Instrument and Service Air Flashcards
What is the purpose of the Instrument Air system and is it safety related?
Not Safety Related
- Portions of the system are treated as safety-related.
- The containment isolation portion of this subsystem is safety-related.
- Safety-related control valves have nitrogen backup.
Designed to provide dry, oil-free air for instrumentation and controls.
Flow Requirements
- 80 standard cubic feet per minute (scfm) for the Nuclear Steam Supply System
- 115 scfm for the remainder of the plant.
What is the purpose of the service air system and is it safety related?
Not Safety Related
Provides unfiltered, undried air, directly from Instrument Air to Service Air hose stations and components throughout the plant.
What is the purpose of the High Pressure Air System and is it safety related?
Has Both Safety Related and Non-Safety Related Portions
Safety Related
- Provides high-pressure control air for operation of vital valves located in each of the Engineered Safeguards rooms.
- Supplied via T-9A/B
Non-Safety Related
- Provides high-pressure control air for operation of non-vital valves located in Turbine Building.
What is the purpose of the Feedwater Purity Air System and is it safety related?
Non-Safety Related
It is an independent air system providing filtered, moisture-free air to Feedwater Building components.
It also can supply filtered, dried air directly to the Instrument and Service Air system if needed. This is done using air dryer M-993 along with pre and post filters.
What is the design and capacity of the C-2 instrument air compressors?
Compressors C-2A, C-2B and C-2C
- Air cooled rotary screw type compressor
- Rated for 288 SCFM - considered full capacity
- Operating range: 95-105 psig
What are the power supplies for Compressors C-2A, C-2B and C-2C?
C-2A - LCC-11 (52-1106)
C-2C - LCC-11 (52-1107)
C-2B - LCC-12 (52-1207)
What starts an Instrument Air Compressor?
Control Room Handswitch on C-13
HAND
- 52‑1106/52-1207/52‑1107 closes
- Red light on in Control Room
OFF
- 52‑1106/52-1207/52‑1107 opens
AUTO
- Amber Light is Lit
- 52‑1106/52-1207/52‑1107 controlled by header pressure
- 92 psig on PS-1213 starts compressor
- Compressor will load after 7 seconds if pressure <95 psig
How long after the red light is lit in the control before the compressor can assume loading?
7-10 seconds
Startup checks for the microprocessor
If an Instrument Air Compressor is running more than 10 minutes unloaded, what happens?
Compressor goes to “sleep”
- Compressor motor shuts down
- Local digital display reads “READY TO START”
- Breaker stays closed and handswitch indication in the Control Room will continue to have a red light on.
- Compressor will restart when discharge pressure is sensed to be less than 95 psig
- There is no alarm for this condition
What trips an instrument air compressor?
Breaker trips (overcurrent or low voltage on bus 1C)
Load shed due on a Loss of Offsite Power (LOOP).
Compressor shutdown initiated by microprocessor due to various ALARM conditions
- Includes low oil pressure, and Emergency Stop (local pushbutton) for example.
- Breaker is NOT tripped
What powers the ventillation for the instrument air compressors?
MCC-3 powers Control panel C-1034 which powers V‑201A/B/C.
V-201 A/B/C individual handswitch in manual - runs, auto - runs if compressor running.
What is the cooling medium for the instrument air compressor aftercoolers?
A is cooled by ‘B’ Critical Service Water
B is cooled by non-critical service water
C is cooled by ‘A’ Critical Service Water
What is the capacity of T-8A/B/C?
- Design Pressure: 125 psig
- Capacity: 57 Cubic feet each
- Normal operating range: 95-105 psig.
How are instrument air pre and post filters aligned and what is their max dp?
1 of each aligned for service
4 psid max
What is the function of CV-1211 “Penet. MZ-65 Instrument Air Cont. Isolation”?
CHP/CHR do NOT impact.
- Isolates Instrument Air from Containment Instrument Air
- Normally open. Air to Open.
- Operated by hand switch in the Control Room.
- No automatic functions associated with CV‑1211.
- Fails open on loss of air or loss of power (DC Bus D-11) to operating solenoid.
- Nitrogen Backup from N2 Station 5 to allow closure in case of loss of operating air.