.27

.954

Table 20-1. Pipe Size Conversion Table(Divide lineal feet of pipe by factor given for sizeand type of pipe to get square feet of surface.)

EXAMPLE: Three tracer lines at 100 psigsteam pressure are used on a 20" diameter,100' long insulated pipe to maintain atemperature of 190°F with an outdoor designtemperature of -10°F. Assume further the pipeinsulation is 75% efficient. What is thecondensate load?

Using the formula:

Now divide by three in order to get the loadper tracer line—24 lbs/hr.

100 ft x 2.44 Btu/sq ft - °F - hr x 200°F x .250.191 lin ft/sq ft x 880 Btu/lb

and purgetrap is recservice.

Safety fac

On most tto the steafore, the sBased onoperatingtime, hand

Q = = 72 lbs/hr

Figure 21-1.

VacuumBreaker

Freeze Protection Drain

Typical Tracer Installation

the system, an inverted bucketommended for tracer line

tor . Use a 2:1 safety factorwhether exposure to ambient weatherconditions is involved or not. Do notoversize steam traps or tracer lines.Select a 5/64"steam trap orifice toconserve energy and avoid pluggingwith dirt and scale.

racer line applications, the flowm trap is surprisingly low, there-mallest trap is normally adequate. its ability to conserve energy by reliably over a long period ofle light loads, resist freezing

Chart 21-1. Btu Heat LUnit heat loss per sq ft odiameters (also flat surfsteam pressures or tem

111098

7

6

5

4.5

4.0

3.53.3

3.0

2.8

2.6

2.5

2.4

2.3

2.2

2.15

PSIG

5.3

10.3

15.3

25.3

PRE

BT

U P

ER

SQ

FT

PE

R H

OU

R P

ER

°F

TE

MP

ER

AT

UR

E D

IFF

ER

EN

CE

150° 160° 180° 20

1"

2"

3"

5"

2"

5"

6"

10"FLAT S

InstallationInstall distribution or supply lines at aheight above the product lines requiringsteam tracing. For the efficient drainageof condensate and purging of non-condensables, pitch tracer lines forgravity drainage and trap all low spots.This will also help avoid tracer linefreezing. (See Figs. 20-1, 20-2 and 21-1.)

To conserve energy, return condensateto the boiler. Use vacuum breakersimmediately ahead of the traps to assuredrainage on shutdown on gravity drainsystems. Freeze protection drains ontrap discharge headers are suggestedwhere freezing conditions prevail.

21

oss Curvesf surface of uninsulated pipe of various

ace) in quiet air at 75°F for various saturatedperature differences.

111098

7

6

5

4.5

4.0

3.53.3

3.0

2.8

2.6

2.5

2.4

2.3

2.2

2.15

2.10

50.3

75.3

100.

3

150.

3

250.

3

450.

360

0.3

900.

3

1500

.324

00.3

SSURE IN LBS PER SQUARE INCH

TEMPERATURE DIFFERENCE0° 240° 300° 400° 500° 700° 900° 1050°

URFACES

22

How to Trap Space Heating Equipment

Space heating equipment, such as unitheaters, air handling units, finnedradiation and pipe coils are found invirtually all industries. This type ofequipment is quite basic and shouldrequire very little routine maintenance.Consequently, the steam traps areusually neglected for long periods of time.One of the problems resulting from suchneglect is residual condensate in theheating coil which can cause damage dueto freezing, corrosion and water hammer.

Trap Selection and Safety FactorsDifferent application requirements involvingconstant or variable steam pressuredetermine which type and size of trapshould be used. There are two standardmethods for sizing traps for coils.

1. Constant Steam Pressure.INVERTED BUCKET TRAPS AND F&TTRAPS—use a 3:1 safety factor atoperating pressure differentials.

STEAM PRESSURE PS

MU

LT

IPL

IER

201715

12

10

87

6

4

5

2 5 10 15 25

2 5 10 15 25

FORCED AIR CIRCULADRYING WET CLAYDAMP ATMOSPHERES

ORDINARY SPACE HEA

Chart 22-1. Multipliers for Sizing Traps

Unit Heaters

Air Handling Units

Finned Radiation & Pipe Coils

B, C, E, K, N IBLV

Alternate Choice F&T

B, C, E, K, N IBLV

F&T

B, C, E, K, N IBLV

Thermo-static

1st Choice and

Feature Code

ConstaPressuEquipment

Being Trapped 0-30

psig 3

Alternate Choice

Alternate Choice T

*Use IBLV above F&T pressure/temperaturPLEASE NOTE: 1. Provide vacuum breaker 2. Do not use F&T traps on


2. Modulating Steam Pressure.F&T TRAPS AND INVERTED BUCKETTRAPS WITH THERMIC BUCKETS

0-15 psig steam—2:1 safety factorat 1/2 psi pressure differential (on F&Ttraps SHEMA ratings can also be used)16-30 psig steam—2:1 at 2 psipressure differentialAbove 30 psig steam—3:1 at 1/2 ofmaximum pressure differentialacross the trap.

INVERTED BUCKET TRAPS WITHOUTTHERMIC BUCKETSAbove 30 psig steam pressure only—3:1at ^ of maximum pressure differentialacross the trap.

5

5

T

T

f

I

*

I

*

I

A0

hs

ew

n

Trap Selection for Unit Heatersand Air Handling UnitsYou may use three methods to computethe amount of condensate to be handled.Known operating conditions will deter-mine which method to use.

IG

MU

LT

IPL

IER

0 100 125 180 250

0 100 125 180 250201715

12

10

87

6

4

5

ION

ING

or Multiple Coils

BLV B, C, G, H, L F&T *F&T

F&T IBLV IBLV

BLV B, C, G, H, L F&T *F&T

F&T IBT IBLV

BLV B, C, G, H, L F&T F&T

nt re

Variable Pressure

1st Choice and

Feature Code

bove psig

0-30 psig

Above 30 psig

Alternate Choice

Alternate Choice

Alternate Choiceermo-tatic IBLV IBLV

limitations.herever subatmospheric pressures occur.

superheated steam.


1. Btu method. The standard rating forunit heaters and other air coils is Btuoutput with 2 psig steam pressure in theheater and entering air temperature of60°F. To convert from standard to actualrating, use the conversion factors in Table24-1. Once the actual operating condi-tions are known, multiply the condensateload by the proper safety factor.

2. CFM and air temperature risemethod . If you know only CFM capacityof fan and air temperature rise, find theactual Btu output by using this simpleformula: Btu/hr = CFM x 1.08 x tempera-ture rise in °F.

EXAMPLE: What size trap will drain a 3,500CFM heater that produces an 80°F temperaturerise? Steam pressure is constant at 60 psig.

Using the formula:3,500 x 1.08 x 80 = 302,400 Btu/hr.Now divide 302,400 Btu/hr by 904.5 Btu (fromthe Steam Tables) to obtain 334 lbs/hr andthen multiply by the recommended safetyfactor 3. The application needs a trap with a1,002 lbs/hr capacity.

Derive the 1.08 factor in the above formula asfollows:1 CFM x 60 = 60 CFH60 CFH x .075 lbs of air/cu ft = 4.5 lbs of air/hr4.5 x 0.24 Btu/lb -°F (specific heat of air) =1.08 Btu/hr °F- CFM.

3. Condensate method.Once you determine Btu output:1. Divide Btu output by latent heat of

steam at steam pressure used. SeeColumn 2 of Table 24-1 or the SteamTables. This will give the actual weightof steam condensed. For a closeapproximation, a rule of thumb couldbe applied in which the Btu output issimply divided by 1,000.

2. Multiply the actual weight of steamcondensing by the safety factor toget the continuous trap dischargecapacity required.

InstallationIn general, follow the recommendationsof the specific manufacturer. Figs. 23-1,23-2, 23-3, and 23-4 represent the consen-sus of space heating manufacturers.

NOTE: For explanation of safety drain trap,see Fig. 42-1.

Trap Selection for Pipe Coilsand Finned RadiationPipe coils. Insofar as possible, trap eachpipe individually to avoid short circuiting.

Single pipe coils. To size traps forsingle pipes or individually trapped pipes,find the condensing rate per linear foot inTable 24-3. Multiply the condensing rateper linear foot by the length in feet to getthe normal condensate load.

For quick heating, apply a trap selectionsafety factor of 3:1 and use an invertedbucket trap with a thermic vent bucket.Where quick heating is not required, usea trap selection safety factor of 2:1 andselect a standard inverted bucket trap.

Multiple pipe coils. To size traps todrain coils consisting of multiple pipes,proceed as follows:1. Multiply the lineal feet of pipe in the

coil by the condensing rate given inTable 24-3. This gives normal conden-sate load.

Figure 23-1. Trapping and Venting Air Heat C

Strainer

Return Main

F&T SafetyTrap

Air

Strainer

Return Main

Figure 23-2. Trapping and Venting Air Heat C

F&T SafetyTrap

To Dra

SteamMain

InvertedBucket Trap

ModulatingSteam Control

Valve

A

T

ModulatingSteam Control

Valve

SteamMain

InvertedBucket Trap

2. From Chart 22-1 find the multiplier foryour service conditions.

3. Multiply normal condensate load bymultiplier to get trap required continu-ous discharge capacity.Note that the safety factor isincluded in the multiplier.

Finned radiation. When Btu output isnot known, condensing rates can becomputed from Tables 24-2 and 24-4with sufficient accuracy for trap selectionpurposes. To enter Table 24-4, observesize of pipe, size of fins, number of finsand material. Determine condensing rateper foot under standard conditions fromTable 24-4. Convert to actual conditionswith Table 24-2.

Safety factor recommendations are to:1. Overcome the short circuiting hazard

created by the multiple tubes of theheater.

2. Ensure adequate trap capacityunder severe operating conditions.

oil

ThermostaticAir Vent

Primary Trap

Primary Trap

oil

in

Vacuum BreakerWhere Return is

Below Trap

OverheadReturn Main(Alternate)

BrokenLines Applyto Overhead

Return

ir

o Drain

Vacuum BreakerWhere Return is

Below Trap

OverheadReturn Main(Alternate)

BrokenLines Applyto Overhead

Return

ThermostaticAir Vent

In extremely cold weather the enteringair temperature is likely to be lower thancalculated, and the increased demandfor steam in all parts of the plant mayresult in lower steam pressures andhigher return line pressures—all ofwhich cut trap capacity.

3. Ensure the removal of air and othernon-condensables.

WARNING: For low pressure heating, use asafety factor at the actual pressure differential,not necessarily the steam supply pressure,remembering the trap must also be able tofunction at the maximum pressure differentialit will experience.

23

Figure 23-3. Generally approved method ofpiping and trapping high pressure (above 15psi) horizontal discharge heaters. Figs. 23-3and 23-4 drip leg should be 10"-12" minimum.

Figure 23-4. Generally approved method ofpiping and trapping low pressure (under 15psi) vertical discharge heaters.

GateValve

CheckValve

ReturnIB TrapDirt Pocket6" Min.

Supply

Pitch Down

Dirt Pocket6" Min.

IB TrapReturn

Pitch Down

Supply

10" to 12"

GateValve10" to 12"

24

Table 24-1. A Table of Constants for determining the Btu output of a unit heater with conditions other than standard—standard being with 2 lbssteam pressure at 60°F entering air temperature. To apply, multiply the standard Btu capacity rating of heater by the indicated constant.(Reprinted from ASHRAE Guide by special permission.)

.9

5

1015

30

60100

125

175

Steam Entering Air Temperature °F

Temp. (°F) 45 55 65 70 75 80 90

Steam Pressure

(psig)

215.0

227.1

239.4249.8

274.0

307.3337.9

352.9

377.4

1.22

1.34

1.451.55

1.78

2.102.43

2.59

2.86

1.11

1.22

1.331.43

1.66

2.002.31

2.47

2.74

1.00

1.11

1.221.31

1.54

1.872.18

2.33

2.60

.95

1.05

1.171.26

1.48

1.812.11

2.27

2.54

.90

1.00

1.111.20

1.42

1.752.05

2.21

2.47

.84

.95

1.051.14

1.37

1.692.00

2.16

2.41

.75

.81

.911.00

1.21

1.511.81

1.96

2.21

Steel Pipe, SteelFins Painted

Black

Copper PipeAluminum Fins

Unpainted

Condensatelbs/hr per

Foot of Pipe

1.12.02.61.62.43.11.52.43.11.62.22.82.23.03.6

PipeSize(in)

11/4

2

11/4

11/4

11/4

FinSize(in)

31/4

41/4

41/4

31/4

41/4

FinsperInch

3 to 4

3 to 4

2 to 3

4

5

No. of PipesHigh on

6" Centers

123123123123123

Table 24-2. Finned Radiation Conversion Factors for steampressures and air temperatures other than 65°F air and 215°F steam.

Table 24-4. Finned Radiation Condensing Rates with 65°F Air and215°F Steam (for trap selection purposes only).

1/23/4

111/4

11/2

221/2

331/2

4

Steam Pressure (psig) Temp. Rise from 70°

15180°

30204°

60237°

125283°

180310°

250336°

sq ft perLineal ft

Pipe Size(in)

.220 .13 .15 .19 .26 .30 .35

.275 .15 .19 .24 .33 .38 .45

.344 .19 .23 .28 .39 .46 .54

.434 .23 .28 .36 .49 .57 .67

.497 .26 .32 .41 .55 .65 .76

.622 .33 .40 .50 .68 .80 .93

.753 .39 .47 .59 .81 .95 1.11

.916 .46 .56 .70 .96 1.13 1.311.047 .52 .63 .80 1.08 1.27 1.501.178 .58 .70 .89 1.21 1.43 1.72

Pounds of Condensate per hr per Lineal ft

Table 24-3. Condensing Rates in Bare Pipe Carrying Saturated Steam

Entering Air Temperature °FLatent Heat of Steam -10 0 10 20 30 40 50 60 70 80 90 100

Steam Pressure lbs per sq in

1.078 1.000 0.926 0.853

1.127 1.050 0.974 0.901

1.211 1.131 1.056 0.982

1.275 1.194 1.117 1.043

1.333 1.251 1.174 1.097

1.429 1.346 1.266 1.190

1.511 1.430 1.349 1.270

1.582 1.498 1.416 1.338

1.640 1.555 1.472 1.393

1.696 1.610 1.527 1.447

1.721 1.635 1.552 1.472

1.748 1.660 1.577 1.497

1.792 1.705 1.621 1.541

1.836 1.749 1.663 1.581

5

10

15

20

30

40

50

60

70

75

80

90

100

2 966.3

960.7

952.4

945.5

939.3

928.5

919.3

911.2

903.9

897.3

893.8

891.1

885.4

880.0

1.640

1.730

1.799

1.861

1.966

2.058

2.134

2.196

2.256

2.283

2.312

2.361

2.409

—

1.550

1.639

1.708

1.769

1.871

1.959

2.035

2.094

2.157

2.183

2.211

2.258

2.307

—

1.456

1.545

1.614

1.675

1.775

1.862

1.936

1.997

2.057

2.085

2.112

2.159

2.204

—

1.370

1.460

1.525

1.584

1.684

1.771

1.845

1.902

1.961

1.990

2.015

2.063

2.108

—

1.289

1.375

1.441

1.498

1.597

1.683

1.755

1.811

1.872

1.896

1.925

1.968

2.015

— 1.155

1.206

1.290

1.335

1.416

1.509

1.596

1.666

1.725

1.782

1.808

1.836

1.880

1.927

0.782

0.829

0.908

0.970

1.024

1.115

1.194

1.262

1.314

1.368

1.392

1.418

1.461

1.502

0.713

0.760

0.838

0.897

0.952

1.042

1.119

1.187

1.239

1.293

1.316

1.342

1.383

1.424

How to Trap Process Air Heaters

Process air heaters are used for dryingpaper, lumber, milk, starch and otherproducts as well as preheating combus-tion air for boilers.

