Circ Water Flashcards
What do the CW Canal & Intake Structure provide ?
Provides suction for the CW pumps
What’re the Trash Screens used for ?
Used to protect CW pumps from debris that has fallen into Canal
Other than the trash screens slot, what is the other slot used for ? What’re stop gates used for ?
Other slot is used for stop gate when maintnence needs to work on CW pump while system is operating
How can you tell a trash screen needs to be cleaned ?
The DP across screen causes a big level difference
When cleaning a trash screen what needs to be placed temporarily, while the dirty screen is being cleaned ?
There has to be a clean screen placed BEFORE removing dirty screen so CW pump is always protected
What water is used to spray & clean the trash screens ? Where does the water drain ?
-Discharge of the PW pump is used to clean the screens
-Drains to Screen Wash Sump & water is returned to intake structure by Screen Wash Sump Pumps
Where are the Turbine Building roof drains routed to ?
-Routed directly to the CW intake canals, this assist n prevention of ADEQ Aquifer protection permit violations
What is the CW canal level automatically maintained at ? How is it controlled ?
It’s automatically maintained at 23’ by one of two level control valves
What is the design makeup rate to the canal ?
19600gpm
What is the rejection rate of the CW Pumps determined by ?
-Based on valves-wide-open(VWO) steam flow
-Condenser back pressure less than 3.6HgA
What’re the parameters of the CW pumps ?
-25% capacity
-140000gpm pumps
-13.8kv
What cooling water cools CW Pump Lube Oil Coolers ? What is the flow rate ?
Turbine Cooling Water is sent at 12.5gpm
What is the low flow rate alarm for turbine cooling water associated with the CW pump lube oil cooler ?
Low flow alarm at 9gpm
What is the normal discharge pressure of all four CW pumps ?
Normally discharging at 45psig
Where is CW pump operated from ?
Control switch provided in control room for each CW pump
What condition does CW Pump need to start ?
-Discharge valve fully closed
-Either same flow train condenser outlet valve is open
OR
-Condenser outlet valve interlock override Pushbutton depressed
What does a CW pump start signal also sends an opening/permissive signal to?
-Open signal to discharge valve
Permissive signals to:
-CI system acid injection pump
-CI system chlorine injection valve
-same flow train CW pump discharge valve
What happens when CW Handswitch is placed in STOP-CLOSE position ?
-Close signal is sent to discharge valve
-Once Discharge is less than 8% open, pump breaker will open stopping pump
-signal also sent to CW Supply header cross tie valve & other CW pump discharge valve control logic
What happens when CW Pump discharge valve closes less than 8% open ?
Pumps breaker will open stopping the pump
What happens when CW Emergency trip Pushbutton is used ?
-Pumps breaker will immediately open stopping pump
-Signal also sent to CW Supply Header Crosstie valve & other CW Pump discharge valve control logics
What does main condenser receive ?
Received low energy turbine exhaust steam & condenses for reuse in secondary cycle
Why’re Tube Lengths in B & C condenser sections greater?
Higher Circ. Water inlet temperatures are present
Where are the butterfly MOV for Circ Water Loop Condenser outlet/inlet valves at?
At the inlet of the first condenser section & outlet of the third section condenser isolation
Why are MOVs used for CW system ?
-Allows remote operation
-Prevents operator fatigue
-Aids in normal & emergency operation
-Provides opportunity protective interlocks & relays
What is the design time for MOVs to open/close ?
Closes the valves in 30 seconds
How is each discharge valve interlocked with its respective pump ?
-One pump operating in its train has discharge valve open to 44%
-Supply Header Crosstie Valve is closed
Why does each discharge valve motor control circuit have a 3 minute timer? When is activated ?
-Controls automatic opening of discharge valve
-Timer is activated once pump is started
What must happen to valve before its opened beyond 44% ?
The 3 minute timer for the MOV must time out before valve can open beyond 44%
Why is 44% position maintained indefinitely when only one CW pump is operating in associated loop?
Opened 44% to prevent pump runout
What happens to discharge valve of second pump when it’s started in same loop where there is already a pump operating with discharge valve at 44%? What happens after second MOV 3 minute timer times out ?
-Second pump discharge will open to 44%
-After 3 minutes time the seconds discharge valve will open 100%
After second pump discharge valve opens to 100%, What will happen to the first pump discharge valve in the associated loop ?
The first pumps discharge valves will go 100% open
What happens if only one pump is started in SEPARATE loops ?
Each pump discharge valve in their separate loops will be opened to 44% & stay there UNTIL a second pump is started in the same loop
What is the OPEN/CLOSE times for the Condenser Inlet Valves MOVs ?
60 seconds is MOV designed open/close times
What’re the interlocks associated with the Condenser Inlet/Outlet Valves ?
-Outlet valves won’t open if “water box full” permissive is satisfied, once water boxes are full valve will open
-Inlet valves have NO interlocks; opened/closed based on switch
If CW Loops cross-tie valve hand switch is in “auto”, it’s interlocked to go closed when ?
Both pumps in one loop are stopped the cross-tie valve will go closed if in AUTO
When will CW Loop Cross-Tie Valve be in operation ?
Only one CW Pump aligned to both AB & CD loops should not exceed 48hrs
Where are the automatic vent & vacuum breaker valves located on the CW system ?
-Located at high points on inlet & outlet water boxes of each shell of main condenser
-supply header crosstie line both side of Circ Water Loops cross-tie valve
-Each CW pump discharge
What’re the CW Auto Vent Valves used for during normal operation ?
