15-Emergencies in power plant operation

 

Emergencies in power plant operation: Following are some of the emergencies that are normally faced during operation of power plant.

1.Tripping of boiler: Following are the main cause of tripping of boiler

• Low drum level
• High furnace pressure
• High/ low bed temperature
• Tripping of boiler due to failure of FD, PA, SA  and ID fan
• Electrical fault in Boiler MCC

2.Tripping of Boiler; Case: 2 Boilers & 2 Turbines

Actions to be taken:

• Reduce load at turbines so that inlet pressure to turbine maintains at operating value.
• Share load equally on both the turbines.
• Close main steam stop valve of the tripped boiler.
• Ensure that all coal feeders (fuel feeding system) and fans are stopped on tripping of boiler.
• Maintain drum level.
• If required stop one boiler feed pump (BFP).
• Check the cause of tripping of boiler and try to rectify the fault.
• If boiler fault is rectified, start the boiler with startup compartment and gradually increase boiler pressure and temperature (Follow hot/warm start up curve)
• Synchronize the boiler with the running boiler.
• Start one more BFP
• Take compartment one by one into line and increase the load
• Maintain the equal load on both turbines as per requirement
• Finally stabilize the power plant operation.
• If the boiler fault cannot be rectified immediately, decision of stopping of one boiler can be taken after due consultation with station manager.

3.Tripping of Turbine

Followings are some of the causes of tripping of turbine

• Any one of the protections or interlocks of turbine or generator generally initiates tripping of turbine.
• In some of the cases spurious tripping is caused due to mal functioning of instruments.
• Due to mal operation of the operating staff.

4.Non-availability of Fuel (Normal Shut Down): (Case: 2 Boilers & 2 Turbines)

Take planned shutdown of power plant in following ways.

• Reduce station load by switching off export feeders.
• Stop one turbine and put it on turning gear once turbine speed comes to zero.
• Stop one boiler by slumping the compartments one by one. Slumping of compartment is done in the reverse direction i.e. 5th compartment is slumped first and so on.
• Reduce further load by switching off the auxiliaries.
• Finally, one turbine runs on auxiliary power load. If STG running on synchronized condition, generator breaker can be opened on auxiliary load. If STG runs on islanding mode, synchronize STG with DG or grid and transfer auxiliary load to DG or grid before opening Generator breaker at minimum STG load.
• Stop the turbine and put on turning gear in due time.
• Stop ACC fans or CT fans, CEP etc. in due time.
• Keep open main steam line & other process steam line drains.
• Once fuel is made available, restart power plant as per cold start up procedure

5.Non-availability of DM Water

• Plan for normal shut down.
• Build up DM water in DM storage tank and restart Power plant as per start up procedure

6.Fuel handling / Fuel feeding system Break down

• Causes of Fuel handling & fuel feeding system failure
• Belt cut
• Mechanical equipments like gear box, coupling & pulley failure
• Electrical equipments like motor & feeders failure

Take following actions

• Inform the station Manager & reduce the steam demand
• Switch off the export feeder
• Trip the Turbine & put it on turning gear as per SOP
• Stop the other fuel feeding & fuel handling system
• Stop the fans sequentially
• Hot box up the Boiler as per SOP
• Attend the breakdown
• Re-start the plant as per SOP

7.Boiler feed pump incomer supply failure

• Causes of incomer supplier failure,
• Breaker trip
• Relay malfunction

Take following actions

• Reduce the steam demand, trip the export feeders
• If supply is not restored within minute,trip the Boiler & Turbine manually
• Hot box up the Boiler
• Put STG on turning gear as per SOP
• Stop the fuel handling system
• Identify & troubleshoot supply failure
• After restoring the BFP incomer power supply, stat the Boiler feed pump & maintain drum water level
• Start the Boiler as per SOP (Hot or Warm)

8.Main steam line leakage

• Probable Causes of main steam line leakage,
• Leakage in welding joint due to corrosion & rusting
• Uneven expansion
• Water hammering

