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CM4120Unit Operations Lab

Piping SystemsPiping Systems in the Chemical

Process IndustriesMarch, 2008 Introduction Basis for Design Piping Codes and Standards Design of Process Piping Systems Joints and Fittings Valves

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CM4120Unit Operations Lab

Piping SystemsPiping Systems include:

Pipe Flanges Fittings Bolting Gaskets Valves Hangers and supports Insulations, coverings, coatings

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CM4120Unit Operations Lab

Piping Systems

“Piping systems are like arteries and veins. They carry the lifeblood of modern civilization.”

Mohinder Nayyar, P.E.Piping Handbook, 7th ed.McGraw-Hill, 2000

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CM4120Unit Operations Lab

Piping SystemsPrimary Design Consideration is Safety

Evaluate Process Conditions Temperature Pressure Chemical compatibility/Corrosion allowances Vibration, flexing, bending Expansion/Contraction due to temperature change Environmental conditions

Evaluate the Effects of a LeakEvaluate Performance in a Fire Situation

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CM4120Unit Operations Lab

Piping SystemsSecondary Considerations

Evaluate any Special Requirements Sanitary requirements – “Cleanability” Serviceability – ease of maintenance of

equipment Possible contamination of process fluid by

piping materials, sealants, or gasketing Earthquake, Hurricane, Lightening, Permafrost

Lowest Cost over the Lifetime

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CM4120Unit Operations LabPiping SystemsPiping System Design Criteria4 areas to consider:

Physical Attributes Loading and Service Conditions Environmental Factors Materials-Related Considerations

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CM4120Unit Operations Lab

Piping SystemsCodes and Standards simplify design,

manufacturing, installation processStandards – provide design criteria for components standard sizes for pipe dimensions for fittings or valves

Codes – specific design/fabrication methodologies Incorporated into local/regional statute It’s the LAW

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CM4120Unit Operations LabPiping Systems

ASME Boiler and Pressure Vessel CodeASME B31: Code for Pressure PipingANSI Standards – dimensions for valves, piping, fittings, nuts/washers, etc.ASTM Standards for piping and tubeAPI – Specs for pipe and pipelinesAWS, ASHRAE, NFPA, PPI, UL, etc.

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CM4120Unit Operations Lab

Piping SystemsASME B31 is the applicable standard

for design of most piping systems in chemical plantsB31.1 – Power plant boilersB31.3 – Chemical plant and refinery pipingB31.4 – Liquid petroleum transportB31.7 – Nuclear power plant radioactive fluids

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CM4120Unit Operations Lab

Piping SystemsASME B31.3 – Chemical Plant and

Refinery Piping CodeIncludes:

Process piping in chemical and refinery plantsProcess piping in pharmaceutical and food processingProcess piping in textile and paper plantsBoiler piping

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CM4120Unit Operations Lab

Piping SystemsASME B31.3 covers:

Materials and designFabricationErection and assemblySupportExamination, inspection, and testing

Web reference: www.piping-toolbox.com

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CM4120Unit Operations Lab

Piping SystemsStandard Pipe Sizes

Diameters are “Nominal” Sizes 12” and less, nominal size < OD Sizes 14” and over, nominal size = OD

Wall thickness inferred thru “Schedule” Schedule = P/S * 1000 Defined Schedules:

5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160

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CM4120Unit Operations Lab

Piping SystemsStandard Tubing Sizes

Steel tubing Diameters are Actual OD Wall thickness is specified

Refrigeration Tubing Single wall thickness available for each size Actual OD

Copper Tubing – Nominal sizes Type K, L, M

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CM4120Unit Operations Lab

Piping SystemsMaterials – Metallic piping

Carbon and low alloy steel Ductile Inexpensive and available Easy to machine, weld, cut Some drawbacks

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CM4120Unit Operations Lab

Piping SystemsMaterials – Metallic piping

Alloy Steels including “Stainless Steels” Good corrosion resistance More difficult to machine, weld, cut Some drawbacks

