GS- 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 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

Where are the Gland Steam regulating valves located?

Answer 6

140’ Turbine Building

Question 7

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

Answer 7

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Leakage is withdrawn from the outer cavity formed by the second and third sets of packing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 8

What is the purpose of the GS Steam Packing Exhauster?

Answer 8

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 9

Where is the GS steam packing exhauster located?

Answer 9

140’ turbine building

Question 10

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

Answer 10

Automatic acting, back pressure regulating valve

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

Question 11

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

Answer 11

NH

Question 12

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

Answer 12

normally Aux steam, or main steam, through the 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 13

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 13

May open regulator bypass valve HV-6

Question 14

At full power operations, where do we get Gland Seal steam from?

Answer 14

HP turbine shaft seal packing leakage

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

Question 15

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

Answer 15

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 16

What will happen if GS is lost?

Answer 16

Loss of condenser vacuum

Question 17

When is GS required to be in service during a startup?

Answer 17

Prior to starting and during the operation of the Air Removal Pumps, when establishing and operating with vacuum

Question 18

How is the GS system affected by a loss of IA?

Answer 18

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 19

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

Answer 19

Turbine Cooling Water

Question 20

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

Answer 20

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 21

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

Answer 21

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

Question 22

What is the main purpose of the GS system?

Answer 22

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 23

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

Answer 23

HX and two exhaust fans

to a drain tank and then the main condenser

Question 24

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 24

ED (extraction steam and drain system)

Low Pressure turbine 9th stage extraction point

Question 25

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

Answer 25

NN

Question 26

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

Answer 26

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 27

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

Answer 27

to seal the turbine shells from the atmosphere

keep the steam in and the air out

Question 28

What controls the level in the GS exhauster drain tank?

Answer 28

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

Question 29

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

Answer 29

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

Question 30

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 30

aux steam or main steam