-Automatically releases any air that collects in system, while maintaining water in system
What’re CW Auto Vent Valves used for during abnormal or infrequent operations, such as, system shutdown & drain or Trip of the CW Pumps ?
If pumps trip the system will drain to canal, the vent valves will open to allow air into system to prevent a vacuum inside water box or piping of system
How do the Auto Vent Valves work ?
-A float chamber is used to open or close valve
-When there’s no water in system float chamber is down allowing air in
-When there’s water in system it’ll make float rise and seat
-Pressure from pump operation helps keep the float seated
What must be done to the Auto Vent Valves during fill & vent of the CW system ?
-Auto Vent Valves will be isolated due to insufficient pressure to seat the valves
-Isolating Prevents water from flooding turbine building
During Filling & Venting of CW system what is used when the Auto Vent valves are isolated ?
Manual vents are provided on same line to allow filling & venting
When during filling & venting when are the Auto Vent Valves placed back in service ?
-Placed in service when enough CW pumps are running to seat the valve
What modification for the vent line is used to prevent down powering ?
Install Isolation valves in each line to allow isolation for repair in case of leak
Which vent lines don’t have isolation valves installed ?
1C & 2C outlet vents have relief valves installed, instead of isolation valves
What’re the position of all the added Isolation Valves supposed to be in ?
They’re all in a “LOCKED OPEN” position
What do you need to close the Vent Line Isolation Valves ?
You need to have fall prevention equipment
What do the cooling towers provide ?
They provide medium heat removal from Circ. Water
What’re the major sections of the Cooling Towers ?
-Water supply riser
-Circumferential distribution flume
-Distribution basin
-Fill ring
-Collection basin
-Fan deck & support columns
What does the concrete riser do for cooling towers ?
Supplies water from CW return pipe to the top of each cooling tower into the Circumferential Distribution Flume
How is each cooling tower isolated ? What can cooling tower #2 do still if CW has been isolated from it ?
-Isolated by manually operated valve
-Cooling Tower #2 has PW return line that’s used, when CW isolation valve is closed
What does the Circumferential Distribution Flume do ?
-It radially distributes water down to the distribution basin
What is used to control flow from the Circumferential Distribution Flume down to the Distribution Basin ?
There are adjustable weirs at top of flume outboard wall control flow to distribution basin
How does the distribution basin work ?
-Has precast panels with small holes in the floor
-Each hole had flow orifice for proper flow & help diffuse uniformly over fill ring
What does the Fill Ring do for the cooling towers ?
-Helps water be broken down over extremely large surface area into individual droplets
What do the cooling fans provide for the cooling towers ?
-It allows turbulent mixing of air & water for optimum heat transfer
What causes the rapid evaporation of water from the cooling towers ?
It’s the combination of broke down droplets and mixed by airflow that causes the rapid evaporation
How does the water in the collection basin get cool ?
It’s cooled by energy being removed by evaporation and dropping into collection basin
What does the collection basin do for the cooling tower ? What can be put in at the exit of the cooling tower for isolation ?
-It collects the cooled water and reuses it
-Basin floor is pitched for proper drainage
-Can place a stop gate at the exit of cooling tower
What’s the purpose for the Cooling Tower Fans ?
Provide forced draft air flow needed for efficient evaporative cooling
What is each fan driven by? What is the fans motor powered by ?
-Driven by a 200hp motor through gear reducer & drive train
-Powered from 480VAC Load Center
How do the fans receive there start/ stop signal for Control Room switches ?
Fiber optic Plant Multiplex system
What does each fan have for vibration?
Has a high vibration switch to trip fan during operation
If fans trips on high vibration what happens when trying to start again ?
Start signals sends a reset signal to High Vibration trip coil
When starting fan how long is High Vibration trip coil overridden ?
Overridden for 30 seconds so it doesn’t trip on start up
What’re indications for a fan tripping on high vibration ?
Blue light on LoadCenter, computer input, & annunciator in control room
Can the fans be started locally if PMUX system isn’t working ?
Yes it can be started locally
Why’re fans started/stopped in specified order ?
Equalizes loading of fans & cooling tower structure & to match heat transfer requirements
Why would cooling tower fans be shutdown during winter months ?
Maintains condenser vacuum, to low of a vacuum will cause increased tube corrosion due to high steam velocities
Where does the Screen Wash Sump collect its water from ?
-Trash Screen cleaning
-CW Pump seal leakage
-Overflow from CW Pump Bays
Where do the two sump pumps transfer the collected water to?
Transfer collected water to CW Canal
How do the two float-type level control switch operate for the CW screen wash sump?
-Lead pumps starts on HI level
-Standby pump starts on HI-HI Lvl
-Both pumps stop on LO-LO Lvl
What is the alternator used for on the Screen Wash Sump Pumps ?
It’s used to change lead pump each cycle to equalize wear on the pumps
What is the flow orifice installed at discharge of sump pump ?
Used to balance flow to control sump runout during one or two pump operation
What level in the CW Canal do the CW pumps start to lose suction ?
Will start to lose suction at approx. 19’
What will happen on complete loss of CW system ? How will decay heat be rejected ?
-Results in immediate plant shutdown due to high condenser pressure
-Decay Heat will be rejected to atmosphere by steam bypass valves 1007 & 1008
What will happen to plant operation during a partial loss of CW system ?
Plant will have to be down powered depending on severity of the loss of Vacuum
Since we don’t have DP alarms on the CW Trash Screens how do we when to clean them to prevent downpowering?
Rely on AOs routine checks for screen level delta
