Operation and maintenance of hydropower stations planning and
management – an Indian perspective
CONTENTS
1
INTRODUCTION
1
2
PREVENTIVE MAINTENANCE OF HYDRO TURBINE
1
3
REQUIREMENT OF EFFECTIVE MAINTENANCE
2
4
MAJOR MAINTENANCE PROBLEMS OF WATER TURBINES
2
4.1 RUNNER
4.1.1 EROSION DUE TO SILT
4.1.2 CAVITATION RELATED CRACKING AND WEAR OF THE RUNNER
4.1.3 PRECAUTION IN WELDING OF RUNNERS
4.2 TURBINE GUIDE BEADINGS
4.3 GLAND SEALS
4.3.1 CARBON OR FERROBESTOS SEGMENT TYPE
4.3.2 RUBBER FLAP TYPE
4.4 GUIDE VANE SERVOMOTOR
4.5 GOVERNOR
4.6 GOVERNING OIL SYSTEM
4.7 HEADER
2
2
2
2
2
2
2
2
2
2
2
2
5
2
PREVENTIVE MAINTENANCE OF HYDRO GENERATORS
1 Introduction
Experience of running hydropower stations in India has shown that even after careful project
planning and good quality control measures from construction to commissioning, unforeseen
problems do occur in service resulting in unplanned outages / low generation and load
shedding etc. This causes disruption to consumers and reduced cash generation for the
operator. A contributing factor to these operational problems is the fact that hydro power
equipment and plant is custom built. The equipment cannot be fully assembled or tested in a
factory before sending it to site. Maintenance activities at predetermined time intervals are
necessary to ensure the following:
1.
2.
3.
Quality and reliable operation of equipment in the service environment through planned,
periodic inspection and checking of components and systems. Together with replacement
or rectification of parts wherever required.
Maximum availability of equipment and a minimum of unplanned shut downs by using
planned / periodic shutdowns to inspect all equipment (serviceable and non-servicable).
Eradication of operational problems by a timely analysis of the cause of faults / problems
and replacement of short term solutions by long lasting and permanent ones.
2 Preventive maintenance of Hydro turbine
In order to achieve above objectives of maintenance, time has to be allotted every year for
each machine. Normally the periodicity and the procedure for maintenance is recommended
by the manufacturer of the equipment. However, experience of operators of Hydro Power
Stations in India has shown that the maintenance is required according to the following
guidelines.
Routine Maintenance
Normally there will be daily, weekly, monthly and quarterly checks as per the maintenance
schedules are done. These checks are necessary for controlling any change in the installed
clearances, commissioning characteristics etc. connected with the performance of equipment.
Rectification and adjustment wherever required should be carried out in order to arrest any
deterioration of the equipment.
The daily, weekly and monthly check schedules designed for Chilla Hydro Power Station are
used to illustrate the kind of maintenance schedule that will be needed:
2.1.1.
Daily Maintenance Checks
1. Foundation Parts and Expansion Joints:
Check for any leakage in draft tube manholes, spiral casing manhole, expansion joint.
2. Vacuum Breaking Valve:
Check the working of both vacuum breaking valve and see that there is no abnormality in the
springs, seats etc.
3. Water Seal and Air Seal:
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•
•
Check the position of water leakage around the water seal and check that there is no
excessive splashing and water level do not rise in top cover.
Note water pressure of water sealing/under sealing.
4. Turbine Guide Bearing:
•
•
•
•
Check the oil level (stand still machine/running machine).
Note the temperature of bearing and check that the temperature of oil and guide bearing
pads are within limits.
Note the maximum and minimum temperature of the previous day.
Check for any oil leakage from the bearing housing and check that oil is flowing above
the bearing pads.
5. Guide Apparatus:
Check any leakage from GV servomotor and its piping.
Oil Leakage Unit:
•
•
Check any leakage from pipe line joints.
Check its satisfactory running on `Auto’.
Top Cover Drain System:
•
•
•
•
Main supply of `ON’ for DPM.
Vibration noise in the pump motor.
Any leakage from the water piping.
Working and water pressure of the ejector.
Centralised Grease Lubrication System:
•
•
Check for any leakage from grease pipes, unions and nipples.
Check grease container and fill grease, if required.
Oil Header:
•
•
•
Check from perspex sheet manhole any splashing of oil from top and bottom bush.
Check any oil leakage from the joints.
Note the pressure difference of opening and closing side of runner.
Oil Pressure System:
•
•
•
•
•
Check if there is any abnormal sound in the running of the motor and pump unit of OPU.
Check the oil level in pressure accumulator.
Check any oil leakage from oil piping and its valve.
Check for over heating of motor.
Note the timing of OPU pumps running.
Mechanical Cabinet of Governor:
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•
•
Pressure in transducer.
Check any oil leakage from joints of piping.
2.1.2.
Weekly Maintenance Checks:
1.
Greasing of guide vanes and servomotor with centralized grease lubrication system and
manually.
i) Oil in the gear box shall be checked.
ii) Check for any leakage
iii) Working of end pressure relay and solenoid valves, if defective, should be reported.
2.
3.
4.
5.
6.
Cleaning of OPU filters
Cleaning of throttle filters in the governor mechanical cabinet.
Cleaning of governor compressor air filters and checking of oil levels.
Checking physically oil of OPU of the running machine after sample taking through the
sampling cock and do the crackle test for detecting presence of water. Take remedial
measures.
Check oil level of all the bearings.
Check wobbling of shaft at coupling flange and at oil header servo-tube.
2.1.3.
Monthly Maintenance Checks
All the checks covered as part of the weekly maintenance are also carried out as part of the
monthly check. In addition to these checks, more attention is paid and short shutdowns, if
required, for rectification are taken.
2.1.4.
Annual Preventive maintenance of Hydro Turbines
After successful running of plant for about one year, a few weeks are required to inspect
rotating parts, control equipment and measuring instruments and to analyze the cause of
changes in the performance characteristics, if any. Modify, repair or replace (wherever
required) worn out parts in order to prevent unplanned outages of plant at later date.
After every five years it is necessary to inspect the machine more critically for abnormalities
like fatigue defects or excessive wear and tear of some parts or any change in original
parameters/clearances etc. This exercise becomes very essential in cases where performance
level has been observed to have gone down in 5 years operation.
The checks for annual and five yearly maintenance specified for Chilla Power Station are
enlisted below:
1.
Foundation Parts:
i)
ii)
2.