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CM4120Unit Operations Lab

Piping SystemsMaterials – Metallic piping

Nickel, Titanium, Copper, etc. Copper is used in residential and

commercial applications and is widely available

Other materials are expensive and difficult to machine, weld, join

Some incompatibilities with each

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CM4120Unit Operations Lab

Piping SystemsMaterials – Non-Metallic piping

Thermoplastics Wide range of chemical compatibility Light weight Easily cut and joined Low temperature limits Need extra supports

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CM4120Unit Operations Lab

Piping SystemsMaterials – Non-Metallic piping

Fiberglass Reinforced Pipe Wide range of chemical compatibility Easily cut and joined Wider temperature limits than thermoplastics Thermal expansion similar to carbon steel Similar structural performance as carbon steel

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CM4120Unit Operations Lab

Piping SystemsMaterials – Others

GlassConcreteLined or coated

Glass Rubber Cement Teflon Zinc (galvanized pipe)

Double Containment piping systems

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CM4120Unit Operations Lab

Piping SystemsPiping Insulation

Prevent heat loss/ gainPrevent condensation – below ambientPersonnel protection – over 125oFFreeze protection – outdoor cold climatesFire protectionNoise control

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CM4120Unit Operations LabPiping SystemsFiberglass Insulation w/ Asbestos

plastered fitting coverings

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CM4120Unit Operations LabPiping Systems

Metal Jacketedinsulation

covering

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CM4120Unit Operations Lab

Piping SystemsHeat Tracing

Prevents flow problems in cold climates Freeze protection Loss of flow due to viscosity increase

Prevent condensation in vapor linesMethods Electric Hot Fluids

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CM4120Unit Operations Lab

Piping SystemsPiping Supports

Prevent strain at connectionsPrevent sagMust allow for expansion/contractionDesign for wind/snow and ice/earthquakeClearance for plant traffic and equipment

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CM4120Unit Operations LabPiping SystemsResults of inadequate support

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CM4120Unit Operations LabPiping SystemsResults of inadequate support:

Flixborough, EnglandMay, 1974 – Leaking reactor removed from

train of reactors and temporarily replaced with a section of pipe

June, 1974 – Supports collapse, pipe breaks28 dead, 89 injured, 1800 houses damaged, 160 shops and factories damaged, large crater where plant stood

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CM4120Unit Operations LabPiping SystemsThe Design Process – a three step

approachDesign for Flow Find min. diameter to achieve desired flow

velocityDesign for Pressure Integrity Find min. wall thickness for process and

external conditions Find appropriate rating of in-line components

Re-check for Flow Criteria

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CM4120Unit Operations Lab

Piping SystemsDesign for Flow

Determined by economicsPiping system must provide reliable service

for expected lifeSmallest diameter usually is lowest cost

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CM4120Unit Operations LabPiping SystemsTypical design velocity Rules of

Thumb when sizing piping...Water lines: 5-7 ft/secPump discharge: (d/2 + 4 ft/sec)Pump suction: (1/3 * discharge velocity)Steam: d in 1000 ft/minSlurries: > min. entrainment velocity

d = I.D. of pipe in inchesfrom Rase and Barrow, Project Engineering of Process

Plants, John Wiley, New York, 1957.

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CM4120Unit Operations LabPiping SystemsNext determine wall thickness:

Pressure Integrity Design methodASME B31.3,

APySE

PDtm

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tm=min. wall thicknessP=design pressure, psigD=O.D. of pipe, in.S=allowable stress, psi

E=weld joint efficiencyy=factor to adjust for

tempA= add’l thickness for

corrosion, external loads, etc.

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CM4120Unit Operations LabPiping SystemsFinally re-check ID

Select in-line components

Determine insulation, coverings, coatings

Design and locate supports and hangers

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CM4120Unit Operations LabPiping SystemsEffect of Thermal ExpansionExample:Calculate the expansion per 20’

length of 2”, schedule 40 carbon steel steam line at boiler startup for a 100 psig steam service.

