Instrument Air Flashcards by Brandon Johnson

What is the purpose of the instrument air system?

Provides continuous supply of filter, dry, oil free air at pressure up to 125psig for pneumatic instrument operation and control of pneumatic actuators

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What is the purpose of the Service air system?

Supplies oil free air at 125 psig to service air stations for tools, resin transfer and refueling machine manual operation

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How can I identify that a pneumatically operated valve has a safety function that may be required to operate to ensure a safe shutdown of the plant following and accident?

It will have a safety related back up air receiver

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The instrument air system has how many air compressors and what type are they?

three 100% capacity rotary screw type

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Where do the instrument air compressors draw air from and what pressure do they compress to?

Drawn from turbine building air and compress to 105-123psig

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What is significant about IAA-UV-2? When will it close?

DC powered solenoid that controls IA into containment

Closes on CSAS 8.5 psig in containment

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What is the backup to IA and when will it align?

Nitrogen and aligns when IA header pressure drops below 85psig

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What powers the IA compressor motors?

NG 480VAC

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What powers the compressor motor space heaters?

NH 480 VAC

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What does PK system do for IA?

power to the containment isolation valve IAA-UV-2

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What system cools the IA compressors?

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What valve opens to admit low pressure nitrogen into the IA header?

PV-52

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IA sends compressed air to the fuel pool cooling system for what purpose?

Gate seals

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How does IA system interact with Extraction steam and Drain system?

Supplies the ARDVs (air relay dump valves) for bleeder air valve operation.

On a turbine trip, the ARDVs close to depress the line and allow the BTV air cylinders to fully stroke close within 2 seconds

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Why is the air inlet control valve minimally opened?

To maintain separator sump pressure

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Why is coolant (oil) sprayed into the airend?

Act as an air seal

lube the bearings

remove heat from the air compressor

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When does the coolant stop solenoid open and close?

Opens when the compressor starts and closes when the compressor stops

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What is the motive force for the coolant?

Separator tank pressure normally at 60psig

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The temp control valve regulates the TC water flow thru the coolant cooler to maintain coolant outlet temp to what temp?

120F

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What is the purpose of the IA compressor inlet air filters?

Removes particulate materials and minimize compressor water

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What size particles can the compressor inlet air filters remove and how effective are they?

3 microns or larger and 99.9% effective

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When the compressor is loaded, what should the inlet filter DP reading be?

less than .7 psi

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The local controller on the air compressor uses PT-4 inlet vacuum information for what purpose?

Confirm drive motor is rotating in the correct direction on start

Indicate the condition of the inlet air filter

Provide logic for positioning the inlet valve during unloaded operation based on coolant (oil) injection temp and separator pressure

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During compressor start up, why is the IA compressor air inlet control valve closed?

It allows the compressor to start with minimal current

Allows the compressor to check proper rotation by checking inlet vacuum is at least 1 psi within 2 seconds

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How is the IA compressor inlet control valve controlled?

Controlled by the intellysis controller with the stepper motor

During loaded operation, if the plant air pressure drops below online pressure set poing of 109 psig. What would I expect to occur as a result?

Intellisys/stepper motor opens the inlet valve and closes the blowdown valve. Compressor will then operate to deliver full capacity air to the plant system

During unloaded operation, how will the system respond if plant air pressure rises to offline setpoint of 119psig?

The inlet valve will nearly close, blowdown valve will open. Compressor will operate at minimum power Inlet valve stays slightly open to maintain proper sump pressure to ensure positive coolant (oil) flow and smooth, quiet operation

When the injected coolant temp is less than 120F, what would I expect the separator (sump) pressure to be maintained at? What about above 120F?

45-50psig 24-33psig

What is the purpose of the IA compressor rotary screw airend?

Compresses the air to 105-123psig

What are the single stage rotary compressor rated for?

571 CFM and 125psig

Describe oil cooling utilized in the rotary compressor

Oil bath compressor that has oil supplied to the inlet of the compressor for lubrication, cooling and compressor sealing

How is compression accomplished in the rotary compressor?

Meshes 2 helicoils

How much head does the compressor add due to compression of air?

95F

What happens if the airend discharge temp exceeds 223F?

Causes the "AIREND DISCHARGE TEMP" warning along with the "?" and actual discharge temp to be displayed on the panel. compressor continues to run

What discharge temp will the compressor trip? What is the reset temp? What are the normal values?