Take following actions

• If leakage is heavy inform the station Manager & reduce the steam demand
• Switch off the export feeder
• Trip the Turbine & put it on turning gear as per SOP
• Stop the fuel feeding & fuel handling system
• Stop the fans sequentially
• Hot box up the Boiler
• Identify & arrest the leakage
• Analyze the causes of leakage
• Start the Boiler & STG as per SOP

9.Turbine HP valve gland leakage

Probable Causes of HP valve gland leakage,

• Turbine Load hunting
• Ageing
• Poor fitment of gland packings during overhauling

Take following actions

• If leakage is heavy inform the station Manager & reduce the steam demand
• Switch off the export feeder
• Trip the Turbine & put it on turning gear as per SOP
• Stop the Boiler as per SOP
• After cooling, attend the gland leakage
• Start the Boiler & Turbine as per SOP

10.Tripping of Auxiliary Transformer

• Following are the probable cause of tripping of auxiliary transformer.
• Heavy earth fault in any of the LT drives.
• Tripping on transformer protection like low oil level, high oil/winding temperature, Buchholz relay operation etc.

On tripping of auxiliary transformer, total power plant will trip. Proceed as follows to tackle the emergency.

• Resume auxiliary power immediately.
• Ensure STG have got tripped and shutdown safely
• Ensure boilers are tripped.
• Close MSSV.
• The drives, which were put on auto, take all of them on manual.
• Close all the control valves.
• Once auxiliary power is available, start one BFP and take water into boilers.
• To resume auxiliary power stand by Auxiliary transformer can be taken to service if HT voltage available in bus or by closing PCC bus coupler.
• Put STG on turning gears after starting AOPs.
• Start the power plant as per hot start up procedure.

11.Tripping of Export Transformer

• Following are the probable causes of tripping of export transformer.
• Heavy earth fault in any of the LT drives.
• Tripping on transformer protection like low oil level, high oil/winding temperature, Buchholz relay operation etc.

On tripping of export transformer,power plant will come to Island mode operation. Proceed as follows to tackle the emergency

• Ensure Turbine has not tripped on high pressure
• Maintain Boiler operating pressure by controlling start up vent control valve
• Operate Boiler & STG on home load
• If process needs steam, charge the steam from PRDSH as per SOP
• Maintain Boiler load as per steam process demand
• After troubleshooting the transformer, synchronize the Turbine with grid & start to export the power
• Slowly cut off the PRDSH steam to process & charge the process steam line through Turbine extraction steam.

Reference books for power plant O&M

 12.Tripping of Export Feeder

Probable cause of tripping of feeders are,

• Over load
• Earth fault
• Maintain main steam header pressure

Take following actions

• Ensure that dumping system has acted to cope up increase in pressure. If dumping system is not available, maintain Boiler pressure by operating start up vent CV & also take combustion system in manual mode to reduce firing as per requirement
• Reduce load on boiler, if required slump one compartment of a boiler or both the boilers.
• Ensure that dumping system ceases to operate and system is stabilized at reduced load.
• Analyze the cause of tripping of feeder and rectify.
• Once problem is sorted out and rectified, take export feeder in service after due consultation with consumer.
• Gradually increase load on power plant and stabilize.

13.Turbine Oil Leakage

• Causes of oil leakage in turbine area,
• Leakage in oil line caused by failure of joints or flanges or due to vibration in oil line.
• Spillage through centrifuge due to seal break.

Take following actions

• If it is in Lube oil (LO) oil or hydraulic oil line, plan for safe shut down.
• Try to attend leakage under emergency plan.
• Analyze the cause for oil leakage to avoid future leakages
• Do leak testing and restart the turbine
• If it is in other area like in Centrifuge, isolate centrifuge.
• Top up oil in MOT, if required.

