Generator Seal Oil System.

Scavenging Type.


To keep the hydrogen inside the generator, various places in the generator are required to seal against hydrogen leakage to atmosphere.

Picture beside is from Siemens Generator which use scavenging system that is very easy to understanding how seal oil works. There are two type of generator seal oil system, scavenging type and vacuum type.











Vacuum type.

The seal oil it self actually a portion of the lube oil, diverted from the lube oil system. It is then fed to a separate system of its own with pump, motor, hydrogen de-training or vacuum degassing equipment, and controls to regulate the pressure and flow.


The seal oil pressure at hydrogen seals is maintained generally about 15 psi above the hydrogen pressure to stop hydrogen from leaking past the seals.

Once of the critical component of the seal oil system is the hydrogen de-gasifying plant. The most common method of removing entrained hydrogen and other gases is to vacuum treat the seal oil before supplying it to the seals. This is generally done in the main seal oil supply tank. As the oil is pulled into the storage tank under vacuum through a spray nozzle, the seal is broken up into the fine spray. This allows the removal of dissolved gases. In addition there is often re-circulate oil back to the tank through a series of spray nozzles for continuous gas removal.

After passing through the generator shaft seals, the oil goes through the detraining sections before it returns to the bearing oil drain. As a safety feature there is often a dc motor driven emergency seal oil pump provided. This motor will start automatically on loss of oil pressure from the main seal oil pump. This is to ensure that the generator can be shut down without risk to personnel or the equipment.











Water and Air Contamination in Seal Oil
Water contamination in seal oil can vaporize when it comes in contact with the spinning turbine shaft. This water
vapor can enter the generator shell, and cause a reduction in the purity of the hydrogen gas. Lower dew point readings are consequently noted. Also, entrained air can be released from the oil and into the hydrogen, again reducing hydrogen purity. Decreased hydrogen purity results in increased windage loss which reduces the amount of usable energy available to produce electricity. This can result in lost revenue to the utility!

To minimize these losses, the concentration of water and entrained air in the oil should be kept well below the
saturation level. Since the seal oil is drawn from the main turbine lube oil reservoir, measures must be taken to
control water and air contamination there. It is recommended that a Pall Vacuum Dehydration Purifier be used on the main turbine lube oil reservoir to remove 100% of the free water and air, and up to 80% of the dissolved water and air present in the oil. This will result in improved performance and reliability of both the hydrogen seal oil and main turbine lube systems

Toshiba's Generator



Click here for Generator Auxiliary System.

More details information, please visit http://idpowerstation.blogspot.com/2013/06/mass-transfer-from-water-vapor-to.htm and http://idpowerstation.blogspot.com/2013/06/water-contamination-on-h2-cooled.html