Gland Seal Steam Flashcards
What is Gland Seal system used for ?
-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
Where does Gland Steam go after being used ?
Returns air/steam mixture to the Steam Packing Exhauster
What does the Steam Packing Exhauster do ?
-Condenses steam & returns it to main condenser
-Exhausts non-condensable gases to atmosphere
What’re the 4 steam sources for Gland Seal System ?
-Main Steam
-Aux. Steam
-Ninth Stage Extraction Steam
-HP turbine leak off
What is Main Steam used for in the Gland Seal System ?
-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
What is Aux. Steam used for in Gland Seal System ?
-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
How is extraction steam & drain system used for in the Gland Seal System?
-Turbine load increases,LP turbine flow increases then 9th stage extraction can supply Gland Seal System
What happens if 9th stage extraction steam is lost for Gland Seal System?
Aux. steam or main steam can supply the necessary amount of sealing steam
What does TC cool in the Gland Seal System ?
It cools the steam packing exhauster condenser
What does the Condenser Air Removal do for the Gland Seal System ?
-Removes air & non-condensable gases discharged from steam packing exhaust fans
-Radioactive gases will be processed through AR effluent filtration system
Where does the Main Condenser receive the condensed steam from the Gland Seal System?
Receives Gland Seal condensed steam from:
-Steam Packing Exhausted Condenser
-Steam dumped from steam pressure unloading valve(GSN-PV-27)
What do the Steam Seal Regulator (GSN-PV-28A & B) valves do ?
Automatically positions Main/Aux. Steam & extraction steam supply valves to maintain 3psig in seal steam supply header
What does the control unit do for Steam Seal Regulator valves ?
Senses seal steam supply header pressure & sends proportional Instrument Air signal to valve operators
Where shaft packing provided on turbine rotors ?
Between turbine shells, or between exhaust hood & atmosphere
How are packing rings for turbine shaft packing made ?
-Machines with teeth fitted with minimum radial clearance between teeth & rotor
Why do the packing rings have small teeth with minimum radial clearance ?
Resists steam & airflow
What kind of steam is sent through turbine shaft packing ?
LP steam is supplied to inner cavity formed by first two sets of packing
What do the steam packing exhauster unit provide ?
-Maintains vacuum on steam exhaust header & between the middle & outer shaft packing rings
Why does there have to be a vacuum on the steam exhaust header ?
Vacuum causes steam/air mixture flow from packing ring to the exhauster to prevent contamination of oil used on journal bearings adjacent to packing
What is the Gland Seal Steam Condenser Unloaded Valve ? How is the valve operated ?
(GSN-PCV-27)
-Automatic acting back pressure regulating valve
-Directly operated from Gland Seal system pressure, so it doesn’t required Instrument Air to function
Where is sealing steam supplied from during low power operation ?
-Aux Steam or Main Steam through regulating valve (GSN-PV-28A)
-LP turbine 9th stage extraction point through regulating valve(GSN-PV-28B)
When would the Regulator Bypass Valve(GSN-HV-6) be opened by the control room ?
If valve GSN-PCV-28A/B capacity is insufficient to maintain pressure @3psig
If HP Turbine shaft packing leak off is insufficient at reduced load, where can additional steam be provided from ?
Supplied from LP Turbine 9th stage extraction through valve GSN-PCV-28B
What happens if HP Turbine Shaft Leakoff is greater than sealing steam requirements ?
Excess steam will be unloaded to Main Condenser by the Excess Steam Unloading Valve (PCV-27)
When would control room open the Unloader Bypass Valve? (HV-7)
May be opened if PCV-27 capacity is insufficient to maintain pressure @4psig
Where does the Steam Packing Exhauster Condenser drain to ?
It drains to the Exhauster Drain Tank, which then drains to the Main Condenser
How many exhauster fans are normally in service ? Where does is it take suction & discharge from ?
-Normally one fans running
-Takes suction from Exhauster Condenser & discharges gases to plant vent
Why is Gland Seal Steam always supposed to be maintained at all times when condenser is at a vacuum ?
If there’s no Gland Seal Steam outside air will be drawn into turbine causing damage to rotor & seals
When is Gland Seal required to be inservice ?
Required to be in-service prior & during the operation of Air Removal Pumps when establishing & operating with vacuum
What provides gland seal steam if Extraction steam is lost ?
Aux. steam can supply necessary amount of sealing steam
What happens if GSN-PCV-28A/B fail open on a loss of Gland Seal Steam ?
-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
What happens to the Drain Tank Level Control Valve (GSN-LV-8) loses instrument air ?
It will fail closed, which will overflow the Exhauster Drain Tank
