The presentation discuss about the operations, causes and remedies for the facing emergencies of steam Turbines. Specially for the 210MW LMW units. The emergencies can be created on simulator and studied on the simulator ACCORDINGLY.

1. HANDLING OF TURBINE DURING
EMERGENCY
Manohar Tatwawadi
Director, tops
A2-806, Palladion, Balewadi, PUNE,
411045
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2. EMERGENCIES IN TURBINE AND
AUXILIARIES
• In day to day power plant operations there
can be any number of emergencies in Turbine
operation.
• Thrust is given on representative emergencies.
• Following are the representative emergency
operations and they are discussed one by one.
• Operational priorities are also to be decided
by the operating Engineer.
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3. EMERGENCIES……TURBINE SIDE
1) Partial load throw off (due to high frequency).
2) Partial load throw off due to Aux. Failure.
3) Sudden increase of load from full load
4) Bearing Vibrations high
5) Differential Expansion high/low
6) Axial shift high
7) Loss of vacuum
8) High level in condenser
9) Loss of Barring gear or barring gear fails to start
The description of probable causes and remedial operation
at the time of occurrence of such emergencies are
discussed in the following slides.
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4. Partial load throw off.
(due to high frequency)
• Probable Reasons : Due to grid frequency going high OR
disconnection of Unit from grid(CPP).
S.N. Plant Disturbances Actions to be taken
1 The steam pressure at
ESV will increase
FSSS operator to control the
boiler pressure by reducing fuel.
2 Governor will control the
load.
If it fails, Throttle the control
valves suitably and maintain
pressure to normal till the
frequency comes down to
normal.
3 The turbine load will
decrease
There should be a constant
watch on the supervisory
instruments
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5. Partial load throw off.
(due to high frequency)
S.N. Plant Disturbances Actions to be taken
4 Disturbances in differential
expansion, vibration, axial
shift & eccentricity
Check and watch.
5 Disturbance in condenser
level
Adjust and maintain the hot well
level by hotwell level control Valve.
6 Disturbance in Condenser
vacuum
Check and adjust ejector steam
pressure and gland steam pressure to
normal.
7 Turbine lubricating oil temp
will change
Adjust Oil cooler’s water flow as
necessary.
8 Disturbance in Deaerator
pressure
Deaerator pressure tends to fall,
maintain it through extraction on 16
ata / PRDS.
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6. Partial load throw off
(due to Auxiliaries Failure)
Probable Reasons and Action to be taken:-
There is a provision for initial load throw off by help of a relay
without time delay which reduces turbine load to half (100 MW
in case of 210 MW unit) in case of tripping of following
equipment’s.
One C.W. pump in case both are running:
• If the partial load relay fails/not in circuit: Reduce the turbine
load and inform the boiler operator to control steam
parameter in case one C.W. pump or one condensate pump
trip.
• Careful watch may be kept on vacuum.
• Inform the local operator to check the cause of tripping.
• Maintain the deaerator and hotwell level.
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7. Partial load throw off
(due to Auxiliaries Failure)
One BFP in case two are running and standby does not come
on auto remote /not available. :
• Reduce generator load to ½ of full load slowly and try to
maintain Boiler drum level
• Inform the local operator to check the cause of tripping.
One condensate pump in case two are running and standby
dose not come on auto/ remote not available:
• Careful watch may be kept on vacuum.
• Take the standby ejector in service if necessary.
And also due to tripping of any one of I.D. fan, F.D. fan P.A.fan.:
• Reduce load to ½ full load.
• Inform the local operator to check the cause of tripping
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8. Partial load throw off
(due to Auxiliaries Failure)
In case of full load throw off (due to opening generator
breaker):
• Unit trip on protection.
The turbine may trip due to over speeding :
• Close the control gear hand wheel
If closing control valve can not control the speed :
• Check that ESV, IV and control valves are closed.
Immediately otherwise trip the Turbine by emergency
trip button.
• Close the Boiler Outlet valves in the M.S. line.
• Close the Extr. steam valves.
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9. Sudden increase of load from full load
• Probable Reasons and Action to be taken:-
Low frequency : Since the turbine is on governor control the load
will increase due to fall in speed.
• Reduce the load by the control gear and bring the boiler
parameter and load to normal.
Due to sudden rise of boiler drum pressure:
• Bring back the load /governing wheel pressure to normal by
control gear and inform the boiler operator.
