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Secondary > ED- Extraction Steam and Drains > Flashcards

ED- Extraction Steam and Drains Flashcards

1
Q

What is the purpose of the ED system?

A

Preheats condensate and feedwater prior to feedwater entering the Steam Generators to increase overall plant efficiency

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2
Q

What system has the ability to provide steam to the #4 LP feedwater heaters during startup?

A

Auxiliary Steam

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3
Q

What system is used to add cool water to the water volume that is maintained in the bottom of the ED blowdown stack?

A

Domestic Water (DS)

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4
Q

What is the purpose of the ED blowdown stack?

A

Provides a collection point for various steam traps, HP heater relief valves and miscellaneous aux steam header drains

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5
Q

When is DS added to the ED blowdown stack? What if DS is not available?

A

When temperature of blowdown stack water volume exceeds 150F

If not available, there will be steam coming out of the blowdown stack and the north condenser area sump

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6
Q

How does GA interact with ED?

A

During long term shutdown conditions, the GA system supplies nitrogen for blanketing of the feedwater heater shells and heater drain tanks to protect against rust and prevent oxygen from dissolving in the water

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7
Q

How does IA interact with ED?

A

MT control system admits IA through Turbine Critical and Non-Critical Relay Dump Valves which provide a signal to control Bleeder Trip Valves

Provides motive force for all air operated valves in ED system

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8
Q

How are BTV’s affected by a loss of IA?

A

BTVs will lose their open permissives and go partially closed

They will remain open due to the extraction steam flow

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9
Q

Where are the Heater Drain Pumps powered from?

A

‘A’ from NBN-S02

‘B’ from NBN-S01

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10
Q

Where does the seal water for each Heater Drain Pump come from?

A

Directly from the Condensate Header at 375-500 psig

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11
Q

What positions the Heater Drain Pump mini-flow valves? When will it close? What controls the position of the heater drain pump discharge valve?

A

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

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12
Q

What three signals would stop the Heater Drain Pumps?

A

A Heater Drain Tank lo-lo level alarm

Heater Drain Pump low flow after a time delay

Electrical protection signal

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13
Q

Where are the Heater Drain Pumps located? What allows one heater drain pump operation?

A

100’ Turbine Building west of the Main Feed Pumps

opening a suction and vent cross-tie between the heater drain tanks

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14
Q

Why does #5 feedwater Heater not have a level control system?

A

Does not contain a drain cooler region and drains directly to the Heater Drain Tank

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15
Q

Which Low pressure Feedwater heaters have four inlets on the top? How many do the others have?

A

1 and #2

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16
Q

Which feedwater heater has an input from S/G blowdown system?

A

3

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17
Q

What is the purpose of the Bleeder Trip Valves in the ED system? Which feedwater heaters have BTVs?

A

3, 4, 5, 6, 7

To prevent reversed steam flow when the Turbine is tripped

(Closure of these valves will ensure the Turbine does not overspeed)

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18
Q

What is installed on the BTVs that assists in opening the disc with a minimum differential steam pressure in the ED system?

A

Balance Arm device

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19
Q

What happens upon activation of the Bleeder Trip Valve test valve?

A

Valve equalizes the air pressure across the operator piston to allow partial closing of the valve disc by spring force

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20
Q

Why is there two BTVs installed on #4 feedwater heater extraction line?

A

4 heater, by itself, has enough energy to cause an overspeed trip

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21
Q

Which level control valves are reverse acting in the ED system?

A

All of the high level control valves and #1 LP heater normal level control valves

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22
Q

At what air signals are the reverse acting valves full open and full closed in the ED system?

A

Full open with 3#

Full closed with 15#

(Direct acting is the complete opposite)

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23
Q

What happens upon a hi-hi signal in a HP feedwater heaters?

A

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

24
Q

What happens upon a hi-hi signal in a LP feedwater heaters?

A

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

25
Q

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?

A

20%

high level control valves operate to keep alarms clear until power level is sufficiently raised

26
Q

When is the first heater drain pump started?

A

25% power

27
Q

When is the second heater drain pump started?

