trombay tps july : 2011 volume : 15 - bhel - pssr · pdf filetrombay tps july : 2011 volume :...

1 JULY 2011 TS TIDINGS

TECHNICAL SERVICES / PSSR

TROMBAY TPS JULY : 2011 VOLUME : 15.02

Published by Technical Services / PSSR For internal circulation

HIGHLIGHTS

NALCO DAMANJODI UNIT 5 :

BOILER REACHED FULL LOAD.

RAICHUR UNIT 8:

BOILER PG TEST WAS COMPLETED.



INSIDE

1. STATUS OF PROJECTS COMMISSIONED / TO BE COMMISSIONED DURING 2010 - 2012.

2. SERVICE RENDERED TO OTHER REGIONS/SAS/PROJECTS AFTER

CONTRACT CLOSING/ CUSTOMER TRAINING.

3. APPRECIATION FROM CUSTOMER FOR SERVICES RENDERED.

4. FEED BACK ON EQUIPMENTS FROM SITES.

5. LET US KNOW. FEED WATER HEATER GROUP PROTECTION VALVES

Feed backs and suggestions from all departments of BHEL for improvement of TS TIDINGS are welcome and may please be addressed to ADDL. GENERAL MANAGER (TSX)/BHEL-PSSR/CHENNAI



STATUS OF PROJECTS COMMISSIONED / TO BE COMMISSIONED DURING 2010 – 2012:

BELLARY 500 MW UNIT 2:

MS-001 & 002 MOVs were commissioned locally.

PRDS interconnecting headers hydraulic test was completed.

ESP – B pass air leak test was completed.

Ash handling system vacuum pump house LT MCC CT and relay testing was carried out,

SAT-2 protection checking was completed.

ID fan A IGV remote commissioning was completed.

220 V DC station battery bank – 1 charging was done.

MDBFP lube oil piping acid cleaning was carried out.

SG DMCW over head tank, suction header, discharge header flushing was completed. TG DMCW system suction line flushing was completed.

MDBFP main motor winding resistance and motor direct electrical testing was carried out.

Spring compression test for mills A,B & c was completed.

TG DMCW A & B, SG DMCW A motor relay testing was carried out.

CW pump house LTMCC outgoing feeders checking was done.

Boiler is under wet preservation.

CPCL PHASE 3 - UNIT 4:

GT lube oil system centrifuge was commissioned.

110V DC battery bank – 1 & 2 : Charging and discharging cycle was completed and battery bank – 1 was put into service.

110 V DC battery charger - 2 load test was carried out.



Turbine load gear box to generator alignment was completed.

GT MCC and PMCC interlock and protection checks were demonstrated to customer.

SAT 1 & 2 oil filtration was completed. SAT 1 & 2 short circuit test was completed.

Lube oil mist eliminator fan – 1 trial run was completed.

ELDB transformer testing was carried out.

KAKATIYA 500 MW UNIT 1 :

Unit tripped on 07.07.2011 due to GT differential protection. TG barring gear got stopped.

Re-erection of repaired CC pump was carried out by customer.

ESP C & D pass: 1st and 2nd field found damaged due to ash evacuation problem. Attended by customer.

Barring gear did not resume even after cooling down to ambient temperature. Jacking oil pressures adjusted. Seal clearances checked. HP rotor float was found less. After repeated trials of moving HP and IP casing, the casing float values and centering were achieved. Barring gear was resumed on 23/07/2011.

Unit was synchronized back on 25/07/11.

Unit was running around 350-400 MW. Unit was shut down on 31/07/11 due to economizer tube leakage.

KOTHAGUDAM 500 MW, UNIT 1:

Coal feeder – A recalibration was completed.

Unit was hand tripped on 02.07.11 due to leak found in PW system.

ESP passes - B, C & D – CERM, EERM motors trial run was carried out.

Auto synchronizer off-line checking was completed.

LRSB - 33 nos. were commissioned.

Unit was synchronized on 10.07.11 and loaded to 190 MW.



PA fan – A motor trial run was carried out after repair work and coupling was completed.

Mill – E was run and ring role setting was completed.

PA fan – A outlet gate problem was attended and fan was taken into service on 12.07.11.

Unit tripped on 14.07.11 due to generator over voltage protection.

Unit was synchronized on 15.07.11 for the first time with auto synchronizer.