 14.DCS failure

• Probable Causes of DCS failure,
• DCS power supply failure
• DCS controllers failure
• DCS other accessories like card, switch & SMPs etc failure

Take following actions

• During DCS failure, DCS operators cannot judge the plant operating condition so need to take following actions.
• If Turbine not tripped automatically, trip it manually through emergency push button provided in Governor panel.
• Trip the Boiler manually (Stop Fuel feeding system, Boiler fans & fuel handling system) & close MSSV manually
• Start Turbine Lube oil pump manually & put STG on barring gear.
• Start BFP manually & operate the control valves manually in field.
• Observe drum level from local level gauge glass
• Analyze the cause of DCS failure.
• After troubleshooting start the DCS as per SOP
• Then start the plant as per SOP (Hot or warm)

15.UPS  failure

• Probable Causes of UPS failure,
• UPS battery failure
• UPS cards failure

Take following actions

• After UPS failure, DCS also gets fail & DCS operators cannot judge the plant operating condition so need to take following actions.
• If Turbine not tripped automatically, trip it manually through emergency push button provided in Governor panel.
• Trip the Boiler manually (Stop Fuel feeding system, Boiler fans & fuel handling system) & close MSSV manually
• Start Turbine Lube oil pump manually & put STG on barring gear.
• Start BFP manually & operate the control valves manually in field.
• Observe drum level from local level gauge glass
• Analyze the cause of UPS failure.
• After troubleshooting of UPS start the DCS as per SOP
• Then start the plant as per SOP (Hot or warm)

 

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Steam Turbine standard operating procedures (SOPs)

 

Lube oil system operation

Pre-checks

• Ensure lube oil tank level is normal
• Ensure lube oil pumps are healthy to operate
• Ensure lube filter & cooler are in service
• Ensure lube oil inlet and outlet valve provided at filters & coolers are open
• Ensure cooling water inlet & outlet valves provided for oil coolers are in closed condition
• Ensure suction & discharge valve of the pumps are in opened condition

Operation

• Start the oil pump (AOP)
• Ensure no abnormal sound & vibrations
• Observe the discharge pressure
• Ensure header pressure is normal, if not adjust with PRV or recirculation valve
• Check the oil filter DP, if high change over the filter
• Check overhead oil tank is getting filling
• Ensure lub oil is supplying to each bearing & adjust the oil pressure to each bearing as per desired requirement
• Maintain the oil temperature by adjusting cooling water inlet & outlet valves.

Note: Keep open cooling water inlet valve 100% open & adjust the temperature by adjusting outlet valve

• Ensure the over head oil tank is full
• Keep stand by lube oil pump & EOP ready

Barring gear operation

• Ensure lube oil system is in service and oil is circulating at the bearings at a desired pressure
• Ensure barring gear motor is healthy to start & its all interlocks are in place
• Engage the barring gear clutch
• Start the barring gear motor
• Observe the rotor is rotating at barring speed without increase in bearing vibrations & temperature
• Ensure there is no any abnormal sound

Cooling water system operation

Pre-checks

• Ensure the cooling tower level is normal
• Ensure cooling water pump is healthy to operate & their protections & interlocks are in place
• Ensure cooling water pump (MCWP) suction valve is open & discharge valve is closed
• Ensure all the field instruments are healthy & inline
• Ensure surface condenser inlet & outlet cooling water line valves are open
• Ensure Condenser water box vents are open
• Ensure cooling tower inlet cooling water line valves are open

 15-Emergencies in Power plant

Operation

• Start the pump from DCS at 70% RPM
• Open the discharge valve slowly
• Observe discharge pressure is increasing gradually
• Ensure the pump’s vibration & bearing temperatures are normal
• After venting air from condenser water box close the vent valves
• Observe cooling water is falling in cooling water
• Increase the pump’s speed as per requirement
• Note down cooling water inlet & outlet water temperature of condenser
• Start cooling tower fans one by one as per requirement