Check condition of water path system. The damage due to cavitation and wear
to be rectified.
Check painting of spiral casing.
Runner:
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i)
ii)
iii)
3.
Guide Apparatus:
i)
ii)
iii)
iv)
v)
vi)
4.
ii)
iii)
iv)
ii)
ii)
Check the functioning of emergency slide valve and the condition of inner
surfaces.
Swift return of the valve in its original position after emergency operation
should also be checked.
Centralised Grease Lubrication System:
i)
ii)
8.
Check the condition of rubbing surface of sealing rings. In case found
damaged change the same.
Check pipe lines and piping joints for any leakage if any, attend the same.
Emergency Slide Valve:
i)
7.
Check the condition of rubbing surfaces of guide bearing. Clean the surface
and polish it with the help of chalk powder.
Adjust the clearances by moving the segments with the help of adjusting bolts.
Thorough cleaning of housing if necessary.
Check all the RTDs and TSDs replace damaged one.
Shaft Gland Seal and Air Seal:
i)
6.
Check the presence of rubber sealing cords and the tightness of the rubber
sealing between the adjacent guide vanes in fully dosed position of guide
apparatus.
Change oil in the regulating ring.
Replace damaged shear pins.
Check cup sealing of guide vane journals and replace, if necessary.
Check the bushes of guide vanes and change the worn out bushes of guide
vanes journals.
Inspect the servomotor and change the seals, if these are worn out.
Guide Bearing:
i)
5.
Check the condition of the surfaces of the runner hub and the blades. The
damage due to cavitations & wear to be rectified by welding and grinding.
Check the runner blade seals by pressurizing the system. Change seals if
necessary. No oil leakage is to be allowed.
Check the runner sealing for hermetic tightness, leakages of water in the runner
hub is not to be permitted.
Check satisfactory working of CGLS system.
Attend wherever fault is located.
OPU:
i)
ii)
iii)
iv)
v)
Check and attend leakage from any valve or flanged joints etc.
Provide proper lubrication to the bearings of pump motor.
Check filter and repair, if required.
Clean oil sump, refill with centrifuged oil.
Check setting of the float relays for proper sequence of operation of pumps.
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9.
Oil Header:
i)
ii)
iii)
10.
Oil Leakage Unit:
i)
ii)
iii)
11.
Check satisfactory working on Auto as well as manual.
Clean the tank.
Check the pipeline joints and valves for leakage, attend wherever necessary.
Oil Cooling Unit:
i)
ii)
12.
Measure clearances of upper and lower bushes, if found increased get the
bushes replaced.
Clean the oil bath.
Check the rubber cord fixed below the guide to check any oil dipping on the
exciter winding.
Check all the oil and water pipe lines for leakage and attend if necessary.
Check satisfactory working of all cooling unit.
Governor Mechanical Cabinet:
i)
Check filter and throttle if found damaged replace the same.
ii)
Attend leakage of oil through pipe line joints and valves.
iii)
Check auto rod setting, if found disturbed; set the same.
iv)
Check (Alpha – Beta) characteristic, if found disturbed set the same.
Alignment of feed back wire rope pulleys.
2.1.5.
Capital Maintenance
Overhauling or capital maintenance of hydro plant is usually recommended after about 10
years of operation services. The whole unit is to be stripped off during capital maintenance
and all the defective/worn out parts/components repaired/replaced with new ones. Then the
unit is re-commissioned as per originally established commissioning practice of the power
station.
After capital maintenance the units are subjected to all maintenance exercise outlined above
before it reach the next cycle of capital maintenance.
Following checks are to be exercised during capital maintenance of a hydro set:
1.
Turbine Bearing:
i)
ii)
2.
Dismantling, inspection, cleaning, measurement of clearances, polishing of
guide pads, centering of shaft, reassembly, setting of clearances, filling of oil
sump with filtered water.
Check the temperature sensing device, if necessary, replace with new ones.
Gland Seals and Isolating Air Inflated Seals:
Dismantling, inspection, cleaning and reassembly. Replacing of worn out rubber flaps
or carbon segments, if necessary.
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3.
Clean Water System:
Clean water pipes are dismantled, cleaned, reassembled with new gasket all the valves
are attended for any leakage etc.
4.
Guide Vane Servomotor:
Dismantling for inspection and cleaning. Reassembling and replacing the seals with
new ones, if necessary.
5.
Guide Vanes Bush Housing:
i)
ii)
6.
Governor:
i)
ii)
iii)
iv)
v)
vi)
7.
Cleaning and checking OPU pumps. Replace bushes, bearings etc. if found
worn out. Also attend pump motors.
Cleaning OPU sump and pressure accumulator and refill with filtered oil.
Attend oil pipeline flanges and valves for leakages.
Check setting of pressure switches installed for Auto Operation for OPU
pumps.
Attend Governor Mechanical cabinet for leakages, loose links. Clean main and
pilot slide valves. Set Auto rod as per designs Alpha Beta setting may also be
checked.
Check electrical circuit. Tightening of all the connections should be done.
Submerged Parts
i)
ii)
8.
Removing, cleaning and inspecting for wear and tear replacing with new ones
if found necessary. Replace seals, if necessary.
Guide vanes are reconditioned.
Cleaning and painting of spiral casing and draft tube liner.
Overhauling of spiral drain valve and draft tube drain valve.
Runner
i)
ii)
iii)
iv)
v)
De-watering of draft tube and fabrication of platform in the draft tube for
inspection of runner.
If it is a Kaplan Runner test the same after applying full governor pressure for
leakage of oil.
Replace blade seals, if necessary.
Inspect blades of the runner and make up profile of the blades by welding. Due
to erosion, abrasion and cavitations, material of the blade washes away with
passage of time.
In case the runner is found to be irreparable arrange to replace the same with
new one.
Turbine Auxiliaries
1.
DPM
i)
Inspect top cover drain system, overhaul the ejector and drainage pumps.
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ii)
Check pipe lines and valves. Replace gaskets and other parts, if necessary.
2.
Oil Cooling Unit
i)
Overhaul cooling pumps
ii)
Attend all the valves and pipe lines for leakage.
3.
Centralised Grease Lubrication System
i)
Overhaul greasing pumps
ii)
Check whole greasing lines. Replace worn out valves and gaskets etc.
iii)
Check all the nylon pipes connected with the guide vane bushes. Replace
damaged pipes.
iv)
Check that all the guide vanes are receiving grease properly.
4.