α=thermal expansion coefficientfor mild steel, α =6.6x10-6 in/inoF

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CM4120Unit Operations LabPiping SystemsTemp of pipe at amb. cond. =70oFTemp of 100 psig sat. steam =338oFΔT=268oFL=20’=240”expansion due to temperatureincrease is α *L* ΔT

=(6.6x10-6in/inoF)*(240in)*(268oF)=0.42” in per 20’ of pipe

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CM4120Unit Operations LabPiping SystemsWhat force is exerted on the end

restraints of that 20’ pipe if it is rigidly installed (end restraints can’t move)?σ=internal stress due to ΔT, and σ = α *(ΔT)*E

E is the material property called Modulus of Elasticity, relationship between stress and strain

E=30x106 psi for low carbon steel

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CM4120Unit Operations LabPiping Systemsσ= α *(ΔT)*E

=(6.6x10-6 in/inoF)*(268oF)*(30x106lbf/in2)=53,000 lbf/in2

since σ=F/A, F=σ*Awhere: F=force on end restraints

A=cross sec. area of 2”, sched 40 pipe

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CM4120Unit Operations LabPiping SystemsA=Π(OD2-ID2)/4

= Π(2.3752-2.0672)/4=1.07 sq.in

F= σ*A=(53,000 lbf/in2)*(1.07 in2)Force on the end restraints =57,000 lbf

or 28.5 tons

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CM4120Unit Operations Lab

Piping SystemsPipe Joints

Threaded Welded Soldered/ Brazed Glued Compression Bell and spigot Upset or expanded

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CM4120Unit Operations LabPiping Systems

Threaded joints

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CM4120Unit Operations LabPiping Systems

Soldered joints

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CM4120Unit Operations LabPiping Systems

Welded joints

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CM4120Unit Operations LabPiping SystemsCompression joints

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CM4120Unit Operations LabPiping SystemsMechanical joints

shown on glass drain piping system

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CM4120Unit Operations Lab

Piping SystemsPipe Fittings

Forged Cast Malleable Iron

Pressure/Temperature Rated by “Class” 125, 250, or 2000, 3000, etc. Need a look-up table to determine max.

allowable P for the design temperature

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CM4120Unit Operations LabPiping SystemsFittings for joining 2

sections of pipe:Coupling

Reducing Coupling

Union

Flange

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CM4120Unit Operations LabPiping Systems

Fittings for changing directions in pipe:

45o Ell

90o Ell

Street Ell

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CM4120Unit Operations LabPiping Systems

Fittings for adding a branch in a run of piping:

Tee

Cross

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CM4120Unit Operations LabPiping Systems

Fittings for blocking the end of a run of piping:

Pipe plug

Pipe cap

Blind Flange

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CM4120Unit Operations LabPiping Systems

Misc. pipe fittings:Nipple

Reducing bushing

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CM4120Unit Operations LabPiping Systems

Gate Valve:Used to block

flow (on/off service)

Sliding “gate”on knife-gatevalve

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CM4120Unit Operations LabPiping Systems

Globe Valve:Used to

regulate flow

Cut-away showsstem seal

plug and seat

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CM4120Unit Operations LabPiping Systems

Ball Valve:Typically used

as block valve

“Quarter-turn” valve

Cut-away shows ball and seat

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CM4120Unit Operations LabPiping Systems

Butterfly Valve:

Can be used for flow control or on/off

Valve actuator/ positioner for accurate flow

control

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CM4120Unit Operations LabPiping Systems

Check Valves:Used to prevent

backflowPiston check

Swing check

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CM4120Unit Operations LabPiping SystemsReferences:

Piping Handbook, 7th ed., Nayyar, McGraw-Hill, New York, 2000.Piping Design for Process Plants, Rase, John Wiley, New York, 1963.Valve Handbook, Skousen, McGraw-Hill, New York, 1998www.flowserve.com, Flowserve Corp., Sept. 2004.www.engineeringtoolbox.com, The Engineering Toolbox, Sept. 2004.