 SOP Lube oil & Oil cooler change over

Condensate system operation

• Ensure the hot well level is adequate. Otherwise make the hot well level with DM water
• Ensure the CEP is healthy & its all interlocks are in place
• Ensure pump’s suction & discharge valves are open
• Ensure ejector & gland sealing steam condenser inlet & outlet cooling water line valves are open
• Start the pump, ensure the water will flow from ejector & Gland steam condenser (GSC)
• Ensure gland steam outlet control valve to deaerator is close & cooling water is recirculating through recirculating control valve
• If the hot well level increases, then GSC discharge valve can be opened
• Once the Turbine comes into line,GSC outlet control valve should be kept in auto mode to maintain hot well level
• Vacuum pulling & Vacuum killing
• Pre-checks
• Ensure auxiliary steam is available at desired pressure and temperature
• Ensure vacuum breaker valve fitted on steam condenser is closed
• Ensure cooling water is circulating in the condenser and the turbine gland is charged fully at 0.1 kg/cm2
• Ensure live steam line to ejector steam lines drain are kept open
• Ensure Hogger & main ejectors steam and air valves are in closed condition

Vacuum pulling through hogger ejector

• Charge the main steam line to ejector steam & temperature control valve
• Ensure the rated pressure (10 kg/cm2) and temperature (220 deg C) for ejector vacuum pulling
• Once the rated parameters are reached open the steam valve of starting or hogger ejector
• Observe the steam is vented to the atmosphere
• Then open the ejector airline valve
• Observe vacuum inside the condenser increasing slowly and will reach 60 to 70% of rated vacuum within 20 minutes

SOP to put main ejector into line

• Ensure CEP is running
• Ensure cooling water inlet and outlet valves of main ejector which is to be taken into line
• Vent out air from water box of the ejector
• Then open the drain valve of inter condenser and after condenser of ejector
• Open the steam valve of after condenser ejector
• Open the steam valve of inter condenser ejector
• Observe the condensate is drained out from both the condensers
• Slowly open the air valve & observe the vacuum is increasing
• When vacuum reaches rated, then stop the hogger or starting ejector

Vacuum killing or Taking out of main ejector

• Close the air valve of the ejector
• Close the steam valve of inter condenser
• Close the steam valve of after condenser
• Close the drain valves of after & inter condensers
• Close the cooling water inlet & outlet valve once the ejector is cooled

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Power plant & Calculations

Slop fired Boiler start up procedure

 

Pre-checks

• Ensure DM water storage tank, feed tank & Deaerator  level are normal
• Ensure availability of start up fuel (wood) & main fuel (coal) and power supply with DG backup
• Ensure maintenance & trial runs (healthiness) of all equipment including fuel handling, ash handling / auxiliaries, motorized valves, actuators, control valves and PRDS controls are completed successfully
• Ensure that all interlocks / protection and controls are checked & taken in line.
• Ensure expansion pointers are cleaned & tramps are in good condition.
• Ensure Boiler manholes and flue gas path system manholes are boxed up.
• Ensure availability of chemical dosing system and readiness of drum level gauge glass with illuminator assembly.
• Ensure availability of cooling water, instrument air and service air.
• Ensure Coal bunker is filled with required level
• Ensure all rotary air lock valves of evaporator, economizer & bag filters are open
• Ensure healthiness of all dampers and keep them in open/close marked positions as per requirement
• Open all air releases/vent valves in boiler drum and open super heater header drains and its vent valves.
• Ensure all boiler bottom ring header drains, blow down valves and main steam stop valves including its bypass valves are closed.
• Ensure Boiler feed pump’s bearings oil level normal, minimum recirculation, balancing leak off valves & suction valves are open, cooling water pressure normal.

