Generator Preventive Maintenance for Hydrogen Leaks

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Hydrogen gas plays important role in cooling steam turbine generators, but it comes with some risks due to its flammability and the potential for leaks. To ensure safe and efficient generator operation, it is essential to understand and address hydrogen leaks through effective generator preventive maintenance.

Statistics With Hydrogen Leaks

Based on historical data the statistics of hydrogen leaks are as follows, based on location, cause, and leak rate.

1. Leak Locations

Leak LocationPercentage
Stator Coil15%
Packing Gland11%
HV Bushing11%
Cooling Water11%
Stator Frame10%
Terminal Box10%
Seal Casing6%
Seal Ring5%
Stator Coil Connection3%
Cooler2%
Auxiliary16%

2. Leak Rate

Leak RatePercentage
Large Leaks10%
Medium Leaks42%
Small Leaks48%

3. Causes of Leaks

CausePercentage
Deterioration62%
Assembly Error24%
Design/Materials8%
Damage6%

Generator Preventive Maintenance Recommendations

  1. Mandatory leaking tests at overhaul in/out.
  2. Prohibition of used gaskets.
  3. Periodical refill and replacement of tight sealing.
  4. Retight and replacement of packing grounds.
  5. Periodic replacement of gaskets of HVB.
  6. Replacement of gaskets of field terminals.
  7. Retight and replacement of shaft bore gaskets.
  8. Inspection of gas control system piping joints.
  9. Modification of an air bent outlet for hydrogen gas purge piping system.

Periodic Inspections & Tests For the Generator

  1. Generator Inspection During Each Shift
    • Check the water pressure and water temperature of each gas cooler, and vent out the air collected in the cooler.
  2. Daily Generator Inspection & Test
    • Check the difference between the generator pressure and the seal oil pressure.
    • Check the drain indicator window of the drain alarm inside the generator.
    • Check the hydrogen purity meter and the hydrogen flow meter indications
  3. Weekly Generator Inspection & Test
    • Test that the emergency seal oil pump starts.
    • Test the various hydrogen alarms
  4. Generator Inspection & Tests Every 3 to 6 Months
    • Calibrate the hydrogen gas purity meter on the hydrogen control board.
    • Check the alarms at the hydrogen control board.
    • Measure the insulation resistance of the generator bearing insulation and the seal casing insulation for the collector end, at T/G outage
  5. Generator Inspection & Tests Every 6 to 12 Months
    • Test the operation of the alarms by each alarm device.
    • Perform leak tests for hydrogen gas, including the generator.
    • Calibrate the hydrogen and seal oil control device meters.
    • Carry out an operation test of hydrogen and CO2 gas safety valves.
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