Gland Seal Steam Flashcards
What is the purpose of the GS system?
Prevents air leakage into and steam leakage out of the main turbine and feedwater pump turbines thru the turbine shaft glands
Valve PV-28B moves from full closed to full open with what pressure air signal change?
15 to 9 psig
valve PV-28A moves from full closed to full open with what pressure air signal change?
9 to 3 psig
how are PV-28A and 28B affected by loss of IA?
they fail open to protect the turbine
What pressure is the GS system header maintained at?
4 psig
Where are the GS regulating valves located?
140’ turbine building
What is the purpose of the steam packing exhauster?
maintain a vacuum on the steam exhaust header and annulus between the middle and outer shaft packings to keep steam from contaminating the oil
What is the purpose of PCV-27, the GS steam condenser unloader valve and how is it controlled?
auto acting, back pressure regulating valve
does not require IA because it is operated directly from the GS system pressure
What powers GSN-HV-5 and -14?
NH
During low power operation, where does sealing steam come from?
AS or SG thru PV28A, LP turbine 9th stage extraction thru point pv28B
What can the operator in the control room do if PCV-28A and 28B capacity is insufficient to maintain 4 psig?
can open regulator bypass valve hv-6
At full power operations where do we get gland seal steam from?
HP turbine shaft seal packing leackage
What happens if HP turbine shaft packing leak off is greater than the sealing steam requirement?
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
What will happen if GS is lost?
Loss of condenser vacuum
When is GS required to be in service during startup?
Prior to starting and during the operation of the air removal pumps, when establishing and operating with vacuum
How is the system affected by a loss of IA?
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
What cools the heat exchanger of the steam packing exhauster?
TC
Where do the exhauster fans take suction from and where is it discharged to? (steam packing exhauster)
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
What is the exhaust header vacuum normally maintained at and how is it controlled?
10-20H20 by manually throttling the air flow
