Desuperheater Equipment&System

Desuperheating Equipment & Systems

2 Weir Power & Industrial First choice for power and industrial protection

BlakeboroughDESUPERHEATING EQUIPMENT & SYSTEMS

BD 1-0207

3Weir Power & Industrial First choice for power and industrial protection

Blakeborough DESUPERHEATING EQUIPMENT & SYSTEMS

BD 1-0207

Quality assurance

Weir Power & Industrial operates qualityprogrammes to cover the full scope of theiractivities. Comprehensive quality systems have beendeveloped to serve the power, oil and gas andindustrial markets which they serve.

The company holds approvals to:

ASME Section III N, NPT, NV

ASME Section I V

BS EN ISO 9001:2000

API Q1 TO API LICENCES API 6D (6D-0182) ANDAPI 6A (6A-0445)

TUV - AD MERKBLATT WRD HP 0

The Quality systems have been approved for thesupply of products to meet the requirements of thePressure Equipment Directive (PED) and compliancemodules A,D1,H,B&D have been applied incategories I through IV respectively.

The company is committed to compliance withlegislation and has an established environment andhealth and safety policy.

Valve Testing Facilities

All pressure containing items are hydrostaticallytested, seat leakage tested and functionally tested.In addition, gas, packing emission, cryogenic andadvanced functional testing can be arranged.

Material testing facilities

Non-destructive examination by radiography, ultrasonics, magnetic particle and liquid penetrant.

Chemical analysis by computer controlled direct reading emission spectrometer.

Mechanical testing for tensile properties at ambient and elevated temperatures, bend and hardness testing. Charpy testing at ambient, elevated and sub-zero temperatures.

Further technical information can be obtained fromour Web site: http://www.weirpowerindustrial.com

6A-04456D-0182

BLAKEBOROUGHThe Control Valve business unit have designed andmanufactured valves for in excess of 50 years. Theircontrol valve product range offers an extensivechoice in terms of size, pressure class, body/trimmaterials, and includes top, top & bottom guidedand cage guided valves. In addition they also supplya wide range of desuperheating equipment tosatisfy power and steam conditioning applications.



BD 1-0207

Pipeline desuperheaters

BV985 - Variable Probe Spray Nozzle

Large range of design Cv options

High rangeability

Swirl chambers and conical nozzles for optimumatomisation

Pipe sizes 150mm (6) and above

Interchangeable nozzles

BV986 - Fixed Area Spray Ring

Pipe sizes 25mm (1) and above

CV designed for each application

Simple and inexpensive system

BV987 - Desuperheater Pipe

Desuperheater pipe and optional liner

BV988 - Fixed Area Probe

Multi nozzle for optimum dispersion in steam flow

Combined temperature & pressure reducingequipment

BV994 - Globe Design

BV995 - Angle Design These units offer an excellent combination ofpressure and temperature control in one cost-effective unit.

Pressure Ratings

ANSI Class 150 to ANSI 4500

PN10 to PN640

Sizes

Inlet - 40mm (112) to 500mm (20)

Outlet - 40mm (112) to 1000mm (40)

Design Features

Large range of trim design options - standard tolow noise

Outlet section for improved mixing and noisecontrol

Spray water injection away from control/seat facesto eliminate problems of thermal shock anderosion

Optional pilot balanced design for tight shut off

Proven design



BD 1-0207

MN1 MN2 MN3 MN4 MN5 MN6

0.5 0.9 1.5 2.7 4.7 8.0

TABLE 1 Nozzle design CV

TABLE 2 Branch height & actuator mount

dimensions

Water Flange OrientationThe pipework inlet flange can be arranged tosuit customers pipework configurations.

BV985 - Variable spray unit

General

The BV985 multi nozzle desuperheater is a provendesign used in thousands of installationsthroughout the world. The latest version offersincreased CV ratings and improved rangeabilitywith the option of modified characteristics.

Design Details

The standard model incorporates 12 carefullyspaced spray nozzles for optimum dispersion inthe steam flow, and to minimise coalescence ofthe droplets.

Nozzles arranged so that at low steam flowswater is injected into high turbulence zone of thevortices shed from the desuperheater probe.

