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Systems > Essential Chilled Water(EC) > Flashcards

Essential Chilled Water(EC) Flashcards

1
Q

Where is Essential Chilled Water supplied to ?

A

Supplied to ESF ACUs & AHUs in the Control building & Aux. Building, when normal chilled is UNAVAILABLE & upon ESFAS signals

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2
Q

What does each Essential Chilled Water train consist of ?

A

-Single 100% chiller (refrigerant unit)
-Single 100% chilled water circ pump
-Expansion Tank
-Chemical Addition Tank
-Required piping,valves, instrument. & controls

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3
Q

What signals automatically starts automatically the ESFAS signals ?

A

-CSAS
-SIAS
-CREFAS
-CRVIAS
-LOP
-AFAS

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4
Q

What ACUs & AHUs receive Essential Chilled Water ?

A

-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

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5
Q

Where does EC Circulating Pump take its suction from & where does it discharge to ?

A

-Takes suction from return headers from ACUs & AHUs
-Discharges to the chiller & gets cooled

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6
Q

What does the Chiller cool down the essential chilled water to?

A

-Essential Chilled Water is cooled down to 44F by the chiller & is supplied to the ACUs & AHUs

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7
Q

What controls a balanced flow through the AHUs & ACUs ? Why just there be a balance flow ?

A

There is a manual valve that is throttled to ensure EC returning to chiller package is 64F

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8
Q

What is the suction temp supposed to be going into the EC Circulating Pump ?

A

It is supposed to be 64F

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9
Q

What is the Energy required for change of state of the refrigerant ?

A

Known as latent heat of vaporization

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10
Q

What is the driving motive force for the refrigerant from the Condenser to the Cooler inside the Chiller ?

A

Driven by D/P between Condenser & Cooler

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11
Q

What is the EC Surge Tank used for ?

A

-Accommodate expansion & ensure NPSH for EC pumps
-Serve as location for makeup water

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12
Q

What’re the Makeup Water sources for the EC Surge Tank ?

A

-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

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13
Q

Why must there be a minimum Nitrogen pressure of 10psig on the Expansion Tank with EC Circ. Water Pump not in service ?

A

-required to prevent flashing at the highest point in the system

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14
Q

What does a Nitrogen pressure >25psig on the Expansion Tank with EC Circ. Pumps not in service do for the system ?

A

Maintain system at highest point ABOVE atmospheric pressure & ensures NO air in-leakage

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15
Q

What happens if air is introduced to the EC system ?

A

Can cause a chilled water flow oscillation large enough to cause a chiller trip on low chilled water flow

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16
Q

What is overpressure protection for the EC Surge Tank ? What is the set point ?

A

-One valve is provided on each tank
-Relief set point @60psig

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17
Q

What is the instrumentation on the EC Surge Tank ?

A

Local Expansion Tank level & pressure gauge are installed

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18
Q

Where is the EC Circ Pump rated for ? What is it Powered by ?

A

-One 100% capacity EC Circ. pump
-400gpm
-Pump driven by 20hp electric motor powered by Class MCC(PH)

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19
Q

Where can the EC Circ. pumps be controlled from?

A

-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

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20
Q

What is the Essential Chilled water Chemical Addition Tank used for ?

A

-Place to add corrosion inhibiting chemicals in EC system

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21
Q

Why’re the Chemical Addition Tanks normally isolated from EC system ?

A

They’re different piping classification than the EC system

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22
Q

What’re the Essential Chillers used for ?

A

Removes heat from Chilled water provided to ACUs & AHUs ESF Equipment Room

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23
Q

What does the EC get cooled by going through cooler ? What will the refrigerant get cooled by ?

A

-Gets cooled by refrigerant in the Cooler & the refrigerant gets cooled by Essential Cooling Water in the condenser

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24
Q

Where the Essential Chillers controlled from ?

A

Normally controlled from control room

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25
Q

What is three position switch at the 4.16kv switchgear for each chiller used for ?

A

Stop/start spring return unmarked neutral control switch

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26
Q

What does the Chiller Control Panel provide ?

A

Local indication of chillers status, alarms, & parameters indication

27
Q

What does the control panel for each Essential Chiller contain ?

A

-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

28
Q

How can the lights be tested on the Essential Chillers control panel ?

A

-All indicators lights can be tested by pressing light cover to turn light on
-No actuations will occur

29
Q

What is the chiller start sequence ?

A

T+0:Chiller start signal
Circ. Water Pump Starts
Program Timer Starts
T+23:Chiller Lube Oil Pump Starts
T+51:Chiller Compressor Starts

30
Q

During the Chiller Start Sequence when the Program Timer Starts, what relays energize ?

A

-20min restart relay energizes, blocking restart attempt
-2minute emergency time delay will bypass 20min restart relay after 2 min on a ESF start signal

31
Q

What is the Chiller Stop sequence ?

