Introduction to the Generator II

Filtered and cooled seal oil, regulated to a pressure slightly in excess of the gas pressure within the generator frame, is supplied by any of three supply pumps (2 main and 1 dc emergency) to the hydrogen shaft seal on the exciter and turbine ends of the generator.

The seal oil acts hydraulically to force the sealing surface against the shaft surface while at the same time lubricating the sealing surfaces and dissipating any heat produced between the mating surfaces.

The majority of oil return flow from the seal migrates to the shaft bearing side of the seal and mixes with the lubricating oil in the bearing oil return line.

A small amount of oil will also migrate to the generator side of the seal against the hydrogen pressure. This oil will return to the seal oil system through the Hydrogen Side Drain Regulator. 

The bearing housings associated with each seal are maintained under a negative pressure by a vapour extraction fan and exhaust line, which also incorporates a path for high volume leakage of hydrogen to atmosphere in the event of seal failure.