A

Between 30 and 40%

28
Q

During a plant shutdown, when are the Heater Drain Pumps secured?

A

First one at 40%, second one at 25%

29
Q

How is the ED system affected by a loss of IA?

A

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

30
Q

What is the purpose of the HDTs (heater drain tanks)?

A

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

31
Q

Where are the heater drain tanks located?

A

120’ turbine building, above the heater drain pumps

32
Q

Concerning the ED system, where do the MSR 1st stage reheater drain tanks flow to? 2nd stage reheater drain tanks?

A

6 FW heaters, then to the heater drain tank

33
Q

How many stages are the heater drain pumps?

A

5

34
Q

What is the purpose of the Feedwater heaters?

A

aid in improving the secondary system efficiency

35
Q

Concerning the High pressure feedwater heaters, what are the flow paths for the extraction steam and feedwater flow?

A

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

36
Q

Concerning the HP feedwater heaters, what are the differences between the #6/7 heaters and the #5 heaters?

A

6/7 have condensing and subcooling zones, has level control system, #7 drains to the #6 heater, #6 drains to the HDT

37
Q

What is the purpose of the vents on the various tanks, heat exchangers and pumps in the ED system?

A

to remove non-condensable gases and direct them to the condenser for removal

38
Q

What is the motive force of extraction steam while traveling from the turbine to the feedwater heaters?

A

the differential pressure between the turbine stages and the feedwater heater shells

39
Q

Which feedwater heaters have the supplying extraction lines cross-connected and what does the cross connect allow for?

A

3a, b, c
4a, b, c
6a, b
7a, b

allows unit operation without all high and low pressure feedwater heaters in service

40
Q

What does the High Pressure turbine provide extraction steam to?

A

3rd stage- 7A/B heaters and first stage reheating steam in the MSRs

5th stage- 6A/B heaters

cold reheat- 5A/B heaters

41
Q

Where do the heater drain pumps send their effluent?

A

to the suction of the main feedwater pumps

combines with the condensate just downstream of the feedwater heaters

42
Q

What is the difference in operation between direct acting and reverse acting level control valves in the feedwater heater level control system?

A

direct acting- higher air pressure opens the valve

reverse acting- higher air pressure closes the valve

43
Q

Where do the MSR drain tanks vent to? Where does the heater drain pump vent its suction line to?

A

their respective MSR/Hot reheat line

respective heater drain tank

44
Q

Where do the first stage reheater drain tanks normally vent to?

A

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)

45
Q

Where do the 2nd stage reheater drain tanks normally vent to?

A

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)

46
Q

Where do the heater drain tanks vent to?

A

to their respective #5 FW heater

both tanks also have a vapor cross-connect line to each other

47
Q

Where do the #5, 6 and 7 feedwater heaters vent to?

A

both trains all tie in together to a common header and vent to the condenser

48
Q

How does the ED system interface with the SC (secondary chemical control) system?

A

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.

49
Q

How does ED interface with GS?

A

LP turbine 9th stage extraction supplies sealing steam to GS on power ascension

50
Q

In the ED system, what is powered by NH?

A

MOVs, HP heater extraction steam block and drain valves, heater drain pump motor space heaters

51
Q

In the ED system, what is powered by NK?

A

solenoids, controls, indication and alarms for various valves

52
Q

In the ED system, What is powered by NN?

A

LP FW heater steam pressure instrumentation

HTR DRN pump discharge/suction D/P, tank level and pump flow instrumentation

53
Q

What cools the HTR DRN pump lube oil coolers?

A

turbine cooling water

54
Q

What maintains water level in the LP feedwater heater drain cooler, or subcooling zone?

A

normal level control valve

55
Q

What is the purpose of having reverse acting normal and high level control valves in the ED system?

A

to ensure that on a loss of IA, the ED system will drain its contents to the main condenser

56
Q

Describe the new level control valves for the LP feedwater heaters.

A

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

57
Q

What is the sequence for putting the MSR and 1st/2nd stage drain tanks in service to their normal level control valves?

A

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

Secondary (37 decks)

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