Oil Flushing Procedures For Steam Turbine & Generator Sets 1

BHEL HYD 32

1.0

OIL FLUSHING FOR STEAM TURBINE AND GENERATOR SETS

ESP: TG & TC :202 4 Page 2 of 8 REV. 01., DT 30 11 10

GENERAL: After completion of fabrication and installation of pipelines the entire oil system should be thoroughly flushed, in order to eliminate all the contaminants, which might have been introduced into the oil system during the erection operations. Oil flushing is to be carried out to make sure that no foreign material which is dangerous to the turbo set is carried by the oil to the bearings and governing elements. During oil flushing, high velocity of flow in the oil lines can be achieved by temporarily removing the throttling points in governing line and opening the bearing inlet orifices such that drain oil pipe is 2/3 full. These high velocities will help in detaching loose particles adhering to the pipe walls, and carrying away by the oil flow.

2.0

FLUSHING OIL: Oil system can be flushed with the same type of oil that is employed for normal turbine operation. Oil quantity required for flushing is approximately 60% to 70% of the quantity of oil required for normal operation of the turbine. However it has to be ensured that oil pump does not starve for oil at its suction, during flushing.

3.0

PREPARATION FOR START UP OF OIL FLUSHING: Ensure the mechanical completion of the oil system lines are per the P&ID. All the temperature and pressure measurement points must be completed. Pressure and temperature measurement instruments to be installed in the following points: 1. Oil temperature before cooler 2. Oil temperature after cooler 3. Pump discharge pressure 4. Lube oil header pressure 5. Governing oil pressure 6. Pressure gages in individual bearing inlet lines.

ISSUED BY:

EXTERNAL SERVICES DEPARTMENT

BHEL HYD 32

OIL FLUSHING FOR STEAM TURBINE AND GENERATOR SETS

ESP: TG & TC :202 4 Page 3 of 8 REV. 01., DT 30 11 10

Before filling with oil, the oil tank and strainer are to be thoroughly cleaned with cloth. cotton waste, wool etc should never be used. The cleaning materials used, should not leave any residue.

LUBRICATING OIL CIRCUIT: STAGE 1 a)

b)

c) d)

Make jump over from Inlet header to the drain header as shown in the sketch 2. The oil inlet lines to the turbine, gear box and generator bearing to be blocked by providing blinds. All filter cartridges in lube oil filter are to be removed, flushing filters to be installed in the filter housing. Jump over to be provided from oil inlet line to overhead tank and overflow line. Initial flushing operation to be carried out in the above mentioned loops in order to achieve cleaning of the main headers. STAGE 2

e)

Make jump over from turbine and generator bearing inlet lines to drain lines, bypassing the bearings. As shown in the sketch 3.

f)

All the adjustable orifices are to be opened such that drain oil pipes are 2/3 full.

g)

Proper tightening of all the flanges is to be ensured.

h)

Flushing of delivery pipe lines of the other oil pumps which are not used for flushing operations can be done by connecting their delivery pipe lines to the oil tank before the strainers.

i)

Gear box inlet line flushing can be done by providing jump over of same size connected to drain line.

GOVERNING OIL CIRCUITS: a)

All the orifices in trip oil, secondary oil and primary oil circuits are to be removed.

ISSUED BY:

EXTERNAL SERVICES DEPARTMENT

BHEL HYD 32

ESP: TG & TC :202 4 Page 4 of 8 REV. 01., DT 30 11 10

b)

Control slide is to be taken out from the governing valve servomotors.

c)

Solenoid valve is to be kept in operating position.

d)

Tripping device is to be engaged into operating position and locked.

e)

Starting device is to be turned into operating position and tripped alternatively.

g)

About 20 to 30mm dia temporary orifice is to be provided in the power oil inlet line to servomotors.

f) g)

.

OIL FLUSHING FOR STEAM TURBINE AND GENERATOR SETS

Emergency stop valve starting and trip oil lines are to be connected to the drain lines with temporary lines. FLUSHING OPERATION: Introduce mesh in the Bucket strainer of the oil tank to retain smaller foreign impurities in the strainer. Mesh to be cleaned by observing the impurities collected in the strainer. Oil pump is to be switched on. In case of centrifugal pump delivery line is to be closed before switching on the pump and to be gradually opened later. Pump input amperage is to be watched and if it rises to high, pump delivery is to be throttled for reducing it. In case of positive displacement pumps, all the valves in the delivery are to be kept fully open before switching on the pump. Any leakages found in the oil systems are to be curbed. Flushing is to be started with lube oil header to drain by blinding oil entry to bearings and providing a temporary line between the two headers. Subsequently the flushing can be extended top individual bearing oil lines, governing system, to all oil pumps, standby coolers, standby filters and over head oil tanks etc. The best cleaning effect can be obtained by using alternatively hot and cold oil for flushing. Oil should therefore be heated up to 60 ºC 65 ºC. Oil temperature should not go up beyond 85 ºC because higher temperatures may be harmful for the oil.

