Condensate (CD) Flashcards
Purpose of the Condensate system
Provides heat sink for Turbine, Feedwater pumps, steam bypass control
Minimize air in-leakage
Chemistry control
Provide suction to FWP’s
Where is the dog bone seal filled from if we need to fill it with water?
Condensate service header
How are the Equalization ducts filled?
Condensate service header
How would the equalization duct water seal blow out?
Seal will blow out if differential temperature 30*F
What is the main cause of vacuum in the condenser?
phase change of steam coming from the LP turbines condensing
What is the purpose of the Hotwells in the main condenser?
One in each condenser section (2 hotwell halves)
100,000 gal. Volume, sufficient for 4 minutes of operation at ‘valves wide open’ condition.
Provide:
Condensate storage
Reheat and deaeration
Detention time
Leak detection
Which hotwell halves do the CD pumps take suction from?
Pump A - hotwells 2A/B/C
Pump C - hotwells 1A/B/C
Pump B - both sides of hotwell
What is the purpose of the mini-flow recirc valves for the CD pumps?
prevent overheating of the pump at reduced flow
Where do the CD pump mini-flow recirc valves direct flow back to?
Pump A - hotwell 2C
Pump C - hotwell 1C
Pump B - 1C and/or 2C depending on suction valve alignment
What type of controllers are provided for the CD pumps?
Foxboro controllers (B05)
CDN-LIC-81/82
What level is the Condenser normally maintained at?
Why?
41”
Basis is on a Heater Drain Pump trip, we could lose 9 inches of level in the hotwell.
The Condensate Pumps trip on a lo-lo level of 30 inches
This gives us margin
What type of valve operator is on the auto makeup valves?
How do they fail?
Where do they flow into directly?
2 AOV’s
fail closed on a loss of air or NK
‘A’ Condenser shell, 140’ TB
If the CST Lo-Lo setpoint is reached, what happens to auto makeup to the Main condenser?
solenoid valve isolates air to the auto makeup valves to isolate the CST auto makeup
What is the motive force for auto makeup to the main condenser from the CST?
vacuum drag
very low pressure in the condenser, higher pressure in the CST
What is the purpose of hotwell draw off?
Hi-level in hotwell, will cause CDN-LV-75 to open and send water to CST
When does CDN-LV-75, Hotwell draw off valve, automatically close?
Why?
How can these interlocks be overridden?
low feedpump suction pressure
–to help with saving a feedpump from tripping on low suction pressure
high cation conductivity
–minimize CST contamination
Key switch in ZTN-C01, HS-75
What type of valve operator is on CDN-LV-75, hotwell draw off valve?
How does it fail?
air operated valve
fails closed on a loss of air
What is special about the draw off valve interlock bypass switch in the ZTN-C01 cabinet (HS-75)?
key switch, captures the key in bypass position
key in SM office
What is needed administratively before overboarding condensate?
Why?
overboard permit
so chemistry can verify water contamination is within release limits
Which CD pumps can be used for overboarding?
A and C ONLY
What is the purpose of long path recirculation?
initial cleaning up during startup and shutdown
What is the flow path for long path recirculation?
1 CD pump takes suction on the hotwells > CD demins > 3 strings of LPFWHs > Feedpump bypass > HPFWHs > V124/V125 > HV-46/VA31 > back to the condensers
What is the issue caused by the HV-46 valve not having a ‘jog’ function?
What plant mod fixed this?
caused thermal shock and water hammering
2” bypass line around HV-46 with VA31 to better control cooldown
What is the prerequisite for opening HV-46 while going into long path recirculation flow?
HPFWH #7 feedwater outlet temperature has to be </= 200*F
What is the purpose of the vacuum breakers?
How are they operated?
allows a rapid slowing of the turbine under emergency conditions
solenoid provides air to open, spring to close
Why do we keep a water seal on top of the vacuum breaker valve disk?
where does the seal water come from?
prevents air leakage into condenser
condensate service header
What is the capacity of the CD pumps?
50% each, but keep all three running normally
What cools the CD pump motor bearing oil?
TC
What is the hotwell low level trip for the CD pumps?
30”
Where is each CD pump powered from?
Pump A and B - NBN-S01
Pump C - NBN-S02
How is the CD pump seal cooled and lubricated?
flow from the condensate service header
CD pump interlocks and trips
suction valve needs to be full open or breaker wont close
pump B needs at least one suction valve open
pump trips:
30” or less in the hotwell pump is aligned to
Low flow less than 3600 gpm for greater than 45 seconds
4.16 kV bus undervoltage
Lockout relay
How much flow are CD pump mini-flow recirc valves capable of passing?
When do they start to modulate open?
4000 gpm
CD pump flow decreases to 4500 gpm
How do they CD pump mini-flow recirc valves fail?
Where do they get power from?
AOV
fail open on a loss of air or NN
pump A and C mini-flow valves from NNN-D11
pump B mini-flow valves from NNN-D12
What is the negative result of CD pump mini-flow valves failing open?
reduced FWP suction pressure
What are the CD pump B mini-flow valves interlocked with?
B pump suction valves
whichever suction valve is open determines which mini-flow valve will modulate to go back to the same hotwell half group that the pump is taking suction on
(normally both are utilized)
What kind of controller (reverse or direct acting) does CDN-PDV-195, Condensate Polishing Demineralizer bypass valve, have?
reverse acting
0% output - Open
100% output - Closed
meaning it fails open on loss of air
What is the purpose of CDN-PDV-195, Condensate Polishing Demineralizer bypass valve?
direct flow around the CD Demins
maintains 55 psid or less when demins are inservice
What are the permissives for opening CDN-PDV-195, Condensate Polishing Demineralizer bypass valve?
Both inlet and outlet valves must be open for an modulate permissive of bypass
What 3 signals will open CDN-PDV-195, Condensate Polishing Demineralizer bypass valve, even when the controller is in manual?
Condensate polishing inlet or outlet valve not fully open
Condensate demineralizer high differential pressure (greater than 55 psid)
Instrument Air header pressure low
What loads does the Condensate service header supply?
condenser expansion joint (dog bone seal), vacuum breakers, and air removal pumps
What controls Condensate Service Header pressure?
What pressure is it maintained at?
How does this valve fail?
air operated PCV (CDN-PV-200)
80psig
fails closed on a loss of air
What is the backup supply to the condensate service header?
DW through valve DWN-HV-275
How is Steam bypass control system tied into the CD system?
SBCVs 1001-1006 discharge to the main condenser shells
What is special about the CD pump discharge valve handswitches in the control room?
push to stop feature on the handswitch
when pushed, it stops the valve movement at whatever position it is currently in
How many demin beds are inservice during full flow operation?
5 beds inservice with one being regenerated
How are the LPFWH inlet and outlet valves controlled?
handswitch in the control room opens/closes them both at the same time
How does the Main Turbine system tie into the CD system?
CD provides hood spray
helps cool the LP turbine hoods and help direct steam down towards the condenser
The CD pumps trip on a hotwell level of 30”, but when does the alarm come in?
34”