Nozzle design incorporates swirl chambers andconical nozzle for optimum atomisation even atlow superior pressures.

Nozzle assemblies can be characterised to suitprocess requirements and nozzle selection can bechanged after installation.

Standard Design Options

Water inlet connection size 25mm, 40mm and50mm (1, 112 and 2)

Connection - flanged, socket weld

Ratings - ANSI 150 to ANSI 2500

Nozzle sizes (see table 1)

Superior Pressure 1 bar to 50 bar (15psi to 740psi)

Nozzle Rangeability - up to 40:1

OptionalHandwheel

Diaphragmactuator

Positioner

Water inlet flange

Desuperheater Pipe(optional extra)

N

MK

L

Pipe to fall towards drain port.Inclination approx 20 mm per munder working conditions.

1 metre

Steamflow

Airsupply

Filterregulator

Refer to Actuator catalogues for dimensions.

Standard Travel 57mm(2 14)Yoke Mtg 89.5mm (3 916)

Typical arrangmentusing BV985 Mark II

Shown with manuallyoperated isolatingvalve

Mainsteamsupply

Hopkinsonsparallel slidevalve

Filterregulator

Positioner

BV500control valvepressurereducing

Filterregulator

Positioner

From temperature loop

Water supply

BV985 Mark II Variable orifice multi-nozzleReduced/Desuperheatedsteam

From pressure loopBV987Desuperheater pipe

SPRAYUNIT

B

A

D

C

Steamflow

BV987 Branch Height Act. MountPipe Size mm L K

150 177 382200 200 405250 226 431300 251 456350 277 482400 302 507450 327 532500 350 555600 372 577650 416 621700 454 659750 480 685800 501 706850 517 722900 547 752

Rating M N

600lb 135 133900lb & 1500lb 184 167

2500lb 210 200



BD 1-0207

BV986 - Fixed area spray ring

General

This unit offers a relatively simple and inexpensivesolution for applications which have low rangeabilityand stable steam demand. The system consists of aspray ring together with a separate spray watercontrol valve. The spray water control valveregulates the flow into an annular feed within thespray ring body. This annular feed passes water intoa number of holes to produce a series of radial jetsinto the steam flow, which assist in the mixingprocess.


Body size - 25mm to 200mm (1 to 8)

Ratings - ANSI 150 to ANSI 2500

Nozzle size designed for specific application

Superior Pressure 1 bar to 50 bar (15psi to 740psi)

Rangeability - up to 8:1 on steam flow

BV987 - Pipeline desuperheater pipe

The BV987 desuperheater pipe offers a convenientmethod to install either the BV985 or the BV988.It is available in sizes from 150mm to 900mm (6to 36).

An 80mm (3) branch flange is provided formounting the desuperheater. The desuperheaterpipe can be supplied in carbon steel or chromemoly. Desuperheater pipes can be supplied withprotective liners when the service conditionsindicate the possibility of thermal shock or toincrease the steam velocity.

BV988 - Fixed area probe

General

This multi-nozzle desuperheater can be fitted intoline sizes >= 6. The nozzle head is the same asused in the BV985 incorporating up to 12 nozzles.The spray water is regulated by a separate spraywater control valve.


Refer to BV985 section

Rangeability - up to 8:1 on steam flow

FACE TO FACE DIMENSIONS

Bore (mm) 25 40 50 80 100 150 200

Dimn (mm) 80 80 80 150 150 150 150

DESIGN CV

MD1 MD2 MD3 MD4 MD5 MD6 MD7 MD8 MD9 MD10

0.03 0.04 0.06 0.1 0.14 0.2 0.4 0.63 1.0 1.4

TABLE 3 Pipeline desuperheater standard materials

Spraywater

Superheatedsteam

Pipe to fall towards drain port.Inclination approx 20 mm per m

under working conditions.

1 metre

Desuperheatedsteam

BV987 Desuperheater Pipe(optional extra)

BV988 Mark IIFixed orifice type

Component BV985/BV988 BV986

Body 427 C Chrome Moly Chrome Moly

Spray unit head 316 L st.st.

Seat 316 L st.st.

Plug/Stem 316 L st.st. + stellite face

Nozzles 316 L st.st.

Swirl Inserts 316 L st.st.



