[CW] - Circulating Water Flashcards
[CW]
Purpose?
-Uses cooling towers to displate waste heat from [PW] - Plant Cooling Water.
-remove heat rejected from Turbine Thermal Cycle.
[CW]
7 sources that discharge to [CW]?
[CD] Pumps A&C Overboard
[CM]
Demin Low TDS Sump
Blowdown Low TDS Sumps,
[SP]
A/B Blowdown Sump Pumps
A/B Backwash Sump Pumps,
[TB] Roof Drains
[??] North Yard Sump
Can be used as an [FP] emergency water source
[CW]
[TB] in [CW]?
Interface
[TB] Cooling Tower Makeup Water (Water Resources)
-Makeup Water
-Replaces water losses due to:
Evap / blowdown / cooling tower drift
blowdown paths to the evaporation ponds to allow constant blowdown for chemistry control and for level control in the canal
[CW]
Silica & [CW]?
Fouls Condenser Titanium tubes
[CW]
What 4 chemicals are added by [CI]?
Hypochlorite
Foam control
Sulfuric acid
Scale dispersant
[CW] - Circulating Water
Screen Wash Sump purpose? (2)
-Screen Cleaning
- Sending Water back to Canal
[CW] - Circulating Water
How are [CW] pumps interlocked with all the MOVs?
- Discharge Valves
- Condenser Inlets
- Condenser Outlets
- Cross-Tie
???
Outlet
- Waterboxes have to be full to open valves
Cross-Tie
- Auto Close - If we lose 2 pumps in the same loops
[CW]
Cooling Water to CW Pumps?
[TC] Turbine Cooling Water
[CW]
How is chemistry maintained in [CW]?
-M/U & Blowdown
(From Reservoirs to Evap Ponds)
[CW] - Circulating Water
[CW] Who maintains [CW] canal chemistry?
Water Resources
[CW] - Circulating Water
[PW] & [CW]?
Plant Cooling & Circulating Water
Plant Cooling & Circulating Water
The [PW] pumps share the intake canal with the CW pumps, utilize the Cooling Towers for cooling, and return discharge to the [CW] return piping
[CW] Circ Water
[PW] Plant Cooling
[CW] - Circulating Water
What provides air to the Cooling Tower Makeup Anti Cavitation Air Injection? Purpose? What else does this system do?
[IA] Instrument Air
Prevent valve chattering in the Canal Level CV?
-operates CVs and Controllers
[CW] - Circulating Water
How much water is lost to blowdown at each [CW] canal?
~700 gpm to 2000 gpm
[CW]
What component at each [CW] pump bay prevents large debris from entering the system?
Trash Screens
[CW]
What is used to isolate [CW] pump bays if maintenance is required on an individual pump while [CW] continues to operate?
Stop Gate
[CW]
Screen spraying water?
[PW] pumps
[CW]
Where are the Turbine Building Roof drains directed to?
Their respective CW intake canals
[CW]
Normal set point of level in [CW] canal?
23 ft
[CW]
How often are local grab samples taken on the canal?
Purpose?
Daily
Chemistry
blowdown flowrate for control of the chemistry parameters
[CW] - Circulating Water
[CW] pump capacity?
Normal discharge pressure?
25% (140,000 gpm)
~45 psi
[CW] - Circulating Water
Cooling water to [CW] pump lube oil cooler?
[TC]
Turbine Cooling Water
[CW] - Circulating Water
What needs to occur in order for the CW pump to start when the switch in the Control Room is taken to START-OPEN?
- Pump discharge valve fully closed
- Open condenser outlet valve condenser for same flow train
or
CONDENSER OUTLET VALVE INTERLOCK OVERRIDE pushbutton is depressed
[CW]
The pump-start signal is sent to what other components?
Pump’s discharge valve - Open signal
Permissive signals to:
[CI] acid injection pump,
[CI] system chlorine injection valves, [CW] Pump Discharge Valve (of the same flow train)
[CW]
What 3 things occurs when [CW] pump switch is taken to “STOP-CLOSE”?
1- Pump’s discharge Valve - closing signal
2- Breaker auto opens to stop pump when the valve closes to < 8% open
3- Signal sent to the [CW] supply header cross-tie valve and other CW pump discharge valve control logics
[CW]
How to stop CW pumps immediately?
“Emergency trip” Pushbutton in Control Room
[CW]
[CW] Pumps local switches and emergency pushbuttons location?
At their switchgear
Why are Condenser tube lengths B/C longer than those in A?
Higher circulating water inlet temperature
How quickly do the MOVs of the [CW] pump open/close?
30 seconds
[CW] pump / discharge valve interlock?
