[ED] - Extraction Steam and Drains Flashcards
[ED]
[ED] purpose?
Extraction Steam & Drains
Preheats CD and FW prior to feedwater entering the S/Gs to increase plant efficiency
[ED]
What provides steam to #4 LP feedwater heater during startup?
Extraction Steam & Drains
[AS]
[ED]
What water system makes-up to the bottom of the ED blowdown stack?
Extraction Steam & Drains
[DS] Domestic Water
[ED]
What is the purpose of the ED blowdown stack?
Extraction Steam & Drains
-collection point for steam traps, HP heater relief valves and miscellaneous [AS] header drains
Aux Steam
[ED]
When is [DS] added to [ED] blowdown stack?
What occurs if [DS] is OOS?
(Domestic Water)
Extraction Steam & Drains
If temp of water >150F
Steam will come out of the blowdown stack and north Condenser sump
[ED]
GA-N2 & ED?
Extraction Steam & Drains
Supplies Nitrogen blanketing of FW Heater Shells & HDTs during long term shutdown operations
Feedwater
Heater Drain Tanks
[ED]
[IA] & [ED]?
2
Extraction Steam & Drains
[MT] control system uses [IA] in Turbine Critical and Non-Critical Relay Dump Valves (provide a signal to control BTVs)
For use all [ED] AOVs
Main Turbine
Bleeder Trip Valves
Instrument Air
Air Operated Valves
Extraction Steam & Drains
[ED]
How are BTV’s affected by a loss of [IA]?
Extraction Steam & Drains
Bleeder Trip Valves
go partially closed (Lose open permissives)
remain open due to [ED] flow
Bleeder Trip Valves
Extraction Steam
Where are the Heater Drain Pumps powered from?
Extraction Steam & Drains
‘A’ from NBN-S02
‘B’ from NBN-S01
[ED]
Where does seal water for each Heater Drain Pump come from?
Extraction Steam & Drains
Condensate Header
(375-500 psig)
[ED]
What positions the Heater Drain Pump mini-flow valves? When will it close? What controls the position of the heater drain pump discharge valve?
Extraction Steam & Drains
Heater Drain Pumps flow transmitter
as the unit comes up in power and more extraction drain flow is available
heater drain tank normal level control valve
[ED]
What signals stop the Heater Drain Pumps?
3
Extraction Steam & Drains
HDT lo-lo level alarm
Heater Drain Pump low flow after a time delay
Electrical protection signal
[ED]
Where are Heater Drain Pumps located?
What allows one heater drain pump operation?
Extraction Steam & Drains
TB 100’ (West of Main Feed Pumps)
Open suction
and vent cross-tie between HDTs
Heater Drain Tanks
[ED]
Why doesn’t #5 FW Heater have a level control system?
Extraction Steam & Drains
No drain cooler region
Drains directly to the HDT
Heater Drain Tank
[ED]
Which LP FW heaters have four inlets?
How many do the others have?
Extraction Steam & Drains
1 & 2
3 & 4 have 1 inlet each
Which feedwater heater has an input from S/G blowdown system?
Extraction Steam & Drains
3
[ED]
What is the purpose of the BTVs? Which feedwater heaters have BTVs?
Extraction Steam & Drains
Bleeder Trip Valves
Prevent [MT] reverse steam flow (overspeed) on Turbine Trip
3-7
Main Turbine
[ED]
What on the BTVs assists disc opening with min differential steam pressure?
Extraction Steam & Drains
Bleeder Trip Valves
Balance Arm device
What happens the Bleeder Trip Valve test valve actuates?
Extraction Steam & Drains
air pressure across the operator piston is equalized to allow partial closing of valve disc by spring force
Why are there 2 BTVs on #4 FW heater extraction line?
Extraction Steam & Drains
Feedwater
there is enough energy in #4 by itself to cause an overspeed trip
[ED]
Which level control valves are reverse acting in [ED]?
