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7th 6 Months > Tpc 433 > Flashcards

Tpc 433 Flashcards

1
Q

Positive displacement compressors use a piston or other device to reduce volume of the refrigerant by…

A

Compressing refrigerant vapor in a compression chamber

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2
Q

What kind of compressor is a kinetic displacement compressor?

A

Centrifugal compressor

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3
Q

What is a part in a scroll compressor?

A

A swing link

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4
Q

A multiple stage refrigeration system has more than one…

A

Compressor

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5
Q

What must be considered when selecting a replacement compressor for a particular application?

A

Discharge pressure

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6
Q

What kind of compressors have a vertical crankshaft/ what kind have a horizontal crankshaft?

A

Vertical crankshaft- full hermetic compressor
Horizontal crankshaft- semi hermetic compressor/ open compressor

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7
Q

What rings prevent refrigerant from escaping around the piston during compression? What rings prevent oil from reaching the compression chamber?

A
  1. Top rings
  2. Bottom rings
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8
Q

What oiling system do reciprocating compressors use?

A

Crankshaft splash method

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9
Q

A cylinder unloader reduces the capacity of a reciprocating compressor by…

A

Allowing refrigerant to flow through the suction port during the compression stroke

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10
Q

One way of reducing vibration problems in reciprocating compressors involves the use of…

A

Spring mounts

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11
Q

One advantage of rotary compressors over reciprocating compressors is that the…

A

Vibration is less

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12
Q

Entry of liquid refrigerant into its compressor is called? Formation and collapse of vapor pockets in a liquid flowing under pressure is called?

A
  1. Slugging
  2. Cavitation
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13
Q

What is the purpose of accumulators in a compressor system?

A

Keep dirt and debris from entering the compressor

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14
Q

Helical compressors differ from rotary compressors in that they have…

A

No vanes. They have rotors

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15
Q

In a scroll compressor, one scroll is stationary while the other? Refrigerants enter the scrolls at the?

A
  1. Orbits
  2. Outer edges
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16
Q

The amount that one impeller compresses the vapor depends upon the impellers? The tip speed depends on?

A
  1. Tip speed
  2. Impellers diameter
17
Q

In reverse hydrostatic sealing, the flow of _____ across the seal opposes the flow of _____ across the bearing.

A

Refrigerant vapor, oil

18
Q

In multistage centrifugal compressors, thrust loads are reduced by?

A

Opposing impellers

19
Q

The purpose of a purge system on a condenser is to eliminate ____ from the refrigeration system.

A

Air

20
Q

Reducing a compressors capacity by closing pre-rotation vanes raises the pressure in the systems?

A

Evaporator

21
Q

Which is an important factor to consider when selecting a motor to run a refrigeration compressor?

A

Horsepower rating

22
Q

Which kind of motor can be used in hermetic compressors?

A

CSIR / capacitor start induction run motors

23
Q

How do you reverse the direction of rotation in a single phase induction motor?

A

You can switch either the starting winding leads or the running winding leads but not both

24
Q

How do you wire a 120v dual voltage motor to 240v?

A

You connect the two running windings in parallel

25
Q

One kind of relay operates when the current in the _______ winding falls to a preset value. Another kind operates when the voltage across the _______ winding rises to a preset value.

A

Running , starting

26
Q

Motor starting devices fall into one of two categories…

A

Contactors and starters

27
Q

A reduced voltage starter limits the current to the motor at start up in order to prevent…

A

Voltage drops to other equipment

28
Q

Overload protection for compressors motors may be provided by a…

A

External bimetallic disk

29
Q

Crankcase heaters are especially useful in compressors that are subjected to…

A

Cold climates

30
Q

Installing a suction line accumulator can protect a compressor from damage caused by…

A

Slugging

31
Q

The first rule of preventative maintenance for compressors and related components is to…

A

Follow the manufacturers PM schedules and procedures in the service manual

32
Q

Typical PM procedures for compressors and related equipment include…

A

Listening for unusual noises

33
Q

A compressor may overheat because of a…

A

Low oil level

34
Q

When pumping down a compressor for service, run the compressor with the valve on the suction line closed, then close the valve on the discharge line and stop the compressor. Repeat this process until the pressure holds at ______ Psig

A

2-5 Psig

35
Q

After disassembling a reciprocating compressor and cleaning the parts, you should inspect the parts for…

A

Excessive wear on bearing surfaces

7th 6 Months (7 decks)

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