FW/FT- Feedwater/Feedwater Pump Turbine Flashcards
What is the purpose of the FW system?
Supply FW from the suction of the FW pumps to the feedwater regulating valves in line to each S/G at the required pressure, temperature, and flow rate
Provide the final three stages of feedwater heating in two parallel heater trains
What is the purpose of the Main Feedwater Pumps? Where are the pumps located?
To provide the motive force to raise the pressure of the supplied condensate from around 350 psig to around 1200 psig to overcome S/G pressure
110’ turbine building, west of the A condenser
What type of impellers are utilized on the Main Feedwater Pumps?
Double Suction Impellers
What system provides lube oil for bearings on the Main Feedwater Pumps?
(LO) Steam Generator Feedwater Pump Turbine Lube Oil system
To what capacity are each of the Feed Pumps designed to handle at rated power? What is the procedural limit?
~65% of the total required flow
Procedurally limited to 62% during a downpower to remove one feedwater pump from service
At what pressure does the seal water enter the main Feed Pump casing from the Gland Seal Regulator?
150 psig
Where does the main feedwater pump seal water come from?
Condensate Seal Water Headers
What is the purpose of the two 2.5” Y-strainers in the main feedwater pump seal water lines?
To protect the feedwater pump seals from damage due to solids
How many Main feedwater pump seal water Y-strainers are normally in service?
Just one, other on standby
What D/P across the seals is normally maintained by the MFWP Gland Seal Regulators?
15 psid
What output pressure do the MFWP Gland Leak-off Regulators maintain?
135 psig
How much air pressure is utilized in the new MFWP inpro seals?
1 psig
What is the purpose of the MFWP Mini-flow valves?
To open or close as feedwater flow changes to maintain approximately 5000 gpm through the Main Feedwater Pump to prevent pump over heating
Why does the Mini-flow valve shut when the Main Feedwater Pump trips?
To prevent the pump from freewheeling due to condensate system flow through the mini-flow valve to the condenser
When would the MFWP Mini-flow valve be fully open?
When the pump discharge valve is fully shut
How do the main feedwater pump Mini-flow valves respond to a loss of IA?
Fail open
The MFWP mini-flow valves use how many air boosters for positioning? How does the annubar measure flow rate?
2 (one for opening, one for shutting)
differential pressure
What happens to the Mini-flow valve when Feed Pump turbine lube oil pressure drops below 75 psig? Why?
Go closed
Prevent pump from freewheeling due to feedwater flowing through an idle pump
How are the Mini-flow valves affected by a loss of 120 VAC?
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 a 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 Feedwater pump turbine HP Stop valve tested? Any precautions? What does the local green indicating light mean?
Daily (Lesson plan)
(actually weekly)
HP Control valve must be closed before testing the stop valve
There’s an interlock which prevents testing of the HP Stop Valve if the HP control valve is open
HP control valve is closed
Feedwater pump turbine HP and LP control valves are operated by one hydraulic operating cylinder. Due to mechanical arrangement, which valve opens first? What does that allow the other valve to do?
LP Control Valve
HP control valve will maintain the desired speed called for by the control system above the capacity of the LP control valve
What is the difference between the HP and LP Stop Valves and Control 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
LP control valves are comprised of 5 valve assemblies in a valve chest cover with one stop valve
(compared to the HP control valves that are one stop and control valve)
Why is there a pressure switch installed on the MFWP control oil pressure line?
Acts to close the turbine control valves whenever the feedwater pump turbine 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 Feedwater Pump Turbine and the position of the FW regulating valves? Why does it control these things?
Main Feedwater Control System (also manually from the control room)
maintain steam generator level during power operations
What system is the FWCS (feedwater control system) a part of?
Reactor Control System
What are the two normal sources of steam to the Feed Pump turbines?
LP control valves: Reheat steam from the MT system moisture separator reheaters (hot reheat line)
HP control valves: Main steam
What is the third source of steam for the Main Feed Pump turbine overspeed trip tests?
Auxiliary Steam
What is the flow path for the Moisture Separator reheater to the Feed Pump?
Flows through the low pressure stop valve and low pressure control valve
What is the flow path for the Main Steam to the Feed Pump?
Flows through the High pressure stop valve and high pressure control valve
Which source is used for normal operation in the Main feedwater pump turbines?
Low pressure reheat steam
When would we use high pressure steam in the main feedwater pump turbines?
During startup and to supplement the low pressure system during periods of light MT loads or overload on the feed water pump turbine
When would I use AS for the main Feed Pump turbines?
over speed Testing
What ultimately controls the Feedwater pump Turbine stop valves 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 main Feed Pump turbine lube oil coolers?
Turbine Cooling Water
Where do the MFWPTs exhaust to?
Underneath the reheat trays in the ‘A’ and ‘B’ Condenser sections to the ‘C’ Condenser section
Where are the FWPT drains directed to?
‘A’ and ‘B’ Condenser sections
How many wheels (stages) make up the Main Feed Pump turbines?
6
6 stage turbine
Where are the Thrust Wear trip and Overspeed trip governors located?
HP end of the rotor and are part of the rotor assembly
Regarding the MFWPTs, where is the engagement gear for the turning gear located?
