Gland Seal Steam

Question 1

What is Gland Seal system used for ?

Answer 1

-Used to prevent air leakage into the Main Turbine & FW Pump Turbines
-Used to prevent steam leakage out of the Main Turbine & FW Pump Turbine

Question 2

Where does Gland Steam go after being used ?

Answer 2

Returns air/steam mixture to the Steam Packing Exhauster

Question 3

What does the Steam Packing Exhauster do ?

Answer 3

-Condenses steam & returns it to main condenser
-Exhausts non-condensable gases to atmosphere

Question 4

What’re the 4 steam sources for Gland Seal System ?

Answer 4

-Main Steam
-Aux. Steam
-Ninth Stage Extraction Steam
-HP turbine leak off

Question 5

What is Main Steam used for in the Gland Seal System ?

Answer 5

-During low power operation of main turbine, main steam is backup steam supply through GSN-HV-5
-As turbine power increases
GSN-PV-28A will isolate Main Steam

Question 6

What is Aux. Steam used for in Gland Seal System ?

Answer 6

-Normal steam supply to GS through supply valve GSN-HV-14
-Used during startup
-As turbine power increases
GSN-PV-28A will isolate Aux. Steam

Question 7

How is extraction steam & drain system used for in the Gland Seal System?

Answer 7

-Turbine load increases,LP turbine flow increases then 9th stage extraction can supply Gland Seal System

Question 8

What happens if 9th stage extraction steam is lost for Gland Seal System?

Answer 8

Aux. steam or main steam can supply the necessary amount of sealing steam

Question 9

What does TC cool in the Gland Seal System ?

Answer 9

It cools the steam packing exhauster condenser

Question 10

What does the Condenser Air Removal do for the Gland Seal System ?

Answer 10

-Removes air & non-condensable gases discharged from steam packing exhaust fans
-Radioactive gases will be processed through AR effluent filtration system

Question 11

Where does the Main Condenser receive the condensed steam from the Gland Seal System?

Answer 11

Receives Gland Seal condensed steam from:
-Steam Packing Exhausted Condenser
-Steam dumped from steam pressure unloading valve(GSN-PV-27)

Question 12

What do the Steam Seal Regulator (GSN-PV-28A & B) valves do ?

Answer 12

Automatically positions Main/Aux. Steam & extraction steam supply valves to maintain 3psig in seal steam supply header

Question 13

What does the control unit do for Steam Seal Regulator valves ?

Answer 13

Senses seal steam supply header pressure & sends proportional Instrument Air signal to valve operators

Question 14

Where shaft packing provided on turbine rotors ?

Answer 14

Between turbine shells, or between exhaust hood & atmosphere

Question 15

How are packing rings for turbine shaft packing made ?

Answer 15

-Machines with teeth fitted with minimum radial clearance between teeth & rotor

Question 16

Why do the packing rings have small teeth with minimum radial clearance ?

Answer 16

Resists steam & airflow

Question 17

What kind of steam is sent through turbine shaft packing ?

Answer 17

LP steam is supplied to inner cavity formed by first two sets of packing

Question 18

What do the steam packing exhauster unit provide ?

Answer 18

-Maintains vacuum on steam exhaust header & between the middle & outer shaft packing rings

Question 19

Why does there have to be a vacuum on the steam exhaust header ?

Answer 19

Vacuum causes steam/air mixture flow from packing ring to the exhauster to prevent contamination of oil used on journal bearings adjacent to packing

Question 20

What is the Gland Seal Steam Condenser Unloaded Valve ? How is the valve operated ?
(GSN-PCV-27)

Answer 20

-Automatic acting back pressure regulating valve
-Directly operated from Gland Seal system pressure, so it doesn’t required Instrument Air to function

Question 21

Where is sealing steam supplied from during low power operation ?

Answer 21

-Aux Steam or Main Steam through regulating valve (GSN-PV-28A)
-LP turbine 9th stage extraction point through regulating valve(GSN-PV-28B)

Question 22

When would the Regulator Bypass Valve(GSN-HV-6) be opened by the control room ?

Answer 22

If valve GSN-PCV-28A/B capacity is insufficient to maintain pressure @3psig

Question 23

If HP Turbine shaft packing leak off is insufficient at reduced load, where can additional steam be provided from ?

Answer 23

Supplied from LP Turbine 9th stage extraction through valve GSN-PCV-28B

Question 24

What happens if HP Turbine Shaft Leakoff is greater than sealing steam requirements ?

Answer 24

Excess steam will be unloaded to Main Condenser by the Excess Steam Unloading Valve (PCV-27)

Question 25

When would control room open the Unloader Bypass Valve? (HV-7)

Answer 25

May be opened if PCV-27 capacity is insufficient to maintain pressure @4psig

Question 26

Where does the Steam Packing Exhauster Condenser drain to ?

Answer 26

It drains to the Exhauster Drain Tank, which then drains to the Main Condenser

Question 27

How many exhauster fans are normally in service ? Where does is it take suction & discharge from ?

Answer 27

-Normally one fans running
-Takes suction from Exhauster Condenser & discharges gases to plant vent

Question 28

Why is Gland Seal Steam always supposed to be maintained at all times when condenser is at a vacuum ?

Answer 28

If there’s no Gland Seal Steam outside air will be drawn into turbine causing damage to rotor & seals

Question 29

When is Gland Seal required to be inservice ?

Answer 29

Required to be in-service prior & during the operation of Air Removal Pumps when establishing & operating with vacuum

Question 30

What provides gland seal steam if Extraction steam is lost ?

Answer 30

Aux. steam can supply necessary amount of sealing steam

Question 31

What happens if GSN-PCV-28A/B fail open on a loss of Gland Seal Steam ?

Answer 31

-Header pressure will increase causing unloader valve to open to control pressure
-Regulator valves can be isolated & Regulator Bypass MOV can be used to provide Gland Seal Steam

Question 32

What happens to the Drain Tank Level Control Valve (GSN-LV-8) loses instrument air ?

Answer 32

It will fail closed, which will overflow the Exhauster Drain Tank