Oil Leakage Unit
i)
ii)
iii)
Check the oil leakage unit overhaul the pumps.
Clean tank and check that float is properly working.
Checking all the pipe liens and valves for leakages.
3 Requirement of effective maintenance
In addition to planning maintenance and implementing a suitable schedule (on the basis of
seasonal water availability perhaps), the following items also require attention otherwise it
may be difficult to keep to the schedules in practice:
1.
2.
3.
4.
5.
6.
4
Man Power Planning and arrangement is essential as without experienced and skilled
staff any maintenance programme may fall.
Planning and arrangement of spares and consumable in advance so that time is not lost in
re-commissioning the plant after the shut down.
The maintenance engineers should have in his possession all the erection and
commissioning log sheets documents to establish a record of installed clearances,
parameters, alignment results, test characteristics of all the power plant equipment. These
may be required at the time of diagnosis of the operational problems as well as defined
maintenance purpose.
Log sheets of the previous maintenance exercise carried out on the machines. These may
be required to compare with the clearances / settings / characteristics achieved during
present maintenance.
History registers of all plant should be kept with records of all the abnormalities observed
on the machine and details of action taken. This data can be used to as a guideline for
future maintenance work at the power station.
Logging of the performance characteristics of the power plants on daily basis recording
all the abnormalities and misbehaviours (if any) of the total plant observed during its
generation programme from one maintenance exercise to another.
Major maintenance problems of water turbines
Some of the major problems encountered in the hydro turbines are damage in runners due to
erosion, cracking and cavitation due pressure pulsation in draft tube, instability of operation at
partial gate opening. Other serious issues include failure of turbine guide bearings, leakages of
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water through turbine guide bearings, leakage of water through guide vane seals and turbine
gland seals. These problems are discussed in detailed in the following section.
4.1
Runner
4.1.1 Erosion due to silt
Erosion of turbine runners, guide vanes and other under water parts is a serious service
problem especially in run-of-river schemes. The rivers in the Northern region of India carry
significant silt loads especially during monsoon period so much so that hydro power stations
are often closed down to prevent serious damage to the turbines parts and water passage.
Greater attention should, therefore, be paid to effective de-silting arrangements. Excessive
wear and damage often occurs on the runner labyrinths, seals, guide vanes, butterfly valves,
shaft seals and draft tube cone. Wear due to silt occurs so fast that the turbine units have to be
taken out for repair every few months in some stations. The solution lies in the original
specification of effective de-silting civil works however, this is of little practical help in the
service environment. In the service environment the use of turbine parts coated with or made
from material with harder and erosion resistant properties is the most practical option to be
pursued.
At Chilla Project following measures of de-silting have been taken:
i) Silt extruders have been provided near under sluice gates of the barrage.
ii) Half a kilometre downstream of the head regulator, a silt ejector has been constructed in
the bed of the power channel.
4.1.2 Cavitation related cracking and wear of the runner
The problem of cracks in turbine rotors and Pelton buckets has been reported in few power
stations. This can be due to following reasons.
i) Faulty design
ii) Poor metallurgy
iii) Metal fatigue
The phenomenon of cavitation occurs due to the vaporization of water in a zone of excessive
low pressure. Cavitation damage can occur if the turbine has to operate at part flow. Limits of
structural wear (metal removal) are normally specified beyond which repair of the plant is
needed. To minimize the effects of cavitation, the following steps are recommended:
i)
Periodically (annual) inspection of the runner and other turbine parts to judge when repair
is necessary.
ii) Operation of the turbine plant according to the manufacturers guidelines. Specifically, a
turbine unit should not be run below the minimum load (discharge), recommended by the
manufacturer.
iii) At design stage, ensure i) proper submergence of the turbine ii) correct specifications of
cavitation resistant materials and iii) specification of the runner profile based on model
tests for cavitation onset.
iv) As a result of draft tube pulsation and surges at no load or part gate opening excessive
noise, vibrations and cavitation is experienced. To minimise pulsations of draft tube
following measures must be taken:
-
Air admission through air admission/ vacuum breaking valve installed at top cover.
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-
Provision of fins or flow splitter in draft tube to break the vortex flow.
Provision of a bypass arrangement for releasing the pressure built up below the top cover.
Normally the discharge side surface of buckets or blades, areas on the crown on the throat
ring and the tip of the blades and the upper portion of the draft tube liner are affected by the
action of cavitation. In rare cases, there may be pitting on the pressure faces of the buckets or
blades due to an unusual amount of over hung of the guide vanes improper design or unusual
operating conditions.
Hydro Power plant operators have, over the years, gained expertise of ways of repairing and
welding of the runner at site, but it becomes a regular maintenance problem as wear and
cracking occurs quickly.
4.1.3 Precaution in welding of runners
Some general remarks about the welding repair of turbine runners are given below. It should
be noted that different materials will require specific (often proprietary) welding processing.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Surface of the parent material should be prepared by chipping or grinding.
To locate cracks, inclusions and the like, a die penetration test must be carried.
Preheating of the blade to about 60oC is necessary
Avoid any localized excessive heating. This is achieved by welding for a short time in
any one particular area and then moving to a diametrically opposite area to continue with
the work.
The parent material should be about 70 to 75 mm from the weld and should not be
allowed to get too hot to be touched with bare hand.
Plenty of time should be allowed for the welded area to cool down since forced cooling
may cause distortion due to locked in stresses. Hot peening is also required.
A close check should be made at least two to three times per day during the repair for
runner to runner chamber clearances.
After welding all the welded areas should be properly ground to match with the desired
profiled.
Die penetration tests should once again be carried out to ensure crack free welding.
Rectification if necessary should be done.
If extensive welding on the runner is required, it will be necessary re-balance statically and
possibly dynamically all rotating parts and stress relieving before recommissioning otherwise.
4.2 Turbine Guide Beadings
A number of turbine guide bearing designs are in use. These may be classified as follows:
i)
ii)
iii)
iv)
v)
Plain water cooled bearing
Bath type with circular cooling turbines
Bath type with cooling water tubes embedded in the pads.
Rotating bath type.
Grease lubrication bearing.
In the case of plain water cooled bearings, either ferrobestos or rubber lined pads are used
against a welded shaft sleeve. The ferrobestos lined bearing have given considerable trouble
at one of the power station and these had to be replaced by rubber lined pads.
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Small diameter cooling pipes embedded in bearing pads have a tendency to clog especially at
the time of high silt contents resulting water starvation.