BD 1-0207


Pressure Ratings

ANSI Class 150 to ANSI Class 4500

PN10 to PN640

Sizes

Inlet - 40mm to 500mm (1 12 to 20)

Outlet - 40mm to 1000mm (1 12 to 40)

Trim Options

Multi-flow, Cascade 2/3/4/5

Combined steam reducing & desuperheatingunit

BV994 & BV995 units

ApplicationThe BV994 and BV995 range of valves have beendesigned specifically for the control of processsteam to meet the various pressures andtemperatures required throughout the plant. Itcan also be specified to work in parallel with aturbine to supplement the supply of steam toprocess, also on turbine by-pass duties where thevalve dumps the flow directly to the condenser orto cold reheat.

DesignThe unit consists of a steam pressure reducingvalve, either of angle or globe body configuration,with a specially designed outlet incorporating aspray water injection system and a combinedmixer/silencer.

Conditions usually associated with this service arehigh pressure drop in the critical flow regimeleading to sonic conditions across standard trimdesigns. The BV994 and BV995 units can be fittedwith either multiflow or cascade trims. These trimsare able to handle the severe service conditions ofthis application without the by products ofvibration, erosion and high noise levels.

The type of plug generally used in this valve seriesis a balanced design to reduce the actuator loadrequirements. This design equalises the pressureabove and below the plug in the open positionthereby significantly reducing actuator loads. Afurther advancement on this design is the pilotbalanced plug, which enables ANSI Class V shut-off to be achieved without the need of high thrustactuators. This design incorporates two plugs (onewithin the other), which creates a high integritysealing system.

The spray system consists of either a spray ringand separate spray water control valve, or a probetype variable spray unit, BV985, depending onsteam turn down requirements. The spray water isnormally injected before a series of baffle plates,which act to improve desuperheating efficiency.The baffle plates are carefully calculated toproduce further stages of pressure drop andimproved mixing of the steam and spray water.

The main steam valve and the spray water valvesare commonly fitted with pneumatic diaphragm orpiston actuators, fitted with positioners foraccurate response.

Valves with low noise trim and outlet silencers destined for a desalination plant in the MiddleEast.



BD 1-0207

Turbine bypass systems

Blakeborough have over 40 years ofexperience in design and manufacturingvalves and desuperheaters. Equipment hasbeen supplied throughout the world rangingfrom small process applications through tolarge power generating installations.

Typical Scope of Supply

High pressure by-pass control valve

High pressure desuperheater

High pressure spray water control valve

IP by-pass control valve

IP desuperheater

IP spray water control valve

Low pressure isolation valve

LP by-pass control valve

LP desuperheater

LP spray water control valve

Schematic of Turbine Bypass System

SUPERHEATSPRAY

ATTEMPERATOR

ATTEMPERATOR

N.R.V.

H.P. STEAMBY-PASS

DESUPER-HEATER

REHEATSPRAY

H.P. TURBINE

I.P. & L.P.TURBINE GENERATOR

CONDENSER

DUMP TUBE

FEEDPUMPS

P

H.P. HEATERS

FLUEGASES TO STACKFUEL

DISTRIBUTIONDAMPERS

DEAERATOR

L.P.SPRAYVALVE

P

L.P.HEATERS

MAIN FEED & START-UPREGULATING VALVES

ELECTRICALOUTPUT

L.P. STEAMISOLATING

VALVE

L.P. STEAMBY-PASS

DRUM

COMBUSTIONCHAMBER

SEC.SUPER-HEATER

ECONMS ECONMS

PRIM. SUPER-HEATER

REHEAT

Design Features

Angle or globe designs.

Tight shut-off with pilot operation to maximiseefficiency.

Cage guided plugs to eliminate vibration potential.

Multi-stage low noise trims.

Erosion resistant trim materials selected which alsoprevent galling and the effects of thermal cycling.

Pneumatic or electro-hydraulic actuation.

Variable spray designs.

Ancillary instrumentation to give fast response,whilst maintaining stable operation.

HP turbine bypassdesuperheater for combinedcycle power plant LP turbine bypass

desuperheater for combinedcycle power plant

Final required degrees of superheat, degrees F.

Final required degrees of superheat, degrees C.

