Gland Seal Steam

Question 1

What is the purpose of the GS system?

Answer 1

Prevents air leakage into and steam leakage out of the main turbine and feedwater pump turbines thru the turbine shaft glands

Question 2

Valve PV-28B moves from full closed to full open with what pressure air signal change?

Answer 2

15 to 9 psig

Question 3

valve PV-28A moves from full closed to full open with what pressure air signal change?

Answer 3

9 to 3 psig

Question 4

how are PV-28A and 28B affected by loss of IA?

Answer 4

they fail open to protect the turbine

Question 5

What pressure is the GS system header maintained at?

Answer 5

4 psig

Question 6

Where are the GS regulating valves located?

Answer 6

140’ turbine building

Question 7

What is the purpose of the steam packing exhauster?

Answer 7

maintain a vacuum on the steam exhaust header and annulus between the middle and outer shaft packings to keep steam from contaminating the oil

Question 8

What is the purpose of PCV-27, the GS steam condenser unloader valve and how is it controlled?

Answer 8

auto acting, back pressure regulating valve

does not require IA because it is operated directly from the GS system pressure

Question 9

What powers GSN-HV-5 and -14?

Answer 9

NH

Question 10

During low power operation, where does sealing steam come from?

Answer 10

AS or SG thru PV28A, LP turbine 9th stage extraction thru point pv28B

Question 11

What can the operator in the control room do if PCV-28A and 28B capacity is insufficient to maintain 4 psig?

Answer 11

can open regulator bypass valve hv-6

Question 12

At full power operations where do we get gland seal steam from?

Answer 12

HP turbine shaft seal packing leackage

Question 13

What happens if HP turbine shaft packing leak off is greater than the sealing steam requirement?

Answer 13

Excess steam unloading valve, PCV-27 discharges steam to the main condenser

If PCV-27 is insufficient, control room operator may open the unloader bypass valve, HV-7, to maintain 4 psig

Question 14

What will happen if GS is lost?

Answer 14

Loss of condenser vacuum

Question 15

When is GS required to be in service during startup?

Answer 15

Prior to starting and during the operation of the air removal pumps, when establishing and operating with vacuum

Question 16

How is the system affected by a loss of IA?

Answer 16

Valves 28A and 28B fail open which will cause header pressure to increase

Steam unloading valve is not air operated so it will open to control pressure

Regulators can be isolated and bypass MOV can supply gland seal steam

Drain tank drain valve fails closed which will cause the tank to overflow

Question 17

What cools the heat exchanger of the steam packing exhauster?

Answer 17

TC

Question 18

Where do the exhauster fans take suction from and where is it discharged to? (steam packing exhauster)

Answer 18

Suction on the heat exchanger and discharge to atmosphere via the condenser AR system piping.

Exhaust can be sent thru the filter and to RU141

Question 19

What is the exhaust header vacuum normally maintained at and how is it controlled?

Answer 19

10-20H20 by manually throttling the air flow