Complaints of excessive oil splashing have been received about the rotating bath type bearing.
Grease lubrication bearings have a tendency to clog when in contact with the water and it is
very essential to use grease with the right type of properties.
A number of cases of turbine guide bearing failures have come to notice. These are:
i) Starvation of oil in the bath
ii) Failure of cooling water due to clogging of pipe.
iii) Mal-functioning of instruments like RTDs, TSDs, oil level relay and flow relays etc.
To avoid failure of bearing due to cooling water tube, a new design of turbine guide bearing
has been developed by BHEL, Hardwar. Two separate oil sumps are located in the top cover
in diametrically opposite locations. These sumps, through pipe lines are connected to the oil
bath of the bearing. The oil is circulated between sumps and the bath. Top cover being
stationed just above the draft tube, separate to cooling water arrangement for bearing oil is not
required. The bearing temperatures with this arrangement never go beyond 40oC to 42oC and
this design is effectively working at Chila Power Station.
4.3
Gland Seals
Normally two types of shaft gland seals are in use in different power stations:
i) Carbon or ferrobestos segment.
ii) Rubber flap type
4.3.1 Carbon or Ferrobestos Segment Type
The seal segments are housed in the stuffing box. Stuffing box being always in touch with the
shaft is subjected to excessive wear and tear. The overhauling of the stuffing box becomes
necessary when it is observed that consumption of cooling water has considerably increased
or excessive water in top cover appears to be coming. In general maintenance of the seal is
required to be done annually.
In the event of breakage or damage to a carbon segment it is advisable to replace the whole
set of carbon segments. In very rare case only the damaged segment is replaced care must be
taken to ensure that the axial thickness of the new segments falls within the limit size to ±
0.002” of the existing ring to which it is to be fitted.
All carbon segments and spacers are fitted to place and match marked on assembly. Whenever
any part is replaced, matching marks / indents should be made after final assembly is
satisfactorily completed. Whenever reassembly of the gland seal with existing gland ring or
new ring is done it is important to ensure:
1.
2.
3.
4.
All carbon/ ferrobestos segments are carefully examined for any chipping or damage.
All stainless steel facings are flat and square with the gland sleeve and there are not steps
at the facing joints.
Stainless steel facing and sleeve are completely free from grease.
Ensure proper bedding of segments with shaft sleeve.
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5.
6.
7.
All segments to segment and segment to stainless steel mating surface are completely free
from grease.
All garter springs are assembled to obtain even tension all around.
Alignment of segments in the lower assembly is carefully checked with a hard wood peg
for similar device before fitting retaining pins.
4.3.2 Rubber flap type
Maintenance of rubber flap type gland seal is comparatively simpler and easier. Only
precaution during assembly of rubber gland is jointing of the rubber seal in the proper way.
The quality of rubber used plays a very important role for satisfactory performance of the
rubber gland. In one of the recently commissioned power stations rubber gland seal used to
fail very frequently. The cause of frequent failure was discussed and analysed to be lying in
the quality of rubber. The problem after selection and use of proper quality of rubber is now
over.
4.4 Guide vane servomotor
Normally main source of trouble is rubber seals which need to be replaced after a few years.
Rubber seals should be replaced during annual maintenance. It is important that all the parts
are match marked before dismantling so that reassembly is correctly done.
4.5 Governor
Different types of governors are in use in different hydro power stations:
a)
b)
c)
Mechanical governor can be classified as follows
i)
Fly ball type
ii)
Accelero technometric type
Governor employing magnetic amplifier.
Governor employing electro hydraulic amplifier.
The governor may require maintenance because of the following reasons:
i) Chocking of oil parts and throttles
ii) Wearing out of throttles due to which oil leakage becomes more and
readjustment of governor becomes essential. In this case governor should be
opened and all the throttles etc. should be cleared. Filters should also be
cleaned, and after cleaning and reassembly governor parameters and
characteristics should be readjusted so that there is no hunting of the governor.
4.6 Governing Oil System
The oil sump should be well cleaned and filled with filtered oil. The oil samples should be got
tested for verification of the desired properties. Regular centrifuging of oil with the help of
De-Laval type oil purifying machine would go a long way in enhancing the life of the oil. In
certain cases oil retained its properties even up to 15 to 20 years of continuous use.
During annual overhauling OPU sump and pressure accumulator should be completely
emptied and cleaned. The strainers should be inspected and repaired of necessary. The OPU
pumps require maintenance when they develop excessive noise or vibrations. This may be due
to some worn out bearing of the pump which would be replaced.
Another problem which has been faced in different power station is entry of water in the
governing oil system. This problem was analysed in detail and remedial measures were taken
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at Chila Power Station. From following two sources the water can enter in the governing oil
system:
1.
2.
From top cover, through oil leakage pumps which caters leakage of servo motor oil. Its
sump being located well below the level of servo motors in the top cover may not be
properly sealed, thus providing access to the top cover water which may ultimately be
pumped in to the OPU sump.
In case of Kaplan turbine water may enter into the runner hub through cup seals.
To eliminate first possibility the oil leakage unit delivery was isolated from the OPU sump
and connected to a separate tank.
But for the second possibility there is no way except replacing blade seals if excessive water
found in the Governor oil.
Daily check of the OPU sump oil sample and test of the sample is necessary to keep training
of such possibilities.
4.7 Header
In Kaplan turbine the oil header is required to supply governing oil to the runner servomotor
and return oil to the OPU sump. Oil header has an oil guide connected with the rotating and
servo tube. The servo tube has ports to receive return oil to the pipes coming from OPU sump.
This tube is guided by three sets of bushes in the oil. Due to run out of the shaft these bushes
had to press the servo tube. Failure of these had been very frequent in one of the recently
commissioned power station.
Monitoring of wobbling of the servo tube with help of dial indicator may provide a guide line
and save the bushes from further wearing. Remedial measures to reduce run out of the servo
tube must be taken at this stage.
At the time of assembly of various parts of header proper match marking and dowelling is
essential so that reassembly may be correctly done.
Due to failure of these bushes oil splashing occur which may drench the PMG, main & Pilot
exciter and reduce the life expectancy of the windings and brush as such all out efforts should
be made to prevent such happenings.
5
Preventive maintenance of Hydro Generators
Preventive maintenance ensures a long trouble free operation of the generator. Given in the
following Table are the recommended daily, monthly, once in 3 months, half yearly & yearly
maintenance checks to be conducted on the generator. While it is appreciated that it is not
always possible to rigidly follow this schedule due to generator loading constraints, the
recommendation given may be taken as a guide line and these may be altered slightly, based
on his experience.
