Boiler Feed pump

Boiler Feed Pump

Basics & Its Construction

Boiler Feed Pump- Heart of the Power Plant.

How to choose a pump for Power Plant.

SYSTEM HEADIt is the total head of a system against which a pump must operate.

Total System Head= (Total static head from supplying level to discharge level+ Discharge pressure) – (Suction Pressure+ Friction losses+ Entrance & Exit losses)

BOILER FEED PUMPS ST-1POWER - 3.5 MW

CURRENT – 361 Amp

SUPPLY – 6.6 KV, 3Φ, 50 Hz

SPEED – 1485 RPM

BFP scheme

Motor speed-1485 rpmBooster p/p speed-1485 rpmMain p/p speed- 4750 rpm

MOTOR

Main p/pBooster p/p

Resilance coupling

Hydraulic coupling

BFP FW scheme

MOTOR

To D/A

Suction v/v

strainer R/C v/v

NRV

Discharge v/v

Transfer line

BPMP

WHY Recirculation ?For minimum FW flow.To avoid churning

BFP discharge header

To D/A

A

B

180 kg

0 kg

180 kg

100kg181kg

BFP(stage-1)

SpecificationNo-3 nos(2X 50%)Main Pump-8 stage centrifugal PumpType-Motor drivenMotor-6.6 KV Motor speed -1485 rpm, 3500 KW.Booster Pump-single stage centrifugal

Main pump

M/S Wier Make. Model-FK8D30.Eight stage horizontal centrifugal pump of the barrel casing design. The pump internals are designed as a cartridge, which can be easily removed for maintenance without disturbing the suction and discharge pipe work, or the alignment of the pump and the turbo coupling.

BFP MAJOR COMPONENTS

BOILER FEED PUMP CARTRIDGE

Shaft Impellers Diffusers Ring Sections Suction Guide Discharge Cover Bearing Housings Bearing Brackets Journal BearingThrust Bearing Mechanical Seals

Mechanical seal

P/p shaftO ringCarbon steel(static)

Tungsten carbide(rotating)

P/p casing

BFP Sealing systemMechanical seals are used in MP & BPClarified water used for seal coolingMechanical seal cooling arrangement in main p/p

Mechanical seal cooler

DM water running in closed ckt

Hot DM cooling water

Cold DM cooling water

Clarified water used for cooling of DM water

Clarified o/l

Thrust balancing

Balancing disc is provided in main p/p

Balance leak off pr-16 ksc.

Balancing Drum.Due to differential pressures acting on the impeller the rotating assembly is subjected to axial thrusts. The balance drum located at the non-drive end is designed to keep these forces neutralised and only the residual thrust remains, which is taken up by thrust bearing.The main components of hydraulic balancing arrangement are the balance chamber machined in discharge cover, the balance drum secured to the shaft and balance drum bush fitted in the bore of discharge cover. The thrust caused by the suction pressure acting on the area inside the wear ring on inlet side of each impeller is overcome by much greater thrust caused by the discharge pressure acting on the equivalent area on the outlet side of each impeller. The resultant thrust is therefore towards drive end of pump. Thrust force varies with load on the pump but hydraulic balance arrangement will reduce its effect enabling residual thrust to be taken by fitting pads of thrust bearing.

BFP Bearing Arrangements

Main p/p - DE side-journal bearing. - NDE side-journal & trust

bearing.

Booster p/p-p/p - DE side-journal bearing. - NDE side-journal & trust

bearing.

Hydraulic coupling - 10 bearings(4 thrust bearings, rest-journal bearings).

BearingsJournal bearings

White metal liner(babbit metal)Thickness-0.5 mm

shaft

Lub oil

Journal bearing

Flexible Coupling

Lub oil scheme

2 no lub oil cooler

AOPAOP motor

MOP(connected to gear box)

Lub oil filter

Oil header

Booster p/p bearings

NRV

Motor bearings Main p/p brg

Return from bearing

Oil tank

Raw water from ARCW discharge

When BFP is in S/B condition motor driven AOP is in service (Cut in Pr-1.2 Ksc), for cooling of bearings, because S/B BFP’s suction v/v is always in open condition & feed water temp. coming from dearator is around 166 Deg C. So BFP metal & Brg. temp. should be always around 160 Deg C, which required cooling even BFP in S/B condition.

AOP discharge pressure- 3 Ksc.

