Feedwater heaters Flashcards
(26 cards)
What is the purpose of the Feedwater heater system?
Use a process of regenerative feedwater heating to increase overall cycle efficiency and minimize induced thermal stresses in the steam generator. This increases efficiency.
What is the path of the Feed water heater?
- Condensate is supplied to the feed water heaters via condensate pumps.
2.Condensate is heated via extraction steam from the turbine and other sources of extraction heat. This takes place in three parallel strings of 5 low pressure (LP) heaters. 3. From the LP heaters, main feed water (MFW) pumps pump condensate to a higher pressure, then passes the feed water (condensate) through three parallel high pressure heaters. - Feed water is then introduced into the steam generators.
What is the extraction steam (ESS) used for?
Heating.
Why do we extract steam from feed water heating?
increases overall efficiency of the secondary cycle & helps remove moisture from the turbine
What are the feed heater vents used for?
removal of non-condensable gases on start-up and normal operation. Also provide a path for introducing nitrogen for dry heater lay up.
Are FWH over pressure protection valves considered part of the feed water vent system?
Yes
What are the feed heater drains used for?
these cascade for heating lower energy heaters (1st-4th pt)
Does this system affect technical specifications or safe shutdown?
no
What part of the condenser are the 5th and 6th heaters?
upper portion of the condenser
Where are the 1st and 3rd heaters?
14 ft of the turbine building in the east
Where are the 2nd and 4th heaters?
38 ft of the turbine building in the east
Why are the heaters laid out in this manner?
Closest steam source and 4th point up a floor provides some head for HDL pps
What cools the 4th point heater drain pump seal coolers and bearing coolers?
Turbine plant component cooling water/CCS
Why is the feed water heater vent and drain system connected to the turbine plant sampling system?
To allow for monitoring of the system chemistry
What are many of the FWH problems because of?
Operating with liquid level too low
What issues may arise with the FWHs?
Flashing in DC abruptly affects heater level and therefore NLCV position
DC low level results in increased velocities, tube vibration damage, exposes supports & baffles to two-phase flow erosion
Where are the Normal Level Control Valves found and why?
Nearest the heater they cascade to because it precludes flashing
Where are the Emergency Level Control Valves found?
Nearest the Condenser because they discharge there
Where are the controllers found?
Aux Condensate Panel in the Turbine Building 66’
Why do we have extraction steam non return valves (NRV)?
Provides a means to rapidly isolate steam turbine supply lines/heaters
Where are the Extraction Steam MOVs and what are they used for?
Upstream of the NRV’s on heaters 1-4, not installed on the 5th and 6th point heaters.
Designed to protect turbine from high levels.
We get a turbine trip, how do the NRV’s close?
A solenoid dumps air and spring assist to close so valves set up to close without any backflow
What happens to the extraction steam MOVs if a turbine trip happens?
They have no signal so should stay open unless they get a HI HI Level. These are not set up to provide overspeed protection, just Hi Hi level protection.
What are indications of a tube leak, besides noise?
Rising water level, Lowering DCA, increased output on LCV