Extraction Steam & Drains
All high level CVs and #1 LP heater normal level CVs
Low Pressure
Control Valves
At what air signals are the reverse acting valves full open and full closed in the ED system?
Extraction Steam & Drains
Full open with 3#
Full closed with 15#
(Direct acting is the complete opposite)
What happens upon a hi-hi signal in a HP feedwater heaters?
Extraction Steam & Drains
Isolates extraction steam
Closes the normal level control valve of the preceding heater
Opens the affected heater’s motor operated extraction steam line drain valve
In addition, for the HP heaters, the 1st and 2nd stage reheater drain tank vents isolate from the affected heater and vent to the main condenser
What happens upon a hi-hi signal in a LP feedwater heaters?
Extraction Steam & Drains
Isolated entire LP heater train by closing the heater train isolation valves
Isolated extraction steam to #3 and #4 heaters
Opens the extraction line solenoid operated drain valves for #3 and #4 heaters
Below what power level may there be insufficient D/P between the heater shells to allow for proper operation of the normal level control valves in the ED system?
Extraction Steam & Drains
20%
high level control valves operate to keep alarms clear until power level is sufficiently raised
When is the first heater drain pump started?
Extraction Steam & Drains
25% power
When is the second heater drain pump started?
Extraction Steam & Drains
Between 30 and 40%
During a plant shutdown, when are the Heater Drain Pumps secured?
Extraction Steam & Drains
First one at 40%, second one at 25%
How is the ED system affected by a loss of IA?
Extraction Steam & Drains
Heater Drain Pump discharge valve fails closed, recirc valve fails open, putting the pump on recirc
Heater Drain Tank, MSR Drain Tank, 1st and 2nd Stage Reheater Drain tank, and Feedwater heater High Level Dump valves will all fail open and the Normal Level Control Valves fail closed (Except #1 heater)
Heater Drain pump will eventually trip on low flow or Heater Drain tank lo lo level signals
The main steam supply to the 2nd stage reheater will isolate and the 1st and 2nd stage Reheater Drain Tanks and Tube Bundles will vent to the condenser instead of their associated Feedwater heaters
What is the purpose of the HDTs (heater drain tanks)?
Extraction Steam & Drains
ultimate collection point for most of the normal drains within the ED system
provides suction for the heater drain pumps
tank level regulated flow to the Main feed pumps
receives mini flow line from heater drain pump
Where are the heater drain tanks located?
Extraction Steam & Drains
120’ turbine building, above the heater drain pumps
Concerning the ED system, where do the MSR 1st stage reheater drain tanks flow to? 2nd stage reheater drain tanks?
Extraction Steam & Drains
6 FW heaters, then to the heater drain tank
How many stages are the heater drain pumps?
Extraction Steam & Drains
5
What is the purpose of the Feedwater heaters?
Extraction Steam & Drains
aid in improving the secondary system efficiency
Concerning the High pressure feedwater heaters, what are the flow paths for the extraction steam and feedwater flow?
Extraction Steam & Drains
extraction steam from HP turbine comes in through the top, condenses and is drained from the bottom
feedwater flows in through the bottom, passes through the U-tubes and exits through the top
Concerning the HP feedwater heaters, what are the differences between the #6/7 heaters and the #5 heaters?
Extraction Steam & Drains
6/7 have condensing and subcooling zones, has level control system, #7 drains to the #6 heater, #6 drains to the HDT
What is the purpose of the vents on the various tanks, heat exchangers and pumps in the ED system?
Extraction Steam & Drains
to remove non-condensable gases and direct them to the condenser for removal
What is the motive force of extraction steam while traveling from the turbine to the feedwater heaters?
Extraction Steam & Drains
the differential pressure between the turbine stages and the feedwater heater shells
Which feedwater heaters have the supplying extraction lines cross-connected and what does the cross connect allow for?