Turbine was rolled for the first time through ATRS.

Mill – F trial run was completed.

H2 gas drier compressor was taken into service.

TDBFP – B – Solo run was completed and actual over speed test was also carried out.

Four hours trial run of Mill – D was completed after coupling replacement.

Feeder – E tracking and calibration was completed.

Feeder – F calibration was completed. KUTTIYADI 2 x 50 MW UNIT 1:

Unit is not in service since 08.07.2011 due to dam level low. Bus duct IR value was found to be low and after attending to the same, unit was brought back into service on 14/07/2011

Unit is under shut down from 25/07/2011 to attend to the deflector feed back mechanism for resolving the runner pitting problem.

KUTTIYADI 2 x 50 MW UNIT 2:

Unit is in service at half load due to nozzle 3 VRVT failure.



NALCO -120 MW UNIT 9:

Unit was under shut down from 04.07.11.

Unit was lighted up and synchronized on 07.07.11 and loaded to 109 MW.

Presently unit is running around 110 MW.

NALCO – 120 MW UNIT 10:

Unit was under shut down since 27.05.11 for carrying out maintenance work.

TG PG test pressure points and temperature points erection was completed.

Condenser On Load Tube Cleaning System COLTCS erection work (piping) was completed. Commissioning of COLTCS by M/s GEA Engineer is in progress.

HPCV passing problem was attended.

Wall blower pending material assembly was completed.

All the 20 nos. of LRSBs mechanical freeness checking was completed.

NALCO – DAMANJODI UNIT 5:

Sox and Nox panel erection work was completed.

Boiler was lighted up on 05.07.11.

Unit tripped on 12.07.11 on drum level low. Boiler was boxed up.

Boiler was lighted up on 18.07.11.

UNIT REACHED FULL LOAD ON 29.07.11 WITH BOTH MILL AB & MILL CD IN SERVICE.

Boiler was boxed up on 30.07.11, as no steam demand was there from customer. Unit planned to restart on 01.08.11.



NEYVELI TS II EXP CFBC, 2 X 250 MW, UNIT 1:

BFP-1C – 8 hours trial run was completed.

DMCW–1B - 4 hours trial run was completed.

Empty chamber pipe correction to match the blower and FBHE was completed.

ID fan – A inlet gates A1 & A2 were commissioned.

ESP – B pass outlet gates B1 & B2 were commissioned.

Lignite – transport feeder - B & D trial run was done after the required adjustments.

Wind box welding of FBHE – 4 bundle chamber was completed.

Empty chamber wind boxes - 1 & 4 leakages were arrested and found to be alright.

HPBP – BP1 actuator assembly was dismantled from unit - 2 and assembled on unit -1. Operation from DCS was checked and found to be alright.

Link assembly of Lignite transport feeders – A & C was completed. No load trial run was done for 30 minutes.

Bearing – 7 housing crack rectification and matching was completed.

DMCWP -1A was run. NEYVELI TS II EXP CFBC, 2 X 250 MW, UNIT 2:

BFP – 2A oil flushing is in progress. RAICHUR – 1 x 250 MW UNIT 8:

Unit is running around 210 MW.

Boiler PG test at 100% BMCR was completed on 29.07.2011.



RAYALASEEMA – 1 x 210 MW - UNIT 5:

Unit is running around 200 MW.

SIMHADRI STAGE II, 2 X 500 MW, UNIT 3:

Unit is under shut down after full load operation on 31/03/2011 for attending to pending jobs and balance system commissioning.

CEP condensate line hydro test was carried out.

Mill-F LOPs - 2 nos. motor trial run completed.

Air tightness test of furnace was carried out.

LP Heaters - Motorised operated valves commissioning was completed.

TDBFP A: Solo run was done and actual over speed test was carried out. TDBFP-A: Alignment and coupling was completed.

ESP-C pass Hopper heaters commissioning was completed.

Mills F, G & H alignment was completed.

Drum safety valve ( 2 nos. ), SH safety valve ( 1 no. ) and HRH ERV ( 1 no. ) floating was completed.

Auxiliary PRDS safety valve floating was completed with CRH steam.

Boiler was hot drained after safety valve floating for shut down activities.

ESP C pass: Ash level indicators commissioning was completed.

ESP D pass : Dummy load test of 18 nos. BAPCON was carried out.