100 80 60 40 20 110 90 70 50 30 10

5

6 8 10 12 14 16 18 20metres

kJ/kg

550

500

450

400

350

300

250

200

150

100

50 Min

imu

m d

ista

nce

7.5

m

EnthalpyChangeGraphs

180 140 100 60 20200 160 120 80 40

10

20 25 30 35 40 45 50 55 60 65 feet

Btu/lb

250

225

200

175

150

125

100

75

50

25

0

Min

imu

m d

ista

nce

25

fee

t

d

300(d = pipe dia. mm)

Graphs based upon 300mm pipe size. For other sizesmultiply distance by



BD 1-0207

Should the recommended location for the temperaturesensing point coincide with a pipe bend, then the sensingpoint should be moved a further two metres downstream.Examples on use of the above graphsSteam pressure 10 bara. Saturation temperature 180C.Required outlet temperature 200CSteam Inlet enthalpy 3253kJ/kg Enthalpy changeSteam Outlet enthalpy 2829kJ/kg 424 kJ/kgFinal required degrees of superheat = 200-180 = 20CDraw line from enthalpy change to intercept degrees ofsuperheat line, read off minimum distance = 15.2 metres.Spraywater TemperatureEffective desuperheater operation depends upon the correctamount of spraywater introduced into the steam flow. Ifthe steam or water temperature conditions dictate a wateraddition of greater than 20% of the steam mass flowunder normal conditions then a two stage nozzle systemmay be necessary. To limit the amount of water enteringthe steam to an acceptable level a maximum watertemperature can be calculated using the followingformulae.Tmax = (P + 0.5DS - 1.427h + 630) C MetricTmax = (0.125P + 0.5DS - 6.1h + 1190) F Imperialwhere P = absolute steam pressure bara (psia)DS = final required degree of superheat C (F)h = enthalpy change from inlet to outlet kJ/kg (Btu/lb)Ideally the water temperature should be within thefollowing range for satisfactory operation:-(TSAT - 100) C < TWATER < (TSAT - 5) C Metric(TSAT - 210) F < TWATER < (TSAT - 10) F Imperialalso applying the maximum water temperature limitationswhen applicable (TSAT is the stream saturation temperature).

Initial calculationsCalculate the required flow of water WW, kg/hr (lb/hr),needed to control the steam temperature at the outlet,by the heat balance method.WW = WS (h1 - h2)

(h2 - hF)where h1 = enthalpy of superheated steam at inletwhere h2 = enthalpy of steam mixture at outletwhere hF = enthalpy of spraywater at inletvalues in kJ/kg (Btu/lb)Total outlet steam flowrate WM = WS + 2W kg/hr (lb/hr)Sizing of low pressure pipelineThis is the recommended pipe size for BV985, BV986 andBV988 pipeline types, or the outlet size for the BV995design for efficient desuperheating.

The pipe is sized so that the steam velocity does not exceed90m/s (300ft/s) or, for BV985, BV986, BV988 types, fall below4.5m/s (14ft/s). The preferred velocity is 75m/s (250ft/s).

The minimum pipe diameter is calculated using thefollowing formulae.

For BV985, BV986 and BV988 desuperheaters there is aselection of standard trim sizes available

BV995 units are often associated with outlet silencersections depending upon the ratio of inlet and outletpressures and the maximum permissible sound pressure.For these reasons each unit receives individualconsiderations based upon customer requirements.

Distance to temperature sensing pointDepending upon the amount of superheat required in thesteam after desuperheating, the minimum recommendeddistance to the temperature sensing point can bedetermined from the graphs shown. To ensure completemixing and absorption of the injected water therecommended distance increases as the steam saturationtemperature is approached.

Information required at enquiry stage

D = 18.8 mm or D = 0.225 in.

where WM = outlet steam flowrate kg/hr (lb/hr)

where VS = outlet specific volume m3/kg (ft3/lb)

Velocity m/sec (ft/sec)

WM x VSVelocity

WM x VSVelocity

}

Initial sizing of desuperheaters

P1 Inlet Pressure Bara (Psia)T1 Inlet temperature C (F)P2 Required outlet pressure Bara (Psia)T2 Required outlet temperature C (F)PW Available spraywater pressure Bara (Psia)TW Spraywater temperature C (F)WS Maximum inlet steam flow kg/hr (lb/hr)Controlled temp. should be higher than 5 C (9 F) above saturation point.