Common examples of this type ofequipment are process dryers, tunneldryers, and combustion air preheaters.Compared with air heaters for spaceheating, process air heaters operate atvery high temperature, 500°F not beinguncommon. These extremely hightemperature applications require highpressure (and occasionally superheated)steam.

Figure 25-1. Process Air Heater

Process Air Heaters

B, F, K, I, M, A IB

*F&T

1st Choice and

Feature Code

ConPresEquipment

Being Trapped 0-30

psig

Alternate Choice

* The pressure break point for F&T trapsome models and sizes.PLEASE NOTE:1. Provide vacuum breaker wherever su2. Do not use F&T traps on superheate


VacuumBreaker

Modulating SteamControl Valve

Trap DrainingStrainerAhead of

ModulatingSteam

Control Valve

Trap Selection and Safety FactorDetermine the condensate load forprocess air heaters with the followingformula:

Q =

Where:Q = Condensate load in lbs/hrF = Cubic feet of air per minuteCp = Specific heat of air in Btu/lb–°F

(from Table 50-2)d = Density of air—.075 lbs/cu ft∆T = Temperature rise in °FH = Latent heat of steam in Btu/lb

(Steam Tables, page 2)

F x Cp x d x 60 min/hr x ∆TH

IB B, C, G, H, L F&T *F&T

IB IBLV IBLV

stant sure

Variable Pressure

1st Choice and

Feature Code

Above 30 psig

0-30 psig

Above 30 psig

Alternate Choice

s may be somewhat different in

batmospheric pressures occur.d steam.


Alternate F&Twith Integral

VacuumBreaker

Air Vent

Air Vent

InvertedBucket

Steam Trap

2,000 x .24 x .075 x 60 x 100915

EXAMPLE: What would be the condensateload on a tunnel dryer coil handling 2,000CFM of air and requiring a 100°F temperaturerise? The steam pressure is 45 psig. Using theformula:

Q =

Q = 236 lbs/hr

Multiplying by a safety factor of 2—which isrecommended for all constant pressureprocess air heaters—indicates that a trap witha capacity of 472 lbs/hr will be required. Thisis based on one coil. For higher air tempera-ture rises, additional coils in series may berequired.

Safety FactorsFor constant steam pressure, use asafety factor of 2:1 at operating pressuredifferential. For modulating steampressure, use a safety factor of 3:1 at ^of maximum pressure differential acrossthe trap.

InstallationGive piping for an entire piece of processair heating equipment—including all steamtrap connections—adequate allowancefor expansion due to the wide tempera-ture variations. Mount traps 10"-12" belowthe coils with a dirt pocket of at least 6".On both constant and modulated pressureheaters, install a vacuum breakerbetween the coil and the steam trap.Install an air vent on each coil to removeair and other non-condensables that cancause rapid corrosion. See Fig. 25-1.

Consider a safety drain if condensateis elevated after the trap or if backpressure is present. See page 42 forpiping diagram and explanation.

25

26

How to Trap Shell & Tube Heat Exchangers & Submerged Coils

Submerged coils are heat transfer elementswhich are immersed in the liquid to beheated, evaporated or concentrated. Thistype of coil is found in virtually every plantor institution which uses steam. Commonexamples are water heaters, reboilers,suction heaters, evaporators, and vaporiz-ers. These are used in heating water forprocess or domestic use, vaporizing indus-trial gases such as propane and oxygen,concen-trating in-process fluids suchas sugar, black liquor and petroleumand heating fuel oil for easy transferand atomization.

Different application requirements involvingconstant or variable steam pressure deter-mine which type of trap should be used.Trap selection factors include the ability tohandle air at low differential pressures,energy conservation and the removal of

Figure 26-1. Shell And Tube Heat Exchangers

ModulatSteam

Control V

Steam Mai

Hot Water Out

Cold Water In

To Drain

Heat Exchanger(Steam in Shell)

Use Safety Drain F&T TrapWhen Going to OverheadReturn. See Page 42 for

Explanation.

PLEASE NOTE:1. Provide vacuum breaker wherever 2. Provide a safety drain when elevati3. If dirt and large volumes of air muswith an external thermostatic air vent

* Use IBLV above Pressure/Temperatu

Embossed Coils and Pipe Coils

I, F, Q, C, E, K, N, B, G IBLV

DCF&T

Shell and Tube Heat Exchangers

1st Choice and

Feature Code

ConPreEquipment

Being Trapped 0-30

psig

Alternate Choice

Recommendation Chart (See Chart

dirt and slugs of condensate. Three stan-dard methods of sizing help determinethe proper type and size traps for coils.

(

in

a

n

sn

c

r

s

Safety FactorI. Constant Steam Pressure.

INVERTED BUCKET TRAPS OR F&TTRAPS—use a 2:1 safety factor atoperating pressure differentials.

II. Modulating Steam Pressure.F&T TRAPS OR INVERTED BUCKETTRAPS.1. 0-15 psig steam—2:1 at ^ psi

pressure differential (on F&T trapsSHEMA ratings can also be used).

2. 16-30 psig steam—2:1 at 2 psipressure differential.

3. Above 30 psig steam—3:1 at ^ ofmaximum pressure differentialacross the trap.

Typical Piping Diagram)

DrainAir Vent

g

lve

Strainer

By-Pass

PrimaryTrap

To Low PressureReturn

ubatmospheric pressures occur.g condensate on modulating service.

t be handled, an inverted bucket trapan be used effectively.

e Limitations

IBLV B, C, G, H, L, I F&T3 *F&T3

DC*F&T

DCIBT

DCIBLV

stant sure

Variable Pressure

1st Choice and

Feature Code

Above 30 psig

0-30 psig

Above 30 psig

Alternate Choice

on Gatefold B for “FEATURE CODE” References.)

Alte

rnat

e to

Ove

rhea

d R

etur

n

III. For constant or modulating steampressure with syphon drainage.An automatic differential condensatecontroller with a safety factor of 3:1should be used. An alternate is anIBLV with a 5:1 safety factor.

Apply the safety factor at full differentialon constant steam pressure. Apply thesafety factor at one half maximumdifferential for modulating steam pressure.

Shell and Tube Heat ExchangersOne type of submerged coil is the shelland tube heat exchanger (Fig. 26-1). Inthese exchangers, numerous tubes areinstalled in a housing or shell with confinedfree area. This assures positive contactwith the tubes by any fluid flowing in theshell. Although the term submerged coilimplies that steam is in the tubes and thetubes are submerged in the liquid beingheated, the reverse can also be truewhere steam is in the shell and a liquid isin the tubes.

Trap Selection for Shelland Tube Heat ExchangersTo determine the condensate load onshell and tube heaters, use the followingformula when actual rating is known.* (Ifheating coil dimensions alone are known,use formula shown for embossed coils.Be sure to select applicable “U” factor):

Q =

Where:Q = Condensate load in lbs/hrL = Liquid flow in GPM∆T = Temperature rise in °FC = Specific heat of liquid in Btu/lb-°F

(Table 50-1)500 = 60 min/hr x 8.33 lbs/galsg = Specific gravity of liquid (Table 50-1)H = Latent heat of steam in Btu/lb

(Steam Tables, page 2)

EXAMPLE: Assume a water flow rate of 50GPM with an entering temperature of 40°F and aleaving temperature of 140°F. Steam pressureis 15 psig. Determine the condensate load.

Using the formula:

* Size steam traps for reboilers, vaporizersand evaporators (processes that create vapor)using the formula for EMBOSSED COILS onpage 27.

L x ∆T x C x 500 x sgH

Q = = 2,645 lbs/hr

50 GPM x 100°F x 1 Btu/lb-°F x 500 x 1.0 sg945 Btu/lb

Rule of Thumb for ComputingCondensing Rate for Water Heaters:Raising the temperature of 100 gallonsof water 1°F will condense one poundof steam.

dati.

Embossed CoilsVery often open tanks of water orchemicals are heated by means ofembossed coils (Fig. 27-1). Upsettinggrooves in the sheet metal of the twohalves produce the spaces for the steamWhen welded together the halves formthe passages for steam entry, heattransfer and condensate evacuation.

Trap Selection for Embossed CoilsCalculate the condensate load onembossed coils with the followingformula:

Q = A x U x Dm

Where:Q = Total heat transferred in Btu per hourA = Area of outside surface of coil in sq ftU = Overall rate of heat transfer in Btu per

hr-sq ft-°F. See Tables 27-1 and 27-2.Dm = Logarithmic mean temperature

difference between steam and liquid(as between inlet and outlet of a heatexchanger) in °F

D1 - D2Loge

D1 = Greatest temperature differenceD2 = Least temperature difference

Dm =(D1)(D2)

Figure 27-1. Thermostatic ControlledEmbossed Coil, Syphon Drained

IB Trap

➤

Table 27-1.Pipe Coil U Values in Btu/hr-sq ft-°F

DC

CirculationType of ServiceNatural50-200

50-150

300-800

10-30

200

180

Forced150-1200

—

—

50-150

500

450

Steam to Water

Steam to Boiling Oil

Steam to Boiling Liquid

Steam to Oil

3/4" Tube Heaters

11/2" Tube Heaters

➤

➤

➤

Logarithmic mean temperature differencecan be determined with slightly lessaccuracy using the nomograph, Chart29-1.

U values are determined by tests undercontrolled conditions. Tables 27-1 and 27-2show the commonly accepted range forsubmerged embossed coils. For trapselection purposes, use a U value that isslightly greater than the conservativeU value selected for estimating actualheat transfer.

EXAMPLE:A = 20 sq ft of coil surfaceU = 175 Btu/sq ft-hr-°FConditions:

Water in: 40°FWater out: 150°F

Steam pressure: 125 psig or 353°FD1 = 353 - 40, or 313D2 = 353 - 150, or 203

Dividing by 4 to get within range of Chart 29-1,we have:

D1 = 78.25D2 = 50.75

Mean difference from chart is 63°F.Multiplying by 4, the mean temperaturedifference for the original values is 252°F.Substituting in the equation:Q = 20 x 175 x 252 = 882,000 Btu/hr

Btu transferred per hour.Latent heat of steam at 125 psig = 867.6882,000 867.6

= 1,016 lbs condensate per hr

IB Trap

Figure 27-2. Continuous Coil,Syphon Drained

WaterSeal

Table 27-2.Embossed Coil U Values in Btu/hr-sq ft-°F

Steam to Watery Solutions

Steam to Light Oil

Steam to Medium Oil

Steam to Bunker C

Steam to Tar Asphalt

Steam to Molten Sulphur

Steam to Molten Paraffin

Steam to Molasses or Corn Syrup

Dowtherm to Tar Asphalt

CirculationNatural Forced

Type of Service

150-27560-110

50-100

40-80

18-60

35-45

40-50

70-90

50-60

100-20040-45

20-40

15-30

15-25

25-35

25-35

20-40

15-30

➤

➤

To determine trap capacity required,multiply condensing rate by the recom-mended safety factor.

ons

Pipe CoilsPipe coils are heat transfer tubesimmersed in vessels which are large involume compared to the coils them-selves (Fig. 27-2). This is their primarydifference when compared to shell andtube heat exchangers. Like embossedcoils, they may be drained by gravityor syphon drained, depending on theconditions prevailing at the installationsite. Unlike embossed coils, most pipecoils are installed in closed vessels.

Trap Selection for Pipe CoilsDetermine the condensate load for pipecoils by applying one of the formulas,depending on known data. If capacity isknown, use the formula under shell andtube heat exchangers. When physicaldimensions of coil are known, use theformula under embossed coils.

InstallationWhen gravity drainage is utilized on shelland tube heat exchangers, embossedcoils and pipe coils, locate the steam trapbelow the heating coil. Under modulatingpressure, use a vacuum breaker. Thiscan be integral in F&T traps or mountedoff the inlet piping on an inverted buckettrap. Place an ample drip leg ahead ofthe trap to act as a reservoir. Thisassures coil drainage when there is amaximum condensate load and aminimum steam pressure differential.

Avoid lifting condensate from a shell andtube heat exchanger, embossed coil orpipe coil under modulated control.However, if it must be done, thefollowing is suggested:1. Do not attempt to elevate condensate

more than one foot for every pound ofnormal pressure differential, eitherbefore or after the trap.

2. If condensate lift takes place after thesteam trap, install a low pressuresafety drain. (See page 42.)

3. If condensate lift takes place ahead ofthe steam trap (syphon lift), install anautomatic differential condensatecontroller to efficiently vent all flashsteam.

27

For Pounds of Steam Condensed per sq ft perHour of Submerged Coil Surface, see Chart 29-2.

28

Concentrate

Steam

How to Trap Evaporators

Figure 28-1. Triple Effect Evaporator System

Steam

Evaporators reduce the water contentfrom a product through the use of heat.They are very common to many indus-tries, especially paper, food, textiles,chemical and steel.

An evaporator is a shell and tube heatexchanger where the steam is normallyin the shell and the product is in thetubes and in motion. Depending upon thetype of product and the desired results,more than one stage or effect of evapo-ration may be required. The triple effectis the most common, although as manyas five or six can be found on someapplications.

Single EffectWhile the product is being forced throughthe tubes of the evaporator, heat isadded to remove a specific amount ofmoisture. After this is completed, boththe product vapor and the concentratedproduct are forced into the separatingchamber where the vapor is drawn offand may be used elsewhere. Theconcentrate is then pumped off toanother part of the process (Fig. 28-2).

Multiple EffectIn using the multiple effect method, thereis a conservation of heat as steam fromthe boiler is used in the first effect, andthen vapor generated from the product isused as the heat source in the secondeffect. The vapor generated here is thenused as the heat source in the thirdeffect and finally heats water for someother process or preheats the incomingfeed (Fig. 28-1).

Alternate Ch

Alternate Ch

1st Choice, Feaand Alternate C


Evaporator Single Effect

Evaporator Multiple Effect

A, F, G, H, K

A, F, G, H, K


There are many variables in the design ofevaporators due to their wide applicationto many different products. The steamcapabilities for evaporators can vary fromapproximately 1,000 lbs per hour to100,000 lbs per hour, while steampressures may vary from a high of 150psig in the first effect to a low of 24 inchesmercury vacuum in the last effect.

As evaporators are normally run continu-ously, there is a uniform load of conden-sate to be handled. It’s important toremember that traps must be selected forthe actual pressure differential for eacheffect.

The three major considerations whentrapping evaporators are:1. Large condensate loads.2. Low pressure differentials in some

effects.3. The evacuation of air and contaminants.

Feed

0-30 psig

Above 30 psig

oices

oices

ture Code hoice(s)

, M, P DC DC

IBLVF&T

, M, P DC DC

IBLVF&T

IBLVF&T

IBLVF&T


Safety Factor■ When load is fairly constant and

uniform, a 2:1 safety factor should beadequate when applied to an actualcondensing load in excess of 50,000lbs/hr.

■ Below 50,000 lbs/hr, use a 3:1 safetyfactor.

For single and multiple effect evapora-tors, automatic differential condensatecontrollers are recommended. In additionto offering continuous operation, DCtraps vent air and CO2 at steam tempera-ture, handle flash steam and respondimmediately to slugs of condensate.