Boiler start up

• Start the ACW pump, Instrument Air & Service Air Compressor
• Start BFP from control room. Ensure suction pressure, balancing pressure & discharge pressure normal. Bearing temperature & Vibrations normal. Ensure motor draws current normal & sound normal. Shut the BFP immediately if any abnormal condition and check thoroughly before restart.
• Start water filling the boiler drum through 30 % control valve and maintain the drum level up to 30%.
• Start the Ash handling plant prior to light up the Boiler. Then start all hoppers RAV.
• Ensure bag filter main damper is closed & bypass damper is open
• Maintain the drum level about 40%.
• Drum vent, super heater vent and main steam line drain should be kept open.
• Start wood firing by spraying small quantity of diesel & slowly raise the furnace temperature
• At furnace temperature > 150 deg C start ID & FD fans at minimum speed
• Close drum air vent at 2.5 kg/cm2
• At 3 kg/cm2, gibe blow down to CBD, IBD & bottom headers one by one for 30 sec to 45 seconds
• At pressure > 4 kg/cm2, open start up vent 10% initially & close the top header drain valves & go on increasing the pressure
• At furnace temperature around 250 deg C, start coal feeding by starting SA fan
• Now slowly increase fuel feeding & FD air
• When boiler pressure reaches 6 kg/cm2 & 150 deg C, charge the main steam line. Before charging the main steam line, open all the drains at 100 % and warm up vents at minimum opening and then open the MSSV bypass valve.
• Start HP & LP dosing and maintain recommended drum water parameters of boiler. Keep the CBD at minimum opening to maintain recommended residual PO4 & conductivity of drum water
• Check & record thermal expansion of boiler pressure parts and record the bearings temperature & vibrations of auxiliary equipment’s associated with Boiler
• After ensured all condensate removed & color less steam comes through drains, keep all the drains in crack position, then open main steam stop valve and close the bypass steam valve
• At Boiler pressure 9 kg/cm2 & temperature 180 deg C, charge Deaerator & SCAPH through PRDSH
• At flue gas temperature > 180 deg C take bag filter into line
• Observe seal air pressure, conveying air vessel pressure of AHP is normal.

Slop firing:

• Ensure sufficient quantity of slop with required brix is available in slop tank
• Ensure tank coil heater & steam tracing lines are charged & tank slop temperature is 70 to 80 deg C
• Ensure slop pumps are healthy & agitator is running condition
• After ensuring above all are normal, start slop transfer pumps & keep slop in recirculation mode for at least 2 to 3 hours before taking into boiler
• As the Boiler reaches 50 to 60% of MCR & furnace temperature is 450 to 500 deg C open the atomizing steam line, slowly introduce the slop into furnace by opening SOV
• Note: Before introducing slop into nozzle, keep open the steam connection line provided with respective nozzle.
• Quantity of slop fired at MCR is 3.91 TPH & slop quantity should be reduced as the load demand reduces
• Always maintain 20 to 25% supporting fuel on heat basis. Never start the Boiler with slop
• During slop firing ensure supplement fuel is supplying continuously to avoid clinker
• The soot blowers provided in economizer, evaporators are operated once in a shift & wall blowers twice in a shift

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Turbine lube oil flushing procedure

 

Oil pipe lines cleaning & flushing:

Generally Steam Turbo Get machineries lube oil supply line & control oil lines are of stain less steel & return oil lines are of carbon steels. The oil pipelines fabricated at site are to be cleaned by acid pickling for CS pipelines and by Caustic Soda for SS pipelines.

Before acid pickling the pipes should be thoroughly flushed with air for removing of loose particles.

Acid pickling pipes should be dummied one end with rubber gasket and filled with acid of 5 to 8% of concentrated HCL acid and keep the pipes filled with acid for 24 hours, so that all loos metal particles will come out. There after remove the acid from pipes & clean the pipes thoroughly with water and neutralize with caustic soda.

Fill the 3 to 4% of concentrated caustic soda solution in the acid cleaned pipelines and keep the pipes for 24 hours, so that all acid contents gets neutralized.

Ensure the time between acid cleaning and soda wash should be kept minimal Also chemical solution should not exceed 60˚C. After that all soda washed pipes are thoroughly cleaned/rinsed with water and dry with Air, Lube oil (ISO VG 46) to be applied inside the pipelines to avoid rusting.