When we give start command to BFP motor driven cut out in auto at 2.3 ksc pr(gear driven MOP will supply lub. oil to bearings .Lub Oil Used in BFP- Servo Prime 46

Main-Motor driven shaft

Meshes with HC gear

Meshes with LO and WO pump gear

Lube oil Working oil pump

Coupled with driven shaft

Auxiliary Lube oil pump

Gear box

MOTOR

Main p/pBooster p/p

Resilance coupling

Gear box & Hydraulic coupling

Gear box

Lub oil p/pWorking oil p/p

Lub oil tank

Hydraulic coupling

1 2

34 5 6 7 8 9 10

* Gear Ratio- 1: 3.3

Working oil scheme

LUB OIL TANK

Regulation control

Working oil make up

drain

Hydraulic coupling

Working oil cooler(2 in number)

Hot working oil Cold working oil

WC p/p

Cooling waterFrom ARCWWOC

MainPump

Oil

MotorCoupling

Gear

Lub Oil header To all bearings

Working oil cooler

Working Oil P/P

Lub Oil P/P

Aux Lub oil P/P

Variable speed thermo coupling

ScoopTube

Regulating Chamber

Motor

Coupling

Lube oil Working oil pump

Coupled with driven shaft

Auxiliary Lube oil pump

Hydraulic Coupling in BFP

Hydraulic Coupling Oil Used- Servo Torque-10

Working oil & Hydraulic coupling Hydraulic coupling used for regulaing BFP speed. Hydraulic coupling is combination of pump & turbine By changing scoop position we can control the Main p/p

speed thus we can control the flow of main p/p

Shaft ConnectedTo motor

P/p

turbine

Driven shaft connectedTo main p/p

Scoop tubescoop

Space filled up with oil

Meshes with motor side gear

Connected to pump shaft

HYDRAULIC COUPLING

Turbine of Hydraulic Coupling: Coupled with

main pump shaft

Hydraulic Coupling bearing Assembly

Slot to fit Scoop-tube

Motor cooler

Motor cooling 2 cooling fans are provided at the both ends of motorCooling air fans sucks cold air which cools motor stator /rotorHot air is cooled by water in the cooler(2 no of cooler provided)Cooling water coming from Aux. Raw cooling water p/p(ARCW p/p)discharge header

Motor cooler

Cold air

Hot air

Motor statorMotor rotor

To WO cooler

Cooling water

BCW v/v

BFP MOTOR

Rotor

Stator

StatorFan Fan

Tray Tray

Cooler CoolerDrain Drain

Bearing Bearing

End Cover

Siphon Drain

BFP motor cooler

Sealing systemMechanical seals are used in MP & BPClarified water used for seal coolingMechanical seal cooling arrangement in main p/pMechanical seal cooling arrangement in main p/p

Mechanical seal cooler

DM water running in closed ckt

Hot DM cooling water

Cold DM cooling water

Clarified water used for cooling of DM water

Clarified o/l

Mechanical seal

P/p shaftO ringCarbon steel(static)

Tungsten carbide(rotating)

P/p casing

Mechanical seal

BFP parameterUCB parameter Normal valueBFP current 290-300ampBFP flow 340 ton/hrBFP(MP) discharge pr 180 kgD/A pr 6.5 kscBFP suction temp 167 degreeBFP suction strainer DP 0.07Drum level +50 mm

Lub oil pr 3 kscLub oil cooler in service normally oneLub oil temp cooler I/l/O/L 60/40 degree

Local parameter

Local parameter Normal value

Working oil pr 1.4 kscWorking oil cooler in service normally oneWorking oil temp cooler I/l/O/L 120/75 degree

Hydraulic coupling max bearing temp 65 degreeMotor air temp 50 degreeClarified water pr 3.5 ksc

Balance leak off pr 16 kscBP suction pr 8 kg

MP suction pr 16 ksc

BFP starting permissive

D/A level normal>800 mmSuction v/v openR/C v/v openBearing p/p& motor temp normal(<75 degree)Lub oil pr normal(>1.5 ksc)Cooling water pr normal>3 kscSuction pr adequate

Protection P/p & motor bearing temp hi-hi(>85 degree) Hyd coupling oil temp Hi-Hi(>130 degree) Lub oil pr low-low(<0.8ksc) Main p/p suction pr low(<8 kg) BFP flow hi-hi(>430 ton/hr-1 minute time delay) EPB pressed Electrical protection

BFP Protections Sr. No.