Figure 28-2. Single Effect EvaporatorSystem

Concentrate

Steam

Steam

Feed

InstallationBecause an evaporator is basically ashell and tube heat exchanger with thesteam in the shell, there should beseparate steam air vents on the heatexchanger. Place these vents at any areawhere there is a tendency for air toaccumulate, such as in the quiet zone ofthe shell. Install a separate trap on eacheffect. While the condensate from the firsteffect may be returned to the boiler,condensate from each successive effectmay not be returned to the boiler due tocontamination from the product.

Trap Selection for EvaporatorsWhen calculating the condensate load forevaporators, take care in selecting theU value (Btu/hr-sq ft-°F). As a generalrule, the following U values can be used:■ 300 for natural circulation evaporators

with low pressure steam (up to 25 psig)■ 500 on natural circulation with high

pressure (up to 45 psig)■ 750 with forced circulation evaporators.

Steam to Watery Solutions

Steam to Light Oil

Steam to Medium Oil

Steam to Bunker C

Steam to Tar Asphalt

Steam to Molten Sulphur

Steam to Molten Paraffin

Steam to Molasses or Corn Syrup

Dowtherm to Tar Asphalt

CirculationNatural Forced

Type of Service

150-27560-110

50-100

40-80

18-60

35-45

40-50

70-90

50-60

100-20040-45

20-40

15-30

15-25

25-35

25-35

20-40

15-30

CirculationNatural ForcedType of Service

Steam to Water

Steam to OilSteam to Boiling LiquidSteam to Boiling Oil

150-1200180

50050-150

——

11/2" Tube Heaters3/4" Tube Heaters

50-200450

20010-30

300-80050-150

Table 29-1. Pipe Coil U Values in Btu/hr-sq ft-°F

Table 29-2.Embossed Coil U Values in Btu/hr-sq ft-°F

Table 29-3. Pipe Size Conversion Table(Divide lineal feet of pipe by factor given for sizeand type of pipe to get square feet of surface)

Iron Pipe Copper orBrass Pipe

Pipe Size(in)

7.635.093.823.052.551.911.521.27.954

4.553.642.902.302.011.611.331.09.848

1/23/4

111/4

11/2

221/2

34

Use the following formula to computeheat transfer for constant steam pressurecontinuous flow heat exchangers.

Q = A x U x Dm

Where:Q = Total heat transferred in Btu per hourA = Area of outside surface of coil in sq ftU = Overall rate of heat transfer in

Btu/hr-sq ft-°F (See Charts 29-1 and 29-2)Dm = Logarithmic mean temperature

difference between steam and liquid(as between inlet and outlet of a heatexchanger) in °F

Dm =

Where:D1 = Greatest temperature differenceD2 = Least temperature difference

Logarithmic mean temperature differencecan be estimated by using the nomograph,Chart 29-1.

D1-D2Loge

(D1)(D2)

Connect greatest temperature difference onscale D1 with least temperature difference onscale D2 to read logarithmic mean temperaturedifference on center scale.

100

90

80

70

60555045

40

35

30

25

20

15

10

5

100

90

80

70

60555045

40

35

30

25

20

15

10

5

100

90

80

70

605550

40

35

30

25

20

15

10

5

45

EquipmentD1 D2

LO

GA

RIT

HIC

ME

AN

TE

MP

ER

AT

UR

E D

IFF

ER

EN

CE

Chart 29-1.Mean Temperature Difference Chart for HeatExchange Equipment

EXAMPLE:A = Heat transfer tubes: eight ˚" OD tubes

12' long

= 20 sq ft of coil surface

U = 500 Btu/hr-sq ft-°FConditions:

Water in: 40°FWater out: 150°F

125 psig or 353°F steam pressure:D1 = 353°F - 40°F, or 313°FD2 = 353°F - 150°F, or 203°F

Dividing by 4 to get within range of Chart 29-1,we have:

D1 = 78.25°FD2 = 50.75°F

Mean difference from chart is 63°F.Multiplying by 4, the mean temperaturedifference for the original value is 252°F.Substituting in the equation:

Q = 20 x 500 x 252 = 2,520,000 Btu/hr transferred per hour

Latent heat of steam at 125 psig = 867.62,520,000 867.6

To determine trap capacity required,multiply the condensing rate by therecommended safety factor.

8 x 12' 5.09 (from Table 29-3)

= 2,900 lbs condensate per hour

29

Condition Factors(Divide chart figures by proper factor)

CONDITION FACTORWill remain bright ___________________ 1Moderate scale _____________________ 2Liquid contains up to 25% solids _____ 3-5Thick viscous liquids _______________ 4-8

Chart 29-2. Pounds of Steam Condensed persq ft per Hour of Submerged Coil Surface(See “Conditions” conversion factors below chart)

400

300

250

200

150

125

1009080706050

40

30

25

20

15

10

8

6

400

300

250

200

150

125

1009080706050

40

30

25

20

15

10

8

6

20°30°

40°50°

80°100°

125°150°

300°250°

200°

20°30°

40°50°

80°100°

125°150°

300°250°

200°

PO

UN

DS

PE

R H

R P

ER

SQ

FT

OF

SU

RFA

CE

TEMP. DIFFERENCE BETWEEN LIQUID AND STEAM

COPPERBRASSIRONLEAD

30

How to Trap Jacketed Kettles

Steam jacketed kettles are essentiallysteam jacketed cookers or concentrators.They are found in all parts of the worldand in almost every kind of application:meat packing, paper and sugar making,rendering, fruit and vegetable processingand food preparation—to name a few.

There are basically two types of steamjacketed kettles—fixed gravity drain andtilting syphon drain. Each type requires aspecialized method for trapping steam,although the major problems involved arecommon to both.

The most significant problem encoun-tered is air trapped within the steamjacket which adversely affects thetemperature. Jacketed kettles usuallyperform batch operations and maintain-ing a uniform or “cooking” temperature iscritical. With an excessive amount of air,wide variations in temperature occur and

Figure 30-1. Fixed Gravity Drained Kettle

Control VThermostatic

Air Vent

ProductDrain Line

Condensto Retu

Line

AirDischargeto Drain

or ReturnLine

SteamTrap

Jacketed Kettles Gravity Drain

Jacketed KettlesSyphon Drain

IBB, C, E

DB, C, E

K, N

1st Ca

FeaCo

Equipment Being

Trapped


may result in burnt product and/or slowproduction. To be more specific, undercertain conditions as little as ^ of 1% byvolume of air in steam can form aninsulating film on the heat transfersurface and reduce efficiency as muchas 50%. See pages 5 and 6.

A second basic concern in the use ofsteam jacketed kettles is the need for asteady, thorough removal of condensate.An accumulation of condensate in thejacket leads to unreliable temperaturecontrol, reduces the output of the kettleand causes water hammer.

L

hnt

Trap Selection for JacketedKettlesTable 31-1 gives the required trapcapacities for various size kettles basedon the following assumptions:U = 175 Btu/hr-sq ft-°FSafety factor of 3 included.

Figure 30-2. Tilting S

ReliefValve

SteamIn

Joint

Steam In

Strainer

alve

atern

V, K, N

F&T or Thermostatic

C, G, H, , P

IBLV

oice d ure de

Alternate Choice


EXAMPLE: What would be the recommendedtrap capacity for a 34" gravity drained kettle at40 psig steam? Reading directly from thechart, a trap with a capacity of 1,704 lbs/hr atthe operating pressure is required.

For an alternative method of determiningcondensate, use the following formula:

Q =

Where:Q = Condensate loads (lbs/hr)G = Gallons of liquid to be heatedsg = Specific gravity of the liquidCp = Specific heat of the liquid∆T = Temperature rise of the liquid °F8.3= lbs/gal of waterH = Latent heat of the steam (Btu/lb)t = Time in hours for product heating

G x sg x Cp x ∆T x 8.3H x t

yphon Drained Kettle

DC ToReturnLine

RotaryJoint

EXAMPLE: Select a trap for a 250-gallonkettle using 25 psig steam to heat a productwith a specific gravity of 0.98 and a specificheat of 0.95 Btu/lb-°F. Starting at roomtemperature of 70°F, the product will beheated to 180°F in one-half hour. (Assume 3:1safety factor.) Using the formula:

Q =

Now simply multiply by a safety factor of 3 toget 1,365 lbs/hr of condensate and select theproper type and capacity trap.

Based on the standard requirements andproblems involved with fixed gravity drainkettles, the most efficient type trap to useis the inverted bucket.

The inverted bucket trap vents air andCO2 at steam temperature and providestotal efficiency against back pressure.The primary recommendation for tiltingsyphon drain kettles is the automaticdifferential condensate controller. Inaddition to providing the same featuresas the IB, the DC offers excellent airventing ability at very low pressure andexcellent flash steam handling ability. Ifan IB trap is selected for syphon drainedservice, use a trap one size larger.

250 gal x 0.98 x 0.95 Btu/lb-°F x 110°F x 8.3 lbs/gal 212,500 933 Btu/lb x 0.5 hr 466.5

= = 455 lbs/hr

Table 31-1. Condensate Rates In lbs/hr For Jacketed Kettles—Hemispherical Condensing SurfSafety factor 3:1 is includedAssume U = 175 Btu/hr-sq ft-°F, 50°F starting temperature

psigpsigpsig

18

19

20

22

24

26

28

30

32

34

36

38

40

42

44

46

48

54

60

72

Heat Transfer Surface (sq ft)

SKettle

Diameter(in)

3.50 7 1.10

3.90 8 1.20

4.35 9 1.35

5.30 12 1.65

6.30 16 1.95

7.40 20 2.30

8.50 25 2.65

9.80 31 3.05

11.20 37 3.50

12.60 45 3.95

14.10 53 4.40

15.70 62 4.90

17.40 73 5.45

19.20 84 6.00

21.10 97 6.60

23.00 110 7.20

25.30 123 7.85

31.70 178 9.90

39.20 245 12.30

56.40 423 17.70

25

267°

426

477

531

648

768

903

103

119

136

153

172

191

212

234

257

280

308

387

478

689

15

250°F

387

432

483

588

699

822

942

1089

1242

1398

1566

1743

1932

2130

2343

2553

2808

3523

4350

6264

10

240°F

366

408

456

555

660

774

891

1026

1173

1320

1476

1644

1821

2010

2208

2409

2649

3324

4104

5910

5 psig

227°F

339

378

420

513

609

717

822

948

1086

1221

1365

1521

1686

1860

2043

2229

2451

3076

3798

5469

U.S. Gallons of Water in Hemisphere

U.S. Gals. Water per in. of Height

Above Hemisphere

General Recommendationsfor Maximum EfficiencyDesirable Cooking Speed. Because theproduct cooked has such an importantbearing on trap selection, a plant withmany jacketed kettles should conductexperiments using different sizes of trapsto determine the size giving best results.

Steam Supply. Use steam lines ofample size to supply steam to the kettles.Locate the inlet nozzle high up on thejacket for best results. It should beslotted so as to give steam flow aroundthe entire jacket area.

InstallationInstall traps close to the kettle. You canfurther increase the dependability andair-handling capability by installing athermostatic air vent at high points in thejacket. See Figs. 30-1 and 30-2.

Never drain two or more kettles with asingle trap. Group drainage will invariablyresult in short circuiting.

31

ace

psig psig psig psig

TEAM PRESSURE

125 psig

353°F

642

714

798

972

1155

1356

1557

1797

2052

2310

2586

2877

3189

3519

3867

4215

4638

5820

7185

10346

100

338°F

603

669

747

912

1083

1272

1461

1686

1926

2166

2424

2700

2991

3300

3627

3954

4350

5458

6738

9703

80

324°F

564

630

702

855

1017

1194

1371

1581

1809

1944

2277

2535

2808

3099

3405

3711

4083

5125

6327

9111

60

307°F

522

582

651

792

942

1107

1269

1464

1674

1881

2106

2346

2601

2868

3153

3435

3780

4743

5856

8433

40

287°F

474

528

588

717

852

1002

1149

1326

1515

1704

1908

2124

2355

2598

2856

3111

3423

4296

5304

7638

F

8

7

8

9

2

7

4

3

7

8

7

5

5

0

32

How to Trap Closed, Stationary Steam Chamber Equipment

Closed, stationary steam chamberequipment includes platen presses for themanufacture of plywood and other sheetproducts, steam jacketed molds for rubberand plastic parts, autoclaves for curingand sterilizing and retorts for cooking.

Product Confined in SteamJacketed PressMolded plastic and rubber products suchas battery cases, toys, fittings and tiresare formed and cured, and plywood iscompressed and glue-cured in equip-ment of this type. Laundry flatworkironers are a specialized form of presswith a steam chamber on one side of theproduct only.

Trap Selection and Safety FactorThe condensate load for closed, stationarysteam chamber equipment is determinedby use of the following formula:

Figure 32-1. Product Confined In Steam Jacke

ValveStrainer

SteamTrap

*An auxiliary air vent is recomm**First choice on large volume v

1st Choand Fea

Code


Product Confined Steam Jacketed Press

IBB, K, E

Direct Steam Injection Into Product Chamber

*IBB, N, K,

Product In Chamber—Steam In Jacket

*IBB, K, E


Q = A x R x S

Where:Q = Condensate load in lbs/hrA = Total area of platen in contact with

product in sq ftR = Condensing rate in lbs/sq ft-hr

(For purposes of sizing steam traps, a3 lbs/sq ft-hr condensing rate may beused)

S = Safety factor

EXAMPLE: What is the condensate load for amid platen on a press with a 2' x 3' platen?Using the formula:Q = 12 sq ft x 3 lbs/sq ft-hr x 3 = 108 lbs/hrEnd platens would have half this load.

The safety factor recommended for allequipment of this type is 3:1.

ted Press

SteamTrap

CondensateDischarge

ended.essels.

ice ture Alternate

Choices

, ACD and

Thermostatic

E, AThermostatic and

F&T and **DC

, AThermostatic and

F&T and **DC


The inverted bucket trap is the recom-mended first choice on steam jacketedchambers, dryers and ironers because itcan purge the system, resist hydraulicshock and conserve energy. Disc andthermostatic type traps may be accept-able alternatives.

InstallationAlthough the condensate load on eachplaten is small, individual trapping isessential to prevent short circuiting, Fig.32-1. Individual trapping assuresmaximum and uniform temperature for agiven steam pressure by efficientlydraining the condensate and purging thenon-condensables.

Direct Steam InjectionInto Product ChamberThis type of equipment combines steamwith the product in order to cure, sterilizeor cook. Common examples are auto-claves used in the production of rubber andplastic products, sterilizers for surgicaldressings and gowns and retorts forcooking food products already sealed incans.

Trap Selection and Safety FactorCalculate the condensate load using thefollowing formula:

Q =

Where:Q = Condensate load in lbs/hrW = Weight of the material in lbsC = Specific heat of the material in Btu/lb-°F

(See page 50)∆T = Material temperature rise in °FH = Latent heat of steam in Btu/lb

(See Steam Tables on page 2)t = Time in hours

EXAMPLE: What will be the condensate loadon an autoclave containing 300 lbs of rubberproduct which must be raised to atemperature of 300°F from a startingtemperature of 70°F? The autoclave operatesat 60 psig steam pressure and the heat-upprocess takes 20 minutes. Using the formula:

Q = = 96 lbs/hr

Multiply by a recommended safety factor of3:1 to get the required capacity—288 lbs/hr.

