Trouble Shooting for Turbine

8/10/2019 Trouble Shooting for Turbine

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TROUBLE SHOOTINGTROUBLE SHOOTING

FORFOR

STEAM TURBINESTEAM TURBINE

MHI TURBO TECHNO CO.MHI TURBO TECHNO CO.HIROSHIMAHIROSHIMA


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INDEX

1. GENERAL

2. VIBRATION3. UNUSUAL SOUND

4. BEARING TEMPERATURE

5. TROUBLE ON GOVERNOR

6. BOILER CARRY OVER

7. VACUUM FAILURE

8. OTHERS


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1.1. GENERALGENERAL

I t is most important to keep the continuous operation without troubleobserving the operating conditions@carefully.

This text describes the possible causes and the necessary check and handlingitems for the unusual operating conditions.

Emergency shut down may be required in worst cases due to the serioustrouble, however causes of the unusual condition shall be investigatedduring operation and the countermeasures shall be taken to avoid shut downand / or to minimize shut down duration.

Usually, one trouble causes another troubles to damage the unit seriously,

the investigation of the prime cause is the most important things to find out.

Troubles as described hereafter can be avoided if appropriatecountermeasures are taken, therefore daily maintenance and care for theunit are fully recommended.

In case that the cause of trouble is not confirmed and that thecountermeasure requires some engineering and technical information and /

or skill, it is recommended to contact toMHI TUR O TECHNO CO

HI TUR O TECHNO CO..


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2.2. UNUSUAL VIBRATIONUNUSUAL VIBRATION

PHENOMENON 1 No indication of

vibration monitor

POSSIBLE CAUSE Monitor failure

Probe failure Wire failure

Driver failure


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By pass the monitor Check the vibration monitor

Check gap voltage of the probe Check the wiring

Check the driver

CHECK & HANDLING ITEMSCHECK & HANDLING ITEMS

DURING OPERATIONDURING OPERATION


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PHENOMENON 2 Excess vibration on NC1

during start up.

POSSIBLE CAUSE Thermal deformation by

steam introductionwithout turning of therotor

Turning duration is tooshort

Long term storage athorizontal condition

NC1

Speed(RPM)

Am

plitude

N


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Speed down keep around 300rpm as long as possible

Retry to speed up If the vibration level dose not reduced,

rebalancing of the rotor would berequired




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PHENOMENON 3 Shaft vibration is

increased correspondingto speed up in governorspeed range

POSSIBLE CAUSE Gear coupling lock

Miss-alignment

NC1

Speed(RPM)

Gov. range

Amplitude


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Continue operation monitoring thevibration

Lower lube oil supply temperature Make frequency analysis




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increased gradually andbearing metaltemperature is alsoconstantly high.

POSSIBLE CAUSE Over heat of bearing

and increasing bearingclearance

Lube oil property isfailed

Time

Amplitude


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Lower lube oil supply temperature Watch drain oil temperature of bearings

carefully Analyze lube oil property

Decrease speed if the vibration levelreaches at alarm point




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increased suddenly andcontinued the amplitudeat same level

POSSIBLE CAUSE Failure of shaft

A part of shaft is blewoff

Time

Amplitude


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Check history of vibration Make frequency analysis

Check phase of vibration




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increased and after awhile it is decreasedperiodically

POSSIBLE CAUSE Light rubbing of rotor

with stationary parts Heavy rubbing of rotor

with stationary parts bymovement of the lower

half case

Time

Amplitude

Cyclic


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Make frequency analysis Check phase

Check thermal expansion of case Monitor bearing metal temperature




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3.3. UNUSUAL SOUNDUNUSUAL SOUND

PHENOMENON 1 Light noise

continuously Heavy noise

continuously

Noise discontinuously

POSSIBLE CAUSE Contact with internal

labyrinth Contact with nozzles

- Contact with foreignmaterial


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Monitoring with sound detecting rodand keep your eye on the vibrationmonitor, try to increase speed

If the noise and/or vibration is notreduced, shutdown the unit and

overhaul the case




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PHENOMENON 2 Noise from Governor

side bearing pedestal

POSSIBLE CAUSE Failure of Governor

driving gear Failure of tripping lever

for emergency tripdevice

Loosening of internal oilpipe if provided


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Analyze frequency of the noise If the noise and/or vibration is not

reduced, shutdown the unit andoverhaul the bearing pedestal




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PHENOMENON 3 Noise from valve chest

during throttling or atfully opening

POSSIBLE CAUSE The valve body is

vibrating by steamstream at small opening

Failure of valve body,stem, seat etc.