All the passivated pipelines are covered both the ends of pipes with plastics caps / lids so that no dust particles can enter inside. All passivated pipelines are to be fitted immediately in the original position and start the oil circulation / flushing.

Reference books for power plant O&M

Turbine oil flushing:

Pre-checks or requirements for oil flushing;

• Fire fighting system at MOT and STG area is ready to use.
• Main oil tank should clean thoroughly using sponge/Cloth, diesel and with compressed air
• Ensure AOP suction strainers are cleaned and boxed up properly
• Fill the Oil Tank with flushing oil of Grade ISO VG 46 (refer O&M Manual) through centrifuge by site suitable temporary flexible hose connection. Temporary hose connection one end is immersed in the oil barrel and another end is connected to oil centrifuge inlet point. Centrifuged oil should be send from oil centrifuge outlet to Main oil tank by permanent piping. Flushing oil should be same as per first fill oil. The detailed specification & makes are specified in the operation & Maintenance manual
• Ensure Main oil tank level should be > 65% or as per requirement in local level gauge
• Before start up the LOS system please ensures there is no bypass in protections of motors like-Over load, single phase preventer etc.
• All the Oil Pumps & Main oil tank fans are kept ready for operation. Ensure Emergency local Buttons of all the motors are released condition.
• MOT heaters should on. Also ensure Heaters to be cut of at 65 ˚C of MOT Oil temperature
• Ensure MOT Mist fans power supply panel are in charged condition and Mist fan kept ready to start
• Ensure Aux. Oil pump power supply panel is in charged condition kept ready to start.
• Ensure STG Barring gear motor, EOP motor & ACOP motors power supply is switched off condition.
• Ensure AOP pump suction and discharge Pressure Gauges are working and its isolation valves are in opened condition.
• Ensure any one of the Lube oil cooler is line up i.e the inlet 3 way valves is directed in one cooler only and cooler equalizing valve is in closed position. Also ensure corresponding lube oil cooler vents and drains are in closed condition
• Lube oil cooler inlet and outlet cooling water valves are in closed condition. Ensure cooling water to be charged up to isolation valves during flushing
• Ensure lube oil cooler inlet Pressure Gauge isolation valves are open. Also ensure All PTs (if applicable) isolation valve is closed condition during flushing to avoid entry of any foreign particles.
• Remove the original filter elements (625 mesh) from filters skid & put Temporary made filters element (perforated pipe and rolled with temporary filter screen having sizes start from 50 mesh and fastened by wire) to both filter shell.
• Ensure any one of the Lube oil filter is line up i.e. inlet 3 way valves are directed in single oil filter only and equalizing valve is in closed condition. Ensure Lube oil temporary filters are cleaned and box up properly. Ensure Lube Oil filter drains and vents are in closed condition. Ensure Lube Oil filter line inlet & outlet Pressure Gauges is working and its isolation valves are open.
• Ensure Lube oil header Pressure Gauge is working and its isolation valve is open and PT‟s isolation valves are closed condition during flushing to avoid entry of any foreign particles.
• Turbine front & Rear bearing pedestal flanges oil inlet to out let, Gear box flanges oil inlet to out let, Alternator Front & Rear bearing pedestal flanges oil inlet to out let should be bypassed during oil flushing by suitable temporary hose pipes.

Procedure:

Stage-1

• Start AOP & check any oil leakage from the pipe lines welding joints & flange joints
• Observe lube oil header pressure rising
• Monitor the lube oil circulating through bearings bypass hose pipes
• Observe AOP oil pressure regularly, if discharge pressure is decreasing it means that, pump’s suction strainer is jammed. So stop the pump, clean the strainer & again restart the AOP
• Observe the Lube oil filter DPs if it crosses 0.6 kg/c2 change over the filter to stand by filter
• Raise the lube oil temperature 55 to 65 ˚C by MOT heaters or Temporary heaters. Once the oil temperature raised 55 to 65 ˚C lightly hammer the line with mallet or soft hammer so that all the loose materials will come out with the oil.
• After duration of two to three hours, change over the filter to the stand by one and check for the cleanliness of the mesh and if required replace the same. These processes are to be repeated by changing the filters in line and also mesh if required at intervals of 2hrs, 4hrs, 8hrs durations..
• Every 4 hours reduce the oil temperature by raking lube oil cooler into line. This thermal shock will helpful for expansion & contraction of pipe lines thereby removing scale & clogged particles inside the pipe lines & other system.
• Once 50mesh cleared then change to 100mesh then 150mesh and then 200mesh.This process to be continued up to 200mesh cleanness. Once 200 meshes are cleared then follow the Stage -2 flushing.