W x C x ∆TH x t

300 lbs x .42 Btu/lb-°F x 230°F904 Btu/lb x .33 hr

Since steam is in contact with theproduct you can anticipate dirty conden-sate. In addition, the vessel is a largevolume chamber which requires specialconsideration in the purging of conden-sate and non-condensables. For thesereasons an inverted bucket trap with anauxiliary thermostatic air vent installed atthe top of the chamber is recommended.

Where no remote thermostatic air ventcan be installed, incorporate the largevolume air purging capabilities in thesteam trap itself. An automatic differen-tial condensate controller should beconsidered a possible first choice onlarge chambers. As an alternative, anF&T or thermostatic trap should be usedand be preceded by a strainer, the latterreceiving regular checks for free flow.

Strainer

Steam ControlValve

Figure 33-1. Direct Steam Injection Into Produ

SteamTrap

InstallationAs the steam and condensate is incontact with the product, the trapdischarge should almost always bedisposed of by some means other thanreturn to the boiler. In virtually all casesthis equipment is gravity drained to thetrap. However, very often there is acondensate lift after the trap. As steampressure is usually constant, this doesnot present a problem. For thorough airremoval and quicker warm-up, install athermostatic air vent at a high point ofthe vessel. See Fig. 33-1.

Product in Chamber—Steam in JacketAutoclaves, retorts and sterilizers arealso common examples of this equip-ment, however, the condensate is notcontaminated from actual contact withthe product and can be returned directlyto the boiler. Steam traps with purgingability and large volume air venting arestill necessary for efficient performance.

Air Vent

Door

Strainer

Figure 33-2. Product inct Chamber

Steam ControlValve

Trap Selection and Safety FactorSize steam traps for “product in chamber-steam in jacket equipment” by using thesame formula outlined for direct steaminjection. The safety factor is also 3:1.

The inverted bucket trap is recom-mended because it conserves steam,purges the system and resists hydraulicshock.

Use the IB trap in combination with athermostatic air vent at the top of thechamber for greater air-handling capabil-ity. As an alternate an F&T or thermo-static trap could be used. On largechambers, where it’s not possible toinstall the air vent, an automatic differen-tial condensate controller should beconsidered a possible first choice.

InstallationWith “product in chamber—steam injacket equipment,” the steam andcondensate do not come in contact withthe product and can be piped to thecondensate return system. Wherepossible, install an auxiliary thermostaticair vent at a remote high point on thesteam chamber. See Fig. 33-2.

33

Air Vent

Steam Jacket

SteamTrap

Door

Chamber—Steam in Jacket

34

How to Trap Rotating Dryers Requiring Syphon Drainage

Figure 34-1. Product Outside Dryer

RotaryJoint

SteamTrap10"-12"

There are two classifications of rotatingdryers which vary significantly in bothfunction and method of operation. Thefirst dries a product by bringing it intocontact with the outside of a steam-filledcylinder. The second holds the productinside a rotating cylinder where steam-filled tubes are used to dry it throughdirect contact. In some applications asteam jacket surrounding the cylinder isalso used.

Safety FactorThe safety factor for both kinds of dryersdepends on the type of drainage deviceselected.

■ If an automatic differential condensatecontroller (DC) is installed, use a safetyfactor of 3:1 based on the maximum load.This will allow sufficient capacity forhandling flash steam, large slugs ofcondensate, pressure variations and theremoval of non-condensables. The DCperforms these functions on bothconstant and modulated pressure.

■ If an inverted bucket trap with largevent is used, increase the safety factor inorder to compensate for the large volumeof non-condensable and flash steam thatwill be present. Under constant pressureconditions, use a safety factor of 8:1. Onmodulated pressure increase it to 10:1.

*On constant pressure uand on modulated press

Rotating Dryers

DA, B,

P,

1st Ca

FeaCo

Equipment Being

Trapped


Rotating Steam Filled Cylinderwith Product OutsideThese dryers are used extensively in thepaper, textile, plastic and food industrieswhere common examples are dry cans,drum dryers, laundry ironers and papermachine dryers.Their speed of operationvaries from 1 or 2 rpm to surfacevelocities as high as 5,000 rpm. Operat-ing steam pressure ranges from sub-atmospheric to more than 200 psig.Diameters can vary from 6" or 8" to 14'or more. In all cases syphon drainage isrequired and flash steam will accompanythe condensate.

A revolving cylinder drained with a syphon—an internal syphon surrounded by steam.Some condensate flashes back to steam dueto the steam jacketed syphon pipe and syphonlifting during evacuation.

se 8:1 safety factor,ure use 10:1.

C K, M, N

IBLV*

hoice nd ture de

Alternate Choice


6"

Trap SelectionCondensate loads can be determinedby use of the following formula:

Q = 3.14D x R x W

Where:Q = Condensate load in lbs/hrD = Diameter of the dryer in ftR = Rate of condensation in lbs/sq ft-hrW = Width of dryer in ft

EXAMPLE: Determine the condensate load ofa dryer 5 ft in diameter, 10 ft in width and acondensing rate of 7 lbs/sq ft-hr.Using the formula:

Condensate load = 3.14(5) x 7 x 10 = 1,100 lbs/hr

Based on its ability to handle flashsteam, slugs of condensate and purgethe system, a DC is the recommendedfirst choice. An IBLV may be adequate ifproper sizing procedures are followed.

Product Inside a RotatingSteam Heated DryerThis type of dryer finds wide applicationin meat packing as well as food process-ing industries. Common examples aregrain dryers, rotary cookers and beancondi-tioners.

Their speed of rotation is relatively slow,usually limited to a few rpm, while steampressure may range from 0-150 psig.These slower rotating speeds permit thecondensate to accumulate in the bottomof the collection chamber in practically allcases. Again, syphon drainage isrequired and flash steam is generatedduring condensate removal.

Figure 35-1. Product Inside Dryer

A revolving cylinder drained with a syphon—an internal syphon surrounded by steam.Some condensate flashes back to steam dueto the steam jacketed syphon pipe andsyphon lifting during evacuation.

Trap SelectionThe condensate load generated by thesedryers can be determined through use ofthe following formula:

Q =

Where:Q = Condensate in lbs/hrN = Number of tubesL = Length of tubes in ftR = Condensing rate in lbs/sq ft-hr

(typical 6-9 lbs/sq ft-hr)P = Lineal feet of pipe per sq ft of surface

(see Table 35-1)

N x L x RP

DC

6"

10"-12"

RotaryJoint

EXAMPLE: What will be the condensateload on a rotary cooker containing 30 1•"steel pipes 12' in length with a condensingrate of 8 lbs/sq ft-hr?Using the formula:

Q = = 1,252 lbs/hr

A differential controller is recom-mended on these dryers for itspurging and flash steam handlingability.

The IBLV again requires proper sizingfor certain applications.

InstallationIn all cases, condensate drainage isaccomplished through a rotary joint,Figs. 34-1 and 35-1. The DC shouldthen be located 10"-12" below therotary joint with an extended 6" dirtpocket. These provide a reservoir forsurges of condensate and also apocket for entrained scale.

30 x 12 x 82.30

35

1

11/411/2

221/2

3

4

Iron PipeCopper orBrass Pipe

Pipe Size(in)

4.55 7.63

3.64 5.09

2.90 3.822.30 3.05

2.01 2.55

1.61 1.911.33 1.52

1.09 1.27

.848 .954

1/23/4

Table 35-1. Pipe Size Conversion Table(Divide lineal feet of pipe by factor given for sizeand type of pipe to get square feet of surface)

36

If exhaust steam is available it may becombined with the flash. In other cases,the flash will have to be supplemented bylive make-up steam at reduced pressure.The actual amount of flash steam formedvaries according to pressure conditions.The greater the difference between initialpressure and pressure on the dischargeside, the greater the amount of flash thatwill be generated.

To determine the exact amount, as apercentage, of flash steam formed undercertain conditions, refer to page 3 forcomplete information.

Trap SelectionThe condensate load can be calculatedusing the following formula:

Q = L -

Where:Q = Condensate load in lbs/hr (to be handled

by steam trap)L = Condensate flow into flash tank in lbs/hrP = Percentage of flash

EXAMPLE: Determine the condensate load ofa flash tank with 5,000 lbs/hr of 100 psigcondensate entering the flash tank held at 10psig. From page 3, the flash percentage isP = 10.5%.Using the formula:

Q = 5,000 - (5,000 x .105) = 4,475 lbs/hr

Due to the importance of energy conser-vation and operation against backpressure, the trap best suited for flashsteam service is the inverted bucket typewith large bucket vent. In addition, the IBoperates intermittently while venting airand CO2 at steam temperature.

In some cases, the float and thermostatictype trap is an acceptable alternative.One particular advantage of the F&T isits ability to handle heavy start-up airloads.

Refer to Chart 3-1 (page 3) for percent-age of flash steam formed when dis-charging condensate to reduced pres-sure.

A third type of device which may be thepreferred selection in many cases is theautomatic differential condensatecontroller. It combines the best featuresof both of the above and is recom-mended for large condensate loadswhich exceed the separating capability ofthe flash tank.

Safety FactorThe increased amount of condensate atstart-up and the varying loads duringoperation accompanied by low pressuredifferential dictates a safety factor of 3:1for trapping flash tanks.

When hot condensate or boiler water,under pressure, is released to a lowerpressure, part of it is re-evaporated,becoming what is known as flash steam.The heat content of flash is identical tothat of live steam at the same pressure,although this valuable heat is wastedwhen allowed to escape through the ventin the receiver. With proper sizing andinstallation of a flash recovery system,the latent heat content of flash steammay be used for space heating; heatingor preheating water, oil and other liquids;and low pressure process heating.

How to Trap Flash Tanks

Flash steam tank with live steam make-up,showing recommended fittings andconnections. The check valves in the incominglines prevent waste of flash when a line is notin use. The by-pass is used when flash steamcannot be used. Relief valves prevent pressurefrom building up and interfering with theoperation of the high pressure steam traps.The reducing valve reduces the high pressuresteam to the same pressure as the flash, sothey can be combined for process work orheating.

L x P100

Flash TanksIBLV

B, E, M, L, I, A, F

1st Choice and

Feature Code

Alternate Choice

Equipment Being

Trapped

F&T or *DC

Recommendation Chart (See Chart on Gatefold B for “FEATURE CODE” References.)

*Recommended where condensate loadsexceed the separating capability of the flashtank.

Figure 36-1. Typical Flash Tank PipingSketch

Make-upValve

ReducingValve

Strainer

AlternateVent

Location

Relief Valve

CVTo Low

PressureSteam Use

Gauge

Air Vent

To Drain

High PressureCondensateReturn Line

FlashTank

To Low PressureCondensate Return

IBLV Steam Trap

InstallationCondensate return lines contain bothflash steam and condensate. To recoverthe flash steam, the return header runsto a flash tank, where the condensate isdrained, and steam is then piped fromthe flash tank to points of use, Fig. 36-1.Since a flash tank causes back pressureon the steam traps discharging into thetank, these traps should be selected toensure their capability to work againstback pressure and have sufficientcapacity at the available differentialpressures.

Condensate lines should be pitchedtoward the flash tank and where morethan one line feeds into a flash tank,each line should be fitted with a swingcheck valve. Then, any line not in usewill be isolated from the others and willnot be fed in reverse with resultantwasted flash steam. If the trap is operat-ing at low pressure, gravity drainage tothe condensate receiver should beprovided.

Generally the location chosen for theflash tank should meet the requirementfor maximum quantity of flash steam andminimum length of pipe.

Figure 37-1. Flash Steam Recovery from an AFlash is taken from the flash tank and combinedthe pressure of which is reduced to that of the fvalve.

Condensate

FlashTank

LowPressureSection

Condensate lines, the flash tank, and thelow pressure steam lines should beinsulated to prevent waste of flashthrough radiation. The fitting of a spraynozzle on the inlet pipe inside the tank isnot recommended. It may becomechoked, stop the flow of condensate, andproduce a back pressure to the traps.

Low pressure equipment using flashsteam should be individually trapped anddischarged to a low pressure return.Large volumes of air need to be ventedfrom the flash tank, therefore, a thermo-static air vent should be used to removethe air and keep it from passing throughthe low pressure system.

l

Flash Tank DimensionsThe flash tank can usually be conve-niently constructed from a piece of largediameter piping with the bottom endswelded or bolted in position. The tankshould be mounted vertically. A steamoutlet is required at the top and acondensate outlet at the bottom. Thecondensate inlet connection should besix to eight inches above the condensateoutlet.

ir Heater Battery with live steam,ash by a reducing

Heater Battery

HighPressure

Steam

AirFlow

The important dimension is the insidediameter. This should be such that theupward velocity of flash to the outlet islow enough to ensure that the amount ofwater carried over with the flash is small.If the upward velocity is kept low, theheight of the tank is not important, butgood practice is to use a height of two tothree feet.

It has been found that a steam velocity ofabout 10 feet per second inside the flashtank will give good separation of steamand water. On this basis, proper insidediameters for various quantities of flashsteam have been calculated; the resultsare plotted in Chart 37-1. This curvegives the smallest recommended internaldiameters. If it is more convenient, alarger size of tank may be used.

Chart 37-1 does not take into consider-ation pressure—only weight. Althoughvolume of steam and upward velocity areless at a higher pressure, because steamis denser, there is an increased tendencyfor priming. Thus it is recommended that,regardless of pressure, Chart 37-1 beused to find the internal diameter.

37

Chart 37-1.Determination of Internal Diameter of FlashTank to Handle a Given Quantity of FlashSteamFind amount of available flash steam (in poundsper hour) on bottom scale, read up to curve andacross to vertical scale, to get diameter in inches.

30

25

20

15

10

5

0 1,000 2,000 3,000 4,000 5,000 6,000POUNDS FLASH STEAM PER HOUR

INT

ER

NA

L D

IAM

ET

ER

OF

FL

AS

H T

AN

K IN

INC

HE

S

38

How to Trap Absorption Machines

Figure 38-1. Generally approved method ofpiping steam absorption machine withstandby trapping system.

H2O Vapor

LB Mixture & H20

Steam Supply15 psig Single Stage150 psig Two Stage

15"

F&T Trap w/Integral VacuumBreaker Draining to Gravity Return

Steam

An absorption refrigeration machine chillswater for air conditioning or process useby evaporating a water solution, usuallylithium bromide. Steam provides theenergy for the concentration part of thecycle and, except for electric pumps, isthe only energy input during the entirecycle.

A steam trap installed on a steam absorp-tion machine should handle largecondensate loads and purge air at lowpressure modulated conditions.

Trap Selection and Safety FactorDetermine the condensate load producedby a low pressure (normally 15 psig orless) single stage steam absorptionmachine by multiplying its rating in tonsof refrigeration by 20, the amount of steamin lbs/hr required to produce a ton ofrefrigeration. This represents consump-tion at the rated capacity of the machine.

EXAMPLE: How much condensate will asingle stage steam absorption machine with arated capacity of 500 tons produce?

Multiply the 500-ton machine capacity rating x20 lbs/hr to get the condensate load—10,000lbs/hr.

The F&T trap with an integral vacuumbreaker is ideally suited for draining bothsingle and double stage steam absorp-tion machines. It provides an even,modulated condensate flow and energy-conserving operation. An inverted buckettrap with an external thermostatic aireliminator may also be acceptable.