Plugging by foreignmaterial


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Passing quickly through this valveopening

Check steam pressure, temperature,flow and lift to compare with expecteddata

If the steam consumption is extremelyhigh, the unit would be shutdown torectify the problem in the valve




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4.4. BEARING TEMPERATUREBEARING TEMPERATURE

PHENOMENON 1 TG indication is lower

than actual temperatureat oil drain line

POSSIBLE CAUSE Failure of TG

Thermo well is notimmersed in oil


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Calibrate TG Check installed position of TG




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PHENOMENON 2

TG indication is

incorrect

POSSIBLE CAUSE

Failure of TG

Shortage of oil flowto thermo well

Thermo well

Oil


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Make calibration of TG Turn back the thermo well to release the

plugging of the oil hole




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PHENOMENON 3

IT indication of thrustbearing metal is toohigh

Maximum allowabletemperature is 125

POSSIBLE CAUSE

Bearing clearance is toosmall

Supply oil flow is tooshort


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Adjust lube oil temperature to lowerward

Adjust to increase lube oil pressure Check oil drain condition

If the bearing metal temperaturereaches to 125 , shutdown the unitand inspect the bearing




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PHENOMENON 4 TI indication of thrust

bearing metal is notsame at upper and lowerpad

POSSIBLE CAUSE Thrust bearing clearance

is not same through allthe pads and thrust discis slightly inclined

Force

Shaft


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Check TI indication per each pad Check thermal distribution of the

flexible support

Check thermal expansion of the turbinecase

If the bearing metal temperaturereaches to 125

, shutdown the unitand inspect the bearing




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PHENOMENON 5 Fluctuation of lube oil

supply temperature

POSSIBLE CAUSE Fluctuation by air inside

of oil Fluctuation of oil

pressure

Fouling of oil cooler


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Vent air from oil lines Check lube oil pressure control valve

Check oil tank level Drain out water from oil tank, if any




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5.5. TROUBLE ON GOVERNORTROUBLE ON GOVERNOR

PHENOMENON 1 Turbine speed is

slightly lower thanindication from C.C.R

PG-PL Governor

POSSIBLE CAUSE Leakage air from

instrument tubing and /or fittings

Miss setting of air signaland speed of Governor

Air pressure 1.0k0.2k

105%

85%

Speed


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Check any leakage from instrumenttubing and / or fittings

Check water contents in the instrumentair

Try to adjust manual knob on Governorto upper ward




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PHENOMENON 2 Governing valve lift is

greater thancorresponding lift tosteam flow

POSSIBLE CAUSE Spindle of inner bar is

damaged and bar isreclined on valve seat

Stem of governing valveis damaged and stayed

on valve seat Plugging strainer in

T.T.V by foreignmaterial from upstream

Steam flow

Valve

Lift


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Check history of valve lift, if any Check vibration and its frequency the

spindle by handy vibro-meter




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PHENOMENON 3 Extraction steam flow is

not increased and thepressure is not increasedeither

POSSIBLE CAUSE Failure of governing valve

and shortage of inletsteam flow

Miss lever setting ingovernor system

Excess consumption ofextraction steam


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Check steam pressure, temperature andflow to compare with expected data

Check relative valve lifts of governingand extraction control valves




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PHENOMENON 4 Governing linkage

levers are not smoothlystroked

POSSIBLE CAUSE Hysterics of linkage by

loosening or hard contact Stick on piston of pilot

valve

Stick on piston of power

cylinder

Stick in PG-PL Governoror E/H actuator


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Changing the load, find out the stickingpoint

Check relation between Governoroutput and lift of E/H actuator




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PHENOMENON 5 Movement of E/H

actuator is not smooth

POSSIBLE CAUSE Piston is sticking by oil

contamination Hunting by air in oil

Reduced manipulationpressure by pressure

drop through in linefilter


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Check actuator lift corresponding tooutput signal of Electronic Governor