After the first 600 hours operation of the unit, the checks having periodicity of half yearly and
yearly in the following schedule should be carried out.
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Sl.
No.
1.00
1.01
1.02
1.03
1.04
1.05
1.06
1.07
1.08
1.09
1.10
1.11
1.12
1.13
2.00
2.01
Description
Periodicity
Stator:
Temperature record on log sheet
for core and winding, hot and cold
air temperature
Visual inspection of the overhang
parts of the stator winding.
Checking the fixing of winding,
condition of winding joints with
bus bars etc.
Clean the winding with dry &
clean compressed air (2 to 3 kg/
cm2).
Check overhang parts of stator
winding, bus bars, inner periphery
of stator core (if possible), parts of
stator winding in slots (specially at
sector joint) binding & spacers
between the winding bars/
bandage rings.
Check looseness of overhang, bus
bars, slot wedges etc.
Check the fixing of stator active
iron with the frame body in all
possible places. If it is necessary,
tighten the studs of pressing plates.
Check pins &fixing of stator with
foundations.
Check D.C. resistance, IR & PI
value.
Check functioning of RTDs of
stator.
Blow the winding, active iron and
bandage rings etc. with dry &
clean compressed air (2 to 3
kg/cm2).
After cleaning apply Red-gel coat
on the overhang.
In case of excessive wetting of
stator winding during conditions
such as flooding, drying of
winding by passing current is not
allowed initially as hydrolysis of
water may take place. This is
harmful to the winding.
ROTOR:
Check
rotor
winding
and
insulation details of current
carrying leads.
SKT-S7-RevB.doc
Section 7
Remarks
Hourly
Once in 3 months
Once in 3 months
Once in 3 months
Cleaning to be done
such that the dust does
not collect in side
machine
Yearly
Yearly
Yearly
Yearly
Yearly
Record to be maintained
Yearly
-do-
Yearly
Yearly
As per requirement
Not required during 600
hours inspection.
External
heating
arrangement is to be
provided till wetness is
removed.
Once in 3 months
Page 13
Sl.
No.
2.02
2.03
2.04
2.05
2.06
2.07
2.08
2.09
2.10
3.00
3.01
3.02
3.03
3.04
Description
Periodicity
Check the condition of inter polar
connections
Check the condition of damper
winding.
Check the locking of pole wedges.
If required carryout additional
wedging.
Check locking of rim wedges.
Once in 3 months
Check the gaps of spider arms,
brake track.
Check tightening & proper locking
of all fasteners.
Clean rotor from dust by blowing
compressed air free from moisture
(2 to 3 kg/ cm2).
Measure D.C. resistance and IR
value of rotor winding.
Check the pole coils for inter turn
fault.
Slip ring and Brush Rocker
Check sparking.
Check pitting & Grooving of slip
ring
Yearly
Check IR value
slip rings before
slip rings.
Clean the brush
slip rings and
areas.
Once in 3 months
Yearly
Yearly
Yearly
Yearly
Keep a record
Yearly
Not required during 600
hours inspection.
Every shift
Monthly
rocker, Brushes, Monthly
the surrounding
3.05
Check brush
tension
3.06
Check for absence of oil or oil Every shift.
vapour slip ring area.
Check distance of brush holder Monthly
from slip ring and keep it as
specified in the drawing.
New brushes to be used after While replacing
3.07
3.08
SKT-S7-RevB.doc
&
spring Monthly
Section 7
In case the wedges are
loose
contact
manufacturer
before
attempting
any
rectification.
Yearly
of rotor through Once in 3 months
& after cleaning
wear
Remarks
In case of excessive
grooving rectify by
grinding.
Keep record
Special care must be
taken to clear carbon
dust from ‘V’ shaped
insulation pieces fitted
between slip rings.
Use a precision spring
balance for adjusting
spring tension. The
carbon brushes can be
used till it is not possible
to measure/ adjust spring
tension.
Oil leakages, if any, to
be removed
Page 14
Sl.
No.
3.09
3.10
3.11
Description
Periodicity
bedding the brushes. The brush
should not be too tight/ loose
inside the holder.
Ensure
use
of
same
&
recommended grade of carbon
brushes on one machine.
Check all fasteners of slip rings, Once in 3 months
brush rocker & current carrying
lead.
Check carbon brushes for absence Monthly
of splits, cracks and severe wear.
3.12
Inter change polarity of slip rings.
3.13
Carryout thorough cleaning of slip Half yearly
ring area. Stop oil leakages in this
area.
In case the original insulating Yearly
enamel unit is peeling off remove
the balance payment and apply
free enamel IE –82 dry
Check wobbling at slip rings.
At
the
time
of
installation/
during
major overhauling
Thrust Bearing
Measurement of temperatures of Hourly
T.B. Pad & Oil by RTD & TSD
and record on log sheet.
Check & record reading of oil Once in a shift.
level relay.
Analysis of oil from oil bath.
Half yearly
Change of oil in T.B. oil bath
When
centrifuging
doesn’t
help
in
improving its quality up
to acceptable values.
Check level of oil from the gauge Once in every shift.
glass. Any increase in level may
be due to leakage of water in the
oil bath from coolers.
3.14
3.15
4.00
4.01
4.02
4.03
4.04
4.05
4.06
4.07
4.08
Half yearly
Measures insulation resistance of Yearly
T.B. disc.
Check calibration of the TSD’s & Yearly
RTD’s of thrust bearing.
Check the working surface of Yearly
thrust bearing pads, scrapping, if
required, should be carried out
SKT-S7-RevB.doc
Section 7
Remarks
In case the damage is
excessive,
replace
complete set.
Not required during 600
hrs. inspection
While cleaning avoid
using insulating paint
removers.
Record to be kept.
Unit should be stopped
in case of leakage from
cooling tube. Plugging
of cooling tubes up to
10% can be done
depending upon bearing
temperature.
Not required during 600
hours inspection.
Not required during 600
hours inspection.
Not required during 600
hrs. inspection
Page 15
Sl.
No.
4.09
4.10
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
5.00
5.01
5.02
5.03
5.04
Description
Periodicity
with respect to T.B. disc after
apply lard (animal fat) on the pads
& giving rotation to the unit. Load
sharing on T.B. pads and the
verticality of the unit is to be
checked thereafter.