-Discharge valve/pump only opens to 44% when only one pump operating in its train,
-Supply header cross-tie valve will be closed
What is the interlock associated with Condenser outlet Isolation Valves? What are the interlocks for the inlet isolation valves?
Such that they will not open unless the “water box full” permissive is satisfied
Once the water boxes are full, the outlet valves can be opened and the head of the cooling tower will maintain the piping full prior to the CW pump start
no interlocks for inlets
[CW]
Automatic vent and vacuum breakers purpose? Where are they located? (3 Places)
-Auto releases air in the system & waterboxes to maintain [CW] full of water during normal ops.
(3) Located:
-high points of the inlet and outlet water boxes of each shell of the condenser,
-on the supply header cross-tie line on both sides of CWN-HV-11
-and at each pump discharge.
[CW]
Major [CW] tower components? (7)
Water supply riser
circumferential distribution flume
distribution basin,
fill ring,
collection basin
fan deck
and support columns
[CW]
Why does Tower 2 have a [PW] return pipe?
When [PW] supplies water if [CW] is OOS for maintenance.
[CW]
How many Cooling Tower fans/tower are there?
16 (10 meter fans)
Cooling Tower fans protections? (3)
Where are they controlled?
1- High vibration
2- bus undervoltage,
3- and electrical protection trip
CR switches to plant multiplexer
How many Screen Wash Sump Pumps are there?
Purpose? (3)
Sump Pump flow orifices purpose?
- 2
1- trash screen cleaning
2 - CW pump seal leakage collection
3 - Pump overflow from [CW] pump bays
- keep pump from run out conditions
When would the Standby Screen Wash Sump Pump auto start?
Hi-Hi level in sump
What are the power supplies of the CW pumps?
‘A’ and ‘B’ – NAN-S01
‘C’ and ‘D’ – NAN-S02
What impact on the system does a loss of CW makeup have?
The pumps ability to take suction
What would happen upon a loss of CW Blowdown?
Would cause the chemicals of the CW system to concentrate and drive the CW water chemistry out of spec which would increase corrosion
What would happen upon a loss of Turbine Cooling Water?
Will cause the CW pump motors to overheat and alarms would be received in the control room on high temperatures
Pumps could fail if no operator action is taken
What happens if CW is completely lost?
Will result in immediate plant shutdown due to high condenser pressure
Decay heat will be rejected to atmosphere through steam bypass valves 1007 and 1008
What happens on partial loss of CW?
Plant will have to be down powered depending on the severity of the loss of vacuum
What are the start permissives for the CW pumps?
pump discharge must be fully closed and same flow train condenser outlet valve is open
Why do the B and C sections of the condenser have longer tube bundles?
to compensate for the increased circulating water inlet temperature
Describe the timer for the motor operated discharge valves of the CW pumps.
When one pump is started, the respective discharge valve will open to 44%. If the second pump to start in the same flow loop is started, the respective discharge valve will open to 44%. The 3 minute timer will pass and the second pumps discharge valve will open to 100% and then the first pumps discharge valve will open to 100%.
If the second pump being started is in the opposing flow loop, both respective discharge valves will stay at 44%.
When would the CW supply cross-tie valve go closed? How long can the system operate with a single CW pump feeding both flow loops?
hand switch in auto and both pumps in one CW flow loop stop
no longer than 48 hours
During the fill and vent of the CW system, pressure is not sufficient to help seat the auto vents and they are manually isolated to prevent spilling water in the turbine building. When are the auto vents placed in service?
When enough CW pumps are running to ensure good seating
Which outlet vents on the main condenser vent lines have no isolation valve and just have relief valves?
1C and 2C
What is the flow path through the cooling towers?
up a concrete return pipe and into the distribution flume for radial distribution to the distribution basin through adjustable weirs. from the basin, the water flows down through holes in the basin floor to the fill ring. water flows through holes in the fill ring down through the fill media and into the collection basin and back to the canal
How do the cooling towers work to remove heat?
As the water falls through the rigorous path of the fill media, the latent heat of vaporization occurs. the cooling tower fans pull air through the fill media perpendicularly to the fall of the water droplets and as some of the water droplets evaporate, it removes the heat from the continuously falling water and air inside the tower
How long is the high-vibration trip disabled for during start up of the cooling tower fans? If there is a problem with the plant multiplexor, how are the fans started?
30 seconds
locally at the breakers
Why are the cooling tower fans started and stopped in a specific order? What changes about fan operation during winter months?
to equalize the loading of the fans and match the heat transfer requirements of the CW system
less fans are in operation to maintain condenser vacuum in spec