InstallationMount the steam trap below the steamcoil of the absorption machine with a dripleg height of at least 15" (Fig. 38-1).This assures a minimum differentialpressure across the trap of 1/2 psi.Whichever trap is used, a standbytrapping system is recommended for thisservice. In the event that a component inthe drainage system needs maintenance,the absorption machine can operate onthe standby system while the repairs arebeing made. This ensures continuous,uninterrupted service.

In some cases very heavy condensateloads may require the use of two trapsoperating in parallel to handle the normalload.

A 2:1 safety factor should be applied tothe full capacity condensate load and thesteam trap must be capable of drainingthis load at a 1/2 psi differential. In otherwords, the machine in the example wouldrequire a trap capable of handling 20,000lbs/hr of condensate at 1/2 psi, and thecapability of functioning at the maximumpressure differential, usually 15 psi.

In comparison, two stage absorptionmachines operate at a higher steampressure of 150 psig. They have anadvantage over single stage units in thattheir energy consumption per ton ofrefrigeration is less (12.2 lbs steam/hr/ton of refrigeration at rated capacity).

EXAMPLE: How much condensate will a twostage steam absorption machine with a ratedcapacity of 300 tons produce?

Multiply the 300-ton machine capacity ratingx 10 lbs/hr to get the condensate load—3,000 lbs/hr.

On two stage steam absorption machinesa 3:1 safety factor should be used. There-fore, the example requires a steam trapwith a capacity of 9,000 lbs/hr. Atpressures above 30 psig, the trapcapacity must be achieved at ^ maxi-mum pressure differ-ential, which in theexample is 75 psi. At pressures below 30psig, trap capacity must be achieved at 2psi differential pressure. However, thetrap must still be capable of operating ata maximum inlet pressure of 150 psig.

Steam Absorption Machine

F&TA, B, G *IB

1st Choice and

Feature Code

Alternate Choice

Equipment Being

Trapped

Recommendation Chart (See Chart on Gatefold B for “FEATURE CODE” References.)

NOTE: Vacuum breaker and standby systemshould be provided.*With external thermostatic air vent.

39

Trap Selection and Safety Factors

This chart provides recommendations fortraps likely to be most effective in variousapplications. The recommended safety

factors ensure proper operation undervarying conditions. For more specificinformation on recommended traps

and safety factors, contact yourArmstrong representative.

Boiler Header

(Superheat)

Steam Mains & Branch Lines

(Non-Freezing)

(Freezing)

Steam Separator

Steam quality 90% or less

Tracer Lines

Unit Heaters & Air Handlers(Constant Pressure)

(0-15 Variable Pressure)

(16-30 Variable Pressure)

(>30 Variable Pressure)

Finned Radiation & PipeCoils

(Constant Pressure)

(Variable Pressure)

Process Air Heaters(Constant Pressure)

(Variable Pressure)

Steam AbsorptionMachine (Chiller)

Shell & Tube HeatExchangers, Pipe & Embossed Coils

(Constant Pressure)

(Variable Pressure)

Evaporator Single Effect &Multiple Effect

Jacketed Kettles(Gravity Drain)

(Syphon Drain)

Rotating Dryers

Flash Tanks

1st Choice 2nd Choice Safety FactorApplication

IBLVIBCVIBTF&TDCThermo.

IBLV

IBCVBurnished

F&T

Wafer

1.5:1

Start-up Load

IB(CV if pressure varies)

IB

F&T

Thermostatic or Disc

2:1, 3:1 if @ end of main,ahead of valve, or on branch

Same as above

IBLV

DC

DC 3:1

IB

IBLV

F&T

F&T

F&T

F&T

IBLV

IBLV

IBLV

3:1

2:1 @ 1/2 psi Differential

2:1 @ 2 psi Differential

3:1 @ 1/2 Max. Pressure Differential

IB

F&T

Thermostatic

IB

3:1 for quick heating2:1 normally

IB

F&T

F&T

IBLV

2:1

3:1 @ 1/2 Max. Pressure Differential

F&T IB Ext.air vent 2:1 @ 1/2 psi Differential

IB

F&T

DC or F&T

DC or IBT(If >30 PSI IBLV)

2:1

DC IBLV or F&T2:1, If Load 50,000 lbs/hr

use 3:1

IBLV

DC

F&T or Thermostatic

IBLV

3:1

DC IBLV

IBLV DC or F&T 3:1

2:1

3:1

<15 psi 2:1 @ 1/2 psi,16-30 psi 2:1 @ 2 psi,

>30 psi 3:1 @ 1/2 Max. PressureDifferential

3:1 for DC, 8:1 for IBconstant pressure, 10:1 for

IB variable pressure

Thermostatic or Disc

3:1

3:1 for quick heating2:1 normally

= Inverted Bucket Large Vent= Inverted Bucket Internal Check Valve= Inverted Bucket Thermic Vent= Float & Thermostatic= Differential Condensate Controller= Thermostatic

Use an IB with external air vent above the F&T pressurelimitations or if the steam is dirty. All safety factors are atthe operating pressure differential unless otherwise noted.

40

Installation and Testing of Armstrong Steam Traps

Before InstallingRun pipe to trap. Before installing thetrap, clean the line by blowing down withsteam or compressed air. (Clean anystrainer screens after this blowdown.)

Trap Location ABC’sAccessible for inspection and repair.Below drip point whenever possible.Close to drip point.

Trap Hookups. For typical hookups,see Figs. 40-1 through 43-4.

Shutoff Valves ahead of traps areneeded when traps drain steam mains,large water heaters, etc., where systemcannot be shut down for trap mainte-nance. They are not needed for smallsteam heated machines—a laundrypress, for example. Shutoff valve insteam supply to machine is usuallysufficient.

Test Valve

ShutoffValve

DirtPocket

Union Un

ShuVa

Figure 40-1.Typical IB Hookup

Shutoff Valves in trap discharge line isneeded when trap has a by-pass. It is agood idea when there is high pressure indischarge header. See also CheckValves.

By-passes (Figs. 41-3 and 41-4) arediscouraged, for if left open, they willdefeat the function of the trap. If continu-ous service is absolutely required, usetwo traps in parallel, one as a primary,one as a standby.

Unions. If only one is used, it should beon discharge side of trap. With twounions, avoid horizontal or vertical in-lineinstallations. The best practice is toinstall at right angles as in Figs. 40-1 and41-3, or parallel as in Fig. 41-4.

Figure 40-2.Typical IB Bottom Inlet—Top Outlet Hookup

ion

tofflve

CheckValve

Standard Connections. Servicing issimplified by keeping lengths of inlet andoutlet nipples identical for traps of agiven size and type. A spare trap withidentical fittings and half unions can bekept in storeroom. In the event a trapneeds repair, it is a simple matter tobreak the two unions, remove the trap,put in the spare and tighten the unions.Repairs can then be made in the shopand the repaired trap, with fittings andhalf unions, put back in stock.

Test Valves (Fig. 40-1) provide anexcellent means of checking trapoperation. Use a small plug valve.Provide a check valve or shutoff valve inthe discharge line to isolate trap whiletesting.

FiTy

P

Strainers. Install strainers ahead of trapsif specified or when dirt conditionswarrant their use. Some types of trapsare more susceptible to dirt problemsthan others— see RecommendationChart on gatefold.

Some traps have built-in strainers. Whena strainer blowdown valve is used, shutoff steam supply valve before openingstrainer blowdown valve. Condensate intrap body will flash back through strainerscreen for thorough cleaning. Opensteam valve slowly.

Dirt Pockets are excellent for stoppingscale and core sand, and eliminatingerosion that can occur in elbows whendirt pockets are not provided. Cleanperiodically.

FiTy

Test Valve

gure 41-1.pical IB Bottom Inlet—Side Outlet Hookup

Check Valvelug

Syphon Installations require a waterseal and, with the exception of the DC, acheck valve in or before the trap.Syphon pipe should be one size smallerthan nominal size of trap used but notless than 1/2" pipe size.

Elevating Condensate. Do not oversizethe vertical riser. In fact, one pipe sizesmaller than normal for the job will giveexcellent results.

Check Valves are frequently needed.They are a must if no discharge lineshutoff valve is used. Fig. 41-2 showsthree possible locations for externalcheck valves—Armstrong invertedbucket traps are available with internalcheck valves, while disc traps act astheir own check valve. Recommendedlocations are given below.

Test

gure 41-3.pical IB By-pass Hookup

Figure 41-2.Possible Check Valve Locations

D

CB

A

Test Valve

Union

Discharge Line Check Valves preventbackflow and isolate trap when test valveis opened. Normally installed at locationB. When return line is elevated and trapis exposed to freezing conditions, installcheck valve at location A, Fig. 41-2.

Inlet Line Check Valves prevent loss ofseal if pressure should drop suddenly orif trap is above drip point in IB traps.Armstrong Stainless Steel Check Valvein trap body, location D, is recom-mended. If swing check is used, install atlocation C, Fig. 41-2.

41

Valve

Valve

Dirt Pocket

Valve

Figure 41-4.Typical IB By-pass HookupBottom Inlet—Top Outlet

Valve

Union

42

A safety drain trap should be usedwhenever there is a likelihood that theinlet pressure will fall below the outletpressure of a primary steam trap,especially in the presence of freezing air.One such application would be on amodulated pressure heating coil thatmust be drained with an elevated returnline. In the event of insufficient drainagefrom the primary trap, condensate risesinto the safety drain and is dischargedbefore it can enter the heat exchanger.An F&T trap makes a good safety drainbecause of its ability to handle largeamounts of air and its simplicity ofoperation. Safety drain trap should besame size (capacity) as primary trap.

The proper application of a safety drainis shown in Fig. 42-1. The inlet to thesafety drain must be located on the heatexchanger drip leg, above the inlet to theprimary trap. It must discharge to anopen sewer. The drain plug of the safetydrain is piped to the inlet of the primarytrap. This prevents the loss of conden-sate formed in the safety drain by bodyradiation when the primary trap is active.The safety drain has an integral vacuumbreaker to maintain operation whenpressure in the heat exchanger fallsbelow atmospheric. The inlet of the

Figure 42-1. Typical Safety Drain Trap Hook

vacuum breaker should be fitted with agoose neck to prevent dirt from beingsucked in when it operates. The vacuumbreaker inlet should be provided with ariser equal in elevation to the bottom ofthe heat exchanger to prevent waterleakage when the vacuum breaker isoperating, but the drip leg and trap bodyare flooded.

u

Protection Against FreezingA properly selected and installed trap willnot freeze as long as steam is coming tothe trap. If the steam supply should beshut off, the steam condenses, forming avacuum in the heat exchanger or tracerline. This prevents free drainage of thecondensate from the system beforefreezing can occur. Therefore, install avacuum breaker between the equipmentbeing drained and the trap. If there is notgravity drainage through the trap to thereturn line, the trap and discharge lineshould be drained manually or automati-cally by means of a freeze protectiondrain. Also, when multiple traps areinstalled in a trap station, insulating thetraps can provide freeze protection

p

4" Typical

Anti-Freeze Precautions.1. Do not oversize trap.2. Keep trap discharge lines very short.3. Pitch trap discharge lines down for

fast gravity discharge.4. Insulate trap discharge lines and

condensate return lines.5. Where condensate return lines

are exposed to ambient weatherconditions, tracer lines should beconsidered.

6. If the return line is overhead, runvertical discharge line adjacent todrain line totop of return header andinsulate drain line and trap dischargeline together. See Fig. 42-2.

NOTE: A long horizontal discharge line invitestrouble. Ice can form at far end eventuallysealing off the pipe. This prevents the trapfrom operating. No more steam can enter thetrap, and the water in the trap body freezes.

Outdoor installation to permit ground leveltrap testing and maintenance when steamsupply and return lines are high overhead.Drain line and trap discharge line areinsulated together to prevent freezing. Notelocation of check valve in discharge line andblowdown valve A that drains the steam mainwhen trap is opened for cleaning or repair.

Check Valve

A

Figure 42-2.

Testing Armstrong Steam TrapsTesting Schedule.For maximum trap life and steameconomy, a regular schedule should beset up for trap testing and preventivemaintenance. Trap size, operatingpressure and importance determine howfrequently traps should be checked.

Table 43-1.Suggested Yearly Trap Testing Frequency

0-100101-250251-450451 and above

Application

Drip Tracer Coil Process

Operating Pressure

(psig)

1 1 2 32 2 2 32 2 3 43 3 4 12

How to TestThe test valve method is best. Fig. 40-1shows correct hookup, with shutoff valvein return line to isolate trap from returnheader. Here is what to look for whentest valve is opened:

Figure 43-1.Typical F&T Hookup

1. Condensate Discharge—Invertedbucket and disc traps should have anintermittent condensate discharge.F&T traps should have a continuouscondensate discharge, while thermo-static traps can be either continuousor intermittent, depending on theload. When an IB trap has anextremely small load it will have acontinuous condensate dischargewhich causes a dribbling effect. Thismode of operation is normal underthis condition.

2. Flash Steam—Do not mistake this fora steam leak through the trap valve.Condensate under pressure holdsmore heat units—Btu—per poundthan condensate at atmosphericpressure. When condensate isdischarged, these extra heat units re-evaporate some of the condensate.See description of flash steam onpage 3.How to Identify Flash: Trap userssometimes confuse flash steam withleaking steam. Here’s how to tell thedifference:If steam blows out continuously, in a“blue” stream, it’s leaking steam. Ifsteam “floats” out intermittently (eachtime the trap discharges) in a whitishcloud, it’s flash steam.

3. Continuous Steam Blow—Trouble.Refer to page 44.

4. No Flow—Possible trouble.Refer to page 44.

Figure 43-2.Typical DC Hookup

Listening Device Test. Use a listeningdevice or hold one end of a steel rodagainst trap cap and other end againstear. You should be able to hear thedifference between the intermittentdischarge of some traps and the continu-ous discharge of others. This correctoperating condition can be distinguishedfrom the higher velocity sound of a trapblowing through. Considerable experi-ence is required for this method oftesting as other noises are telegraphedalong the pipe lines.

Pyrometer Method Of Testing. Thismethod may not give accurate resultsdepending on the return line design andthe diameter of the trap orifice. Also,when discharging into a common return,another trap may be blowing throughcausing a high temperature at the outletof the trap being tested. Better results canbe obtained with a listening device.Request Armstrong Bulletin 310.

43

Figure 43-3.Typical Disc Trap Hookup

TestValve

Figure 43-4.Typical Thermostatic Hookup

TestValve

44

Troubleshooting Armstrong Steam Traps

The following summary will prove helpfulin locating and correcting nearly allsteam trap troubles. Many of these areactually system problems rather than traptroubles.

More detailed troubleshooting literatureis available for specific products andapplications—consult factory.

Whenever a trap fails to operate and thereason is not readily apparent, thedischarge from the trap should beobserved. If the trap is installed with atest outlet, this will be a simple matter—otherwise, it will be necessary to breakthe discharge connection.

Cold Trap—No DischargeIf the trap fails to discharge condensate,then:

A. Pressure may be too high.1. Wrong pressure originally specified.2. Pressure raised without installing

smaller orifice.3. PRV out of order.4. Pressure gauge in boiler reads low.5. Orifice enlarged by normal wear.6. High vacuum in return line

increases pressure differentialbeyond which trap may operate.

B. No condensate or steam coming totrap.1. Stopped by plugged strainer ahead

of trap.2. Broken valve in line to trap.3. Pipe line or elbows plugged.

C. Worn or defective mechanism.Repair or replace as required.

D. Trap body filled with dirt.Install strainer or remove dirt atsource.

E. For IB, bucket vent filled with dirt.Prevent by:1. Installing strainer.2. Enlarging vent slightly.3. Using bucket vent scrubbing wire.