Exhaust end of the rotor
What is the normal position of the MFWP Turbine Drain Valves under full steam load? Where do the drain lines tap into the HP and LP stop and control valves?
Normally closed
above the seat and below the seat
If the Turbine Drain Valves are closed, how do we remove condensate during normal ops? When would the lead drain valves be opened?
They’re provided with a continuous bypass drain line through orifices
to drain the condensate prior to opening the stop valve, preventing a slug of water from entering the turbine
What is the purpose of the Feed Pump turning gear?
To provide low speed turning of the turbine rotor for cooling down the turbine before complete shutdown or for prestart rotation of the turbine rotor before steam is admitted to the turbine wheels
What is the interlocked associated with the Feed Pump turning gear and what is it trying to prevent?
Two pressure switches, one monitoring oil pressure on the feedwater pump bearings and the other to 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
a reset/ jog button is at the turbine
What are the various Feedwater Pump Turbine trips?
Turbine bearing low oil pressure
Pump bearing low oil pressure
Exhaust vacuum low
Feedwater Pump suction pressure low
Feedwater Pump discharge pressure high
Thrust bearing wear high (active or inactive)
What are the three Feedwater Turbine thrust bearing test switches?
Thrust Wear device Test switch
Active Thrust Wear Test Switch
Inactive Thrust wear Test Switch
Describe the operation of the Overspeed Governor
Located on the rotor, there’s a plunger held against its seat in the governor housing by a spring
As the rotor spins faster, the centrifugal force will cause the plunger to move out of the housing, and once it reaches the overspeed setpoint, the plunger will throw out. When this happens, it strikes the emergency trip mechanism actuating tripper and trips out the turbine
(trips the stop valves closed)
At what nominal setpoint 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 Feedwater Pump started?
Prior to exceeding a reactor power of ~3%, which is the capacity of one AFP
When is the second Main Feedwater Pump 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 Feedwater Pumps?
If plant load decreases below 62%
What is meant by ‘Standby’ when referring to the Main Feedwater Pumps?
The pump and turbine in a warmed ready condition
During shutdown, when do the AF pumps take over feeding the steam generators? After each shutdown, why is the Main Feedwater System place in Long Path Recirc?
When the MFWPs would cause over cooling of the RCS
For shutdown chemistry control and system cooldown
What will happen if I lose a single 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 I lose two Feedwater Pumps while at 100% power?
Reactor would trip on low S/G level
S/G level would have to be maintained by Aux feed system
What does the CD system do for the feedwater system?
Provides the water to the Steam Generator Feedwater Pump suctions.
Source for the Steam Generator Feedwater Pump seals.
Provides the return path for both Long Path Recirc and feedwater pump miniflow recircs.
Provides the Main Condenser which receives the feedwater turbine exhaust steam, turbine
drains and steam line drains, and provides exhaust vacuum.
What is the purpose of the feedwater pump turbine rotor assembly?
to absorb thermal and kinetic energy and transform it to mechanical energy
What all is attached to the feedwater pump turbine rotor shaft?
turbine, pump and governor assembly
thrustwear trip and overspeed trip governors at the HP end of the rotor
engagement gear for the turning gear at the exhaust end of the rotor
flexible coupling joining the turbine end to the pump end
Where is the seal water on the main FW pumps directed to when leaving the pump?
condenser shell A
steam packing exhauster
When seal water is leaving the Main FW pump, what components does it go through?
gland leak-off piping and gland leak-off regulator
Where are the MFWPT high pressure and exhaust casings bolted together? What is on each FWPT casing?
at the centerline of the turbine
a blow-out diaphragm
What is the flow path through the MFWPT?
high/low pressure steam admitted through respective control valves to the high pressure casing head, then directed to the first stage by a steam ring (high pressure) or by nozzle plates (low pressure), then to the exhaust casing, directing the expanded steam to the condenser via condenser vacuum
What happens when there is a trip on the MFWPT?
HP and LP stop and control valves go closed
mini-flow valves go closed
(when trip is reset, all valves will go open)
What is the purpose of the MFWPT thrust bearing and what happens when it wears down? How often are the thrust wear device trips tested?
absorbs thrust in the turbine
shaft movement can damage the turbine
weekly
How does the MFWPT thrust wear device test switch work?
key operated
key can only be removed when in the test position to be used for the other two test switches
in the isolate position, the switch energizes a solenoid that isolates the thrust wear trip device
in the test position, it enables the active and inactive thrust wear test switches and turns on their green lights
in normal, both thrust wear trip devices are enabled
How does the MFWPT active wear test switch work?
key removable in the normal position
normal position does nothing
in test the switch tests the active thrust wear device and enables a green light
How does the MFWPT inactive thrust wear test switch work?
key removable in normal
normal position does nothing
in test, the switch tests the inactive thrust wear device and produces a green light
How is MFWPT speed determined?
by the relative position of the 5 LP control valves and the high pressure control valve
Referring to the MFWPT speed control, How are the valve positions controlled?
an operating cylinder that’s controlled by a speed governor. the governor responds to signals from the feedwater control system
