ED: Extraction Drain Flashcards
Where does Stage #9 extraction steam from the Low Pressure Turbine go?
LPFW Heaters #3 (A,B,C - cross connected)
Gland Steam Supply
What are the operational flowrates associated with the Heater Drain Pump Recirc Valve?
- Opens at 1600 gpm and on a pump stop
- Closes at 3200 gpm
When will Extraction Steam Block Valves re-open if they automatically closed?
They will re-open when the Hi-Hi Level that initiated the closure clears.
How do the BTVs fail on a loss of air?
Closed
How do the High Level Drains on a loss of air or power?
Open on a loss of both
What happens on a Hi-Hi level in a LPFWH?
- LPFWH train isolations close
- BTVs (for #3 and #4) close
- Extraction Steam low point drains open
Where does Stage #5 extraction steam from the High Pressure Turbine go?
HPFW Heaters #6 (A and B)
How do the BTVs fail on a loss of IA?
Closed
To where do the 2nd Stage Drain Tanks A and C vent?
Normally to the #7A HPFWH (via 711A)
Alternate to the Main Condenser (via 711B)
What happens on a Hi-Hi level in a HPFWH (or HDT for 5A/B)?
- All inputs’ Normal Level Control Valves close
- Inputs’ vents swap
- Extraction Steam Block Valve closes
- Bleeder Trip Valve closes
- Extraction Steam low point drain opens
What level in the MSR Drain Tank will trip the Main Turbine?
-3” in the MSR
What valves in the ED System does the 1st Stage Scavenging Mode Selector Switch (EDN-HS-615) control?
It controls the operation of the 1st Stage Drain Tank Vent Valves to the #6 HPFWHs and the Main Condenser.
What are Extraction Steam Block Valves?
Each HPFWH steam line has a motor operated block valve that will:
- for #6/#7 HPFWHs isolate on Hi-Hi level in that HPFWH
- for #5 HPFWHs isolate on Hi-Hi level in its associated HDT
Extraction Steam Block Valves will re-open when the Hi-Hi level clears.
LPFWHs do NOT have Extraction Steam Block Valves.
To where do the HPFWHs vent?
Continuously vented to the Main Condenser. All join to a common header.
What would cause the Feed Water Heater low point drains to auto open?
Turbine Trip
Hi-Hi level in the associated Feed Water Heater
Of course, they can be operated from the Control Room as well.
What is special about the BTV’s on the #7 HPFWHs?
7 HPFWHs BTVs are located upstream of their MOVs. Allows isolation for maintenance while maintaining 1st Stage Reheat in service.
How do the Normal Drains fail on a loss of air or power?
Closed on a loss of both
What are the Heater Drain Pump power supplies?
HDP A - NBN-S02
HDP B - NBN-S01
How do the BTVs and drain valves behave on a Turbine Trip?
- BTVs close (they will reopen once the trip is clear)
- Drain valves open (they will not reclose when the trip clears)
Do LPFWHs have Extraction Steam Block Valves?
No
To where does the MSR Drain Tank vent?
Hot Reheat (discharge from the MSRs)
What is the status of the MSR Drain Tank High Level Control Valve when power is <10%?
It its failed open until Hot Reheat steam pressure reaches a pressure equivalent to ~10%
What is special about HPFW Heater #5?
It has no level control due to being connected to the Heater Drain Tank.
The Normal Level Control Valve for the 1st Stage Drain Tank will auto close on what?
Hi-Hi level in the #6 HPFWH
Where can the 2nd Stage Drain Tank send water?
To the #7 HPFWHs or the Main Condenser
Where does Stage #11 extraction steam from the Low Pressure Turbine go?
LPFW Heaters #2 (A,B,C)
Where is Cold Reheat extraction steam sent?
HPFW Heaters #5 (A and B)
To where do the 2nd Stage Drain Tanks B and D vent?
Normally to the #7B HPFWH (via 712A)
Alternate to the Main Condenser (via 712B)
What happens on a Heater Drain Tank high level?
- Comes in at 9’
- 2 associated MSR Drain Tanks Normal Level Control Valves close
- Associated #6 HPFWH Normal Level Control Valve closes
- Associated #5 BTV and Extraction Steam Block Valve close
Do #1 and #2 LPFWHs have BTVs?
No. They have flow baffles. There’s not enough pressure in these FWHs to warrant protection from a Main Turbine Overspeed.
How do the Normal Level Control Valves fail?
- Closed
- The one exception is the Normal Level Control Valve for the #1 LPFWHs which fail open to the Main Condenser.
Where does Stage #3 extraction steam from the High Pressure Turbine go?
HPFW Heaters #7 (A and B)
1st Stage Reheat in the MSRs
Why do #4 LPFWHs have two BTVs?
Because there’s enough energy in the #4 LPFWHs alone to cause a Main Turbine Overspeed
The Normal Level Control Valve for the 2nd Stage Drain Tank will auto close on what?
Hi-Hi level in the #7 HPFWH
How are the BTVs distributed across the Feed Water Heaters?
One on each HPFWH and #3 LPFWH
Two for #4 LPFWHs
The Normal Level Control Valve for the MSR Drain Tank will auto close on what?
Hi-Hi level in the HDT
Where can the 1st Stage Drain Tank send water?
To the #6 HPFWHs or the Main Condenser
Where can the MSR Drain Tanks send water?
To the Heater Drain Tanks or the Main Condenser
What is the sequence of events on a Heater Drain Pump start?
- Motor Starts
- 5 seconds later, recirc opens
- 2 minutes after pump start the discharge valve will open (starting current)
Where does Stage #8 extraction steam from the Low Pressure Turbine go?