228F alarm or trip along with "!" and "HIGH AIREND DISC TEMP" 217F reset temp norm - 185-210F

What is the backup to the high temp alarm (trip)?

temp switch high set at 245F with 30 degree differential to reclose (215F)

If the high temp switch opens on high temp, what would I expect to see on the display?

control power loss

What is the purpose of the separator tank?

Removes coolant from the air to provide clean air to the system while maintaining the coolant for the compressor package

What is the coolant/air separating system composed of?

Separator with a 2 stage coalescing separator element and provision for return of the separated fluid back to the compressor

How does oil/air separation occur in the separator tank?

Rotates around the tank and heavier sticks to the wall and runs down

What is the purpose of the thermostatic control valve?

Controls how much of the coolant flows thru or bypasses the coolant cooler. mixed to provide 160F into the airend

Why do we want the injecting coolant (oil) at a sufficiently high temp?

Being above the dew point keeps water vapor from condensing into the reciever

When TC is secured what do we use to cool the compressor?

DS 1 instrument air compressor and 1 service air compressor

What is the purpose of the air after cooler?

cools the discharge air so vapor is condensed and removed from the piping and we also send cool air

What makes up the air aftercooler?

heat exchanger, separator and auto drain trap

What temp does the air aftercooler cool the compressed air to?

within 15F of TC water inlet temp

How much moisture could I see flowing out of the traps on a daily basis?

18-50gallons

If TC is unavailable what system can I use to remove heat from the air aftercooler?

What is the purpose of the IA compressor master controller?

Controls the loading and unloading of multiple compressors controls the run sequencing of the 3 compressors to equalize wear

What commands does the master controller send to the compressors?

Start/load and stop/ unload commands. The compressors will stop themselves

Why does the master controller not start more than 1 compressor at at time?

to prevent overloading the power supplies

What pressure will the master controller maintain in the IA system?

114+-5psig

How will the master controller respond if pressure were to rise 5 psig above the upper pressure limit of 119 psig?

It will well all the compressors to unload at once

How will the master controller respond if the pressure drops to the upper pressure limit within 1 minute? What would be different if it were to take longer than 1 minute?

It will tell all previously loaded compressors, except the last one to load The master controller will tell only the first compressor to load

How often will the master controller auto resequence the air compressors?

twice a week on the turnover sheet

master controller records internal activities into what 3 categories?

Events, warnings and alarms

Who resets master controller display?

I&C If you do it you will be writing a statement

What will happen if you try to start an already running compressor?

it will trip

what will i need to start a compressor that is in stopped in auto restart?

Take it to off first to take it out of "stopped in auto restart"

What happens if I stop a compressor that is "stopped in auto restart"?

It will go to auto and not respond to the master controller

Local Intellysis controllers maintain the compressors at what pressure?

'A' 113-123psig 'B' 109-119psig 'C' 105-115psig

What is considered the normal display for the local controllers?

"current status" screen

What is the purpose of the IA receivers?

Provide 30 sec storage cap on compressor trip as well as pulsation dampening

what pressure does the receiver relief lift at?

136psig

What is the purpose of the IA dryer prefilters? What size impurities can the pre filter remove?

removes liquid aersols Down to 10 microns and oil to 1 ppm

When placing a prefilter online what can happen if I open the IA pre-filter isolation valve too quickly?

May cause damage to the air dryer desiccant

What DP will the prefilter alarm the control room?

10psid

What is the purpose of the IA dryers?

dehumidify IA and lower the dew point of air

How many air dryers per train?

How is regen accomplished in the air dryers?

a portion of the inservice discharge flow is directed thru the regen

What is the purpose of the instrument air after filters?

removes the desiccant dust

After filters remove what micron size?

down to .9

What does a normal IA compressor look like?

1 in service, either loaded or unloaded the other 2 in "stopped in auto restart" pressure maintained at 114+/-5 psig

What will happen as IA system fails and pressure is dropping?

pneumatic components fail to their safe positions IA header pressure of less than 70psig will affect plant power production stability Most unstable pressure will be 40psig where letdown, RMW, Charging, pressurizer spry and reactor drain tank are impacted

At what pressure will the IA supply be considered lost to the spent fuel pool gate seals?

36psig

What if nitrogen backup is insufficient for IA system?

Flex connection available to install backup nitrogen bottles on the north end of the fuel building

What will happen if I lose power to IAA-UV-2?

Valve will fail closed and loss of IA to containment

How can I align nitrogen to IA if the nitrogen backup valve fails to repostion?

Manual bypass

When will the nitrogen backup valve close?

When IA header pressure rises above 105psig