Vent air from control oil line Switch over in line filter



5 O O GO OTROUBLE ON GOVERNOR


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PHENOMENON 6 T.T.V is not fully closed

when emergencyshutdown is made

POSSIBLE CAUSE Stationary parts such as

hydraulic shutdownpiston, shutdown cams,valve stem is sticking inlong term operation

The valve stem isbending by roughhandling

Scale accumulation in

the bush in long termoperation


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Close main stop valve in steam inletline

After the shutdown, overhaul the T.T.V Activate partial stroke test device

periodically during operation



66 B ilB il


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6.6. Boiler carry overBoiler carry over

PHENOMENON 1 Steam header pressure

and temperature arewent down suddenly

Excess thrust force isindicated by axial

displacement probes

POSSIBLE CAUSE Water mist is carried

over to Turbine


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Check fluctuation of Boiler drum Observe steam pressure and

temperature

Observe thrust bearing metaltemperature and axial displacement

In case axial displacement reaches tothe trip level, the turbine will be trippedas a one of interlock system



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PHENOMENON 2 Turbine thermal

efficiency goes downand steam consumptiongoes up gradually

POSSIBLE CAUSE SiO2 in steam makes

deposit on blade andnozzle, and steampassage area becomesnarrow to reduce

thermal efficiency Hematite (Fe2O3), which

is formed in boiler andalso inlet steam pipe,

will also attack turbineto accumulate on bladeand nozzle

CHECK & HANDLING ITEMS


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Check relation of steam flow and valvelift of Governing valve and Extractioncontrol valve

Check steam pressure after 1st stage ofHP or LP case corresponding to inlet

steam flow



66 Boiler carry overBoiler carry over


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PHENOMENON 3 Shaft vibration is grown

up suddenly undernormal operation

POSSIBLE CAUSE Corrosive material (SO2,

NaOH, NaCl) attacksblade and breaks it dueto repeated stress

Time

Amp

litude



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Make frequency analysis and checkphase change

Decrease speed if the vibration levelreaches at alarm point



77 VACUUM FAILUREVACUUM FAILURE


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7.7. VACUUM FAILUREVACUUM FAILURE

PHENOMENON 1 Condenser absolute

pressure is higher thanspecified pressure

Shortage of vacuum

POSSIBLE CAUSE Air leakage to condenser

is more than the capacityof air ejector system



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Check the driving steam pressure to airejector

Check the cooling water quantity andsupply temperature

Check sealing water distribution system



77 VACUUM FAILUREVACUUM FAILURE


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7.7. VACUUM FAILUREVACUUM FAILURE

PHENOMENON 2 Air ejector system is not

stable and the vacuum isfluctuated

POSSIBLE CAUSE Foreign material is

plugging to the ejectornozzle or strainer

Air trap in drain line forafter cooler is not

functioned well

Time

Vacu

um(P)



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Stop operating of air ejector system toknow the vacuum retention timewithout service of air ejector

Prepare spare of ejector nozzle and /orair trap to replace under operation



88 OTHERSOTHERS


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8.8. OTHERSOTHERS

PHENOMENON 1 Condenser hot well tank

level is increasecontinuously

POSSIBLE CAUSE Fluctuation of level

control Suction strainer is

plugging due to scalesor foreign materials

Cavitation of thecondensate pump

Cooling water leaks tothe shell side



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Check pressure of suction anddischarge of condensate pump

Check abnormal sound fromcondensate pump

Adjust level controller (P and I), if

necessary Check conductivity of condensed water



88 OTHERSOTHERS


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8.8. OTHERSOTHERS

PHENOMENON 2 Oil leaks through

bearing pedestal

POSSIBLE CAUSE Large clearance of oil

slinger ( Labyrinth ) Air breather is plugging

( higher internal pressure )

Windage by the coupling

( higher internal pressure )

Insufficient bolting of thestud bolts ( split bolts )



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Check internal pressure of the bearingpedestal by manometer

Check condition of the air breather

Retighten stud bolts of the bearingpedestal



Trouble Shooting for Turbine

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