F. For F&T traps, if air vent is notfunctioning properly, trap will likely airbind.

G. For thermostatic traps, the bellowselement may rupture from hydraulicshock, causing the trap to fail closed.

H. For disc traps, trap may be installedbackward.

Hot Trap — No DischargeA. No condensate coming to trap.

1. Trap installed above leaky by-passvalve.

2. Broken or damaged syphon pipe insyphon drained cylinder.

3. Vacuum in water heater coils mayprevent drainage. Install a vacuumbreaker between the heatexchanger and the trap.

Steam LossIf the trap blows live steam, the troublemay be due to any of the followingcauses:

A. Valve may fail to seat.1. Piece of scale lodged in orifice.2. Worn parts.

B. IB trap may lose its prime.1. If the trap is blowing live steam,

close the inlet valve for fewminutes. Then gradually open. Ifthe trap catches its prime, thechances are that the trap is all right.

2. Prime loss is usually due tosudden or frequent drops in steampressure. On such jobs, theinstallation of a check valve iscalled for—location D or C in Fig.41-2. If possible locate trap wellbelow drip point.

C. For F&T and thermostatic traps,thermostatic elements may fail toclose.

Continuous FlowIf an IB or disc trap discharges continu-ously, or an F&T or thermostatic trapdischarge at full capacity, check thefollowing:

A. Trap too small.1. A larger trap, or additional traps

should be installed in parallel.2. High pressure traps may have

been used for a low pressure job.Install right size of internalmechanism.

B. Abnormal water conditions. Boilermay foam or prime, throwing largequantities of water into steam lines.A separator should be installed orelse the feed water conditionsshould be remedied.

Sluggish HeatingWhen trap operates satisfactorily, butunit fails to heat properly:

A. One or more units may be short-circuiting. The remedy is to install atrap on each unit. See page 14.

B. Traps may be too small for job eventhough they may appear to behandling the condensate efficiently.Try next larger size trap.

C. Trap may have insufficient air-handling capacity, or the air may notbe reaching trap. In either case, useauxiliary air vents.

Mysterious TroubleIf trap operates satisfactorily whendischarging to atmosphere, but trouble isencountered when connected with returnline, check the following:

A. Back pressure may reduce capacityof trap.1. Return line too small—trap hot.2. Other traps may be blowing

steam—trap hot.3. Atmospheric vent in condensate

receiver may be plugged—trap hotor cold.

4. Obstruction in return line—trap hot.5. Excess vacuum in return line—trap

cold.

Imaginary TroublesIf it appears that steam escapes everytime trap discharges, remember: Hotcondensate forms flash steam whenreleased to lower pressure, but it usuallycondenses quickly in the return line.See Chart 3-2 on page 3.

Pipe Sizing Steam Supply and Condensate Return Lines

The table below gives the color designationsas they correspond to the velocities:

Above Velocities Less ThanViolet 6,000 fpmYellow 8,000 fpmBlue 10,000 fpm

DefinitionsSteam mains or mains carry steam fromthe boiler to an area in which multiplesteam-using units are installed.

Steam branch lines take steam fromsteam main to steam-heated unit.

Trap discharge lines move condensateand flash steam from the trap to a returnline.

Condensate return lines receive conden-sate from many trap discharge lines andcarry the condensate back to the boilerroom.

Table 45-3. Steam Pipe Capacity at 30 psig—


Table 45-1. Steam Pipe Capacity at 5 psig—S

410245281

160270490730

1,0401,9303,1606,590

12,02019,290

6153168

100210350650970

1,3702,5404,1708,680

15,84025,420

9214497

150300500920

1,3701,9403,6005,910

12,31022,46036,050

111/411/22

21/23

31/24568

1012

Pressure drop per 100 ft Pipe Size(in) 1/8 1/4 1/2

1/23/4

3/4

1/2

111/411/22

21/23

31/245681012

513275991

180300560830

1,1802,1803,5807,450

13,60021,830

8183883

130260430790

1,1801,6603,0805,060

10,53019,22030,840

112653

120180370600

1,1101,6602,3504,3507,150

14,88027,15043,570

136

14224574

1,362,042,885,338,75

18,2233,2553,37

Pressure drop per 100 ft oPipe Size(in) 1/8 1/4 1/2 3/4

31/2

1

221/23

45681012

Pressure drop per 100 ft ofPipe Size(in)

3/4

1/2

11/411/2

1/2 3/41/41/87

163270

110223368675990

1,4202,6254,3159,000

16,40026,350

10224599

156316520953

1,4052,0203,7206,100

12,70023,20037,250

143264

142220446735

1,3402,0102,8505,2608,650

18,00033,30052,500

137

17275490

1,652,473,496,45

10,6022,0040,2564,50

NOTE: The velocity ranges shown in SteamPipe Capacity Tables 45-1 through 46-4 canbe used as a general guide in sizing steampiping. All the steam flows above a givencolored line are less than the velocities shownin the tables.

S

S

c

o

f

799406020000000

Red 12,000 fpmGreen 15,000 fpm

Pipe SizingTwo principal factors determine pipesizing in a steam system:1. The initial pressure at the boiler andthe allowable pressure drop of the totalsystem. The total pressure drop in thesystem should not exceed 20% of thetotal maximum pressure at the boiler.This includes all drops — line loss,elbows, valves, etc. Remember, pressuredrops are a loss of energy.

chedule 40 Pipe

chedule 40 Pipe

Table 45-6. Steam Pip

hedule 40 Pipe Table 45-4. Steam Pip


112654

120180370610

1,1301,6802,3804,4107,250

15,09027,53044,190

1

133062

140210430710

1,3001,9402,7505,0908,360

17,40031,76050,970

f pipe length3/4

PrPipe Size(in)

8204089

139282465853

1,2751,8003,3205,475

11,36020,80033,300

1126

1,21,82,54,77,7

16,129,447,1

111/411/22

21/23

31/24568

1012

1/23/4

11/8

425000000000000

1163776

160260520860

1,5702,3503,3306,160

10,12021,06038,43061,690

22352

110230360740

1,2102,2203,3204,7008,700

14,29029,74054,27087,100

pipe length Pipe Size(in)

^

2150

100220340690

1,1402,0903,1204,4208,170

13,42027,93050,97081,810

111/411/22

21/23

31/24568

1012

1/23/4

1194591

202312630

1,0401,9052,8504,0257,450

12,20025,42046,50074,500

22864

129283440892

1,4722,6904,0205,700

10,55017,30036,00065,750

105,500

pipe length

14,71030,65056,00089,900

2354

109241375760

1,2502,2803,4304,8408,950

1/23/41

11/411/22

21/23

31/245681012

Pipe Size(in) 1/2

2. Steam velocity. Erosion and noiseincrease with velocity. Reasonablevelocities for process steam are 6,000 to12,000 fpm, but lower pressure heatingsystems normally have lower velocities.Another consideration is future expan-sion. Size your lines for the foreseeablefuture. If ever in doubt, you will have lesstrouble with oversized lines than withones that are marginal.

45

e Capacity at 125 psig—Schedule 40 Pipe



essure drop per 100 ft of pipe length1

2557

115253395800

1,3182,4103,6055,1009,440

15,45032,20058,90094,500

23581

163358558

1,1301,8603,4105,0907,220

13,30021,90045,55083,250

133,200

555

128258567882

1,7902,9405,4008,060

11,40021,10034,60072,100

131,200210,600

122857279782600500501025000000

174081

179279565930

1,6902,5503,6106,660

10,95022,80041,50066,700

2149

100219342691

1,1402,0903,1204,4628,150

13,42027,90051,00081,750

1/2 3/4/4

Pressure drop per 100 ft of pipe length˚

2661

120270420850

1,4002,5603,8305,420

10,02016,45034,25062,500

100,300

13070

140310480980

1,6202,9604,4206,260

11,58019,02039,58072,230

115,900

24399

200440680

1,3902,2804,1806,2508,840

16,35026,84055,870

101,900163,600

568

160320690

1,0802,1903,6106,6109,870

13,96025,84042,41088,280

161,100258,500

575

172347764

1,1852,4103,9607,260

10,88015,35028,40046,50097,100

177,000284,100

247

109220483751

1,5202,5504,5906,8509,700

17,95029,50061,400

112,000179,600

13377

155341532

1,0751,7753,2454,8506,850

12,70020,80043,40079,100

127,100

3/42966

134296460930

1,5352,8154,2005,930

11,00018,07037,55068,500

110,200

Pressure drop per 100 ft of pipe length

46

Steam MainsThe sizing and design of high capacitysteam mains is a complex problem thatshould be assigned to a competentengineer.

Tables 45-1 through 46-4 will prove help-ful in checking steam main sizes or indetermining main size for small plants.An existing 3" steam main may besupplying one department of a plant with3,200 lbs/hr at 125 psig. Could the steamuse of this department be increased to7,000 lbs/hr without a new supply line?Table 45-6 shows that 1 psi pressuredrop is produced in 100 feet of 3" pipewhen supplying 3,200 lbs/hr. To increasethe flow to 7,000 lbs/hr would produce apressure drop of 5 psi per 100 feet witha velocity of 8,000 feet per minute. Thisvelocity is acceptable, and if the pressuredrop and corresponding decrease insteam temperature are not objection-able, the existing 3" pipe can be used.However, if this much pressure drop isnot permissible, an additional 3" mainwill have to be installed, or the existing3" main will have to be replaced with a4" main which can handle 7,000 lbs/hrwith a pressure drop of about 1 psi per100 feet with a velocity of less than6,000 fpm.

Steam Branch LinesWhen a new heating or process unit isinstalled in an existing plant, Tables 45-1through 46-4 are entirely practical forchecking the size of pipe to run from the

Table 46-1. Steam Pipe Capacity at 180 psig—Pressure drop per 100 ft Pipe Size

(in)

111/4

11/2

221/2

331/2456810

3990

182400624

1,2602,0803,8055,6958,500

14,90024,42050,85093,000

13478

158347540

1,0921,8003,3004,9306,980

12,90022,20044,10080,500

˚

2864

129283441895

1,4702,6754,0405,700

10,50017,30036,00065,800

^

1/23/4


3274

150330510

1,0401,7103,1304,6706,600

12,22020,06041,750

3991

180400620

1,2702,0903,8205,7108,080

14,95024,54051,100

45105210470720

1,4702,4104,4206,6109,340

17,29028,38059,100

1

Pressure drop per 100 ft Pipe Size(in) 1/2 3/4

111/411/22

21/23

31/24568

1/23/4

steam main to the new unit. The useof the tables is best described by solvinga typical problem:

Assume a boiler operates at a steampressure of 15 psig and is supplying a300-ton steam absorption machine whichrequires a minimum operating pressureof 12 psig. There is a 2 psig pressuredrop along the steam mains and theabsorption machine is rated to condense6,000 lbs/hr. The branch line is 50 feetlong and has three standard elbows plusa gate valve. Allowable pressure drop isnot to exceed 1 psi. Assuming that a 5"pipe will be needed, use Table 48-2 todetermine the equivalent length of pipe tobe added to compensate for fittings.

3—5" standard elbows at 11 = 33.0 ft1—5" gate valve at 2.2 = 2.2 ft

Total for valve and fittings = 35.2 ft

Adding this to the 50-foot length of pipegives a total effective length of 85.2 feet—call it .85 hundred feet. Dividing ourmaximum allowable pressure drop of 1.0by .85 gives 1.18 psi per 100 feet. Referto Table 45-2 for 15 psig steam. With apressure drop of 1.0 psi per 100 feet, a5" pipe will give a flow of 6,160 lbs/hr. Onthe basis of pressure drop only, a 5" pipecould be selected, however, the velocitywill be between 10,000 and 12,000 fpm.Because of this, it may be wise toconsider the next size pipe, 6", asvelocity will then be less than 8,000 fpm.

Schedule 40 Pipeof pipe length

88202407895

1,3942,8204,6508,550

12,74018,00033,30054,600

113,900207,000

556

128258566882

1,7852,9405,3908,050

11,40021,08034,60072,000

131,300

2

Schedule 40 Pipe

64150300660

1,0202,0703,4106,2509,340

13,21024,44040,10083,500

2102230470

1,1601,6203,2805,4009,880

14,77020,89038,65063,400

132,000

5

of pipe length


200

415

700

1,350

2,200

4,100

8,800

15,900

27,500

56,000

Pipe Size(in)

1

11/4

11/2

2

21/2

3

4

5

6

8

1/2


Pipe Size(in)

^

270

550

820

1,600

2,750

4,800

9,900

18,500

30,500

68,000

1

11/4

11/2

2

21/2

3

4

5

6

8

Trap Discharge LinesTrap discharge lines are usually short.Assuming the trap is properly sized forthe job, use a trap discharge line thesame size as the trap connections. Atvery low pressure differential betweentrap and condensate return pipe, trapdischarge lines can be increased onepipe size advantageously.

Condensate Return LinesFor medium and large-sized plants,the services of a consultant should beemployed to engineer the condensatereturn pipe or pipes. Usually it is consid-ered good practice to select return pipeone or two sizes larger to allow for 1) in-crease in plant capacity and 2) eventualfouling of pipe with rust and scale.

Traps and High Back PressureBack pressures excessive by normalstandards may occur due to fouling ofreturn lines, increase in condensate loador faulty trap operation. Depending onthe operation of the particular trap, backpressure may or may not be a problem.See Recommendation Chart on GatefoldB. If a back pressure is likely to exist inthe return lines, be certain the trapselected will work against it.

Back pressure does lower the pressuredifferential and, hence, the capacity ofthe trap is decreased. In severe cases,the reduction in capacity could make itnecessary to use traps one size larger tocompensate for the decrease in operat-ing pressure differential.


330

640

1,100

1,990

3,150

5,900

15,000

24,500

38,000

80,000

1

460

910

1,350

2,850

4,600

8,500

18,500

33,000

56,000

115,000

2

800

1,400

2,350

4,650

7,800

15,000

31,000

56,000

90,000

200,000

5

1,150

2,200

3,300

6,850

11,500

22,000

46,000

80,000

130,000

285,000

10

Pressure drop per 100 ft of pipe length


Pressure drop per 100 ft of pipe length1390

750

1,200

2,350

3,700

7,200

15,500

28,000

46,000

96,000

2550

1,100

1,650

3,350

5,400

9,900

22,000

38,500

68,000

130,000

5910

1,850

2,800

5,400

9,000

17,500

35,000

68,000

110,000

230,000

101,300

2,650

4,150

8,250

13,000

25,000

52,000

96,000

150,000

325,000

How to Size Condensate Return Lines

The sizing of condensate return linespresents several problems which differfrom those of sizing steam or water lines.The most significant of these is thehandling of flash steam. Although areturn line must handle both water andflash steam, the volume of flash steam ismany times greater than the volume ofcondensate. For the values in Chart 47-1the volume of flash steam is 96% to 99%of the total volume. Consequently, onlyflash steam is considered in Chart 47-1.

Condensate return lines should be sizedto have a reasonable velocity at anacceptable pressure drop. Chart 47-1 isbased on having a constant velocity of7,000 feet per minute or below, usingSchedule 40 pipe. Additional factorswhich should also be considered—depending on water conditions—are dirt,fouling, corrosion and erosion.

For a given supply pressure to the trapand a return line pressure, along with anassumed pressure drop per 100 feet ofpipe (∆P/L) and knowing the condensateflow rate, the proper pipe diameter canbe selected from Chart 47-1.

