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Systems > Instrument Air(IA) > Flashcards

Instrument Air(IA) Flashcards

1
Q

What’re the differences in Instrument Air & Service Air ?

A

Instrument Air- 125psig for pneumatic instrument operation & pneumatic actuators
Service Air- 125psig for pneumatic tools,resin transfer,refueling machine,& manual operation

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2
Q

Why is instrument air a safety related system ?

A

All AOVs will fail into there fail-safe position to safely shut plant down

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3
Q

What’re the capacity of the 3 compressors for the IA system ?

A

Three 100% capacity air compressors

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4
Q

When will LP Nitrogen automatically align to IA header ?

A

Will automatically align when IA header pressure goes down to 85psig

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5
Q

Where do the air compressors draw their air from ? What does it compress it down to ?

A

-Draws air from turbine building & compresses it down to 105-123psig

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6
Q

What size are the Inlet Air Filters for the compressors ?

A

Removes particles 3micron or larger 99.9% effective

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7
Q

What does the PT-4 pressure sensor represent ?

A

-Represents Inlet Filter cleanliness, calibrated to read 0psig for Atm. Press.
-Will sense lowering pressure(rising vacuum)

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8
Q

What does local controller PT-4 Inlet Vacuum information to do what ?

A

-Confirm drive motor is rotating in correct direction upon start
-Indicate condition of Inlet Air Filter
-Provide logic for positioning inlet valve during unloaded operation based on coolant injection temp &separator press.

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9
Q

What is the Air Inlet Control Valve opened & closed by ?

A

-Open & closed by a stepper motor, which is control by Intellysis Controller

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10
Q

What does the Intellysis Controller do ?

A

Regulated stepper motor to position Air Inlet Control Valve based on demand plant air system

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11
Q

During compressor startup why is the Air Inlet Control Valve closed ?

A

-Allows compressor to startup with minimum current
-Allows compressor to check for proper rotation by checking Inlet Vacuum is at 1psi within 2seconds

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12
Q

What will happen if Air Inlet Control Valve fails to open & close during startup?

A

This will cause an alarm

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13
Q

How does “loaded operation” work ?

A

-The Intellisys/stepper motor opens inlet valve & closes blowdown when plant pressure drops below Min. Setpoint of 109psig
-Then compressor will start to deliver air to plant system

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14
Q

How does “unloaded operation” work ?

A

-Plant air reaches Max. Press. of 119psig then Inlet valve will slightly close
-Blowdown will open
-Compressor will be at Min. Power
-Intellisys controller will maintain Inlet Valve open to maintain pressure

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15
Q

What pressure do the Compressors compress to ? What’re the compressors driven by ?

A

-They compress press. between 105-123psig
-Driven by 480VAC motor driven

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16
Q

Where do the compressors discharge to ?

A

-They discharge into separator tank

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17
Q

What’re the compressors alarms when discharge temp is to high ?

A

-If discharge of compressor reaches a temperature watching it’ll be on Compressor Display Panel
-If compressor continues to operate until it reach alarm setpoint, it’ll trip due to alarm

18
Q

What is used to prevent water vapor from condensing in Air Receiver ?

A

Injecting coolant at high temp which will keep discharge above dew point

19
Q

What does the Thermostatic Control Valve do for the IA Compressor at Coolant Cooler discharge ?

A

Controls how much COOLANT flows through or bypasses Coolant Cooler

20
Q

What cools the Air Compressor Cooler during normal operation ? What is used a backup cooling source ?

A

-Turbine Cooling Water
-Domestic Water is aligned when TC isn’t available

21
Q

What is the Separator Tank used for ?

A

-Removes Coolant from compressed air to provide clean air for system
-While maintaining Coolant for Compressor package

22
Q

How does the coalescing separator element work that’s installed at airside discharge of Separator Tank ?

A

-Two filters remove compressed air oil
-Droplets collected on first filter fall to Separator Tank sump
-Droplets on second filter are drawn to After cooler (<3ppm oil)

23
Q

What is the Air Aftercooler used for ?

A

-Prevents damage to excessive temps, condenses moisture

24
Q

What is the Air Aftercooler cooled by?

A

-Cooled by Turbine Cooling Water normal operation
-Domestic water is used at backup cooling water

25
Q

In unloaded operation what is the position of the Air Inlet Control Valve? Why is it in that position ?

A

Air Inlet Valve is minimally opened to maintain Separator Tank Sump pressure

26
Q

During unloaded operation of compressor where is the Separator Tank vented to ?

A

Vented through a blowdown solenoid operated valve to suction side of Airend

27
Q

During unloaded operation what does Minimum Pressure Check valve do ?

A

-It maintains 60psig in Separator Tank for motive force of coolant flow through system
-Prevents back flow of air into the compressor package

28
Q

Where does the Separator Tank Sump drains the coolant to ?

A

Flow from bottom of sump to Coolant Cooler & three-way TCV

29
Q

When does the Coolant stop solenoid valve open/close ?

A

It opens & closes when the compressor starts

30
Q

What do the Instrument Air Receivers provide on a compressor trip ?

A

Provides 30seconds of storage capacity on compressor trip & providing pressure dampening of system

31
Q

What is the check valve at the discharge of the Air Receivers used for ?

A

Prevents failure upstream of check valve from allowing downstream header to discharge through failure & depressurize system

32
Q

Why must you not open Pre-Filter isolation valve so quickly when playing filter in operation ?

A

May cause damage to Air Dryer Desiccant if the Chambers aren’t at system pressure

33
Q

When will Air Dryer chambers be automatically switched ?

A

Will automatically switch by moisture detector in middle of chamber

34
Q

How many chambers are in service ?

A

Usually one chamber in service

35
Q

How long are drying cycles per chamber?

A

between 2min 45sec & 3min 15sec per chamber

36
Q

When one chamber is in service what is the second chamber doing ?

A

-Pressurized in standby
-Used for regeneration cycle for removal of previously absorbed moisture

37
Q

How many air dryers are there? How many chambers per air dryer ?

A

-Two air dryers in parallel
-Two chambers per air dryer

38
Q

What happens inside the Air Dryer during Drying Cycle ?

A

-Alternately cycles air through ONE of the TWO desiccant filled chambers, then sends dry air to IA header
-Adsorption through exothermic process later contributed regeneration

39
Q

What happens during Regeneration Cycle for Air Dryer chambers ?

A

1.)The chamber not in service will be isolated & depressurized
2.)Portion of the in service discharge chamber will be directed backward through Regenerating Chamber and purged to atmosphere
3.)After Regeneration Cycle controller places chamber in Standby

40
Q

What does Blue & Pink mean for the Air Dryer Moisture Indicator ? Where does the Moisture Indicator get it’s sample from ?

A

Blue -DRY
Pink-WET
Local Moisture Indicator receives a sampling line at discharge of dryer

41
Q

What needs to be done for Air Dryers if there is a High Humidity alarm on control panel ? What kind of alarm will control room get ?

A

Descant must be replaced & the control room will receive a trouble alarm to have AO switch Air Dryers

Systems (62 decks)

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