HRH spring loaded safety valve was serviced, setting was done and assembly was completed by BHEL/Trichy Service Engineer.

Steam blowing of all 88 nos. of wall blowers with APRDS was completed.

Mill – F motor trial run was completed.

PA fan was run and air tightness test was carried out for ducts from Boiler to ESP – C & D passes inlet.

Mills – H & J lube oil pump motors trial run was completed.



SERVICES RENDERED TO CUSTOMER /SAS/MUs:

--- NIL ---

CUSTOMER TRAINING & TECHNICAL PAPER PRESENTED:

Shri. M V Bhaskaran, DGM/Technical services, Chennai was deputed to North Chennai Thermal power Station on 14/07/2011 as Guest faculty for delivering lecture on “Operation and Maintenance of BFP & CEP”. The training programme was conducted by TANGEDCO Thermal Training Institute and attended by O & M engineers from all thermal power stations of TANGEDCO (TAMIL NADU GENERATION & DISTRIBUTION CORPORATION). APPRECIATION FROM CUSTOMER FOR SERVICES RENDERED :

--- NIL ---



FEED BACK NO.1 Project: Kakatiya TPS, Boopalapally, 1 x 500 MW Problem: Problem of Turbine Barring Gear stoppage. Problem detail:

On 07/07/2011, Kakatiya TPS Unit 1 tripped on GT “R” phase differential protection at 16:09 hrs. TG came to barring gear with normal coasting down time. After a period of three hours on baring gear, when the unit was on HP-LP Bypass operation, the speed gradually came down to zero speed. Hand barring also could not be done and it was found very tight. Intermittent hand barring gear was tried and there was some movement on 13/07/11. This was very hard(Tried with 8-10 persons and at temperatures of around 350 deg.) and the total movement was less than 1 rotation. After that it was totally jammed. With past experience of two occasions of barring gear stoppage, it was resumed on barring gear at casing temperature below 400 degC. But this time the rotor was not moving even at temperature below 100 deg C. All the operating parameters like vibrations, expansions and bearing metal temperatures were observed to be normal before tripping and during initial period of barring gear.

Checks and activities carried out:

An expert from BHEL, SAS, Secunderabad was deputed on 16/07/2011 and following checks were carried out.

1. All the jacking oil pressures and lifts were checked and found in order. The jacking oil header pressure was 148 ksc. The header pressure was improved to 166 ksc and the lifts were further optimsed as below. The machine did not rotate even after these adjustments.

Brg no 1 2 3 4 5 6 7 Before adjustment

Lift in mm Pressure

0.06 NW

0.07 90

0.15 80

0.16 105/120

0.11 NW

0.05 73

0.03 12

After adjustment

Lift in mm 0.06 0.07 0.10 0.09 0.09 0.08 0.04

* NW : Gauge not working



2. Clearances at oil guards of bearing pedestals 1 to 4 were checked and found normal except no. 4 rear left side which was found to be zero at one point. The same was corrected.

3. LP Turbine front and rear gland boxes clearances were checked and found all around clearance was available.

4. It was decided to lift up and lower down the HP casing at front and rear by 0.15 mm and IP casing front and rear by 0.25 mm sequentially and attempted to rotate at every step. The shaft did not move.

The following activities/checks were carried out from 19.07.2011 to 23.07.2011 to resume barring gear, by Shri. Bikash Mishra, who was deputed from Simhadri site:

1) IP casing was moved left and right without removal of radial keys. Hand barring was tried but was not successful. The movement of IP casing in left right direction was only 0.05mm.

2) The HP casing was also moved in left right direction in a similar manner. This time also Hand barring was not possible and 0.05mm movement was observed.

3) IP casing was moved axially towards Front and Rear side by 1.4mm after removal of axial key. The movement was made in increments of 0.1mm and hand barring was tried at all stages. Now also rotation was not successful.

4) HP casing was also moved axially by 1.4 mm and hand barring was tried but it was not successful. During the axial movement of HP casing it was observed that the HP rotor was also moving along with the casing. This observation leads to suspect for the problem within HPT instead of IPT.

5) After this, HP casing front was moved up by 0.3 mm and it was observed that the rotor started rotation by hand but was very hard. The rear side of HP casing was also raised by 0.1 mm but it was counterproductive. The rear side was then lowered by 0.1mm and similar movement was restored. The rear side was taken down to 0.2mm but no further improvement was observed. Subsequently the HP rear side was brought back to original



position. Meanwhile the rotor rotation became slightly free and as it turned by 360 deg. , It was jammed again.

