Normal Chilled Water Flashcards
What is the purpose of the WC normal chill water system?
Provide chilled water at 45F to the cooling coils of the normal HVAC in containment, Aux and Radwaste buildings
Chilled water is also sent to:
non-nuclear sampling
polishing demin sample coolers
blowdown demin sample coolers
main generator collector housing cooler.
What is the interlock associated with the containment ACUs?
Closes an isolation valve and stopping chilled water flow when the fan is not running
What system provides cooling to each chiller package?
NC (low flow of NC will trip a chiller)
What is the power supply to ‘A’ normal chiller?
PB (4160)(4.16kv)
What system is used as a makeup source of water for WC?
DW
What powers the WC recirc pumps?
NH
What system powers the ‘B’, ‘C’, & ‘EO2’ chilers?
NB (4160) (4.16kv)
what system can I use if NC is unavailable for cooling?
EW
What are the 3 circ pumps associated with the large chillers rated for?
1200gpm @ 100ft
What is the small chiller circ pump rated for?
320gpm @100ft
Why does the compressor start after a time delay?
To allow oil pressure, chilled water and cooling water flow to establish
Where are the WC circ pumps located?
Roof of the aux building
What is the normal level in the WC expansion tank?
36 inches
What pressure is the nitrogen maintained in the WC expansion tank?
15psig
What are the high and low pressure setpoints for the WC expansion tank?
When will the expansion tank relief lift?
When will the vacuum breaker relieve?
When would the makeup valve open and close for the expansion tank?
High 45psig
Low 5psig
lift 60psig
Relieve 2 in Hg
Opens at 24 inches and closes at 48 inches
Where is the WC chem add tank located?
Next to ‘A’ Chiller on the aux building roof
What are the precautions associated with adding chemicals to WC?
Water drained from system needs proper disposal
Do not add more than 1 chemical at a time
Wear proper PPE (apron, face shield and gloves)
Temp eye wash station required
What is the basic refrigeration cycle?
Compressor(low press high temp) to
Condenser (hi press hi temp) (NC) to
Flash economizer (hi press low temp) to
Cooler (low press low temp)(WC)
Draw the T diagram temp up goes up and pressure low to high left to right.
Why do chillers ‘B’ and ‘C’ have increased capacity greater than 1000 tons?
Due to increased amperage
How are the compressor and motor cooled and lubed?
refrigerant cooled and oil lubed
How long does the oil pump run before the compressor starts?
28 seconds
Where is the vapor from the flash economizer directed?
to the 2nd stage of the impeller inlet
What is purpose of the float valve in the flash economizer?
Ensures liquid level is maintained in the economizer to prevent equalizing pressure between the cooler and condenser
What are the 3 efficiency designs of the normal chillers?
Which of the 3 increase refrigeration effect?
Integral thermal economizer
Flash economizer
Two stage compressor
Integral thermal economizer increases refrig effect
What is surging?
When refrigerant pressure in the condenser momentarily becomes higher than the pressure of the compressor discharge and allows back flow thru the compressor
‘Back flow from the condenser thru the compressor’
When does surging occur?
How do we prevent it?
During low load conditions
prevented by hot gas bypass - routes hot gas from the compressor discharge to the evaporator
What happens when you take the chiller switch to start?
Circ pump starts
NC water valve opens
23 seconds later the lube oil pump starts
28 seconds later the lube oil starts
compressor starts
What happens when the switch is taken to STOP or if the compressor trips?
Compressor motor and circ pump motor stop and the NC valve closes
41 seconds later the lube oil pump will stop
15 min timer starts preventing the restart of the chiller package
What is the high level and low level alarm setpoint for the WC expansion tank?
High 72 inches
Low 12 inches
What are the 3 most limiting concerns upon loss of WC?
Main gen collector housing temp exceeding 50C, requiring shutdown
Containment temp not being maintained within tech spec
CEDMCS cabinet room temps reaching limit of 104F which could lead to rod slippage
What is the temp limit of the control room?
80F
IA dropping to 27psig would have what effect on WC?
auto make up valves will fail closed and WC tank makeup will need to be done manually
How is WC affected by a loss of NC?
Running chillers will trip on loss of condenser cooling flow.
Control room may shift priority loads to EW