SOP lube oil cooler & oil filter change over

Stage-2

• Remove top half of the bearings (Thrust, Front & Rear) of T u r b i n e Rotor and keep them at safe location-Clean the preservatives which applied in the rotor. Re-place the bearing caps and their housing/cover in its position and ensure that oil will not spill out during flushing.
• Turbine front and rear pedestal loop line (flexible hoses) to be removed and normalized the inlet and out let connections as per original. Ensure Loop will be continued in the gearbox & Alternator bearings which are bypassed with flexible hoses.
• Ensure the temporary made filters element filter screen having sizes start from 50 mesh.
• Repeat the procedure as per Oil flushing Stage -1 Continue flushing further till system is clear. Once 200 meshes are cleared Oil flushing is completed.

Stage-3

• Completely drain the oil from MOT, coolers, filters and piping system.
• Once the MOT is drained completely, open oil tank cleaning, Clean the tank internals using site suitable special wipers with long rod along with compressed air. After cleaning, fill fresh lube oil inside the tank, ensure that oil is sprayed throughout inside of the tank (Sprayer-site suitable hose connection). Once the oil fogging is over fix the oil cleaning door with oil gasket and apply the grease on the gasket before tightening the bolts.
• Remove the Turbine thrust, front & rear bottom half the bearings from respective pedestals by small amount of lifting the Turbine rotor (max 0.1mm only)
• Remove the Turbine thrust, front & rear bottom half the bearings from respective pedestals by small amount of lifting the Turbine rotor (max 0.1mm only)
• Completely disassemble and clean the Turbine thrust, front & rear bearings by petrol or site suitable cleaning medium. All bearings pads to be inspect. Clean/polish both top & bottom halves. Ensure their correct fitting. Clean the holes provided in Thrust Bearings Pads holder & Journal Bearing holes also
• Insert the Turbine thrust; front & rear bottom half of the bearings in the respective places. Rest the Turbine rotor on the bearings
• Assemble thrust, front & rear top half of the bearings in the respective places. Ensure required clearances as O&M Manual recommendations
• Position the bearing caps/cover and tightens the cap studs as per torque recommended
• Ensure all pumps (AOP, MOP, EOP & ACOPs) suction strainers are well cleaned and boxed up properly
• Ensure both filters skid temporary filters are removed and filter skid is thoroughly cleaned. Insert the original filters in the respective places.
• Main oil tank – Oil should be filled through centrifuge with first fill oil of OEM recommended Grade 

Do not use: Flushing oil for final filling of MOT, if required get it tested from authorized party or OEM.

• Ensure Loop lines (flexible hoses) to be removed in the gearbox & Alternator bearings and normalized the inlet and out let connections as per original
• Ensure all dummies are removed which installed in PRVs, MOP & EOP discharge piping, control oil line and trip oil line system.
• Ensure all field instruments are fitted properly & they are taken into line
• Take All PRV’s into line
• Ensure all flange joints are fitted correctly
• Ensure all interlocks are in line
• Start the AOP & circulate the lube oil throughout the system

 

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Slop fired Boiler bag filter commissioning & shutdown procedure