BD 1-0207

The pipes connecting the water supply to theinjection nozzle should be no less in diameter thanthe water isolating valve flange connectionsindicate.

Condensate supply should be free from debris andeffectively filtered to less than 0.25mm.

Lagging of pipes

The fact that a desuperheater is a device forreducing the steam temperature sometimes leadsto the mistaken impression that the lagging ofsteam and water pipes is not important. Unlike theabsorption of heat by the spray water, any loss ofheat should be avoided. Unless the pipework canbe maintained at the proper temperaturesuccessful desuperheating may not be possibleand a preliminary trial of a plant before it hasbeen lagged may prove disappointing.

Design & installation of pipelinedesuperheater systems

Location in pipework

The desuperheater should be installed so that thespray nozzle is located at the steam inlet of the tube(if supplied). A filter should be fitted in the spraywater inlet line to prevent ingress of dirt.

Pipe Joints

Owing to the severe expansion strains which maybe imposed on the joints when starting up it isessential that all flange joint bolts aremanufactured from high tensile alloy steelirrespective of the steam pressure. These remarksalso apply to the water joint flanges which arealso subject to sudden temperature changes.

Drainage and drainage systems

Efficient drainage of the pipework following thedesuperheater is essential. To ensure that watercannot accumulate at any point the pipe shouldbe arranged to fall in the direction of flowapproximately 20mm per metre (14 per foot)under actual working conditions and be providedwith an efficient large capacity trap (10% ofmaximum flow to facilitate start-up and shut downof plant) at the lowest point. To prevent the trapbecoming airbound the drain pipe should haveample capacity to deal with the drainage and befixed as near to vertical as possible. There must besufficient space in the drain pipe for water to flowdown and air to pass up the pipe.

When starting up the plant it is advisable to openthe trap by-pass valve to deal with any excesswater. If a by-pass valve is not fitted the trapshould be inspected to ensure that it is passingwater and has not become airbound. When thepipework has warmed through to workingtemperature and a reasonable amount of steam isflowing the drainage of water should practicallycease and the trap by-pass valve can then beclosed.

Successful operation of a desuperheater dependsto a large extent on the injection of water beinghot, preferably near to the saturation temperatureof the steam to be cooled so that it is mainly thelatent heat which is extracted from the steam toevaporate the injected water. This minimises thetime of the suspension of the water particles in thesteam so that all the water is evaporated and nonefalls to the inside walls of the pipework. Asmentioned below the pipes connecting the watersupply to the injection nozzle should be efficientlylagged to minimise the loss of heat.

The water pressure and temperature should be noless than the values originally specified at theenquiry/order stage since these figures are usedfor design purposes in sizing the injection nozzle.



BD 1-0207

Design & installation of pipeline desuperheater systems

SELECTION CHART

PRESSURE REDUCINGAND DESUPERHEATING

DESUPERHEATINGONLY

1YES2

YES3

YES4

YES NO

NO

NO

5

NO

NO

NO

NO

NOYES

YES8

YES

YES6

7

1 Is inlet pressure rating less than PN250?

2 Is inlet pressure rating greater than PN100 and outlet pressure rating less than PN100?

3 Is outlet pipe size greater than 100mm?

4 Is steam flow variable?

5 Is outlet pipe size greater than 100mm?


7 Is pipe size greater than 100mm?


RECOMMENDED SYSTEM

BV985 MARK II

BV988 MARK II

BV986

BV994/5

USED IN CONJUNCTION WITHCONTROL VALVE OF SERIES STATED

BV990

BV990

BV990

BV500

BV500

BV500

NOTE:- This chart is for guidance only.Other factors, such as customerconditions or special requirementsmay result in a different systemthan recommended by this chart.

Britannia House Huddersfield Road Elland, West Yorkshire HX5 9JR England

Tel: +44 (0) 1422 282 000Fax: +44 (0) 1422 282 100Email: [email protected]

ExcellentPower & IndustrialSolutions

Weir Power & Industrial UK Ltd

BD 1-0207

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Desuperheater Equipment&System

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