Hydrogen Cooled Generator Seal Oil
Very large generators have their casing filled with hydrogen to reduce windage losses from the huge rotating generator rotor. In order to contain the extremely volatile hydrogen in the casing‚ pumps are used to pump oil into the generator shaft labyrinth seals at a pressure higher than the hydrogen. This keeps the generator seals pressurized containing the hydrogen.
The oil gravity drains to a tank located about 2 meters above the oil pumps. As a result‚ the oil pump inlet pressure is extremely low. Three screw pumps are used for their high reliability and ability to operate at extremely low suction pressures as well as their ability to operate at higher speeds than comparable flow gear pumps. Other systems integrate the seal oil system into the lube oil tank and use centrifugal pump.
Each hydrogen cooled generator is served by a main and auxiliary seal oil pump driven by an AC motor. There is also an emergency DC motor driven pump to provide the critical oil in the event of a turbine trip where AC power is not available. This allows the generator to safely coast down with out leaking the hydrogen gas.
| Flow Rates up to | Pressures to up to | Max Fluid Temperature | CIRCOR Brand‚ Series & Pump Type |
| 51 m^3/h 225 GPM | 16 bar 232 psi | 155C 311F | IMO AB ACG Three Screw |
| 51 m^3 / h 225 GPM | 16 bar 232 psi | 120C 250F | Allweiler ALLlub RUV Three Screw |
| 91 m^3/h 400 GPM | 34.5 bar 500 psi | 120C 250F | IMO 3D Three Screw |
| 180 m^3/h 793 GPM | 16 bar 232 psi | 130C 266F | IMO AB ACF Three Screw |
| 317 m^3/h 1‚400 GPM | 100 bar 1‚450 psi | 250C 482F | Allweiler SN Three Screw |
| 550 m^3/h 2‚500 GPM | 16 bar 232 psi | 120C 250F | Allweiler NSSV Centrifugal |