IA-Instrument Air

Question 1

What is the purpose of IA instrument air?

Answer 1

Provides a continuous supply of filtered, dry, oil-free air at a pressure up to 125 psig for pneumatic instrument operation and the control of pneumatic actuators.

Question 2

What is the purpose of IA Service Air?

Answer 2

Supplies oil-free air at a pressure of 125 psig to service air stations located throughout the generating unit (eg. pneumatic tools, resin transfer, refueling machine manual operation, and other service requirements)

Question 3

What is the design of the Instrument Air subsystem?

Answer 3

Three 100% capacity rotary screw Air Compressors
Compresses air to 105-123 psig
Three Air Receivers
Two Air Dryers consists of a Pre-Filter, a duplex heatless desiccant Air Dryer, and an After-Filter

Question 4

What is the flow path of Instrument Air?

Answer 4

Air compresor > Filter > Air Receiver > Prefilter > IA Dryer C/D > MSSS and Turbine bldgs

Question 5

What the purpose of the IA Inlet Air filters on the compressor?

Answer 5

Remove particulate materials and minimize compressor wear.
Air inlet press should read 0

Question 6

What is the purpose of the Air Inlet Control Valve?

Answer 6

Butterfly valve that is opened and closed by a stepper motor, controlled by the Intellysis Controller set by based upon the demand of the plant air system
Closes when down to 109psig loaded
Closes when up to 119psig unloaded

Question 7

What is the purpose of the Instrument Air Compressors Airend?

Answer 7

Compresses air to 105-123 psig for use by the Instrument Air system.

Question 8

What is the design of the Instrument Air Compressor’s Airend?

Answer 8

Single Stage Rotary Compressors are electric, 480 VAC motor driven, screw, air compressors.
Oil bath compressor that has oil supplied to the inlet of the compressor for lubrication, cooling, and compressor sealing

Question 9

What is the purpose of the Instrument Air Compressor’s Coolant Cooler and Thermostatic Control Valve?

Answer 9

The min airend injection temp is controlled to make sure no water vapor condensing in the air receiver.
It puts coolant/oil at higher temp the discharge air and lube mixture will be kept above the dew point

Question 10

What is the design of the Instrument Air Compressor’s Coolant Cooler and Thermostatic Control Valve?

Answer 10

Controls how much of the coolant flows through or bypasses
Mixing valve to provide injection of 160°F oil into the Airend

Question 11

What cools the Coolant Cooler?

Answer 11

Turbine Cooling Water (TC) normal
Domestic Service Water (DS) alt, in outage

Question 12

What is the purpose of the Separator Tank?

Answer 12

Removes the Coolant/oil from the compressed air to provide clean air to the system while maintaining the coolant for the Compressor package

Question 13

What is the design of the Separator Tank?

Answer 13

Cyclone Separator with a two-stage coalescing separator element

Question 14

What is the purpose of the IA Compressor’s Air Aftercooler?

Answer 14

Cools the compressed air to prevent damage to components from excessive temperatures. It also condenses moisture in the air to prevent damage to components.

Question 15

What is the design of the IA Compressor’s Air Aftercooler?

Answer 15

Consists of a heat exchanger, a condensate separator, and an automatic drain trap. It cools the compressed air and removes the condensate which is drained to a floor drain.

Question 16

What cools the IA Air Aftercooler?

Answer 16

Turbine cooling water-norm
domestic service water-outage

Question 17

What is the path of air on a loaded IA compressor?

Answer 17

Turbine bldg air > inlet filter > MOV Air inlet CV to airend/compressor > discharge to sparator tank > aftercooler >moisture separator > drain tap > exit compressor

Question 18

What is the path of air on an unloaded IA compressor?

Answer 18

Air inlet valve min open to maintain separator tank sump press
Separator tank vented thru BD solenoid op valve to airend suction

Question 19

What is the purpose of Coolant/Oil in the Airend?

Answer 19

• Act as an air seal
• Lubricate the bearings
• Remove heat of compression from the air

Question 20

What is the flow path of coolant/oil in the IA compressor?

