Instrument Air Flashcards
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
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
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
The instrument air system has how many air compressors and what type are they?
three 100% capacity rotary screw type
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
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
What is the backup to IA and when will it align?
Nitrogen and aligns when IA header pressure drops below 85psig
What powers the IA compressor motors?
NG 480VAC
What powers the compressor motor space heaters?
NH 480 VAC
What does PK system do for IA?
power to the containment isolation valve IAA-UV-2
What system cools the IA compressors?
TC
What valve opens to admit low pressure nitrogen into the IA header?
PV-52
IA sends compressed air to the fuel pool cooling system for what purpose?
Gate seals
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
Why is the air inlet control valve minimally opened?
To maintain separator sump pressure
Why is coolant (oil) sprayed into the airend?
Act as an air seal
lube the bearings
remove heat from the air compressor
When does the coolant stop solenoid open and close?
Opens when the compressor starts and closes when the compressor stops
What is the motive force for the coolant?
Separator tank pressure normally at 60psig
The temp control valve regulates the TC water flow thru the coolant cooler to maintain coolant outlet temp to what temp?
120F
What is the purpose of the IA compressor inlet air filters?
Removes particulate materials and minimize compressor water
What size particles can the compressor inlet air filters remove and how effective are they?
3 microns or larger and 99.9% effective
When the compressor is loaded, what should the inlet filter DP reading be?
less than .7 psi
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
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
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?
DS
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?
2
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
