Condensate Flashcards
Where do each of the CD pumps recirc back to?
“A” => 2C hot well
“B” => either 1C or 2C hot well
“C” => 1C hot well
What are the purposes of the CD system?
1) provide NPSH to feed pump
2) provide heat sink for exhaust steam from MT, FWPT, as well as bypass steam and other cycle flows
3) hot well storage for surge capability and retention in the event of a condenser tube leak
4) deaeration of CD
5) minimize air leakage into the steam thermal cycle
6) provide first 4 stages of feedwater heating
7) provide makeup, cooling, and seal water to various 2* components
Where does makeup to the hot well come from?
The CST via vacuum drag
What does the hotwell draw off valve do?
Sends excess condensate back to the CST using the CD pump discharge pressure.
It comes off d/s of the demins for chemistry control
When is long path recirc used and what is the flow path?
Used for CD and FW system startup, warm up, and clean up.
Main condenser=> CD pumps => demins => LPFW htrs => bypass MFPs => HPFW htrs => back to condenser
What cools the CD pump motor lube oil coolers?
TC
What is the alternate supply for the CD service header?
DW through a motor operated valve
What are the power supplies to the CD pumps?
A & B on NBN-S01
And C on NBN-S02
How is the CD system cross tied to the other plants and why?
Through the aux steam system.
It’s done so that the plant supplying aux steam can collect the drains.
Why is condenser temperature and pressure progressively higher in the condenser sections?
Because the CW flows through it in series so the CW takes on more and more heat as it flows through.
What does the dog bone seal do?
Connects the LP turbine to the associated condenser shell and prevents air leakage in while allowing for movement between the condenser and the turbine
What are the condenser equalization ducts and where are they located?
They are water sealed and are located above the A & B shell false bottoms. They allow for pressure equalization between the sections if the temperature difference between two sections exceeds 30F. The water seals will blow out and equalize.
What is the purpose of the vacuum breaker that is installed on the condenser?
Installed to allow rapid turbine slowing in an emergency and condenser equalization during normal shutdown.
How is the positive seal between the main condenser and atmosphere maintained on the vacuum breakers?
A water seal is in the vacuum breaker line
Why do the tube lengths vary in the main condenser?
To accommodate for the progressively higher CW temperatures in the tubes
Describe CD flow inside the condenser.
In the A & B sections, condensate falls into an inner bottom and flows to a sump. Water falls onto reheater trays above the hotwell. Water is heated by the exhaust of the MFPT. It then falls into the hotwell.
C section does not have the reheater trays and Cd falls directly from the inner bottom into the hotwell.
What is detention time and how is it provided?
It is a delay in time that allows the condensate to stay in the condenser longer. This is provided by the baffle plates in the hotwell and it aids in condensate reheating and sampling.
How much storage does the hotwell provide?
100,000 gallons which is 4 minutes of operation at valves wide open.
What will cause the two vacuum drag valves to close on the main condenser?
CST level reaching approx. 30 feet.
What will cause the condenser draw off valve to close and not be allowed to re-open?
Any hotwell conductivity level high
Either s/g feedwater pump suction pressure low
You can bypass the interlock for conductivity using the key in the local control panel and putting it to bypass.
How are the “B” condensate pump suction valves normally lined up?
Both are normally open and the pump will trip if BOTH are closed.
What will cause a condensate pump to trip?
B pump will trip if both suction valves are closed
Hotwell level of 30” aligned to a CD pump will trip it
Low mini-flow of 3600 GPM for 45 seconds will trip it
What are the CD overboard valves used for?
Hotwell clean up after startup. “A” & “C” can discharge to the CW canal for feed and bleed.
What are the loads on the CD service header?
90 psig CD goes to: CD pump seals Condenser expansion joints Vacuum pump makeup Hydrazine and ammonia dilution Cooling jacket for htr drain pump seal
What pressure does the bypass valve modulate to maintain with both the inlet and outlet valves open?
< 55psid
Bypass valve full opens above 55 psid
What temperatures does CD enter and exit the LPFHs at?
Enters at about 130F and exits at about 330F
What happens to the LPFH if it has a severe tube rupture?
Each heater has a high level control valve that will try to send excess water to the condenser.
If level reaches the Hi-Hi level, then CD is isolated to that heater string by 2 motor operated valves.
How many air removal units are used to maintain condenser vacuum?
3 in service normally
What happens on a loss of vacuum?
SBCVs will not be allowed to dump to the condenser
Main turbine trips
MFPs trip
RX trips on low steam generator water level
Aux feed starts to restore SG level.
How do the CD pump mini-flow valves fail on a loss of IA or electrical?
Fail open (could cause loss of feed)
How do all other CD valves fail on a loss of IA?
All valves fail closed except the demin bypass valve that fails open.
