Compressed Air Flashcards
What are the PAC trips?
- Loadshed (T11/21B)
- Load Conser (Train B)
- Motor Overload
- Lo Lube Oil Press - < 20#
- Hi Lube Oil Temp - > 150°F
- Hi 1st Interstage Temp > 125°F
- Hi 2nd interstage temp > 125°F
- PAC Motor Lo Current
- PAC DCCS loss of control power
- Loss of most transmitters
- Manual (Several Inputs)
When will the PAC Aux Lube Oil Pump start?
- On PAC start - remains running until > 42 psig.
- PAC is stopped (for 15 minutes) ***
- lo lube oil press
- loss of DCCS control power
- PA header - 97# with PAC in AUTO
Unit 1 Plant Air Compressor is supplying all compressed air needs. Unit 2 Plant Air Compressor is in STANDBY. Unit 1 PAC develops a slow OIL leak. What will occur FIRST?
- PAC Aux Lube Oil pump will auto start
What are the CAC trips?
- Overload
- LO # Low (15# with 12 sec delay)
- NESW # Low (< 6# for 5 sec) (U1) (includes on start)
- NESW # Low (< 4.2 ΔP for 10 sec) (U2) (includes on start)
- Manual
Does the CAC trip on a Load Shed?
- No
What are the BACPAC trips?
- Motor Overload
- LO Press low at 20#
- LO Temp High at 175°F
- 1st Stage Disch Temp high at 425°F
- 2nd Stage Disch Temp hi at 425°F
- 2nd Stage Suction Temp hi at 145°F
- Manual
What are the Compressed Air System header pressure actions?
- 95# - PAC Start
- 90# - CAC Start (WAR #)
- 85# PA Header Iso Valves Close
- 80# - Manual Reactor Trip
What is the correct sequence of events that automatically occur in the Control and Plant Air Systems as air pressure lowers?
A. - 95 psig at PPS-10 (20) Standby PAC starts
- 90 psig CAS wet receiver pressure CAC starts
- 85 psig at PPS-11 (21) Plant air header isolates
What can cause PAC surge?
- Discharge Valve Closed/Blocked
- Inlet Valve Throttled too far Closed
- Insufficient Inter-stage Cooling
- Opening demister valves too quickly
- Hi System Press
What is a Surge of the PAC?
- Performance characteristic of a centrifugal compressor that arises when the compressor can’t overcome the system resistance
Seal air pressurizes the PAC seals when ?
- Standby
- Start-up
- Unloaded
When loaded, the PAC seals are pressurized from?
- Leakage from itself
At what pressure on the PAC seal will cause an alarm?
- 12#
At what pressure on the PAC seal alarm reset?
- 15#
What problem does a loss of PAC seal air cause?
- May allow oil leakage from the drive casing into the compressor housing
Where does the BACPAC tie into the Air System at and why is this important?
- Supplies air to the Plant Air ring header between the Ring Header Isolations (ie can supply CA system directly with Plant Air Ring Header isolation valves closed)
Both Units are responding to a loss of Plant Air (PA) and Control Air (CA) event.
The following conditions exist:
Both Unit’s Plant Air Compressors (PAC’s) have failed.
Both Unit’s Control Air Compressors (CAC’s) have failed.
Both Unit’s PA Header pressures are 70 psig and lowering.
Both Unit’s CA Header pressures are 80 psig and lowering.
An AEO has been dispatched to start the Back-up Plant Air Compressor (B/U PAC), per 01-OHP-4022-064-001, Control Air Malfunction.
What describes the B/U PAC ability to repressurize both Unit’s Control Air Systems under these conditions?
- C. The B/U PAC will discharge to both Unit’s Control Air Systems
How does Suction Throttle Control work?
- Throttles inlet valve prior to throttling the unloader valve in order to maintain discharge pressure and minimum current setpoint.
Compressor air mass flow is controlled using what valve based on what parameters?
- Via the first stage inlet valve with feedback from motor current.
The suction throttle control eliminated the need for?
- NESW cooling flow control to intercoolers.
- NESW flow is now free flowing for intercoolers
What is the purpose of the Cnt CA Safety Valves?
- 50 psig header and 85 psig header SV’s are safety related and prevent overpressurization of safety related PZR PORVs
Do the Ctrl Air Cnt Safety valves have isolations?
- Yes, they have manual isolations
Can the Ctrl Air Cnt Safety valves be actuated locally?
- Yes, the safeties have manual actuate levers
What are the causes of PAC surge?
- Discharge valve closed/blockage.
- Inlet valve throttled too far closed.
- Insufficient cooling to interstages
- Opening demister blowdown valves too far too quickly
What will happen on a loss of 600v AC to PAC and CAC?
- A loss of 600V AC will prevent operation of the PAC and CAC causing a loss of Control Air.
If you lost NESW to CAC, will the CAC still start?
- No, it will not start
What are the reasons for cooling the air on the PAC?
- Physically reduces the necessary pipe size for the system
- Causes moisture to condense so it can be removed by moisture separators
How many running PACs are required to supply both units?
- 1 PAC can supply both units
Can one CAC supply both units CA?
- No, each CAC can only supply its own unit
Will the PAC automatically restart after a trip?
- No, The PAC will not start automatically after it has been manually shutdown or has tripped. Check for the message “Ready Auto Start”
- Must wait 2 minutes ***
What is the CAC flow path if the CAC is running??
- Inlet Air Filter
- CAC
- CAC Aftercooler
- Moisture Sep
- Wet CA Receiver
- CA Prefilters
- CA Dryers
- CA After filters
- Dry CA Receivers
Where does the PA tap into the CA system?
- Feeds downstream of the Wet CA receiver before the CA Prefilters
What happens on a Phase “A” signal with respect to CA?
- The CA CIVs will close
When will the CAC auto start?
- 90# at the Wet CA Receiver
If all the Plant Air Header isolation valves close, will the PAC still be able to feed CA?
- NO, PA feeds in upstream of PRV-10/20, so if they were to isolate along with PRV-11/21, the CAC will start to supply the CA header
If you had an air leak downsteam of PA-128, what would happen?
- If pressure dropped to 95# the stby PAC would start
When unloaded or in stby, the PAC seals are pressurized from?
- CA system
Which Pzr Porvs have back air tanks?
- NRV-152 and NRV-153 have backup air tanks
Where do the Pzr PORVs (NRV-151/152/153) get their normal air supply?
- From 85# Cnt CA header
What provides pwr to both CACs?
- 600v AC AB-D in both units
Will the CAC trip if there is a loss of NESW #?
- yes, it trips on loss of NESW #