Extraction Steam & Drains
3a, b, c
4a, b, c
6a, b
7a, b
allows unit operation without all high and low pressure feedwater heaters in service
What does the High Pressure turbine provide extraction steam to?
Extraction Steam & Drains
3rd stage- 7A/B heaters and first stage reheating steam in the MSRs
5th stage- 6A/B heaters
cold reheat- 5A/B heaters
Where do the heater drain pumps send their effluent?
Extraction Steam & Drains
to the suction of the main feedwater pumps
combines with the condensate just downstream of the feedwater heaters
What is the difference in operation between direct acting and reverse acting level control valves in the feedwater heater level control system?
Extraction Steam & Drains
direct acting- higher air pressure opens the valve
reverse acting- higher air pressure closes the valve
Where do the MSR drain tanks vent to? Where does the heater drain pump vent its suction line to?
Extraction Steam & Drains
their respective MSR/Hot reheat line
respective heater drain tank
Where do the first stage reheater drain tanks normally vent to?
Extraction Steam & Drains
A and C vent to #6A heater extraction line
B and D vent to #6B heater extraction line
all four vent back to their respective 1st stage reheater tube bundle outlet for steam scavenging
(on high level, vent to the condenser)
Where do the 2nd stage reheater drain tanks normally vent to?
Extraction Steam & Drains
A and C vent to #7A heater extraction line
B and D vent to #7B heater extraction line
all four vent back to their respective 2nd stage reheater tube bundle outlet for steam scavenging
(on high level, vent to the condenser)
Where do the heater drain tanks vent to?
Extraction Steam & Drains
to their respective #5 FW heater
both tanks also have a vapor cross-connect line to each other
Where do the #5, 6 and 7 feedwater heaters vent to?
Extraction Steam & Drains
both trains all tie in together to a common header and vent to the condenser
How does the ED system interface with the SC (secondary chemical control) system?
Extraction Steam & Drains
Blowdown Flash Tank (BFT) vents to both of the Heater Drain Tanks by way of the vapor cross tie line between the HDT’s.
The blowdown flow from the Blowdown Flash Tank can be directed to the shell side of the #3 LP Heaters.
Cooling water from the blowdown heat exchanger is returned to the discharge of the heater drain pumps, which is then directed to the main feedwater pump suction.
How does ED interface with GS?
Extraction Steam & Drains
LP turbine 9th stage extraction supplies sealing steam to GS on power ascension
In the ED system, what is powered by NH?
Extraction Steam & Drains
MOVs, HP heater extraction steam block and drain valves, heater drain pump motor space heaters
In the ED system, what is powered by NK?
Extraction Steam & Drains
solenoids, controls, indication and alarms for various valves
In the ED system, What is powered by NN?
Extraction Steam & Drains
LP FW heater steam pressure instrumentation
HTR DRN pump discharge/suction D/P, tank level and pump flow instrumentation
What cools the HTR DRN pump lube oil coolers?
Extraction Steam & Drains
turbine cooling water
What maintains water level in the LP feedwater heater drain cooler, or subcooling zone?
Extraction Steam & Drains
normal level control valve
What is the purpose of having reverse acting normal and high level control valves in the ED system?
Extraction Steam & Drains
to ensure that on a loss of IA, the ED system will drain its contents to the main condenser
Describe the new level control valves for the LP feedwater heaters.
Extraction Steam & Drains
Vee style ball valve, provides beter throttling and seal off flow
can be positioned in either fail open or fail closed designation with the same valve mounting configuration, causing less installation errors
rotory positioners with rotary actuators with a lever
4 gauges instead of three
smaller in size
What is the sequence for putting the MSR and 1st/2nd stage drain tanks in service to their normal level control valves?
Extraction Steam & Drains
At 10% turbine power, 1st stage and MSR drain tanks go to normal level control valves, leading to the #6 FW heaters (1st stage) and the HTR DRN tank (MSR drain tank)
At 20% turbine power, 2nd stage drain tank goes to normal level control valve, leading to #7 FW heaters