Parameters Alarm Value

Trip Value / Remarks

1 Motor [DE/NDE] bearing temperature 75ºC 85ºC

2Main pump [DE/NDE] bearing temperature

75ºC 85ºC

3 Lube oil pressure low < 1.2 Ksc< 0.8 Ksc

(Time delay – 5 sec)

4 Working oil temp Hi-Hi 90ºC > 130ºC

5BFP running & Main pump suction pressure low

< 12 Ksc < 8 Ksc

6 BFP Flow Hi-Hi 450 T/hr450 T/hr

(Time delay – 55 sec)

7 Deaerator level low-low550 mm 400 mm

8Emergency Push Button Pressed

BFP Isolations

1. Ensure that pump is in stopped condition.

2. Get the main motor breaker isolated ( Electrical

isolation).

3. Close discharge valve and isolate its electrical supply .

4. Close the suction valve .Ensure there is no rise in

suction press.

5. Open suction strainer, booster pump casing, discharge

line and main pump casing drain valves.

6. Open the transfer line vent, booster pump vent.

7. Close the manual recirculation valve at deaerator level.

8. Stop AOP .Isolate its electrical supply. (bearing temp.<

45ºC)

BFP Normalisations

1. Physically check that work is complete and all men and

materials are removed from site.

2. Get the electrical supply of AOP normalised.

3. Ensure that one lube oil cooler and one working oil

cooler are charged from oil and water side.

4. Check oil level ( It should be more than 50 %)

Start AOP, observe lube oil pressure (It should be more

than 2.5 ksc) and oil filter DP (It should be less than 0.5

ksc).Check return oil flow in all bearings.

5. Open motor cooling inlet/outlet valves .

BFP Normalisations

6. Ensure booster pump,transfer line & recirculation line

vents open , Close all drains. (To avoid pressurisation of

pump).

7. Charge clarified water to mech seal coolers and jacket

cooling. Ensure clarified water Pressure is more than 3

ksc .

8. Open manual recirculation valve at deaerator and

ensure recirculation control valve is open. Also ensure air

supply to recirculation control valve.

9. Crack open suction and observe the discharge through

the vents. Close the vent valves after venting is over.

10. Open suction valve fully and ensure the suction

pressure is adequate.

11. Get the discharge valve and its integral bypass valves

supply, BCW valve supply normalized .

12. Open its discharge valve from UCB, Ensure there is

no reverse rotation of the pump.

13. Get the main motor electrically normalised.

BFP Normalisations

Two lube oil filters provided in BFP Main pump.

1. No charging line provided.

2. No venting provided in both lube oil filters.

Lube oil filter chocked alarm provided in alarm fascia.

(Lube oil filter chocked at DP > 0.5 Ksc)

BFP tripping on lube oil pressure low-low at 0.8 Ksc,

Time delay- 5 seconds.

BFP Lube Oil Filter Change Over.

Lube oil Filter-A in-service

Hydraulic Coupling

Pointer, T shape bottom

For Lube oil filter change over moves the handle in this direction

Match Yellow Mark on Handle & Nut

Lube oil Filter-B in-service

Hydraulic Coupling

Pointer, T shape bottom

For Lube oil filter change over moves the handle in this direction

Match Yellow Mark on Handle & Nut

BFP Lube Oil Filter Change Over.During Changeover :-

Place the handle over nut by matching the Yellow Mark.(Half Yellow mark on Nut & Half Yellow mark on handle)

Slowly rotates the change over handle (180 degree) so that the pointer (bottom part of T) provided in the nut always moves towards the Hydraulic coupling side.

When pointer moves towards Hydraulic coupling- both filters remain in service in pointer mid position.

When pointer moves opposite to Hydraulic coupling- both filters became out of service in pointer mid position.

The pointer (bottom part of T) shows the Lube oil filter in-service.

Observe the rise in DP of filter to be taken in service.

Drum level control

When BLI <20% low range CV i/s , drum level control is single element control it see only drum level)When BLI>20% it becomes 3-element control. steam flow, feed water flow& drum level)Hi range CV try to maintain drum level. (CV opening<100% )BFP scoop try to maintain DP

DP control

FRS Drum level controlled by 1) FRS CV 2)BFP

scoop

BFP

DP

Low range CV

Drum

Drum level control(stage-I)

Initially there was DP controlNow there is two control 1)DP control 2)Scoop control

In Scoop control auxiliary power is saved ,as BFP draw less power

DP control

If drum level increase CV throttle, DP increase(>4 KSC)BFP master DP set point is 4 kscBFP master try to maintain 5 ksc DPBFP scoop will reduce

Scoop control

Drum level is controlled directly by BFP scoop.FRS CV=100% openDP maintained zeroWhen load <70% scoop control to DP control take place

BFP isolation/normalisation

1-Booster p/p strainer drain2-Booster p/p casing vent3-transfer line drain4-transfer line vent5-main p/p casing drain6-discharge line drain7-recirculation line drain