Term
| Function of Generator Hydrogen Seal Oil |
|
Definition
| "Provide a seal between the generator housings and rotor shaft to maintain the pressurized hydrogen gas inside the generator. Also, provides a trap-vent system to prevent the release of hydrogen into the turbine generator lube oil system and building atmosphere." |
|
|
Term
| Why is oil for shaft seals vacuum treated? |
|
Definition
| So that a minimum amount of air and moisture will be released to the generator casing; thereby maintaining hydrogen purity at a satisfactory level without necessity of purging or adding hydrogen other than makeup. |
|
|
Term
| Shaft seal oil vacuum (level) and hydrogen purity. |
|
Definition
| ABSOLUTE PRESSURE of 1.0" Hg or less in the vacuum tank results in hydrogen purity of 97% or higher in generator. |
|
|
Term
| Function of recirc seal oil pump |
|
Definition
Recirculates oil in vacuum tank through recirc spray header to aid in air and moisture removal from oil and to reduce foaming in vacuum storage tank. NOTE: Recirc seal oil pump driven by Main Seal Oil Pump motor. |
|
|
Term
| Normal and backup pumps that supply seal oil |
|
Definition
Normal: main seal oil pump (66 gpm); Backup: Emergency seal oil pump (54 gpm) |
|
|
Term
| Besides main seal oil pump and emergency seal oil pump, what other method is there to supply oil to the seals? |
|
Definition
| Can be supplied directly from bearing header. However, this can only provide sealing for machine gas pressure up to about 8 psig. |
|
|
Term
| How is excess discharge pressure prevented? |
|
Definition
Pressure relief valves on the discharge side of each seal oil pump relieves back to seal oil system. Emergency seal oil pump relief valve is set at 80 psig and returns oil to pump suction line. Main seal oil pump relief valve is set at 90 psig and returns oil to vacuum tank via recirc seal oil pump discharge line.
|
|
|
Term
| Which two seal oil pumps are driven from the same motor? |
|
Definition
| Main seal oil pump and recirc seal oil pump; both are driven by Main seal oil pump motor |
|
|
Term
| When does Emergency Seal Oil Pump automatically start? |
|
Definition
| When its pressure switch senses Main Seal Oil Pump discharge pressure reduced to 78 PSIG. |
|
|
Term
| Capacity of Main Seal Oil Pump |
|
Definition
|
|
Term
| Capacity of Emergency Seal Oil Pump |
|
Definition
|
|
Term
| When must the seal oil system be operable? |
|
Definition
| Before Hydrogen is injected into the generator. |
|
|
Term
| State the required differential pressure between seal oil and hydrogen pressure |
|
Definition
When operating, seal oil pressure must be maintained at a minimum pressure of 3 psig above hydrogen pressure; At a standstill, it is 1 psig. |
|
|
Term
| Maximum differential pressure between seal oil and hydrogen |
|
Definition
| 8 psid (seal oil should be higher) |
|
|
Term
| What is the consequence of not maintaining hydrogen (or air) pressure in generator casing at a value above atmospheric pressure when seal oil system is in service? |
|
Definition
| Failure to do so will cause excessive seal oil to be drawn into the generator |
|
|
Term
| When must the seal oil system remain in operation? |
|
Definition
| At any time that the turbine is operating or on the turning gear. |
|
|
Term
| What is the consequence of high seal oil temperature? |
|
Definition
| Foaming, which could restrict drain flow and may cause oil to back up into the generator. |
|
|
Term
| When can high seal oil temperatures be expected? |
|
Definition
| If seal oil pumps operate for an extended period of time with low generator gas pressure (since very little seal oil flows to the generator seals, resulting in most of the oil recirculating back to the tank through the relief valve, raising oil temperature. |
|
|
Term
| Power supply to Main Seal Oil Pump |
|
Definition
|
|
Term
| Power supply to Emergency Seal Oil Pump |
|
Definition
| Motor: D-71; Control Power: D-21 |
|
|
Term
| Power supply to Seal Oil Vacuum Pump |
|
Definition
|
|
Term
| Power supply to Annunciator Panel C-83 |
|
Definition
|
|