Pre-Coating & Pre-heating

• Box – up the bag house and close all access doors properly.
• Keep the module outlet damper full open.
• Close the Bypass dampers 100%.
• Close the inlet damper 100%.
• Make sure that the lime injection system is ready
• Run the ID Fan and adjust the fan controls for effective suction for pre coating. (the air will flow from the boiler section .If required doors in the economizer section can be opened to draw fresh air into the bag filter)
• Run the ID Fan and adjust the fan controls for effective suction for pre coating. (the air will flow from the boiler section .If required doors in the economizer section can be opened to draw fresh air into the bag filter)
• Switch ON the lime injection system and start lime spray into the inlet duct. (Note : Dolomite powder can be used for pre coating)
• Do not start pulsing during this period.
• Observe the change in Differential pressure across the tube sheet.
• After sufficient pre coating, as observed from the Diff Pressure gauge, around 10-  15 mmWG increases, stop the pre coating. Record the readings.
• Stop the ID fan.
• Switch on the hopper heaters
• Switch on the Close Circuit heating system as follows
• Close the bag filter inlet & outlet dampers.
• Open the heating system inlet and outlet valves.
• Start the blower.
• Switch on the heaters.
• Allow the hot air circulation to push up the internal temp > 140 Deg C (Approx).

Bag filter start up

• Open the Bypass dampers both multi lower and puppet dampers by 100%
• Keep Bag filter inlet and outlet dampers closed.
• Ensure that the operation of dust conveying system below the hoppers is checked thoroughly and should be kept in operation
• Light up the boiler and take the exhaust gases through the bypass path.
• Continue with only coal firing.
• Once the gas temperature reaches 140 Deg C +, then take the bag filter in line
• Keep the BF pulsing OFF from the beginning
• Open the bag filter inlet and outlet dampers 100%
• Start closing the multi lower damper in the bypass line gradually, by maintaining the furnace pressure. This will divert the gas gradually through the bag filter. The ID fan speed will go up gradually. This process will take some time
• When the entire gas is diverted through the bag filter and the multi lower damper in the bypass line is fully closed, and then close the puppet damper in the bypass line fully. (Caution: If the bypass dampers is not fully closed then the dust gases can escape to the stack through this route and push up the emission level).
• Continue Coal firing and allow Bag filter inlet temperature to cross 180 Deg C.
• Put the Bag pulsing in demand cleaning mode – Cleaning to start at 175 mmWG and stop at 150 mmWG. This can be readjusted if required.
• Adjust the pulse air pressure to 3.5 Kg/Cm2.
• Adjust Sol. Valve ON time 100 msec , OFF time 25 Sec (to start with)
• Start spent wash firing and increase it gradually in small steps. (Caution: Sudden increase in spent wash firing rate can lead to clinker formation in boiler and chocking of bags in the filter.)
• Start the lime injection system ( Quantity : Lime powder with 50 to 150 microns mesh size @ 150 kg/Hr)
• Restrict the bag filter inlet temp between 180 – 220 Deg C (Max 240 DegC for ½ Hr).
• Record all readings every one hour as given in the log sheet.

Bag filter shut down

Slop fired boiler start up procedure

• After shutdown or tripping the boiler follow following procedures to shutdown bag filter
• Start opening the puppet
  
  
  
  damper fully, after full opening of puppet damper, slowly start opening regulating damper adjusting the furnace pressure & ensure full opening of the damper.
• Close inlet and outlet dampers of the bag filter.
• Keep the pulsing on through timer mode for around ½ hr to dislodge the dust from the bags when the inside temp is high (Caution: Do not pulse the bags when the inside temp is low this may clog the bags.
• Keep the hoper heaters ON.
• Open the inlet and outlet valves of the heating system.
• Start the heating system fan & heater to keep the internal temp to above 140Deg C for ½ hr, till the bag pulsing is over. Keep the dust conveying system ON for at least 1 hr to remove all the dust from the hopper.
• After ½ hour a) Stop the bag pulsing b) Stop the close Circuit heating system. c) Stop the hopper heating system
• Allow the bag filter to cool down in boxed up condition before opening the access doors. Then open the access doors and allow the natural purging before entering inside the filter. 

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