Check the condition of mirror During
capital
surface of T.B. Disc. Polishing of maintenance
the surface can be done to remove
minor scratches.
Clean all inner surfaces of oil bath Once in Two years.
from dust, wash them with
Kerosene and dry with clean cloth.
Check the condition of weld seam
of oil bath & oil pipe lines for
leakages visually.
Check the condition of insulation
of RTD leads.
Check if excessive foaming is
taking place in oil through gauge
glass. This is normally due to
mixing of water leaking from oil
coolers. If oil level is not rising,
the oil may need changing. Oil
sample to be checked.
Check if any insulating segment
over T.B. Disc is displaced.
Check (in case of problem) the
intactness of spherical surface of
thrust bolt
In case of uneven wear of pad,
check that the pad eccentricity is
correct.
Check for proper seating of pads
during each
Change rubber seals & woolen
felts
GUIDE BEARINGS
Measurement of temperatures of
G.B. pads, oil by RTD & TSD &
record on log sheets
Check & note reading of level
relay
Analysis of oil from oil bath
Change of oil in T.B. oil bath
SKT-S7-RevB.doc
Section 7
Remarks
This will require partial
dismantling of unit.
Oil bath is to be finally
flushed
with
fresh
turbine oil; to be
discarded after use.
Yearly
Yearly
As required.
Watch carefully for rise
in water level to confirm
leakage
and
attend
accordingly.
During
capital
maintenance
As per requirement.
As per requirement
As required
As required
Hourly
Once in every shift
Once in 3 months
Record to be kept.
When
centrifuging
doesn’t
help
in
improving its quality up
to acceptable values
Page 16
Sl.
No.
5.05
5.06
5.07
5.08
5.09
5.10
5.11
5.12
5.13
5.14
5.15
5.16
5.17
5.18
5.19
6.00
6.01
Description
Periodicity
Measures insulation resistance of
G.B. pads.
Check calibration of TSD’s &
RTDs of G.B.
Prior to removal of pads, measure
and
record
guide
bearing
clearances.
Check each pad for:
i)
Absence of scratch marks.
Scrapping to be done with
respect to the journal, if
required
ii)
Heavy damage on Babbit
surface of pads – full set must be
replaced with genuine spares. The
spare set to be scrapped with
respect to its respective journal
surface by giving rotation to the
unit.
Check the centering of the unit
vis-à-vis the labyrinth/runner
chamber of turbine.
Check the friction surface of the
bearing journal. Clean and polish
if necessary.
Wash pads & journal with aviation
petrol and then carryout assembly
of the guide bearing.
Check the condition of welding
seams of oil bath & leakages from
them and oil pipe liens.
Clean all inner surfaces of oil bath
from dust, wash them with
Kerosene and dry with clean cloth.
Yearly
Change rubber seals and woolen
felts
Check operation of the level relay
and its calibrations.
Check welding of pad support
block with oil bath.
Check looseness of pad and pad
support bolts.
Check condition of pad insulation.
Check looseness of bolts holding
‘Z’ clamps (in wedge type
construction of guide bearings.
Air/Oil Coolers
Check water boxes for clogging by
As required
SKT-S7-RevB.doc
Section 7
Yearly
As per requirement
Yearly
Yearly
as
requirement.
Remarks
Not required during 600
hrs. inspection
To be readjusted if
required,
during
reinstallation
Not required during 600
hrs. inspection
per Not required during 600
hours inspection.
Yearly
Yearly
Not required during 600
hrs. inspection
Yearly
Once in tow years
Oil bath is to be finally
flushed
with
fresh
turbine oil; to be
discarded after use.
Yearly
Yearly
Yearly
Yearly
Yearly
Yearly
This checking may be
Page 17
Sl.
No.
6.02
6.03
6.04
Description
Periodicity
opening them. In case of clogging
clean tubes water boxes with wire/
nylon brush. Remove all dirt etc &
finally clean with fresh water &
dry.
Check the gasket between oil Yearly
cooler & oil bath & between air
cooler & stator frame. Gaskets to
be replaced if required.
When the shutdown exceeds 10 As required
days, water from coolers is to be
drained and the coolers kept dry.
Coolers are to be immediately On flooding of the unit.
attended to as given above at 6.03
6.05
Normally up to 10% of the cooling As required
tubes of coolers can be plugged, if
required.
7.00
UPPER DRACKET/ LOWER
BRACKET
External inspection & tightening
of the lock nuts in the radial jacks,
if required.
Check fixing of the generator
cover plate
Check all fasteners of Upper and
lower air baffles.
Check the value of air gap
between air baffles and rotor.
7.01
7.02
7.03
7.04
Yearly
7.06
Check fastening between upper
bracket & stator and stator and
foundation plates.
Check foundation bolts tightening
for stator & lower bracket.
Check all fasteners for locking/
tightness
Brake pipe line
Record air pressure available at
brake panel.
Check thickness of brake pad
Yearly
8.02
SKT-S7-RevB.doc
Section 7
Not required during 600
hrs. inspection
This is to safe guard
failure on subsequent
commissioning of the
unit.
Temperature of the
bearing pads/ stator
winding to be taken in
view while plugging
tubes of the coolers.
Once in 3 months
Yearly
8.00
8.01
if
Once in 3 months
Clean the brackets of dirt & dust.
7.08
done
frequently
clogging is more.
Once in 3 months
7.05
7.07
Remarks
Theses gaps are to be
compared with original
values during erection
and maintained as such,
if required.
Cleaning can be done
more often if possible.
Yearly
Yearly
Every shift
Record on log sheet
As required
Record to be maintained
along with number of
Page 18
Sl.
No.
Description
Periodicity
8.03
Measure:
i)
Time for unit to come
braking speed from rated speed
after signaling the unit to stop.
8.04
Check if excessive brake dust is
generated and find its cause.
During jacking operation lifting of
the rotor is to be limited to the
specified value (7.0 mm)
Keep the unit on jacks which are
mechanically locked during each
shut-down of the unit
After each jacking operation
ensure cleaning of pipe with air
under pressure as provided in the
system.
Check no oil leaks from return line
during jacking operation
Check function of the braking
system on manual and automatic
and the operation of the limit
switches of brake. Check leakage
through pipelines during braking/
jacking.
Check all fasteners of brakes and
brake pipe lines & gaskets
wherever provided.
Check the condition of brake track
and its holding with the rotor
Open brake cum jack assembly.
Clean the inner surface of dust
with kerosene & reassemble.