Answer 20

flow w/ air thru discharge > separator tank > spins and drops to separator tank sump > coolant cooler > filter > airend.

Question 21

How is coolant moved through the airend?

Answer 21

There is no pump, the motive force for the coolant is the separator tank sump pressure.

Question 22

What is the flow path of the cooling water in the IA compressor?

Answer 22

TC flows thru control valve > after-cooler/coolant cooler > discharge header > TCV regulates water flow to keep coolant/oil outlet temp at 120° so when it mixes with bypass coolant the combined temp will be 160°

Question 23

What is the purpose of the IA Air receivers?

Answer 23

Provide 30 seconds of storage capacity on a Compressor trip, as well as providing pressure dampening for the system.

Question 24

What is the design of the IA air receivers?

Answer 24

Three Air Receivers maintain a supply of compressed air to provide the IA header if the running Compressor trips, while another Compressor starts and loads.
* A drain line with an automatic drain trap routed to a floor drain.
* A relief valve set at 135 psig for over pressure protection.

Question 25

What is the purpose of the IA Air Pre-Filter?

Answer 25

Pre-Filter is provided upstream of each Instrument Air Dryer string
After-Filter just downstream of each dryer string

Question 26

What is the purpose of the IA dryers?

Answer 26

Dehumidify Instrument Air and lower the dew point of the air to between minus 20ºF and minus 40ºF, depending on flowrate and inlet air temperature.

Question 27

What is the design of the IA Dryers?

Answer 27

Two IA Dryers in parallel, duplex, heatless, desiccant dryer, and includes two drying towers (Left and Right Chambers) and a control panel
No local controls only Power Disconnect/Alarm Disable

Question 28

What is the normal operation for the IA Dryers?

Answer 28

One Chamber is always in service in a timed Drying Cycle lasting between 2 min 45 sec and 3 min 15 sec per Chamber. The opposite, off stream chamber, is either in a pressurized “standby” condition, or a timed “regeneration cycle” for removal of the previously absorbed moisture.

Question 29

What is the purpose of the IA Compressor’s Local Controller?

Answer 29

When the Master Controller not in use the air compressors are programmed to START, LOAD, UNLOAD, and STOP on to pre-determined setpoints loaded into the memory of each air compressor’s local controller.

Question 30

What is the design of the Compressor’s Local Controller?

Answer 30

Intellisys SG Controllers
On-Line/Off-Line
2 points-100% full-flow (Loaded) and the second is 0% flow (Unloaded)

Question 31

What are the pressure set points for the A, B, C air compressors?

Answer 31

• IA Compressor ‘A’ 113 psig to 123 psig.
• IA Compressor ‘B’ 109 psig to 119 psig.
• IA Compressor ‘C’ 105 psig to 115 psig.

Question 32

What are the pressure display status’?

Answer 32

Running Loaded or Unloaded (On/Off Line) Master Cntrllr can restart
Stopped In Auto Restart-in this cond after 15mins of inactivity, Master Cntrllr can restart
Stopped By Alarm CANNOT be restarted by Master Cntrllr
Ready To Start (Local or Remote) must be manually started before Master Cntrllr can restart

Question 33

How are warning lights on the Compressor’s Local Controller reset and what is a warning indicator?

Answer 33

You have to push the reset button locally and a flashing question mark.

Question 34

What is an alarm indicator and how is it reset on the Local Compressor Controller?

Answer 34

An exclamation point will flash, and you reset it locally by pushing the reset button twice.

Question 35

What is the Power Outage Restart for the compressors?

Answer 35

• ‘A’ Compressor – 10 seconds
• ‘B’ Compressor – 20 seconds
• ‘C’ Compressor – 30 seconds

Question 36

What is the purpose of the IA Compressors Master Controller?

Answer 36

Has an independent air pressure sensor and communicates with the three local controllers for the compressors to maintain the IA system pressure within the desired values.

Question 37

What is the timer rotation of the IA Master Controller?

Answer 37

To efficiently operate a compressed air system. Rotates every 56 hours.
ABC Tues 0800 - Thurs 1600
BCA Thurs 1600 - Sun 0000
CAB Sun 0000 - Tues 0800