GS- Gland Seal Steam

Question 1

[GS] purpose?

Answer 1

Prevents air leakage into, and steam leakage out of, the Main Turbine and Feed Water Pump turbines through the turbine shaft glands and through various Main Turbine valve stems

Question 2

Valve GSN-PV-28B, 9th stage extraction point steam seal feed valve, moves from full-closed to full-open with what pressure air signal change?

Answer 2

15 to 9 psig

Question 3

Valve main/aux. steam supply to GS regulator valve, GSN-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 the steam supply to GS regulator valves, GSN-PV-28A and -28B, affected by a loss of instrument air?

Answer 4

They will fail open to protect the turbine

Question 5

What pressure is the GS system header maintained at?

Answer 5

4 psig

Question 6

Concerning the GS system, where in the shaft packing is low pressure steam applied?

Answer 6

The inner cavity formed by the first two sets of packing

Leakage is withdrawn from the outer cavity formed by the second and third sets of packing

Question 7

What is the purpose of the GS Steam Packing Exhauster?

Answer 7

To maintain a vacuum on the steam exhaust header and annulus between the middle and outer shaft packing rings, which causes the steam/air mixture to flow from the packing ring annulus to the exhauster, and prevents steam from contaminating the oil used in journal bearings adjacent to the packing’s

Question 8

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

Answer 8

Automatic acting, back pressure regulating valve

Operated directly from the GS system pressure and therefore does not require IA to function

Question 9

What powers the main/aux. steam supply to GS regulator valves??

Answer 9

NH

Question 10

During low Rx power, where can I get sealing steam from?

Answer 10

normal AS or SG, through GS steam seal regulator PV-28A

LP turbine 9th stage extraction point through GS steam seal regulating valve PV-28B

(both isolate as turbine power increases)

Question 11

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

Answer 11

May 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 leakage)

valve shaft leakage from the HP turbine control valves, stop valves and combined intercept valves

Question 13

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

Answer 13

The excess steam unloading valve discharges steam to main condenser

If discharge flow is insufficient, control room operator may open the excessive steam unloading bypass valve 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 a 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 GS system affected by a loss of IA?

Answer 16

Steam seal feed valves fail open, which will cause header pressure to increase
(Steam unloading valve (not air operated) will open to control pressure. If desired, the regulators can be isolated and a bypass MOV can supply gland seal steam.

The GS exhauster drain tank drain valve fails closed which will cause the tank to overflow

Question 17

What cools the heat exchanger of the GS steam packing exhauster?

Answer 17

Turbine Cooling Water

Question 18

Concerning the GS steam packing exhauster, where do the Exhaust fans take suction from and where is it discharged to?

Answer 18

Suction on the heat exchanger shell side and discharge to atmosphere via the condenser air removal system exhaust piping

Exhaust can be diverted through an exhaust filter unit if a set amount of radioactivity is sensed by RU-141

Question 19

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

Answer 19

12-20 in H20, by manually throttling the air flow

Question 20

What is the main purpose of the GS system?

Answer 20

to prevent air leakage in, and steam leakage out, of the main turbine and feedwater pump turbine

returns air/steam mixture to the steam packing exhauster to be condensed, drained to the main condenser and exhaust non condensable gases to atmosphere

Question 21

What does the GS steam packing exhauster consist of? Where does the condensate drain to?

Answer 21

HX and two exhaust fans

to a drain tank and then the main condenser

Question 22

As turbine load increases, the low pressure turbine extractions flow increases and the low power ops steam supplies isolate, where does GS get supplied steam from?

Answer 22

ED (extraction steam and drain system)

Low Pressure turbine 9th stage extraction point

Question 23

What system provides power to the GS control and instrumentation panel?

Answer 23

NN

Question 24

In the GS system, what is the purpose of the Steam Seal Regulator?

Answer 24

hydro-pneumatic control unit automatically positions the main/auxiliary steam and extraction steam supply valves to maintain 4 psi in the seal steam supply header

Question 25

What is the purpose of the main turbine shaft seal packing rings?

Answer 25

to seal the turbine shells from the atmosphere

keep the steam in and the air out

Question 26

What controls the level in the GS exhauster drain tank?

Answer 26

air-operated level control valve, GSN-LV-8

Question 27

Concerning the GS steam supply regulating valves, which one opens first and closes last?

Answer 27

9th stage extraction point seal steam supply regulator valve PCV-28B

Question 28

Regarding the GS system, if LP turbine 9th stage extraction steam is lost, what can supply enough steam until the HP turbine seal leak off is established?

Answer 28

aux steam or main steam