6) The HPT was again moved axially as above and the HP front was lifted by 0.35mm and rotation was established. Initially it was very tight then it became relatively free and afterwards it became tighter and again jammed after rotation of 360 Deg.

7) HPT casing was moved axially again but this time the JOP lifts were also adjusted. The rotor started moving and it became free to rotate but this time also it stopped after 2 rotations.

8) Axial movement of HPT casing was repeated again and the front of the HP casing was lifted by 0.35mm with the help of shims. The rotor movement along with the HP casing left right movement was tried but no benefit came out of it. The rotor stopped after 1 rotation. Axial movement of HP casing was again tried along with movement of casing from right to left by 0.05 mm. When the shaft was rotated it was tight initially, subsequently becoming free. The rotation was continued but after 6 revolutions it came to abrupt stop

9) Bearing pedestals covers for No1 (HPT front) and No2 (HPT rear) were removed and the centering of HPT and IPT were checked with slip gauges. The centering of casings was corrected and the rotor was checked and found to be jammed.

10) Axial movement of casing was repeated 3 times but after switching off the JOP's. This time the rotor rotated by 360 deg. but was very hard. (During rotation JOP was switched on)

11) The same exercise was repeated and rotor became slightly free. With rotor in slightly free condition the IP casing was moved axially to check the axial float and the IP float was found to be in order.



12) Axial movement of casing was repeated with intermittent rotation till the rotor was free and then the rotor rotation was continued for 1.5 hours and 30 revolutions were made.

13) The revolutions were continued till the rotor was free to rotate with only one person at hand barring.

14) Then HP rotor float was checked and the total float was found to be 5.05mm as against the erection value of 5.16mm.

15) IP rotor float was checked and found to be 3.5mm.

16) HP casing centering was checked and was brought to the following values:

5.42

5.54

5.52 5.43

HP Casing Front



17) Pedestal no1 was boxed up

18) IP casing front centering was checked and brought to following values:

19) IP casing rear centering was checked and found to be:

2.05

2.52

2.14 2.43

IP Casing Front

2.40 2.53

3.96

4.27

4.12 4.10

HP Casing Rear

4.19 4.21



20) HP casing reference and float were as follows:

21) IP casing reference and float are as follows:

22) JOP Lifts were set again.

23) Pedestal no 2 was boxed up

Machine was put on Barring gear at 11:50 PM on 23/07/11.The speed rise was observed upto 80 RPM.All parameters were seen to be normal with machine on Barring gear.

23.21

22.94 23.01

IP Casing Rear(With Slip

23.00 22.95

HP reference: L=115.30 R=115.25

HP Float: +ve=2.45 -ve=2.58

IP reference: L=194.59

IP Float: +ve=1.80 -ve=1.70



The machine was rolled to 360RPM at 8:30PM on 24/07/11 and all parameters were kept under observation. The machine was synchronized at 9:30 AM on 25/07/11. All parameters were observed to be normal.

Conclusion:

From the above it is suspected that the jamming of Barring Gear was due to the problem in HP Turbine. It is suspected that the gland fins of HP turbine might have damaged due to which the rotor is getting jammed. The cause of this severe jamming may probably be due to the following reasons:

1) After stoppage forced hand barring (with 8-10 persons) was tried in machine at hot (430-350 deg) condition. This might have resulted in a deformation/damage to the HP turbine labyrinth seals/Balance piston seals. This damage in turn resulted in the jamming of the rotor at cold condition. Similar forced hand barring at hot condition was tried on a previous occasion also but that time the machine has come to barring gear. There may be some residual damage of seals from the previous occasion also.

2) This machine was first synchronized on 31/03/2010 and it is now running for more than a year. As all spring loaded foundations tend to settle in the first year, it is recommended as per BHEL, Hardwar circular that the springs are to be adjusted after 1 year of operation. This disturbance in catenaries might have caused disturbance in centering of the HP and IP Modules. This may also have caused the initial jamming of the barring gear in the last two occasions. There was no barring gear problem reported from this site prior to these two occasions.

It is recommended that no forced hand barring operation should be tried in case of stoppage of rotor in hot condition.

