Seal Oil (SO)

Question 1

How fast will hydrogen purity degrade in the seal oil system when the vacuum tank is not in service?

Answer 1

One purpose of the Seal Oil Vacuum Pump and the Recirculating Seal Oil Pump and the Vacuum
Tank is to provide for Vacuum Treatment of the oil. Without this vacuum treatment, the entrained
air from the oil will be released in the generator. This will gradually reduce the hydrogen purity in the casing at a rate of about 2% in eight hours.

Question 2

What pressure is maintained in the Seal Oil Vacuum tank?

Answer 2

Tank is maintained 25-28 in Hg with a vacuum pump.

Question 3

At what pressure does the Emergency Seal Oil Pump autostart?

Answer 3

It starts automatically upon receipt of a low pressure signal of 110 psig from the main seal oil pump discharge. (With the emergency pump in operation, oil enters the pump suction through valve SON-V014 which connects with the bearing oil return header. The vacuum tank becomes inoperative with the emergency oil pump in operation.)

Question 4

How is seal oil pressure maintained on a loss of the Main and Emergency Seal Oil Pumps?

Answer 4

If the Emergency Seal Oil Pump is lost along with the Main Seal Oil Pump, the **Main Lube Oil System will supply seal oil **at a reduced pressure. **Hydrogen pressure will drop **(leak past seals) until it stabilized at a few pounds less than the lube oil supply pressure. The

Question 5

Is the Vacuum tank in service when the Emergency Seal Oil Pump is in service?

Answer 5

No

• Seal oil vacuum tank bypassed when ESOP is in-service
  o H2 purity would lower
  o Pump suction from bearing oil return header.

Question 6

What pressure does Regulating valve SON-PDCV-10 maintain the seal oil supply pressure at the seals?

Answer 6

Regulating valve (SON-PDCV-10) maintains constant differential pressure of approximately** 8 psid **between the seal oil supply pressure at the seals and the hydrogen pressure in the generator
casing (note, normal ops is 75 psig in casing, which means **83 psig **for seal oil at the seals).

Question 7

How does the seal oil supply pressure at the generator end compare to the pressure at the turbine end?

Answer 7

The seal oil supply pressure to the turbine end seal and the generator end seal is compared. They
should be approximately equal, if they are not it could be in indication of a degraded seal.

Question 8

What is the suction source for the Emergency Seal Oil Pump?

Answer 8

With the emergency pump in operation, oil enters the pump suction through valve SON-V014 which connects with the bearing oil return header. The vacuum tank becomes inoperative with the
emergency oil pump in operation.

Question 9

How is level maintained in the Seal Oil Vacuum Tank?

Answer 9

Oil from the main turbine lube oil system enters the vacuum tank though the level control float valve.

Question 10

Where does the seal oil from the inboard shaft seals drain? Outboard seals?

Answer 10

• Seal oil flowing** inboard** from shaft seals (H2 side), drains to the H2 detraining section.
  o Drainage from H2 detraining section passes through a float trap preventing passage of H2.
• Seal oil flowing outboard from shaft seals (Air side) mixes with oil discharged from the bearings and drains to the auxiliary detraining section.

Question 11

How is the Standby seal oil filter changed?

Answer 11

Manually

The seal oil filter consists of a pair of filters, one active and one standby, connected by a duplex
three-way transfer valve.