Essential Chilled Water(EC) Flashcards
Where is Essential Chilled Water supplied to ?
Supplied to ESF ACUs & AHUs in the Control building & Aux. Building, when normal chilled is UNAVAILABLE & upon ESFAS signals
What does each Essential Chilled Water train consist of ?
-Single 100% chiller (refrigerant unit)
-Single 100% chilled water circ pump
-Expansion Tank
-Chemical Addition Tank
-Required piping,valves, instrument. & controls
What signals automatically starts automatically the ESFAS signals ?
-CSAS
-SIAS
-CREFAS
-CRVIAS
-LOP
-AFAS
What ACUs & AHUs receive Essential Chilled Water ?
-Control Room essential ACU
-DC Equipment Room EssentialACU
-ESF Switchgear Room Essential AHU
-Elect. Penetration Room AHUs
-HPSI Pump Room Essential ACUs
-LPSI Pump Room Essential ACUs
-CS Pump Room Essential ACUs
-AF Pump Room Essential ACU
-EW Pump Room Essential ACU
Where does EC Circulating Pump take its suction from & where does it discharge to ?
-Takes suction from return headers from ACUs & AHUs
-Discharges to the chiller & gets cooled
What does the Chiller cool down the essential chilled water to?
-Essential Chilled Water is cooled down to 44F by the chiller & is supplied to the ACUs & AHUs
What controls a balanced flow through the AHUs & ACUs ? Why just there be a balance flow ?
There is a manual valve that is throttled to ensure EC returning to chiller package is 64F
What is the suction temp supposed to be going into the EC Circulating Pump ?
It is supposed to be 64F
What is the Energy required for change of state of the refrigerant ?
Known as latent heat of vaporization
What is the driving motive force for the refrigerant from the Condenser to the Cooler inside the Chiller ?
Driven by D/P between Condenser & Cooler
What is the EC Surge Tank used for ?
-Accommodate expansion & ensure NPSH for EC pumps
-Serve as location for makeup water
What’re the Makeup Water sources for the EC Surge Tank ?
-Demineralized Water normal makeup
-Condensate Transfer Storage is available backup makeup water following seismic event for 24HR
-Firewater header is makeup source via hose connections
Why must there be a minimum Nitrogen pressure of 10psig on the Expansion Tank with EC Circ. Water Pump not in service ?
-required to prevent flashing at the highest point in the system
What does a Nitrogen pressure >25psig on the Expansion Tank with EC Circ. Pumps not in service do for the system ?
Maintain system at highest point ABOVE atmospheric pressure & ensures NO air in-leakage
What happens if air is introduced to the EC system ?
Can cause a chilled water flow oscillation large enough to cause a chiller trip on low chilled water flow
What is overpressure protection for the EC Surge Tank ? What is the set point ?
-One valve is provided on each tank
-Relief set point @60psig
What is the instrumentation on the EC Surge Tank ?
Local Expansion Tank level & pressure gauge are installed
Where is the EC Circ Pump rated for ? What is it Powered by ?
-One 100% capacity EC Circ. pump
-400gpm
-Pump driven by 20hp electric motor powered by Class MCC(PH)
Where can the EC Circ. pumps be controlled from?
-Control switch in control room starts pump & after time delay will start the chiller
-Local switch at pump breaker that’ll ONLY start the EC Circ. Pump
What is the Essential Chilled water Chemical Addition Tank used for ?
-Place to add corrosion inhibiting chemicals in EC system
Why’re the Chemical Addition Tanks normally isolated from EC system ?
They’re different piping classification than the EC system
What’re the Essential Chillers used for ?
Removes heat from Chilled water provided to ACUs & AHUs ESF Equipment Room
What does the EC get cooled by going through cooler ? What will the refrigerant get cooled by ?
-Gets cooled by refrigerant in the Cooler & the refrigerant gets cooled by Essential Cooling Water in the condenser
Where the Essential Chillers controlled from ?
Normally controlled from control room
What is three position switch at the 4.16kv switchgear for each chiller used for ?
Stop/start spring return unmarked neutral control switch
What does the Chiller Control Panel provide ?
Local indication of chillers status, alarms, & parameters indication
What does the control panel for each Essential Chiller contain ?
-Two rows of red indicating light alarms
-One Row of whites indications lights for chiller status
-Amber indicating light for oil heater energized
-Push button locally operate chillers oil pump
How can the lights be tested on the Essential Chillers control panel ?
-All indicators lights can be tested by pressing light cover to turn light on
-No actuations will occur
What is the chiller start sequence ?
T+0:Chiller start signal
Circ. Water Pump Starts
Program Timer Starts
T+23:Chiller Lube Oil Pump Starts
T+51:Chiller Compressor Starts
During the Chiller Start Sequence when the Program Timer Starts, what relays energize ?
-20min restart relay energizes, blocking restart attempt
-2minute emergency time delay will bypass 20min restart relay after 2 min on a ESF start signal
What is the Chiller Stop sequence ?
