Extraction steam and Drain System Flashcards
What is the purpose of the ED system?
Preheats condensate and feedwater prior to entering the steam generators to increase overall plant efficiency
What system has the ability to provide steam to the 4th point heater during startup?
Aux steam
What system is used to add cool water to the water volume that is maintained in the bottom of the blowdown stack?
DS domestic service
What is the purpose of the blow down stack?
A collection point for steam traps, HP heater relief valves and Misc aux steam drains
When is DS added to the blowdown stack? What if DS is not available?
When temp of the blowdown stack exceeds 150F
If not available there will be steam coming out of the blowdown stack and the north condenser sump
how does GA interact with ED?
Supplies nitrogen for steam blanketing when shut down to prevent corrosion
How does IA interact with ED?
MT control system admits IA thru both critical and non critical relay dump valves which provide a signal to the bleeder trip valves
Also provides motive force for all AOVs in ED system
how are the BTVs affected by a loss of IA?
They lose open permissive and go partially closed. They stay open due to ED steam flow
Where are the Heater drain pumps powered from?
‘A’ NBN-S02 AND ‘B’ NBN-S01
Where does the seal water for each heater drain pump come from?
Directly from the condensate header at 375-500 psig
What provides cooling to each heater drain pump stuffing box?
Condensate service header at 50-100psig
What positions the heater drain pump mini flow valves?
Heater drain pump flow transmitter
What 3 signals would stop the heater drain pump?
Heater drain tank lo-lo level
Heater drain pump low flow after a time delay
Electrical protection signal
Why does the #5 heater not have a level control system?
It drains directly to the heater drain tank and does not have a drain cooler region
Which LPFW heaters have 4 inlets?
1 and 2
which LPFW heater has an input from the S/G blowdown system?
3
What is the purpose of the BTVs?
To prevent reverse steam flow when the turbine trips and prevent turbine overspeed
What is installed on the BTVs to assist in opening the disc with a minimum differential steam pressure?
Balance arm device
What happens upon activation of the BTV test valve?
Valve equalizes the air pressure across the operator piston to allow partial closing of the valve disc by spring force
why is there 2 BTVs on the #4 LPFW heater?
4 has enough energy to overspeed the turbine
Which control valves are reverse acting?
All the valves that dump to the condenser (all high levels and #1 LPFW heater normal)
what air pressure are the reverse acting valves full open and full closed?
Full open at 3psig
Full closed at 15psig
(Normals) full closed 3 psig and full open 15psig
What happens upon a hi-hi signal in a HP heater?
Extraction steam isolated
Close the normal level control valves of the preceding heater
opens the affected heaters motor operated extraction steam drain line
The 1st and 2nd stage drain tanks will vent to the condenser also
What power level may there be insufficient D/P between the heater shells to allow for proper operation of the normal level control valves?
20%