Due to HP Heaters Bypassing on protection:
• Keep a close watch on the Generator output current, Stator
winding temp, Hydrogen temp, Boiler Drum Level.
• Slowly reduce the control gear to reduce generator load to
normal value.
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10. Turbine Bearing Vibrations High
Normally the vibration in bearings should be within 40 microns.
If it exceeds the limit, turbine should be shut down:
• Check the turbine cylinder drain should not be cold (if necessary
open the drain valve for few minutes if turbine is on load).
• Check bearing oil press flow and temp. to be normal .
• Check for any rubbing sound etc.
Turbine bearing oil press low :
• Reduce the load /speed.
• Check the main Oil line pressure and maintain it.
Bearing oil inlet temp. High :
• Check the cooling water valves are open in oil coolers and vent the
coolers.
• Put the standby cooler in service, ensure C.W.P. is running normal.
• Check bearing oil outlet temp. (less then 65° c ).
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11. Differential Expansions high/low
Probable Reasons and Action to be taken:-
• Normally the rotor gets long during running and gets short
during shut down.
• The expansion is to be controlled by admitting steam or
shutting off supply to flange and stud heating, chamber
heating accordingly.
• In case if it goes beyond control, the machine to be tripped:
• Check the steam temp. reduce load / speed.
• Check the valve for flange heating is in open condition if
rotor is long or Close if rotor is short.
• Check and adjust gland steam temp.
• Check the vacuum to be normal
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12. Axial shift high
Probable Reasons and Action to be taken:-
• In case of excessive shift the turbine will trip through the protection
• Due to Sudden change in load : Control the load and maintain the
steam parameter.
• Abrupt change of steam parameter: Control the load and maintain
the steam parameter
• Sudden closure of FCNRV of heater (HP/LP): Control the load and
maintain the governing pressure, if heaters are healthy open
FCNRV.
• Variation in lub. Oil temp .pressure and quality : Maintain lub. Oil
pressure and temp. for quality get the oil tested from laboratory
and if necessary oil is to be changed.
• Difference of oil temp . from thrust bearing front & rear outlet
should not be more than 3°c.
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13. Loss of vacuum
Probable Reasons and Action to be taken
• If there be any loss of vacuum, start the standby
ejector at the earliest.
• Still if it does not improve start starting ejector.
• With no further improvement of vacuum, reduce the
load as required to maintain the vacuum at 700 MM.
• Meanwhile try to detect the specific reason which may
be as follows…..
: Steam ejector not properly functioning
: Check that steam pressure in 6 kg/ cm².
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14. High level in condenser
Probable Reasons and Action to be taken:-
• Malfunctioning of condensate pump or valve: Check the normal
running of the condensate pump, start standby.
• Check the operation of valve from UCB by taking it to manual, if not
all right control the hot well level bypass valve.
• Malfunctioning of DM make up valve : Close valve from UCB and
watch that hot well level falls.
• Condenser tube leakage : If the above operation fails to control the
hot well level, get the condensate water tested by laboratory to
confirm the leakage .if the tube leakage is very high, it may not be
possible to pump out the condensate from the condenser when the
condensate level will gradually increase. Ultimately if the water
level rises up to the air suction space of condenser , water will be
sucked in to air suction pipe line of the ejector. When the same well
be supercooled and ejector will not function. Shut down the turbine
at the earliest to get the leakage attend.
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15. High level in condenser
Probable Reasons and Action to be taken:-
CW pump failure :
• If one pump is tripped , reduce the load. Meanwhile determine the
cause of CWP failure and rectify the defects. Of course if both the
CW pumps fails , there is no way out other than to trip the unit.
Malfunctioning of DM make up valve
Condenser tube leakage
Air leak into system :
• Check scaling water pressure to valves under vacuum is normal.
Check starting ejector air vale and vacuum break valve are tightly
closed. Measure the amount of air leakage At air removal
equipment outlet and investigate the source of leak.
Condenser tube choking : Check the CW inlet and outlet temperature.
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16. Loss of Barring gear or barring gear
fails to start
Probable Reasons and Action to be taken:-
• For loss of electrical supply: D.G. set will start
automatically Otherwise start. : If not possible to
start the DG set, attempt to turn the Turbine
shaft by slings with the help of over head crane
by 180 Degrees at regular intervals of 15 minutes
after cutting in the D.C. emergency lub oil pump.
• Smoke from turbine seals. : Check differential
expansions are normal
• Reduce seal steam temperature, if high.
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