LPFW Heaters #4 (A,B,C - cross connected)
What are the Heater Drain Pump trips?
- HDT Lo-Lo Level - 4’
- HDP Lo Flo - 711 pm for > 15 sec
- LPFWH outlet pressure Hi - 575#
What will cause the BTVs to trip closed?
- A Turbine Trip
- Hi-Hi Feedwater Heater Level
- a redundant signal is supplied to all BTVs (through the Turbine Critical Relay Dump Pressure Switch Low [EDN-PSL-76]) to ensure BTVs close on a Turbine Trip
The 2nd Stage Scavenging Mode Selector Switch (EDN-HS-715) is in AUTO. In what position will the controlled valves be placed and what is the requirement for these valves to move?
Vent to #7 HPFWH opens and the vent to the Main Condenser closes.
These valves will only reposition if the associated Extraction Steam Block Valve is full open.
What cooling water is sent to the Blowdown Stack?
Domestic Water (DS) cools the Blowdown Stack.
How do the High Level Dump Valves fail?
Open
What do LPFWHs have instead of BTVs?
Installed Flow Baffles
What valves in the ED System does the Steam Blanketing Mode Selector Switch (MTN-HS-519)control?
It controls the operation of the 1st and 2nd Stage Drain Tank High Level Control Valves.
Why do we have MSRs?
Improved cycle efficiency and minimizes LP turbine blade erosion.
What happens to the Heater Drain Tank when its Heater Drain Pump is secured?
The Heater Drain Tank will fill all the way to its high level dump. (Basis for keeping hotwell level at 41”)
What supplies 2nd Stage Reheat in the MSRs?
Main Steam
What type of valves do the HPFWHs have for low point drains upstream of the BTVs?
MOVs
How does the BTV Test Valve work?
It equalizes air pressure to allow the disc to fall into the steam flow, resulting in a partial closure.
What purpose do the Bleeder Trip Valves serve?
- Prevents reverse steam flow on a turbine trip (overspeed)
- Prevents moisture carryover on Heater Drain Tank or Feed Water Heater Hi-Hi Level (blade damage)
When does the High Level Control Valve for the 2nd Stage Drain Tank close on a startup?
It its failed open until Hot Reheat steam pressure reaches a pressure equivalent to ~20%
How does the Heater Drain Pump Recirc Valve fail on a loss of air or power?
Open
Where does the Blowdown Flash Tank vent?
Primary is the Heater Drain Tank. Secondary is LPFW Heater #3.
How does the Heater Drain Pump Discharge Valve fail on a loss of air or power?
Closed
To where do the Heater Drain Pumps vent their suctions?
Back to their respective Heater Drain Tanks
When does the High Level Control Valve for the 1st Stage Drain Tank close on a startup?
It its failed open until Hot Reheat steam pressure reaches a pressure equivalent to ~10%
Where does the Blowdown Stack drain?
To the North Condenser Area Sump
What is special about how the BTVs close?
It’s spring assisted
Where do all the High Level Dumps put water?
- The Main Condenser
- The one exception is the #5A/B HPFWHs. They don’t have level controllers and dump directly to the Heater Drain Tank.
Where does the cooling water go after it leaves the SGBDHX?
To the Heater Drain Pump discharge
To where do the 1st Stage Drain Tanks A and C vent?
Normally to the #6A HPFWH (via 611A)
Alternate to the Main Condenser (via 611B)
What valves in the ED System does the 2nd Stage Scavenging Mode Selector Switch (EDN-HS-715) control?
It controls the operation of the 1st Stage Drain Tank Vent Valves to the #7 HPFWHs and the Main Condenser.
To where do the 1st Stage Drain Tanks B and D vent?
Normally to the #6B HPFWH (via 612A)
Alternate to the Main Condenser (via 612B)
Why do all the vents for the #7 HPFWHs go closed if there’s a Turbine Trip coincident with a loss of power to the 2nd Stage Reheater Isolation Valves (RSS)?
Without this, a flowpath would exist through the second stage heaters directly to the condenser.
What type of valves do the LPFWHs have for the low point drains upstream of the BTVs?
AOVs
They fail open
Where does Stage #12 extraction steam from the Low Pressure Turbine go?
LPFW Heaters #1 (A,B,C)
The 1st Stage Scavenging Mode Selector Switch (EDN-HS-615) is in AUTO. In what position will the controlled valves be placed and what is the requirement for these valves to move?
Vent to #6 HPFWH opens and the vent to the Main Condenser closes.
These valves will only reposition if the associated Extraction Steam Block Valve is full open.
What is special about HPFWH #5A in regards to low point drains upstream of the BTVs?
HPFWH #5A doesn’t have low point drains upstream of the BTVs due to the short pipe run from the turbine to the 5A HPFWH.
When do the 1st and 2nd Stage Drain Tank vent valves swap to the Main Condenser?
The circuitry is run off of the Extraction Steam Block Valves. If they come off of their open seats, the vents will swap.
To where do the Heater Drain Tanks vent?
To its associated #5 HPFWH
How are the Turbine Critical Air Relay Dump Valves aligned to the Bleeder Trip Valves?
- ARDV #1 is aligned to the two BTVs on the #4 LPFWHs (Critical)
- ARDV #2 is aligned to all other BTVs (Non-Critical)
How do the BTVs behave on a HPFWH Hi-Hi Level?
The BTV associated with the Hi-Hi level will go closed.
How do the BTVs behave on a LPFWH Hi-Hi Level?
BTVs for #3 and #4 LPFWH go closed.
