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Flashcards in SA/IA Deck (21):
1

IDENTIFY the function of the plant compressed air subsystem

• Supply dry, compressed Instrument Air to power actuators and pneumatic instrumentation throughout the plant “outside” containment.
• To supply various SA loads.

2

IDENTIFY the major components of the plant compressed air subsystem

• Air cooled rotary screw compressors
• Normal-service air receivers (“A” & “B”)
• Instrument air dryers
• Industrial package-type backup compressor
• “C” Sierra air receivers (“C” & “D”)
• Service Air Isolation Valves (SA-V-92 & 93)
• Service Air Headers
• Temporary Service Air Connection / Compressor(s)
• Instrument Air Loops A / B
• Instrument Air Headers
• Instrument Air Supply to Containment

3

STATE the purpose of the service air receivers.

• To supply stored compressed air for system use on demand
• Provide for moisture removal
• Provide for system over-pressure protection

4

EXPLAIN how and why service air must be further processed to produce suitable instrument air.

• IA must be dried to prevent failure of safety related components with unpredictable and unanalyzed consequences.
• Using Filters and Air Dryers
• ANSI standard for instrument air:
• Particle size no greater than 3 micron
• Dewpoint at least 18oF below minimum expected temperature

5

DESCRIBE the major effects of a complete loss of:
Plant instrument air

• Sends operators to reset compressors in switchgear if they have tripped by cycling supply breakers.
• Opens IA-V-530
• Guidance for Rx trip and RCP shutdown

6

DESCRIBE the major effects of a complete loss of:
Containment instrument air

• Sends operators to manually start compressors.
• Notifies the station of a loss of air pressure, secures use of service air.
• Verifies SA Isolates.
• Guidance for Rx trip and RCP shutdown.
• Isolates air system leaks.
• Initiates temperature monitoring.

7

DESCRIBE the operation of the rotary screw air compressor including:
Major components in the air flowpath

Air filter(inlet) -> compressor first stage -> inter cooler -> moisture separator -> compressor 2nd stage -> after cooler -> moisture separator -> air receivers

8

DESCRIBE the operation of the rotary screw air compressor including:
Means of cooling

Air cooled

9

DESCRIBE the operation of the rotary screw air compressor including:
Means of loading and unloading

• When outlet pressure falls to the Sierra’s load setpoint, the Sierra loads by fully opening its inlet valve and fully closing its blowdown valve
• When pressure rises to the Sierra’s unload setpoint, the Sierra unloads by positioning its inlet valve to a minimum stop and fully opening its blowdown valve
• If the Sierra runs unloaded for 10 minutes, the Sierra shuts down but will automatically restart and load if pressure falls to its load setpoint

10

DESCRIBE the operation of the plant instrument air dryer, including the stages of moisture removal and the desiccant regeneration cycle

• Raw Service Air is supplied to a coalescing filter where moisture and particulate matter are removed
• The filtered air then enters a drying chamber where moisture is absorbed by desiccant
• Dry air exhausts through a post filter to the IA system
• A second “off line” chamber undergoes a drying cycle by slip streaming “dried” air through the off line chamber
• The slip stream of purge air is heated to enhance moisture removal and following the heat addition cycle, the purge air flow is maintained to cool the desiccant bed
• After cooling, the dried bed is pressurized and remains in standby
• Desiccant Beds automatically shift:
• Hi moisture
• Every 24 hours (normal)
• 10 hour design regeneration time
• 3 hours of heating
• Purge air removes moisture released from desiccant
• 6.5 hours of cooling
• 0.5 hours of repressurization

11

EXPLAIN how to prevent inadvertent starting and loading of the rotary screw air compressor due to the loss of power restart feature.

To prevent inadvertent starting and loading of compressor 137A, B and C, due to the loss of power restart feature, the EMERGENCY STOP push-button should be pressed prior to CLOSING the 480V supply breaker.

12

IDENTIFY the automatic trips for the rotary screw air compressor

• Inlet Restriction High Vacuum
• High Air Temperature
• First Stage Temperature
• Intercooler Temperature
• Second Stage Temperature
• High Air Pressure
• Intercooler Pressure
• Second Stage Pressure
• Outlet Pressure
• Oil
• Low Bearing Oil Pressure
• High Oil Temperature
• Excessive Unloaded Operation (>20 minutes)
• Starter Fault
• Main Motor Overload
• Fan Motor Overload
• Sensor Failure
• 2nd Stage Over Ratio
• Emergency Stop Engaged

13

DESCRIBE the lead-lag scheme used to operate two rotary screw compressors in parallel

• Lead cycles between 115 and 125 psig
• Lag cycles between 110 and 120 psig
• If needed, the Sullair compressor provides still another source of compressed air and will auto start at 100 psig.

14

DESCRIBE the automatic operation of service air isolation valves SA-V-92 & V-93 including setpoints.

• These valves isolate the SA piping and separate the IA loops during abnormal periods of low air pressure, thus ensuring that all available air is directed to the intact IA header(s).
• Isolation Valves SA-V-92 & 93 auto close to isolate service air @ 90 psig decreasing sensed on Air Receiver A or B.
• Valves will not auto reopen.
• The operator is permitted to reopen them from MCB @ 95 psig per VAS.

15

IDENTIFY the function of the Containment Compressed Air Subsystem.

• Supply dry, compressed Instrument Air to power actuators and pneumatic instrumentation inside containment.

16

IDENTIFY the major components of the Containment Compressed Air Subsystem

• Reciprocating Air Compressors A / B
• Aftercoolers A / B
• Air Receivers A / B
• Instrument Air Dryers A / B
• Instrument Loops A / B
• Containment IA Backup Supply via IA-V-530

17

DESCRIBE the operation of the containment reciprocating air compressor including:
Major components in the air flowpath

• dust prefilter -> double acting reciprocating piston -> aftercooler ->moisture separator -> air receiver -> refrigerant charged, air cooled dryer
• Check valves prevent reverse flow and insure isolation / separation of the headers, as well as the connection from the Plant Instrument Air supply.

18

DESCRIBE the operation of the containment reciprocating air compressor including:
Means of cooling

PCCW

19

DESCRIBE the operation of the containment reciprocating air compressor including:
Means of loading and unloading

• The compressor unloads by simultaneously opening both sets of inlet valves.

20

IDENTIFY the two automatic trips for the containment air compressor.

• Low Bearing Oil Pressure (bypassed for 15 seconds during compressor start)
• High Compressor Discharge Air Temperature

21

DESCRIBE the design response of the compressed air system to a loss of offsite power

• EDGs start and load IAW the EPS load sequence
• As air pressure drops, the SA-SKD-1A and/or -1B LAG/STANDBY compressors will receive load signals
• Each compressor will start when its associated EDG load sequencer reaches HR9
• If air pressure drops to 100 psig before the Sierra compressors can start and load, the Sullair will start and maintain air header pressure at approx. 115 psig
• Once the Sullair has started, it does not auto shutdown