A

T+0:
-Chiller Stop Signal
-Program Timer Signal
-Chiller Compressor & Circ. Water Pump both stop
T+41:
-Lube Oil Pumps Stop

32
Q

Where is the Refrigerant Head Pressure Control Valves installed at & what is it used for ?

A

-Installed on EW lines downstream of Condensers to prevent condenser stacking

33
Q

How is the Refrigerant Head Pressure Control Valves supposed to be operated ?

A

-RHPCVs close when condenser pressure is below 14psig
-RHPCVs is opened when condenser pressure is greater than 23psig

34
Q

How are the Refrigerant Head Pressure Control Valves throttle proportionally between ?

A

Throttled proportionally between 14-13psig

35
Q

What’re the normal positions of the RHPCVs bypass valves ?

A

The bypass valves are normally maintained in Locked Closed position

36
Q

When’re the bypass valves for the RHPCVs unlocked & opened ?

A

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

37
Q

What is the EW flow requirement necessary through condenser to provide sufficient cooling capacity during design basis accident in hottest part of summer ?

A

EW flow of 720gpm through the condenser at a temperature of 132F

38
Q

What should be the position of the RHPCVs when degraded EW pump & EW aligned to Fuel Pool Coolinh HEX?

A

Bypass valves should be opened

39
Q

When would a AO be asked to manually operate Essential Chiller Refrigerant Head Pressure Control Valve ?

A

-Chemical addition to EW train
-EW train flow adjustments
-Performing flow balance after cross tying to provide fuel pool cooling backup

40
Q

What’re the methods for manually overriding RHPCV?

A

-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

41
Q

How does the RHPCV Manual Override Screw operate ?

A

-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

42
Q

When will the Essential Chillers automatically start with ESF actuations ?

A

-SIAS
-CSAS
-LOP
-CREFAS
-CRVIAS
-AFAS

43
Q

What temp will the Chiller trip on ?

A

Trips on a low EC temp

44
Q

What temp will the Chiller package be shutdown at ?

A

-Will be shutdown if EC temp leaving cooler reaches a low temp of 38F
-Circ. Water will continue operating

45
Q

What does Auto Reload Cycle do ?

A

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

46
Q

What is the indication for Auto Load Recycle ?

A

White “Load Recycle” light being lit on local control panel

47
Q

What can the essential chiller be started ?

A

-Control room
-Locally at breaker
-Automatic ESF sequencing

48
Q

How is the Essential Chilled Water supply temp auto maintained at 44F ?

A

Maintained at 44F by varying chiller packages cooling rate via compressor inlet guide vanes

49
Q

What happens if Chilled water supply temp decreases to 38F what will happen ?

A

-Chiller will stop in Auto Load Recycle
-Chiller will restart after chilled water exceed 45F

50
Q

What must be done if the Essential Chilled water temp is to low?

A

Control room will start additional essential ACUs/AHUs to raise temp to avoid Auto Load recycle

51
Q

How is cooling controlled for each ACU & AHU, EXCEPT Control Room Essential ACU?

A

-Controlled by a three way temp control valve, that’s locked in throttled position to obtain specific flow rate
-Bypass lines are capped off

52
Q

How do you prevent condensation buildup in the filter housing of the Control Room Essential AHU?

A

Chilled water cooling coils are normally bypassed when ACU fan is not running

53
Q

How does the interlock work to bypass cooling coils when ACU fan isn’t running for the Control Room Essential AHU ?

A

Interlock positions 3way valves to full bypass position when fan motor is deenergized

54
Q

What temp is Essential Chilled Water suppose to be at when it returns to Essential Chillers cooler ?

A

Supposed to be at 64F

55
Q

When chemicals are added to chemical addition tank how’re they flushed throughout the system ?

A

Portion of EC Pump discharge through tank & back to the pump suction

56
Q

What happens on loss of Essential Chilled Water ?

A

If a Train of Essential Chilled Water is lost then that Trains ESF equipment is INOPERABLE by Tech Spec

57
Q

How does loss of 4.16kV PB system affect the EC system?

A

Essential Chiller Compressor will have no power

58
Q

How does loss of 480VAC MCC affect EC system ?

A

-Circ. Water Pump & Lube Oil Pump will lose power

59
Q

How does loss of Demon. Water(DW) affect EC system ?

A

-Loss of normal makeup water to EC Surge Tank

60
Q

How does loss of Essential Cooling Water(EW) affect EC system ?

A

EC chillers will trip on Condenser high refrigerant pressure

61
Q

How does loss of Service Gas affect EC system ?

A

-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

62
Q

How does loss of Spray Pond affect EC system ?

A

EC chillers will trip on condenser high refrigerant pressure

63
Q

What make an EC train to be considered OPERABLE modes 1-4?

A

-Associated pump & expansion tank are OPERABLE
-Associated piping,valves,HEX,Refrigerant Unit, & instrumentation & control to perform safety related functions are operable

Systems (62 decks)

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