Courtesy: 1. Shri. Bikash Mishra, Manager/Simhadri site.

2. Shri. R. Kalyanasundaram, Engineer/Kakatiya site.

***************



FEED BACK NO. 2

Project: NEYVELI TS II, CFBC, 2X250 MW, UNIT-1

Problem: Frequent failure of diaphragm and gaskets of pressure transmitter in LDO system. Type of Pressure transmitter: Pressure diaphragm with capillary tube

In Neyveli TS II expansion CFBC boiler, Light diesel oil and Heavy Fuel Oil is used for start up purpose.

LDO was supplied from the existing unit of TS II, stage 2 pumps through a pressure regulating station with strainers which is located at new Fuel oil pump house. The system was commissioned and the boiler was lighted up with LDO. With LDO firing, commissioning activities of Boiler chemical cleaning with EDTA and steam blowing were carried out. During this period especially at daytime when the oil system / boiler was not in service repeated failures of LDO pressure transmitter gaskets and diaphragms were taking place both at pump house and at boiler station.

Problem analysis:

While analysing the cause for failure, initially it was suspected on pumps and requested customer to check whether the LDO pump has developed pressure more than the design values. The design pressure of LDO system is 22 kg/cm2. Customer confirmed that the pump was running only at 15 kg/cm2 or less. Hence this cause was eliminated.

If over pressurisation by the pump is not the cause then it could be due to expansion of locked up oil in the pipeline between the boiler and new Fuel oil pump house due to raise in ambient temperature by sunlight.

Since there is a recirculation line with valve for the LDO supply pump, LDO should not get locked up and should have been drained to the tank. While examining the scheme thoroughly it was observed that one NON RETURN VALVE is provided in between filter assembly and pressure control station in the pump house. The scheme of LDO system is attached for reference. This NRV prevented back flow of LDO from boiler to LDO tank via recirculation line. Because of this the locked up cold oil between boiler and pump house during shutdown of boiler gets



slowly heated up by sun light and increases specific volume of oil. This increase in volume resulted in increase of LDO pressure, which went as high as 45 kg/cm2 and damaged the diaphragms and gaskets of all pressure transmitters which are of ANSI 300 Class (the design pressure of 20 kg/cm2). The local pressure gauges were indicating out of scale of range 0-40 kg/cm2. Hence to resolve this problem the internal of NRV was removed with the concurrence of customer. Conclusion: Subsequently, there are no failure of diaphragms and gaskets of pressure transmitters in LDO system. The pressure raise is also not observed as the expanded fuel due to raise in ambient temperature, is released to the LDO tank. It has to be ensured during design of any oil system that there is no locked up oil remains during any operating or standby condition. Safety valve shall be provided where locked up situation is unavoidable in the system.

LIGHT FUEL OIL SCHEME OF CFBC BOILER 2 X 500 MW UNIT – 1 NEYVELI

PCV

NRM

M PUMPS

MV STRAINER

PT

PT

P

P

P

P

PT

PT MV

MV

MV

MV

MV

MV

MV

MV

MV

MV

PCV

MV

PCV

MV

PCV

PCV

FC

FCV

MV

MLOTV

CT

CT

CT

CT

SUB - 1

SUB - 2

SUB - 3

SUB - 4

NRV IN WHICH INTERNALS WERE

RE LOCATION: TS – II STAGE – 2 PUMP HOUSE

TS II - EXPANSION PUMP HOUSE (FOR 250 MW CFBC)

BOILER - 1

NOTE:- MV – MANUAL CONTROL VALVE, PCV – PRESSURE CONTROL VALVE, FCV – FLOW CONTROL VALVE, PR – PRESSURE GAUGE, PT – PRESSURE TRANSMITTER, MLOTV – MAIN LIGHT OIL TRIP VALVE, SUB – STARTUP BURNER, CTV – CORNER TRIP VALVE.

DRAWN BY : K.HARIDOSS, AE-II, TSX. APPROVED BY : P. GOVINDARAJU, DGM, TSX.



FEED WATER HEATER GROUP PROTECTION VALVES

BHEL has introduced the group protection valves for feed water heaters at Neyveli TS II Expansion, 2X250 MW units, replacing the individual heater isolation valves and bypass valves. These valves are supplied by Sempell Germany.

