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.

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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