ISSUED BY:

EXTERNAL SERVICES DEPARTMENT

BHEL HYD 32

OIL FLUSHING FOR STEAM TURBINE AND GENERATOR SETS

ESP: TG & TC :202 4 Page 5 of 8 REV. 01., DT 30 11 10

After flushing for a period of about four hours, at a temperature of 60 ºC to 65 ºC, oil is to be allowed to cool down fast to about 30ºC to 35 ºC. When the pipes also were cooled to that temperature, oil is to be again heated to 60 to 65 ºC. All the pipes must be hot during oil flushing. If any pipes are found to be cold, the reason why oil is not flowing through those lines is to be investigated and the fault to be rectified. Tapping on the pipes at intervals, further improves the removal of foreign materials from the pipe walls. Oil centrifuging equipment (if available) is to be kept in service during oil flushing as an additional means of purification. Flushing operation has to be continued until no substantial amounts of contaminants are found in the Bucket strainer in the oil tank. Subsequently the fine meshes to be inserted in the bearing inlet lines and oil circulation is to be carried out. The meshes need to be inspected after an interval of 4 5 hrs. The operation to be repeated till all the debris is cleared from the inlet lines. POST FLUSHING OPERATIONS: Drain flushed oil from oil lines, oil tank, oil filter and oil coolers totally. a)

Oil tank, NRVs, strainers and duplex filter body, are to be cleaned. The Oil tank is to be filled up with operating oil to the required level.

b)

Removed orifices and damping devices are to be assembled back in oil lines.

c)

Secondary oil pipes and other pipe which could not be taken during flushing are to be separately cleaned by steam/ air blowing and drying.

d)

Temporary Orifice at the power oil inlet to servomotor is top be removed.

e)

Overhauling and assembly of control slide in servomotor is to be carried out.

f)

Temporary lines provided for flushing operation are to be removed.

g)

Fill the fresh oil in the tank.

ISSUED BY:

EXTERNAL SERVICES DEPARTMENT

BHEL HYD 32

OIL FLUSHING FOR STEAM TURBINE AND GENERATOR SETS

ESP: TG & TC :202 4 Page 6 of 8 REV. 01., DT 30 11 10

h)

With fresh oil ensure the cleanliness of oil lines by providing line meshes at the flange connections of all bearings.

i)

Temporary meshes must be removed before machine start up, after ensuring the cleanliness of the oil circuit.

j)

Flushing filter cartridges to be removed and new filter cartridges to be installed. Notes:

a) b) c) d)

Temporary lines, drain points and vent points to be installed at site as per the requirement and site routing. The materials specified in the flushing procedure viz. bucket strainers, meshes, temporary pipe lines, valves etc. are out of scope of BHEL supply. Arrangement for oil heating and cooling are out of scope of supply of BHEL. The oil removed after flushing should not be used for regular operation.

Format for oil flushing data: Date Time Pump discharge pressure Lube oil temperature Lube oil header pressure Oil temp before thermal shock Oil temp after thermal shock Oil pressures in bearings inlet lines Turbine FJB Turbine Thrust bearing Turbine RJB Gear Box inlet Generator FJB Generator RJB Hydraulic Barring gear

ISSUED BY:

EXTERNAL SERVICES DEPARTMENT

BHEL HYD 32

OIL FLUSHING FOR STEAM TURBINE AND GENERATOR SETS

ESP: TG & TC :202 4 Page 7 of 8 REV. 01., DT 30 11 10

Stage-1, Schematic arrange of Lube oil circuit

ST-GB-GEN

Stage-2 Arrangement of Jump-overs for flushing of main lines. oil flushing-2 Jump over

Jump over Inlet header

blinded ST-GB-GEN

filters

Return header

coolers

ISSUED BY:

EXTERNAL SERVICES DEPARTMENT

BHEL HYD 32

OIL FLUSHING FOR STEAM TURBINE AND GENERATOR SETS

Stage-3 Arrangement of Jump-Overs for bearing inlet lines. oil flushing-3 Overhead oil tank

Inlet header

orifice Jump over

filters

ST-GB-GEN

Return header

coolers

ISSUED BY:

EXTERNAL SERVICES DEPARTMENT

ESP: TG & TC :202 4 Page 8 of 8 REV. 01., DT 30 11 10