Feedwater/Feed Pump Turbine System Flashcards
What is the purpose of the FW system?
Supply feedwater from the suction of the FW pumps to the feedwater regulating valves in the line to each S/G at the required pressure, temp and flow rate.
provide the final 3 stages of feedwater heating in two parallel heater trains.
What is the purpose of the MFWPs?
Provide motive force to raise the pressure of the supplied condensate from around 350psig to around 1200 psig to overcome the S/G pressure.
what type of impellers are utilized on the MFWPs?
Double suction
What system provides lube oil for the bearings on the MFWPs?
Steam generator feedwater pump turbine lube oil system
What capacity are each of the feed pumps designed to handle rated power? what is the procedural limit?
65% of the total required flow.
Procedurally limited to 62% during a downpower to remove one FWP from service
What pressure does the seal water enter the feed pump casing form the gland seal regulator?
150psig
Where does this seal water come from?
Condensate service header
what is the purpose of the 2, 2.5 inch “Y” strainers in the seal water lines?
how many are normally in service?
to protect FWP seals from damage due to solids.
1 in service
What D/P is normally maintained across the seals by the gland seal regulators?
15psid
What output pressure do the gland leak off regulators maintain?
135psig
how much air pressure is utilized in the new inpro seals?
1 psig
What is the purpose of the mini flow valves?
To open or close as feedwater flow changes to maintain approx 5000gpm thru the MFWP to prevent overheating
why does the mini flow valve shut when the MFWP trips?
to prevent the pump from freewheeling due to condensate system flow thru the mini flow valve to the condenser
When would the mini flow valve fully open?
When the pump discharge valve is fully shut
How do the mini flow valves fail on loss of IA?
full open
the mini flow valves use how many air boosters for positioning?
2, one for opening and one for shutting
what happens to the mini flow valve when feed pump turbine lube oil pressure drops below 75 psig? why?
Go closed to prevent pump from freewheeling due to feedwater flowing thru an idle pump
how are the mini flow valves affected by a loss of 120VAC?
Fails open. if the FWPT trips or is already tripped the valve will close due to the energization of the DC solenoid
how are the mini flow valves affected by loss of 125 VDC?
Normal ops, no effect.
If FWPT is tripped, a loss of DC will result in the valve failing open
How often is the HP stop valve tested? any precations?
Daily.(Weekly) look this up!
HP control valve must be closed before testing the stop valve.
There is an interlock which prevents testing the HP stop valve if the HP control valve is open.
HP and LP control valves are operated by one hydraulic cylinder. Due to mechanical arrangement which valve opens first?
LP control valve
What is the difference between the HP and LP stop valves concerning design features?
LP stop valve has its own valve body and when testing the LP stop valve it only goes half way closed
Why is there a pressure switch installed on the control oil pressure line?
Acts to close the turbine control valves whenever the FWPT is tripped.
This prevents an uncontrolled start which could occur since on turbine reset the LP and HP stop valves immediately go wide open
what controls the speed of the FWPT?
Main feedwater control system
What system is the Feedwater control system part of?
Reactor control system
What are the 2 normal sources of steam to the feed pump turbines?
main steam and reheat steam from the MT system MSRs
What is the 3rd source of steam for the MFPTs?
Aux steam
what is the flow path for the MSR reheater to the feed pump?
Flow thru the low pressure stop valve and low pressure control valve. ‘D’ MSR
What is the flow path for the main steam to the feed pump?
flows thru the high pressure stop valve and high pressure control valve
What is the normal source of steam?
low pressure reheat
When would we use high pressure steam in MFWP?
During startup and to supplement the low pressure system during periods of light MT loads or overload on the FWPT
When would we use AS for feed pumps?
Testing
What ultimately controls the stop and control valves?
FWPT control oil
what system provides shaft sealing steam to A and B FWPTs?
Turbine steam seal and drain system (GS)
What cools the feed pump oil system?
NC
Where do the FWPTs exhaust to?
‘A’ and ‘B’ condenser reheat trays and into the ‘c’ condenser
Where are the FWPT drains directed to?
‘A’ and ‘B’ condenser sections
how many wheels make up the feed pump turbine?
6
Where are the thrust wear trip and overspeed trip governors located?
HP end of the rotor and are part of the rotor assembly
where is the engagement gear for the turning gear located?
exhaust end of the rotor
What is the normal position of the turbine drain valves under full steam load?
normally closed
If the turbine drain valves are closed, how do we remove condensate during normal ops?
They are provided with a continuous bypass drain line thru an orifice
What is the purpose of the feed pump turning gear?
to provide low speed turning of the rotor for cooling or heating up to prevent warping
What is the interlock associated with the feed pump turning gear and what is it trying to prevent?
2 pressure switches, 1 monitioring oil pressure on the feedwater pump bearings and the other monitor the oil pressure to the turbine bearings.
a low pressure in either switch will prevent the turning gear motor from operating.
This interlock is for bearing protection.
Where is the feed pump turning gear normally operated from?
control room
What are the various FWPT trips?
1)Turbine bearing low oil pressure
2)Pump bearing low oil pressure
3)Exhaust vacuum low
4)Feedwater pump suction pressure low
5)Feedwater pump discharge pressure high
6)Thrust bearing wear high
What are the three feedwater turbine thrust bearing test switches?
Thrust wear device test switch
Active thrust wear test switch
Inactive thrust wear switch
What nominal set point is the mechanical overspeed trip tested to?
110%
What is another way to test out the overspeed without getting up to that speed setpoint?
A jet of oil, controlled by a solenoid valve, can be sprayed into the emergency governor housing to unbalance the plunger and actuate the emergency trip at speeds up to rated
During a startup, when is the first main feed pump started?
Prior to exceeding a reactor power of 3% which is the capacity of 1 AFP
When is the 2nd MFWP started?
50% power
Prior to startup what must be done with the Condensate/feedwater systems to improve the water quality?
Long path recirc
During normal operation when can i secure one of the FWPs?
If plant load decreases below 62%
What is meant by “Standby” when referring to the MFWPs?
The pump and turbine are in a warmed and ready condition
After each shutdown, why is the main feedwater system placed in long path recirc?
For shutdown chemistry control and system cooldown
What will happen if i lose a feedwater pump while at 100% power?
Reactor power cutback, lowering reactor power and turbine power to within capacity of a single main feedwater pump
What will happen if we lose a FWP while at 100% power?
Reactor would trip on low S/G level.
S/G level would have to be maintained by aux feed system