FEATURES AND BENEFITS

• These valves are designed to bypass high pressure feed water around a group of heaters in the event of high water level in the shell caused by a defective tube, weld or drain system.

• The time available to give protection to a turbine in modern feed systems is short but these valves can operate in approximately 5 seconds in a 300mm bore pipe system with the minimum of hydraulic shock.

• Protection is achieved in the system by installing fast closing tee and changeover valves in the pipe work around a heater or group of heaters.

• The motive power employed is the feed water pressure and the system is designed to 'fail safe' in that the heaters will be by-passed if either electric or pneumatic supplies fail.

• Protects the feed water heater steam jacket in case of tube rupture or leakage.

• Protects the turbine extraction from excessive backpressure. • Allows the feed water heater to be isolated from the system for inspection or

repair without disrupting the circulation through the plant. • Allows bypassing of the feed water heater during plant start-up at low turbine

load. • Allows bypassing of the feed water heater at peak loads to increase power

output from the turbine.



ACTUATING SYSTEM Three actuating systems are available:

1. Hydraulic, using the feed water as fluid 2. Pneumatic, using standard piston actuators 3. Electric, using standard electric actuator.

The actuating time for the valves can be varied, but typical is approx. 3 sec for hydraulic and pneumatic actuators and approx. 15-25 sec for electric actuators. Hydraulic actuators using the feed water

The hydraulic actuators are double-acting or single-acting and use the feed water as power fluid. No external power is required for this system. The control systems are supplied such that the valves will fail in the safe mode (normally bypass mode). The actuator control manifold contains both the valves and the electronics for the control of the system. Pneumatic piston actuators

Standard piston pneumatic actuators are used. Air is required at a minimum pressure level of 4 bar (60 psi). The system control included in the actuator assemblies. The actuator controls are configured to provide safe operation (normally bypass mode).

Electric actuators

Standard electric actuator with all available voltage is provided. System control is included in DCS.

In this project (Neyveli TS II expansion) hydraulic actuating system is used for

controlling the valves.

THREE DIFFERENT VERSIONS

1. Automatic bypassing and manual resetting. 2. Automatic bypassing and spring-opening upon signal, except electric actuators. 3. Automatic bypassing and resetting upon signal with hydraulics in both directions.



FUNCTION Operation

In case of damage happening to the preheater pipes (heater bank), the feed water supply upstream of the heaters bank and the feed-water backflow from the boiler to the heater bank must be shut off in the shortest possible time. Quick shut off and deviation of the flow will both prevent the heater steam jacket designed for low pressures from being endangered, and also maintain the feed-water supply to the boiler. Moreover, the turbine is protected against water breaking in by flow backs through the bleeder pipe. Due to the automatic shut off of the heater and the simultaneous opening of the by-pass line, the feed-water keeps on flowing steadily.

Even excessive pipe lengths between the pump and the quick closing change over valve will not create any additional dynamic forces. Due to the deviation of flow, the water column contained in the by-pass will have to be accelerated. Short by-pass pipes will keep such acceleration forces on a low level.

The quick closing valves are controlled by their own medium and will respond

within a second's time, without varying operating forces and almost free of friction, because the valve seating faces close axially and do not slide on each other like in gate valve. If the feed-water pressure within the preheater pipes rises due to faulty control or during trial runs, the valves will act as safety valves and open slightly.

In normal operation pump pressure will prevail in the inlet of the changeover

valve. Due to pressure losses, the pressure in the by-pass line is somewhat lower. This pressure differential as well as the balanced stem that is passed to the outside, will safely hold the disc of the valve in open position, providing a shut off towards the by-pass.

Minor pressure fluctuations within the range of 5% of the inlet pressure will

not affect the operation of the valves. In case of damage in the preheater, the level control emits an electric impulse

to the solenoid control valve. The valve opens and relieves the cylinders "A" of the valves. Cylinders "B" receive the full pressure of the feed-water line via a small passage, which causes the discs to move into their closing positions.

The preheater is no longer in operation and the feed-water flow passes through

the by-pass line. When the solenoid control valves closes, the changeover valve will



only remain in its closed position, if the feed-water pressure in the preheater has lowered by at least 10% as compared with the pump pressure and does not rise again. Therefore, with power test runs, the valves will open automatically, and the preheater is put into operation again, as soon as the solenoid control valve is closed. This automatic opening is effected by the valve stems being balanced and passed through to the outside. The pistons of the valves have been so dimensioned, that any opening towards the preheater is prevented, if the latter is pressure less or under low pressure. This design prevents any sudden and harmful admission of pressure to the preheater piping.