Chart 47-1. Flow Rate (lbs/hr) for Dry-Closed R

a For these sizes and pressure losses the velocityReprinted by permission from ASHRAE Handboo

∆P/L

psi/100' D, in

Supply Pressure = 10Return Pressure = 0

∆P/L

psi/100' D, in

62

134

260

540

810

1,590

2,550

4,550

9,340

a

a

Supply Pressure = 5Return Pressure = 0

240 520

510 1,120

1,000 2,150

2,100 4,500

3,170 6,780

6,240 13,300

10,000 21,300

18,000 38,000

37,200 78,000

110,500 a

228,600 a

28

62

120

250

380

750

1,200

2,160

4,460

13,200

27,400

1

2

3

4

6

11/4

11/2

21/2

1/23/4

8

1

2

3

4

6

11/4

11/2

21/2

1/23/4

8

1

2

3

4

6

11/4

11/2

21/2

1/23/4

1/41/16

1/41/16

How to Use Chart 47-1Example 1: A condensate system has thesteam supply at 30 psig. The return line isnon-vented and at 0 psig. The return lineis to have the capacity for returning 2,000lbs/hr of condensate. What must be thesize of the return line?

Solution: Since the system will bethrottling the condensate from 30 psig to0 psig, there will be flash steam (assum-ing no subcooling), and the system will bea dry-closed (not completely full of liquidand not vented to atmosphere) return.The data in Chart 47-1 can be used. Apressure of 1/4 psig per 100 feet isselected. In Chart 47-1 for a 30 psigsupply and a 0 psig return for ∆P/L = 1/4,a pipe size for the return line of 2" isselected.

eturns

is above 7,000 fpm. Select another combination ok —1985 Fundamentals.

11/41/16

0 psig psig

Supply Pressure = 150 psigReturn Pressure = 0 psig

Supply PrReturn Pr

133 23 51 109 56

290 50 110 230 120

544 100 210 450 240

1,130 200 440 930 500

1,700 310 660 1,400 750

a 610 1,300 a 1,470

a 980 2,100 a 2,370

a 1,760 3,710 a 4,230

a 3,640 7,630 a 8,730

a 10,800 a a 25,900

a 22,400 a a 53,400

psig psig


Supply PrReturn P

1,100 95 210 450 60

2,400 210 450 950 130

4,540 400 860 1,820 250

9,500 840 1,800 3,800 520

14,200 1,270 2,720 5,700 780

a 2,500 5,320 a 1,540

a 4,030 8,520 a 2,480

a 7,200 15,200 a 4,440

a 14,900 31,300 a 9,180

a 44,300 a a 27,300

a 91,700 a a 56,400

1 1/16

11/41/161 1/16

Example 2: A condensate return systemhas the steam supply at 100 psig and thereturn line is non-vented and at 0 psig.The return line is horizontal and musthave a capacity of 2,500 lbs/hr. Whatsize pipe is required?

Solution: Since the system will bethrottling non-subcooled condensatefrom 100 psig to 0 psig there will be flashsteam, and the system will be a dry-closedreturn. Selecting a pressure drop of 1 psiper 100 feet yields from Chart 47-1 anon-recommended situation (a). Select apressure drop of 1/4 psi per 100 feet andthen a 21/2" pipe can be used for thissystem.

47

f size and pressure loss.

essure = 100 psigessure = 15 psig


120 260 43 93 200

260 560 93 200 420

500 1,060 180 390 800

1,060 2,200 380 800 1,680

1,600 3,320 570 1,210 2,500

3,100 6,450 1,120 2,350 4,900

5,000 10,300 1,800 3,780 7,800

8,860 a 3,200 6,710 a

18,200 a 6,620 13,800 a

53,600 a 19,600 40,600 a

110,300 a 40,500 83,600 a

essure = 30 psigressure = 0 psig


130 274 42 92 200

280 590 91 200 420

530 1,120 180 380 800

1,110 2,340 370 800 1,680

1,670 3,510 560 1,200 2,520

3,270 a 1,110 2,350 a

5,250 a 1,780 3,780 a

9,360 a 3,190 6,730 a

19,200 a 6,660 13,800 a

a a 19,600 a a

a a 40,500 a a

11/4 11/41/16

11/4 11/41/16

48

Useful Engineering Tables

3/4

1/8

111/2

Diameters Circumference Transverse Areas Length of Pipeper sq ft

Nominal Weightper foot

External(in)

Approx-imate

Internal(in)

NominalThick-ness(in)

External(in)

Internal(in)

External(sq in)

Internal(sq in)

Metal(sq in)

ExternalSurface

Feet

InternalSurface

Feet

Length ofPipe

ContainingOne Cubic

Foot Plain EndsThreaded

andCoupled

NumberThreadsper Inch

ofScrew

Size(in)

Feet

4

5

6

8

10

12

14

16

18

20

24

0.405

0.540

0.675

0.840

1.050

1.315

1.660

1.900

2.375

2.875

3.500

4.000

4.500

5.563

6.625

8.625

10.750

12.750

14.000

16.000

18.000

20.000

24.000

0.269

0.364

0.493

0.622

0.824

1.049

1.380

1.610

2.067

2.469

3.068

3.548

4.026

5.047

6.065

7.981

10.020

11.938

13.125

15.000

16.874

18.814

22.626

0.068

0.088

0.091

0.109

0.113

0.133

0.140

0.145

0.154

0.203

0.216

0.226

0.237

0.258

0.280

0.322

0.365

0.406

0.437

0.500

0.563

0.593

0.687

1.272

1.696

2.121

2.639

3.299

4.131

5.215

5.969

7.461

9.032

10.996

12.566

14.137

17.477

20.813

27.096

33.772

40.055

43.982

50.265

56.548

62.831

75.398

0.845

1.114

1.549

1.954

2.589

3.296

4.335

5.058

6.494

7.757

9.638

11.146

12.648

15.856

19.054

25.073

31.479

37.699

41.217

47.123

52.998

59.093

71.063

0.129

0.229

0.358

0.554

0.866

1.358

2.164

2.835

4.430

6.492

9.621

12.566

15.904

24.306

34.472

58.426

90.763

127.640

153.940

201.050

254.850

314.150

452.400

0.057

0.104

0.191

0.304

0.533

0.864

1.495

2.036

3.355

4.788

7.393

9.886

12.730

20.006

28.891

50.027

78.855

111.900

135.300

176.700

224.000

278.000

402.100

0.072

0.125

0.167

0.250

0.333

0.494

0.669

0.799

1.075

1.704

2.228

2.680

3.174

4.300

5.581

8.399

11.908

15.740

18.640

24.350

30.850

36.150

50.300

9.431

7.073

5.658

4.547

3.637

2.904

2.301

2.010

1.608

1.328

1.091

0.954

0.848

0.686

0.576

0.442

0.355

0.299

0.272

0.238

0.212

0.191

0.159

14.199

10.493

7.747

6.141

4.635

3.641

2.767

2.372

1.847

1.547

1.245

1.076

0.948

0.756

0.629

0.478

0.381

0.318

0.280

0.254

0.226

0.203

0.169

2533.775

1383.789

754.360

473.906

270.034

166.618

96.275

70.733

42.913

30.077

19.479

14.565

11.312

7.198

4.984

2.878

1.826

1.288

1.069

0.817

0.643

0.519

0.358

0.244

0.424

0.567

0.850

1.130

1.678

2.272

2.717

3.652

5.793

7.575

9.109

10.790

14.617

18.974

28.554

40.483

53.600

63.000

78.000

105.000

123.000

171.000

0.245

0.425

0.568

0.852

1.134

1.684

2.281

2.731

3.678

5.819

7.616

9.202

10.889

14.810

19.185

28.809

41.132

—

—

—

—

—

—

27

18

18

14

14

111/2

8

8

8

8

8

8

8

8

—

—

—

—

—

—

111/2

111/2

11/4

11/2

21/2

31/2

1/43/81/2

1

2

3

Table 48-1. Schedule 40 Pipe, Standard Dimensions

Table 48-4. Diameters and Areas of Circles and Drill Sizes

13/4

13/8

17/16

11/2

15/8

17/8

11/4

15/16

3/4

5/8

9/16

7/32

3/16

11/64

Dia. Area Dia. Area Dia. Area Dia. AreaDrill Size.13920.15033.16117.17257.18398.19635.20831.22166.24850.27688.30680.33824.37122.40574.44179.47937.51849.55914.60132.64504.69029.73708.78540.88664.994021.10751.22721.35301.48491.62301.76712.07392.40532.76123.1416

111/16

2

.04600

.04753

.04909

.04909

.05187

.05350

.05515

.05557.05811.06026.06202.06213.06605.06835.06881.07163.07670.07843.08194.08449.08657.09026.09281.09511.10066.10122.10636.11045.11163.11702.11946.12379.12819.12962.13396

.2420

.2460

.2500

.2500

.2570

.2610

.2656

.2660

.2720

.2770

.2810

.2812

.2900

.2950

.2969

.3020

.3125

.3160

.3230

.3281

.3320

.3390

.3438

.3480

.3580

.3594

.3680

.3750

.3770

.3860

.3906

.3970

.4040

.4062

.4130

CD

EFG

HIJK

LM

N

OP

QR

ST

U

VW

XY

Z

.01629

.01697

.01705

.01815

.01863

.01917

.01936

.01986

.02036

.02164

.02256

.02320

.02351

.02461

.02545

.02602

.02688

.02761

.02806

.02865

.02941

.03017.03110.03173.03241.03268.03317.03431.03563.03758.03836.04083.04301.04314.04449

.1440

.1470

.1495

.1520

.1540

.1562

.1570

.1590

.1610

.1660

.1695

.1719

.1730

.1770

.1800

.1820

.1850

.1875

.1890

.1910

.1935

.1960

.1990

.2010

.2031

.2040

.2055

.2090

.2130

.2188

.2210

.2280

.2340

.2344

.2380

2726252423

2221201918

1716151413

121110987

6543

21A

B

.00173

.00212

.00238

.00278

.00307

.00317

.00353

.00385

.00419

.00454

.00479

.00484

.00515

.00528

.00581

.00622

.00687

.00690

.00724

.00754

.00778

.00809

.00850

.00891

.00940

.00950

.00968

.01003

.01039.01131.01227.01242.01453.01550.01553

.0469

.0520

.0550

.0595

.0625

.0635

.0670

.0700

.0730

.0760

.0781

.0785

.0810

.0820

.0860

.0890

.0935

.0938

.0960

.0980

.0995

.1015

.1040

.1065

.1094.1100.1110.1130.1160.1200.1250.1285.1360.1405.1406

555453

5251504948

474645444342

414039383736

3534333231

302928

Drill Size Drill Size Drill Size

1.00001.06251.12501.18751.25001.31251.37501.43751.50001.62501.75001.87502.0000

.4219

.4375

.4531

.4688

.4844.500

.5156

.5312

.5625

.5937

.6250

.6562

.6875

.7187

.7500

.7812

.8125

.8437

.8750

.9062

.9375

.9687

3/64

1/16

5/64

7/64

3/32

1/8

9/64

5/32

13/64

15/64

1/4

17/64

11/32

5/16

19/64

21/64

23/64

3/8

25/64

13/32

27/647/16

29/6415/3231/641/2

33/6417/32

19/32

21/32

23/32

11/16

25/3213/1627/32

7/829/3215/1631/32

11/8

13/16

9/32

StandardElbow

SideOutlet

Tee

Length in Feet to be Added RunPipeSize(in)

1.31.82.23.03.54.35.06.58.09.011.013.017.021.027.0

GateValve*

GlobeValve*

AngleValve*

345678111315182227354553

0.30.40.50.60.81.01.11.41.61.92.22.83.74.65.5

14182329344654668092112136180230270

7101215182227344045566792112132

111/411/22

21/23

31/24568

1012

1/23/4

Table 48-2. Equivalent Length of Pipe to beAdded for Fittings—Schedule 40 Pipe

Table 48-3.Thermal Expansion of Pipe

*From Piping Handbook, by Walker andCrocker, by special permission.

This table gives the expansion from -20°F totemperature in question. To obtain the amount

of expansion between any two temperaturestake the difference between the figures in thetable for those temperatures. For example, ifcast iron pipe is installed at a temperature of

80°F and is operated at 240°F,the expansion would be 1.780 - 0.649 = 1.13 in.

*Valve in full open position

Cast Iron Pipe Steel Pipe Wrought

Iron PipeCopper

Pipe

Elongation in Inches per 100 Ft from -20°F UpTemp.

(°F)

0.0000.2040.4420.6550.8881.1001.3381.5701.7942.0082.2552.5002.9603.4223.9004.3804.8706.1107.388

0.0000.1520.3060.4650.6200.7800.9391.1101.2651.4271.5971.7782.1102.4652.8003.1753.5214.4775.455

0.0000.1450.2930.4300.5930.7250.8981.0551.2091.3681.5281.6912.0202.3502.6903.0293.3754.2965.247

0.0000.1270.2550.3900.5180.6490.7870.9261.0511.2001.3451.4951.7802.0852.3952.7003.0083.8474.725

-200

20406080

100120140160180200240280320360400500600

49

PowerMultiply By To GetBoiler hp 33,472 Btu/hr

lbs H2O evap.Boiler hp 34.5 at 212°FHorsepower 2,540 Btu/hrHorsepower 550 ft-lbs/secHorsepower 33,000 ft-lbs/minHorsepower 42.42 Btu/minHorsepower 0.7457 KilowattsKilowatts 3,415 Btu/hrKilowatts 56.92 Btu/minWatts 44.26 ft-lbs/minWatts 0.7378 ft-lbs/secWatts 0.05692 Btu/minTons refrig. 12,000 Btu/hrTons refrig. 200 Btu/minBtu/hr 0.00002986 Boiler hplbs H2O evap.at 212°F 0.0290 Boiler hpBtu/hr 0.000393 Horsepowerft-lbs/sec 0.00182 Horsepowerft-lbs/min 0.0000303 HorsepowerBtu/min 0.0236 HorsepowerKilowatts 1.341 HorsepowerBtu/hr 0.000293 KilowattsBtu/min 0.01757 Kilowattsft-lbs/min 0.02259 Wattsft-lbs/sec 1.355 WattsBtu/min 1.757 WattsBtu/hr 0.0000833 Tons refrig.Btu/min 0.005 Tons refrig.