8.05
8.06
8.07
8.08
8.09
8.10
8.11
8.12
9.00
9.01
9.02
9.03
Remarks
braking in the period
with Air pressure used
for braking.
During first spinning/ Record by kept. In case
yearly
if this time has increased
abnormal then look for
increased guide vanes
clearances. Presence of
oil on brake track or
reduction in air pressure,
defective gauge etc.
Yearly
Clean the affected areas
periodically as required
During jacking
Limit switch to be
suitably mounted to
check the rotor lift.
As required
As required
As required
Yearly
Yearly
Yearly
Yearly
Record
must
be
maintained. In case of
any problem brake panel
& brakes are to be
checked & rectified as
required.
Not required during 600
hours inspection.
Not required during 600
hrs. inspection
Replace the gas if
required. Not required
during
600
hours
inspection.
GENERAL
External examination of parts of Once in each shift
generator which are accessible.
External inspection of air coolers, Once in each shift
oil coolers, pipe lines, sealing &
control etc. for leakages.
Ensure cleanliness of all external Once in each shift
accessible parts of the generator &
wipe with clean & dry cloth.
SKT-S7-RevB.doc
Section 7
Page 19
Sl.
No.
9.04
9.05
9.06
9.07
9.08
9.09
9.10
9.11
9.12
9.13
9.14
9.15
10.00
10.01
10.02
Description
Periodicity
Check wobbling of the shaft at
turbine generator flange/ TGB
Blow with compressed air the
internal surface of the generator
External inspection of current
carrying leads PMG, Bus Bars,
Terminal Blocks, Panels etc.
Check the condition of lighting
inside the barrel
Check the recordings of lighting
inside original results.
Check for proper cleaning of slip
rings.
Check the vibrations at TGB,
UGB & LBG predetermined
points.
Check connections of current
carrying leads & cables. Tighten
the bolts, if required, after
removing the insulation.
Check the calibration of Electrical
measuring
instruments
i.e.
voltmeter,
ammeter,
Active/
Reactive Power meter. Frequency
meter, P.F. meter for Stator output,
Voltmeter & Ammeter in Field
winding circuit, energy meter etc.
Check the Sensitivity & Stability
of Generator Electrical Protection
scheme.
Check the working of Fire
Extinguishing
(CO2)
system
without actually releasing the CO2
gas on manual and on auto
operation as per the instructions
provided in O&M manual of the
Fire
Extinguishing
System
provided by its supplier
Check the characteristics of Static
Excitation system in both auto &
manual mode and sensitivity of
various limits.
OIL PIPE LINE/ EXTERNAL
OIL COOLING SYSTEM (if
applicable)
Check oil pressure at the pump
across the filter & point of entry to
the bearing.
Check the operation of the
Daily
SKT-S7-RevB.doc
Section 7
Remarks
Monthly
Monthly
To be
necessary
cleaned
if
Monthly
Daily
Reasons for variance to
be investigated
As per requirements
Yearly
Yearly
Yearly
As specified
supplier.
by
its
Yearly
As specified in its O&M
manual.
Every shift
Record
is
maintained.
Monthly
Page 20
to
be
Sl.
No.
10.03
10.04
10.05
10.06
10.07
10.08
10.09
10.10
10.11
10.12
Description
Periodicity
Remarks
electrical contact pressure gauge.
Check temperature of bearings of Daily
the Pump-motor set.
Check conditions of gland packing
of the pump and see that air is not
being sucked from here into the
system.
Completely clean the oil tank &
T.B. oil bath
Clean the oil pipe line after
disconnecting it
Check the operation of the valves
of the pipe line.
Check the Operation of D.C. pump
motor set (if provided)
Remove sludge from oil tank.
Check the temperature of cold &
hot oil.
Check the air ventilation cocks of
the oil tank are open during.
Operation of the unit.
Check pipe line for leakage of oil.
This temperature is not
to exceed the specified
limits. If the temperature
is excessive, check if
lubricating grease is
filled as required.
These are holes in pipes
which feed oil in
between the pads.
Monthly
Yearly
Not required during 600
hours inspection.
Not required during 600
hours inspection.
Not required during 600
hours inspection.
Yearly
Yearly
Monthly
Monthly
Hourly
Keep record in the log
sheet
During start of the unit/
during each shift.
Once in each shift
10.13
Check oil sample for acidity, Once in 3 months
viscosity,
moisture
content,
foreign material & sludge.
Formations.
10.14
Clean holes for oil entry into the Yearly
T.B. housing
Separate oil sample from
each bearing should be
sent
for
chemical
analysis & record to be
kept.
Not required during 600
hrs. inspection
HYDRO GENERATORS
DAILY CHECKS
Sl.
No.
1.
Assembly
Item
Check Point
Method
Stator Core
Core Noise
Abnormal
noise
around stator
Periodic
listening
SKT-S7-RevB.doc
Section 7
Remark & Remedial
Measures
Checking for core looseness
especially at frame joints
If abnormal add additional
Page 21
2.
Wound stator
Stator core and
coils
Bear pads
Core & winding
temp.
Bear. Temp.
3.
Guide
&
thrust bear
4.
Temp. scanners
RTDs.
Bear oil
Oil level
Level gauge
Visual
5.
6.
Air coolers
Collector
Cooler tubes
Brushes
Visual
Visual
7.
Brake & Jack
Air Pr.
Water leakage
Sparking, Mix of CDust/ Oil
Pr. Gauge
8.
D.C. Exciter
Commutator
brush gear
Commutation
Visual
Pr. Gauge
paramax paper in core
joints
Check cooled air & cooling
system
Abnormal
Vibrations,
Balancing of rotor, dirty oil
coolers, cooling water flow
contaminated oil, bearing
clearances
High- Due to Water
Leakage
Low- Leakage of Oil From
Housing
Plug the leaking tubes
Cleaning
Check for leakage, pipeline,
joints
MONTHLY/ WEEKLY CHECKS
Sl.
No.
Assembly
Item
Check Point
Method
Remark &
Measures
1.
Weekly
Collector ring
Cleaning
Visual
Clean compare, IR value
2.
Brushes
Accumulation
of
Dirt
Sparking, chattering
wear & clearance
3.
Brake
Lining
Air leakage,
excessive wear
Visual
4.
Brake
Track
Visual
5.
Dc. Exciter
Commutator
Brush Gear
Clean liners & Oil
Sludge/
Moisture
Trap
Commutation
Visual
Brushes are not sticking in
their boxes, rough or high
spot
on
commutator
smooth surface.
