Extraction Drain Flashcards
What does the Bleeder trip valve do?
- Prevents reverse steam flow on a MT trip
- Ensures turbine won’t overspeed
How does the Bleeder trip valve test work?
Pull on the handle and it equalizes pressure across operator piston to allow partial closing of the valve disc by spring force
If we lose IA to a bleeder trip valve what happens?
BTV will lose its open permissive and the valve would go partially closed. Steam pressure would keep it open.
Which FW heater has more then one BTV?
LPFW Htr #4
Where is the Heater Drain Tank?
120’ Turbine Building
Which valves in the ED system are direct acting?
Normal level control valves except #1 LPFW htr.
Which valves in ED system are reverse acting?
High level control valves and #1 LPFW HTR normal level control valve.
Where does the ED blowdown stack drain to?
North area condenser sump
What is the concern with MSR drain tank level?
If it back up to 3” below the associated MSR, the MT will trip.
Explain the when HDP’s start when starting the reactor?
1st pump starts at 25%
2nd pump starts at 40%
What cools the HDP LO coolers?
TCW
What are the trips on a HDP?
- Lo-lo level in HDT
- low flow (711 gpm for 15 seconds)
- Electrical protection
- High condensate line pressure (575 psig)
If we lose IA what happens to the HDP?
The discharge valve will fail closed and the pump will be put in recirc.
Explain the HDP?
- Powered from NB
- 5 stage centrifugal
- Vertical suction
- 6000-6500 gpm
Where does the HDP get seal water from?
Seal water is supplied from the condensate header (375-500 psig)
How is the seal water cooled at the HDP?
By the condensate service header. (50-100 psig)
Explain the purpose of the ED system?
Utilizes steam from the MT system to preheat CD/FW to increase overall plant efficiency
Where does the blowdown flash tank vent to?
HDT vapor space
Where does the BDHX cooling water discharge to?
discharge of HDP’s
Explain the operation of the normal level control valves for the reheat drain tanks. (1st stage/2nd stage)
- Normal acting valves
- Send drains to associated FW heater
What happens to the normal level control valves on the 1st or 2nd stage drain tank on a loss of air or power?
Fail closed
Where do the high level control valve send the drains from the 1st and 2nd stage drain tanks to?
Condenser on a high level or loss of air or power; which the high level control valves will fail open.
How are the heater drain tank and 1st stage reheater drain tank high level control valves operated during startup from 0%?
High level control valves will be open until 10% power is achieved.
How are the 2nd stage reheater drain tank high level control valves operated during startup?
High level control valves will be open until 20% power is acheived
How is level maintained in the FW heaters?
by the level control valves
What is different about the #5 FW heater compared to #6/7?
No level control valve
No direct dump to condenser on high level
Explain what happens on a hi-hi level in a HPFW Htr?
- Supply isolation valve closes
- Depressurize the BTV
- Open ext. line drain valve
- Closes normal level control valve of previous heater (if applicable)
What is drain cooler approach used for?
used to measure heater performance
How is DCA measured?
Drain temperature minus incoming condensate temperature
What is a concern when a heater drain pump trips?
Hotwell level can lower 9 inches. (30” setpoint for CD pump trip)
What kind of valve is the HDP dishcharge valve?
Air operated valve. Fails closed on loss of power or air.
What kind of valve is the HDP recirc valve?
Air operated valve. Fails open on loss of power or air.
Explain the operation of the HDP recirc valve?
- closes when flow is greater than 3200 gpm
- opens when flow is less than 1600 gpm
- closes when HDP stops
What is the HDT hi-hi level?
9 feet
Why don’t the #1 and #2 LPFW heaters have BTV’s?
Due to low energy present.
What do the #1 and #2 LPFW heaters have that the other FW heaters don’t?
Flow baffles in lieu of the BTV’s.
Why are there two BTV’s in LPFW heater #4?
Because the energy in this LPFW heater is great enough to cause an overspeed if the BTV would fail to close.
How is level maintained in the LPFW heaters?
- by level control valves in the drain lines
How do the drains flow from the #7 HPFW heater?
The drains are the result of differential pressure between the #7 HPFW heater and the #6 HPFW heater.
What positions the HDP discharge valve?
- Normal level controller of the heater drain tank to ensure adequate level and suction is maintained for the pump
What is individual heater performance measured by?
- DCA (Drain Cooler Approach)
- TTD (Terminal Temperature Difference)
How is DCA measured?
Fluid draining from the heater subtracted by the temperature of the incoming condensate
How is TTD measured?
How closely the exiting condensate temperature approaches Tsat of the extraction steam
How does the plant react to a trip of a Heater drain pump?
- Condenser level will drop
- Reactor power could increase due to colder FW
- Main Feedwater Pump suction pressure will decrease
- HDT level will increase
What is our target DCA?
10 degrees F
What if our DCA is too high; what does it indicate?
Water level is too low which allows higher fluid velocities to cause tube fretting and vibration induced fatigue
What if our DCA is too low; what does it indicate?
Water level is too high which reduces heat transfer
When will the BTV’s for a HPFW heater close?
- HPFW heater hi-hi
- HDT hi-hi (9 feet)
- Turbine trip
Explain what happens on a hi-hi level in a LPFW heater?
- MOV’s (inlet/outlet) automatically close
- BTV’s in that train close
- Normal level control valves close
- High level dumps open to send drains to condenser
Why do we want to minimize HDP mini-flow recirc ops?
- oscillation of FWP suction pressure
- damage to the HDT from the hydraulic effects of recirculating water.