T+0:
-Chiller Stop Signal
-Program Timer Signal
-Chiller Compressor & Circ. Water Pump both stop
T+41:
-Lube Oil Pumps Stop
Where is the Refrigerant Head Pressure Control Valves installed at & what is it used for ?
-Installed on EW lines downstream of Condensers to prevent condenser stacking
How is the Refrigerant Head Pressure Control Valves supposed to be operated ?
-RHPCVs close when condenser pressure is below 14psig
-RHPCVs is opened when condenser pressure is greater than 23psig
How are the Refrigerant Head Pressure Control Valves throttle proportionally between ?
Throttled proportionally between 14-13psig
What’re the normal positions of the RHPCVs bypass valves ?
The bypass valves are normally maintained in Locked Closed position
When’re the bypass valves for the RHPCVs unlocked & opened ?
They’re opened to ensure adequate condenser cooling flow rate during the most limiting postulated EW system condition of a 17% degraded EW pump while being aligned to SFP Cooling HEX
What is the EW flow requirement necessary through condenser to provide sufficient cooling capacity during design basis accident in hottest part of summer ?
EW flow of 720gpm through the condenser at a temperature of 132F
What should be the position of the RHPCVs when degraded EW pump & EW aligned to Fuel Pool Coolinh HEX?
Bypass valves should be opened
When would a AO be asked to manually operate Essential Chiller Refrigerant Head Pressure Control Valve ?
-Chemical addition to EW train
-EW train flow adjustments
-Performing flow balance after cross tying to provide fuel pool cooling backup
What’re the methods for manually overriding RHPCV?
-Preferred method is hydraulically using pilot bypass stem on top of valve bonnet
-Other method is to use Manual Override Screw located on bottom of valve
How does the RHPCV Manual Override Screw operate ?
-Manual override screw forces valve in open direction
-Pilot bypass Steam allows vent path from top of diaphragm
-Wrench is used to manually open RHPCV to allow EW flow through EC chiller condenser
-Bypass valve around RHPCV will open if there is not enough
When will the Essential Chillers automatically start with ESF actuations ?
-SIAS
-CSAS
-LOP
-CREFAS
-CRVIAS
-AFAS
What temp will the Chiller trip on ?
Trips on a low EC temp
What temp will the Chiller package be shutdown at ?
-Will be shutdown if EC temp leaving cooler reaches a low temp of 38F
-Circ. Water will continue operating
What does Auto Reload Cycle do ?
1.)Outlet cooler temp reaches 38F
2.)Chiller shutdown
3.)20min timer starts if, after 20 min if temp is back above 45F, then chiller will restart
What is the indication for Auto Load Recycle ?
White “Load Recycle” light being lit on local control panel
What can the essential chiller be started ?
-Control room
-Locally at breaker
-Automatic ESF sequencing
How is the Essential Chilled Water supply temp auto maintained at 44F ?
Maintained at 44F by varying chiller packages cooling rate via compressor inlet guide vanes
What happens if Chilled water supply temp decreases to 38F what will happen ?
-Chiller will stop in Auto Load Recycle
-Chiller will restart after chilled water exceed 45F
What must be done if the Essential Chilled water temp is to low?
Control room will start additional essential ACUs/AHUs to raise temp to avoid Auto Load recycle
How is cooling controlled for each ACU & AHU, EXCEPT Control Room Essential ACU?
-Controlled by a three way temp control valve, that’s locked in throttled position to obtain specific flow rate
-Bypass lines are capped off
How do you prevent condensation buildup in the filter housing of the Control Room Essential AHU?
Chilled water cooling coils are normally bypassed when ACU fan is not running
How does the interlock work to bypass cooling coils when ACU fan isn’t running for the Control Room Essential AHU ?
Interlock positions 3way valves to full bypass position when fan motor is deenergized
What temp is Essential Chilled Water suppose to be at when it returns to Essential Chillers cooler ?
Supposed to be at 64F
When chemicals are added to chemical addition tank how’re they flushed throughout the system ?
Portion of EC Pump discharge through tank & back to the pump suction
What happens on loss of Essential Chilled Water ?
If a Train of Essential Chilled Water is lost then that Trains ESF equipment is INOPERABLE by Tech Spec
How does loss of 4.16kV PB system affect the EC system?
Essential Chiller Compressor will have no power
How does loss of 480VAC MCC affect EC system ?
-Circ. Water Pump & Lube Oil Pump will lose power
How does loss of Demon. Water(DW) affect EC system ?
-Loss of normal makeup water to EC Surge Tank
How does loss of Essential Cooling Water(EW) affect EC system ?
EC chillers will trip on Condenser high refrigerant pressure
How does loss of Service Gas affect EC system ?
-Loss of low pressure nitrogen would potentially allow oxygen into system, which could cause Chilled Water flow oscillation large enough to cause Chiller trip on Low Chilled Water flow
How does loss of Spray Pond affect EC system ?
EC chillers will trip on condenser high refrigerant pressure
What make an EC train to be considered OPERABLE modes 1-4?
-Associated pump & expansion tank are OPERABLE
-Associated piping,valves,HEX,Refrigerant Unit, & instrumentation & control to perform safety related functions are operable