1.
Monthly
Stator core
Back of core
Visual
Adjust core packing of jack
screws, insert paramax
paper
2.
Field wind
Field coil top
Visual Feeler
Gauge Visual
Clean Comp. Air
3.
DC Exciter
Commutator,
Brush Gear, Air
Filter
Rusting, flatness of
core
lamination
looseness of punch
top and bottom
Gen.
Condition
Tightness
Deformation
Abnormal wear of
Brushes,
accumulation
of
dust.
Visual
Replace brushes, clean
com., Risers, clean with
detergent sol. Dry.
SKT-S7-RevB.doc
Section 7
Remedial
Smoothen collector surface
clean adjust brush (5 to 8
mm for 1000 R-hour)
Attend leakages
More than 4 to 5 mm Per
50 OP
Reduce application, speed
& PR.
Check air PR, Clean Track,
Change Lining
Clean Drain Trap & Clean
Brake Track
Page 22
ANNUAL INSPECTION
Sl.
No.
1.
2.
Assembly
Item
Check Point
Method
Stator
(i) Frame
Hammering
(ii) Core
Joint bolt tightness
& Dowel Pins
Tightness of Core
Core Duct
Contamination
Visual
Stator winding
Cleanliness
&
general condition
Visual
Field winding
Field coil & rotor
General condition
of coil, Pole &
cleanliness
Field coil & rotor
leads
Inter turn faults
General Conditions
& Cleanliness
3.
Brush
gear
and Slip rings
Brushes & Slip
rings
4.
DC exciter
Core & Winding
Measure
values
cleaning
Visual
Remark & Remedial
Measures
Retighten if Necessary
Check the tightness of
core especially at the
top & bottom most
packets. Any local
looseness
between
stampings can be filled
up with asbestos of
paramax paper glued
with epoxy varnish &
core bolts retightened.
After repairs spray the
top & bottom three
packets (both from I.D.
& O.D.) with loctite –
290 Marketed By M/s
Fit Tite Chemicals Ltd.
Clean
with
Dry
compressed air
Clean the end windings.
IR
after
Measure
impedance
field coils
applying 60
100 V AC, 50
supply
Visual
Dry out if IR Value is
low
Clean the field coil with
compressed air
of
by
to
Hz
Check the coil joints for
any cracks overheating
etc.
If impedance of some
coils is very Low (say
less than 40%) they
must be checked for
possible inter-turn faults
The slip ring is running
out, correct it, any
groves etc to be
removed by oil stone
for excessive sparking
For cleaning the exciter
Accumulation
of Visual
dust
Note: For cleaning stator ducts, stator winding, field coils, rotor leads, brush gear, PMG and DC
Exciter, Use cleaning agents as recommended by manufacturer
5.
Bearings
Top & Bottom Clearance
Feeler Gauge
Check guide bearing
Guide
Bearing
pad clearance. If pad
Pads
clearances have to be
reset the shaft must be
centered first.
Examine the condition
of guide pads and any
slight scouring marks
can be attended by
water emery paper (GR400)
6.
Air coolers
Coolers tubes
Clean inside and outside
SKT-S7-RevB.doc
Section 7
Page 23
7.
Oil coolers
Coolers tubes
8.
HS
Lubrication
System
HS Lubrication
Motor
HP
Hose
Assembly
9.
PMG
Air gap winding
10.
Shaft run out,
centering and
rotor level
Water
flow
relays, visual
flow
indicators &
flow meters
Oil
level
indicator
Braking
&
Jacking
system
11.
12.
13.
14.
15.
Thrust & top
guide bearing
Electrical
Connections
General condition
& cleanliness
Inspect, clean water
passages, if necessary to
remove silt etc.
Clean rod probe
• Combinatory
unit and air
supply
pipe
line,
• Brake
fixing
• Brake
switch
Bearing
track
limit
Bearing insulation
IR value
Oil vapour seal of
top bearing
Vapour
insulation
IR value
Pole to pole
connections
Electrical joints
Brush
gear
connection RTD
terminal
connection heater
SKT-S7-RevB.doc
of air cooler tubes
Check for any tube
leakage by pressurizing
to a pressure slightly
more than maximum
expected
working
pressure.
Clean inside & outside
of oil
Check for any tube
leakage by pressurizing
to a pressure slightly
more than maximum
expected
working
pressure.
Inspect
bearing
&
Grease if necessary
check the condition of
the hoses & if necessary
replace them.
Check air gap
Clean the stator & field
windings check the
open circuit voltage and
if less than 100 V remagnetise
Readjustment
statement, if necessary.
seal
Tightness
Clean the filter element
and bowl of filter,
similarly clean the bowl
of
lubricator
also,
cessation of oil dripping
through that sight glass
is an indication that
cleaning is done
Tightness
of
Dog
clamps
Proper Operation &
Cleaning
Check IR value of
bearing
Insulation & replace
insulation if damaged
Check IR value of
vapour seal insulation
and replace, if damaged
Tighten all electrical
joints
Tighten
joints
Section 7
all
Page 24
electrical
16.
Brush gear
terminal
connection
Cleaning
17.
Rotor
assembly
Tightening
fasteners
18.
Rotor
Shaft vibration
Insulated parts
of
Looseness
fasteners
Slip
ring
coupling
Visual
of
and
Bracket vibration
Vibration
19.
Rotor pole
20.
Top shaft
21.
Generator
Auxiliaries
22.
Cooling water
valves
Over
speed
device
23.
SKT-S7-RevB.doc
Damper system
Current carrying
leads
Visual
Dial gauge
Balancing
equipment
Interconnection
between poles
Visual
Supporting
structure for proper
tightness
By tapping
By shaking
Insulation provide
on
supporting
structure
Tightness of clamps
General condition
General operational
healthiness
Visual
Check for proper
operation
Plunger
&
contact
mechanism
Visual
As per supplier’s
recommended
actions
Clean the insulated
parts by compressed air
Tighten
all
the
approachable fasters on
rotor
assembly
including
tightening
pole and rim keys &
lock all of them.
Check for run out at slip
ring
and
turbine
coupling and readjust if
found more than the
specified value.
Rebalance if necessary
Tighten
and
lock
properly if supporting
structure found loose
Rectify
damaged
if
found
Repair insulation if
found damaged
Ensure that these are in
good working condition
Clean & replace glands
where needed
Proper operation
Section 7
Page 25