EnergyMultiply By To GetBtu 778 ft-lbsBtu 0.000393 hp-hrsBtu 0.000293 kw-hrs

{lbs H2O evap.Btu 0.0010307 at 212°FBtu 0.00000347 Tons refrig.Btu 0.293 Watt-hrsft-lbs 0.3765 Watt-hrsLatent heat}of ice 143.33 Btu/lb H2Olbs H2O evap.}at 212°F 0.284 kw-hrslbs H2O evap.}at 212°F 0.381 hp-hrsft-lbs 0.001287 Btuhp-hrs 2,540 Btukw-hrs 3,415 Btulbs H2O evap.}at 212°F 970.4 BtuTons refrig. 288,000 BtuWatt-hrs 3.415 BtuWatt-hrs 2,656 ft-lbs

{Latent heatBtu/lb H2O 0.006977 of ice

{lbs H2O evap.kw-hrs 3.52 at 212°F

{lbs. H2O evap.hp-hrs 2.63 at 212°F

PressureMultiply By To Get

{in Mercuryatmospheres 29.92 (at 62°F)

{in H2Oatmospheres 406.8 (at 62°F)

{ft. H2Oatmospheres 33.90 (at 62°F)atmospheres 14.70 lbs/in2

atmospheres 1.058 ton/ft2

in. H2O} {in. Mercury(at 62°F) 0.0737 (at 62°F)ft H2O} {in. Mercury(at 62°F) 0.881 (at 62°F)ft H2O}(at 62°F) 0.4335 lbs/in2

ft H2O}(at 62°F) 62.37 lbs/ft2

in. Mercury}(at 62°F) 70.73 lbs/ft2

in. Mercury}(at 62°F) 0.4912 lbs/in2

in. Mercury}(at 62°F) 0.03342 atmospheresin. H2O}(at 62°F) 0.002458 atmospheresft. H2O}(at 62°F) 0.0295 atmosphereslbs/in2 0.0680 atmosphereston/ft2 0.945 atmospheresin. Mercury} {in. H2O(at 62°F) 13.57 (at 62°F)in. Mercury} {ft H2O(at 62°F) 1.131 (at 62°F)

{ft H2Olbs/in2 2.309 (at 62°F)

{ft H2Olbs/ft2 0.01603 (at 62°F)

{in. Mercurylbs/ft2 0.014138 (at 62°F)

{in. Mercurylbs/in2 2.042 (at 62°F)lbs/in2 0.0689 Barlbs/in2 0.0703 kg/cm2

Velocity of FlowMultiply By To Getft/min 0.01139 miles/hrft/min 0.01667 ft/seccu ft/min 0.1247 gal/seccu ft/sec 448.8 gal/minmiles/hr 88 ft/minft/sec 60 ft/mingal/sec 8.02 cu ft/mingal/min 0.002228 cu ft/sec

Heat TransmissionMultiply By To GetBtu/in} {Btu/ft/sq ft 0.0833 /sq ft/hr/°F /hr/°FBtu/ft} {Btu/in/sq ft 12 /sq ft/hr /°F /hr/ °F

Conversion FactorsWeight

Multiply By To Getlbs 7,000 grainslbs H2O(60°F) 0.01602 cu ft H2Olbs H2O(60°F) 0.1198 gal H2Otons (long) 2,240 lbstons (short) 2,000 lbsgrains 0.000143 lbs

lbs H2Ocu ft H2O 62.37 (60°F)

lbs H2Ogal H2O 8.3453 (60°F)lbs 0.000446 tons (long)lbs 0.000500 tons (short)

Circular MeasureMultiply By To GetDegrees 0.01745 RadiansMinutes 0.00029 RadiansDiameter 3.142 CircumferenceRadians 57.3 DegreesRadians 3,438 MinutesCircumference 0.3183 Diameter

VolumeMultiply By To GetBarrels (oil) 42 gal (oil)cu ft 1,728 cu incu ft 7.48 galcu in 0.00433 galgal (oil) 0.0238 barrels (oil)cu in 0.000579 cu ftgal 0.1337 cu ftgal 231 cu in

Temperature

Fractions and DecimalsMultiply By To GetSixty-fourths 0.015625 DecimalThirty-seconds 0.03125 DecimalSixteenths 0.0625 DecimalEighths 0.125 DecimalFourths 0.250 DecimalHalves 0.500 DecimalDecimal 64 Sixty-fourthsDecimal 32 Thirty-secondsDecimal 16 SixteenthsDecimal 8 EighthsDecimal 4 FourthsDecimal 2 Halves

Gallons shown are U.S. standard.

F = (°C x 1.8) + 32C = (°F - 32) ÷ 1.8

50

Specific Heat—Specific Gravity

Acetic acid, 100%

Acetic acid, 10%

Acetone, 100%Alcohol, ethyl, 95%

Alcohol, methyl, 90%

AluminumAmmonia, 100%

Ammonia, 26%

AroclorAsbestos board

Asphalt

Asphalt, solidBenzene

Brickwork & Masonry

Brine - calcium chloride, 25%Brine - sodium chloride, 25%

Clay, dry

CoalCoal tars

Coke, solid

CopperCork

Cotton, cloth

Cotton seed oilDowtherm A

Dowtherm C

Ethlene glycolFatty acid - palmitic

Fatty acid - stearic

Fish, fresh, averageFruit, fresh, average

Gasoline

Glass, pyrexGlass, wool

Glue, 2 parts water 1 part dry glue

Glycerol, 100% (glycerin)Honey

Hydrochloric acid, 31.5% (muriatic)

Hydrochloric acid, 10% (muriatic)

Ice Cream

LardLead

Leather

Linseed oilMagnesia, 85%

Maple syrup

Meat, fresh, average

Nickel

Nitric acid, 95%Nitric acid, 60%

Nitric acid, 10%

No. 1 Fuel Oil (kerosene)No. 2 Fuel Oil

No. 3 Fuel Oil

No. 4 Fuel OilNo. 5 Fuel Oil

No. 6 Fuel Oil

Ice

Milk

Liquid (L)or

Solid (S)

L

L

LL

L

SL

L

LS

L

SL

S

LL

S

SS

S

SS

S

LL

L

LL

L

SS

L

SS

L

LL

L

LS

S

SS

S

LL

L

SL

S

LL

L

LL

L

LL

L

1.05

1.01

0.780.81

0.82

2.640.61

0.90

1.440.88

sp. gr. @ 60-70°F

1.00

1.1-1.50.84

1.6-2.0

1.231.19

1.9-2.4

1.2-1.81.20

1.0-1.4

8.820.25

1.50

0.950.99

1.10

1.110.85

0.84

0.73

2.250.072

1.09

1.26

1.15

1.050.90

0.9211.34

0.86-1.02

0.930.208

1.03

8.90

1.501.37

1.05

0.810.86

0.88

0.900.93

0.95

0.48

0.96

0.5140.60

0.65

0.231.10

1.00

0.280.19

sp. ht. @ 60°F

Btu/lb-°F

0.42

0.22-0.40.41

0.22

0.6890.786

0.224

0.26-0.370.35@40

0.265

0.100.48

0.32

0.470.63

0.35-0.65

0.580.653

0.550

0.75-0.820.80-0.88

0.53

0.200.157

0.89

0.580.34

0.60

0.750.50

0.70

0.640.031

0.36

0.440.27

0.48

0.700.90-0.93

0.11

0.500.64

0.90

0.470.44

0.43

0.420.41

0.40

Table 50-1. Physical Properties Liquids and Solids

API Mid-continent crude

API gas oil

PaperParaffin

Paraffin, melted

Phenol (carbolic acid)Phosphoric acid, 20%

Phosphoric acid, 10%

Phthalic anhydrideRubber, vulcanized

SAE - SW (#8 machine lube oil)

SAE - 20 (#20 machine lube oil)SAE - 30 (#30 machine lube oil)

Sand

Sea water

Sodium hydroxide, 50% (caustic acid)

Sodium hydroxide, 30%Soybean oil

Steel, mild @ 70¬F

Steel, stainless, 300 seriesSucrose, 60% sugar syrup

Sucrose, 40% sugar syrup

Sugar, cane & beetSulfur

Sulfuric acid, 110% (fuming)

Sulfuric acid, 98%Sulfuric acid, 60%

Sulfuric acid, 20%

Titanium (commercial)Toluene

Trichloroethylene

Tetrachloride CarbonTurpentine, spirits of

Vegetables, fresh, average

WaterWines, table, dessert, average

Woods, vary from

WoolZinc

Silk

sp. ht. @ 60°F

Btu/lb-°F0.44

0.42

0.450.62

0.69

0.560.85

0.93

0.2320.415

0.19

0.940.33

0.78

0.840.24-0.33

0.11

0.120.74

0.66

0.300.203

0.27

0.350.52

0.84

0.130.42

0.215

0.210.42

0.73-0.94

1.000.90

0.90

0.3250.095

sp. gr. @ 60-70°F

0.85

0.88

1.7-1.150.86-0.91

0.90

1.071.11

1.05

1.531.10

0.88

0.890.89

1.4-1.76

1.031.25-1.35

1.53

1.330.92

7.90

8.041.29

1.18

1.662.00

1.841.50

1.14

4.500.86

1.62

1.580.86

1.001.03

0.35-0.9

1.327.05

Liquid (L)or

Solid (S)

L

L

SS

L

LL

L

LS

L

LL

S

LS

L

LL

S

SL

L

SS

L

LL

L

SL

L

LL

S

LL

S

SS

AirAmmoniaBenzeneButaneCarbon dioxideCarbon monoxideChlorineEthaneEthyleneFreon - 12HydrogenHydrogen sulfideMethaneNitrogenOxygenPropaneSulfur dioxideWater vapor (steam)

sp. gr. @ 60-70°F

1.000.60

2.001.500.972.501.10

0.97

0.0691.200.550.971.101.50

2.30

sp. ht. @ 60°F

Btu/lb-°F0.240.54

0.3250.4550.21

0.2550.1180.50

0.450.163.420.250.60

0.2530.2250.46

0.1620.453

Table 50-2. Gases

Alphabetical Index

Abbreviations, Gatefold BAir

cause of slow heating,low temperatures, 6effect on steam temperature, 6

Air venting, 12Automatic differential condensate controller, 13Boiler headers, 16Branch lines, 18By-passes, 40Charts Btu heat loss from bare pipe,

17, 21Mean temperature difference, 29Multiplier for selecting traps for draining pipe coils, 22Percentage of flash steam, 3Recommendations, Gatefold, 16, 18, 20, 22, 25, 26, 28, 30, 32, 34, 36, 38

Circles, areas, 48Closed, stationary steam chamber equipment, 32, 33Controlled disc trap, 11Conversion factors, 49Drip leg sizing, 16Embossed coils, 26, 27Evaporators, 28, 29Finned radiation, 23Flash steam, 3Flash tanks, 36, 37Float & thermostatic traps, 10, 11Freezing, protecting traps, 42Individual trapping, 14Inspection of traps, 43Installation, 40, 41, 42, 43Inverted bucket principle, 8, 9Jacketed kettles, 30, 31Leaks, steam, cost of, 7Maintenance of traps, 43, 44Mains

Returns, 45Steam, 16, 17, 18, 46

Pipe coils, 22, 23, 27Pressure differential, 15Process air heaters, 25Recommendation chart, Gatefold, 16, 18, 20, 22, 25, 26, 28, 30, 32, 34, 36, 38Rotating dryers, 34, 35Safety drain trap, 42Safety factors

explanation, 14, 15for different jobs, 16-39

Secondary steam, 3Shell and tube heat exchangers, 26, 27Short circuiting, 14Sizing, pipe and condensate return lines, 45, 46, 47

Sizing, traps for:air handling units, 22autoclaves, 32boiler headers, 16branch lines, 18, 19closed, stationary steam chamber equipment, 32, 33coils

embossed, 26, 27finned, 23pipe, 22, 23, 27space heating, 22, 23submerged, 26, 27

combustion air preheaters, 25concentrators, 30, 31dryers, rotating, 34, 35evaporators, 28, 29finned radiation, 23flash tanks, 36, 37heat exchangers, 26, 27jacketed kettles, 30, 31kettles, jacketed, 30, 31pipe coils, 22, 23, 27platen press, 32process dryers, 25reboilers, 26retorts, 32, 33separators, 19space heating equipment, 22, 23steam absorption machine, 38steam distribution system, 5, 16, 17, 18, 19steam mains, 16, 17, 18, 46steam separators, 19steam tracer lines, 20, 21submerged coils, 26, 27suction heaters, 26tracer lines, 20, 21tunnel dryers, 25unit heaters, 22vaporizers, 26water heaters, 26

Space heating equipment, 22, 23Specific gravity, 50Specific heat, 50Steam

basics, 4-7flash, 3how heat is used, 4leaks, cost of, 7leaks, testing for, 43, 44need for draining, 5tables, 2

Steam absorption machine, 38Steam distribution systems, 16, 17, 18, 19Steam mains, 16, 17, 18, 46Steam tables, 2Steam tracer lines, 20, 21

Steam trapsautomatic differential condensatecontroller, 13controlled disc, 11float & thermostatic, 10, 11inverted bucket, 8, 9thermostatic, 12

Submerged coils, 26, 27Tables, technical, useful information

air, effect on steam temperature, 6circles, area, 48condensing rates in bare pipe, 24constants for determining unit heaterBtu output, 24finned radiation, condensing rates, 24finned radiation, conversion factors, 24leaks, steam, cost of, 7pipe

capacitycondensate, 47steam, 45, 46, 47

conversion factors, 49conversion, lineal feet to squarefeet of surface, 29, 35dimensions, schedule 40, 48equivalent, length of fittings, 48expansion, thermal, 48steam condensed in, due to normal radiation, 17steam condensing during warm-up, 17steam, saturated properties of, 2

temperature reduction caused by air, 6U values,

embossed coils, 27, 29pipe coils, 27, 29

warming up, Schedule 40, 17weight per foot, 19

Testing, trap, 43, 44Thermostatic steam traps, 12Tracer lines, 20, 21Trap selection, 14, 15Troubleshooting, 44Unit trapping, 14U values

embossed coils, 27, 29pipe coils, 27, 29

Water hammer, 5

51

Printed in U.S.A.

Other Products

Handbook N-101 50M 11/97 www.armstrong-intl.com

Y-Type StrainersArmstrong Y-type strainers are manufactured in a widechoice of sizes and materials to meet the bulk of allpipeline straining requirements. Request Bulletin No. 171.

Pumping TrapsArmstrong’s pumping traps are an ideal non-electricsolution for returning condensate in special applica-tions such as evacuating a vacuum, entering apressurized return line or elevating condensate.Request Bulletin No. 230.

ManifoldsArmstrong’s condensate collection and steam distribu-tion manifolds are designed especially for the low loadscommon in the chemical, petrochemical and rubberindustries. Request Bulletin No. 615.

Float Type Drain TrapsThe Armstrong float type drain traps are designedfor draining liquids from gases under pressure or fordischarging water from a light liquid (dual gravity).Capacities to 800,000 lbs/hr. Pressures to 1,800 psig.Request Bulletin No. 402.

Thermostatic Air VentsTwo models available:■ The Model TV-2 is available with straight-through

connections, has a cast bronze body and a 125 psigmaximum working pressure. Request Bulletin No. 455.

■ The Series TTF is available in straight-through orright angle connections. It features an all-stainlesssteel body and is suitable for pressure from 0 to 300 psig.Request Bulletin No. 457.

Training for Energy ConservationBelieving that knowledge not shared is energy wasted,Armstrong appreciates the importance of training andoffers a wide variety of materials, including a library ofmore than a dozen educational video tapes. Many trainingaids are offered free of charge, and others are available ata nominal charge. For a descriptive listing of availabletraining aids, request Bulletin No. 815.

Application assistance is a most important part of thecomplete service provided by Armstrong International.Armstrong Representatives are qualified by factorytraining and extensive experience to assist you. Backingthe Representatives are Armstrong specialists who areavailable to assist with especially difficult or unusualrequirements.

© 1997 Armstrong International, Inc.

®

Armstrong International, Inc.

816 Maple Street, P.O. Box 408, Three Rivers, Michigan 49093 - USA Phone: (616) 273-1415 Fax: (616) 278-6555

Parc Industriel Des Hauts-Sarts, B-4040 Herstal/Liege, Belgium Phone: (04) 2409090 Fax: (04) 2481361

Steam Traps \ Humidifiers \ Steam Coils \ Valves \ Water Heaters \ Air Vents \ Pumping Traps

Steam Guide by Armstrong

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