For the start-up or after repairs the preheater is filled via the refill pipe by

the pump line. Only then the valves can be opened, or will open automatically after the pressure has been balanced within the system. With low operating pressures, the open hand-operated control valve relieves the cylinder "B" sufficiently for allowing the disc to move into its open position.

Closing the solenoid control valve after changeover is necessary, because a

permanent relief via the control pipe may cause erosion. As shown in the drawing, a corresponding closing impulse is emitted by the electric indicator (limit switch) in "closed" position. Contactors C1 and C2 are lagging at approx. 30 seconds. OPERATION:

At Neyveli site 2 quick closing type change over valves for each of HP heaters

are provided as shown in fig.5. When Heater shell side level becomes very high the two solenoid valves for inlet and outlet change over valve get de-energised and change over valve actuator cylinder B portion is drained so that heaters will be by passed immediately. After getting Signal from valves bypassed limit switch provided in the change over valve, the dumping valve will operate and empty the heater tube side to protect the turbine from back pressure or water entry. There is manual control valve in the actuator of the change over valve provided to operate the valves manually in case of any problem with solenoid valve.



Fig.1: General Scheme of the Feed water heater system with Protection valves



Fig. 2: General Scheme of Feed water heater bypass self action hydraulic control system in bypass mode


Fig.3: Typical cross section of Change Over Valve


Fig.4: Typical Cross Section of check valve


. 5: Scheme of Feed water system with Group Protection Valves



UNITS WHICH HAVE ACHIEVED 100% OA

THERMAL

500 MW RAMAGUNDAM UNITS – 4, 6 & 7

TALCHER UNIT - 6 SIMHADRI UNIT – 1 & 2

SIPAT UNIT – 5 VTPS UNIT - 7

250 MW

KOTHAGUDEM UNIT - 10

210 MW

METTUR UNIT – 4

TUTICORIN UNIT – 1 & 5 NORTH CHENNAI UNIT - 1 & 2

UNITS WHICH HAVE ACHIEVED PLF MORE THAN 100%

500 MW

RAMAGUNDAM UNIT - 4 & 6 SIMHADRI UNIT – 1 & 2

SIPAT UNIT – 5

210 MW

TUTICORIN UNIT - 5



UNITS WHICH HAVE ACHIEVED PLF BETWEEN 90 & 100%

THERMAL

500 MW

RAMAGUNDAM UNIT – 5 & 7 SIPAT UNIT - 4 VTPS UNIT – 7

250 MW

KOTHAGUDAM UNIT – 10

210 MW

VIJAYAWADA UNITS – 2, 4, 5 & 6 MUDDANUR UNITS – 1, 3 & 4

METTUR UNITS – 1, 3 & 4 TUTICORIN UNITS - 1, 2 & 4

NORTH CHENNAI UNITS – 1, 2 & 3 NEYVELI UNIT - 4

AMARKANTAK UNIT - 5



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20.00

40.00

60.00

80.00

100.00

120.00

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Raich

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Ram

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Mud

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Kot

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VTP

S -

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Met

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Am

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2010 - 11 2011 - 12

PERFORMANCE OF BHEL THERMAL SETS IN SR (210 MW AND ABOVE) FOR THE PERIOD FROM 01/04/2011 TO 31/07/2011 COMPARED WITH THE

CORRESPONDING PERIOD IN THE PREVIOUS YEAR. ( PLF IN PERCENTAGE )

STATION 2010-11 2011-12 North Chennai 74.81 92.28

Neyveli 90.27 91.46 Raichur 56.40 75.44 Tuticorin 86.12 89.42

Ramagundam 100.91 92.30 Muddanur 90.19 90.66

Kothagudam 73.21 79.25 Vijayawada 75.35 92.23 VTPS - 7 69.03 98.10 Mettur 85.77 95.23 Talcher 90.38 83.17 Simhadri 101.03 102.21 Sipat 96.52 93.46

Amarkantak -- 93.47

trombay tps july : 2011 volume : 15 - bhel - pssr · pdf filetrombay tps july : 2011 volume :...

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