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School > Compressor Fundamentals - Part B > Flashcards

Compressor Fundamentals - Part B Flashcards

1
Q

What does a crankshaft do in a compressor?

A

Turns Rotary motion into Reciprocating motion to drive the pistons

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2
Q

What is a Crosshead?

A

The part which the small end of a connection rod connects to.

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3
Q

What is this?

A

Double-acting compressor crosshead

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4
Q

What is the purpose of a crosshead and its guides?

A

To keep the piston rod centred through the packing to minimize leakage from the compression cylinder.

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5
Q

What connects the crosshead to the piston?

A

Piston Rod

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6
Q

How do Compressor Cylinder Valves differ from common engine valves?

A

Compressor Valves open and close automatically due to changes in pressure on either side

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7
Q

Label these

A
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8
Q

Does cool air hold more or less moisture?

A

Less

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9
Q

Give two reasons why cool air should be used for intake systems?

A
  • Cool air is more dense and therefore more efficient to use.
  • Cool air has less moisture in it.
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10
Q

What is Luminar Flow?

A

Flow in a straight line

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11
Q

What is a Turbulent Flow?

A

Flow other than a straight line

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12
Q

Sharp bends in lines cause what four things?

A
  • Turbulance
  • Friction
  • Resistance to flow
  • Pressure Drop
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13
Q

What is choked flow?

A

When too many joints are used in a air line and the turbulance caused restricts the flow where little if any fluid gets through.

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14
Q

What is Resonance?

How can you stop it?

A
  • When the reciprocating compressors set up pulsations in the piping that match with the natural frequency of the compressor. This can cause loud noises and damage.
  • Change the length of the pipe or mounting the pipes on flexible hangers to eliminate vibration transfer
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15
Q

What does a Venturi Silencer do?

A

Dampens the intake pulsations by causing the air to speed up and then slow down while going through the venturi and then slowing down even more in the housing.

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16
Q

What can cause a compressor to explode?

A

Running the compressor at all times without some form of control to limit the amount of gas being delivered.

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17
Q

When are compressors unloaded?

Why?

A
  • Normally on start-up

- To reduce starting torque and prevent compressor damage.

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18
Q

How is Compressor Unloading done?

A

Not allowing compression cycle to happen.

Reciprocation Compressors hold open the suction valves so that gas merely goes in and out of the suction valves without compresson.

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19
Q

Can a compressor be unloaded during operation?

What is the problem with this?

A
  • Yes

- The compressor won’t deliver full volume of air during unload.

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20
Q

When is a pressure switch normally used to limit/control compressor unload?

A

Smaller Reciprocating Compressors (10HP)

21
Q

Where does the pressure switch normally sense pressure?

Where is it controlled?

A
  • Compressor discharge at the reciever

- Between upper and lower set points

22
Q

What is this?

A

Pressure Switch

23
Q

How are Large Compressors controlled?

A
  • They use a Inlet Valve Unloader
24
Q

What happens if you keep running a compressor in unload mode with a Inlet Valve Unloader?

A

The valve temperature will increase. Compressor will shut down on a timer.

25
Q

What does the Inlet Valve Unloader do?

A

Reduces the output of a compressor by holding open one or more suction valves.

26
Q

What is this?

A

Inlet Valve Unloader

27
Q

What is a Intercooler?

A

Basically a heat exchanger used to cool the compressed gas between stages.

28
Q

What is this?

A

Two Stage Compressor with Intercooler

29
Q

How does an Intercooler work?

A

Heat from the gas travels to the fins on the outside where the convection air currents (fan blowing air across) takes the heat away.

30
Q

Does the Intercooler decrease or increase the amount of power required to compress gas?

A

Decrease

31
Q

What is this?

A

Aftercooler with a Cyclone Separator

32
Q

Can variable speed control be accomplished on a Inlet Valve Unloader?

How?

A
  • Yes

- By verying the speed of the driver

33
Q

Give an example of a Variable Speed Controlled Inlet Valve Unloader.

Explain

A
  • Engine drivers with a centrifugal clutch
  • Slowing the engine causes the clutch to disengage, which stops the compressor. When demand increases, the engine picks up speed, the clutch engages and the compressor starts to deliver air.
34
Q

Where do you find Bypass Unloading?

What do they enable?

A
  • In large systems

- They enable the compressor to run under full load at all times

35
Q

What is this?

A

Desiccant-type Dryer

36
Q

Each of the two towers of the Desiccant-Type Dryers are filled with what?

Can what’s in the tower be reused?

A
  • A chemical that attracts moisture.

- Yes, by driving off the moisture.

37
Q

What is a Deliquescent (absorption) Dryer?

A

Basically a pressure vessel filled with a chemical that melts away as it absorbs water.

38
Q

What is the least efficient of the Dryers?

A

Deliquescent Dryer

39
Q

What is the problem with Deliquescent Dryers?

A

The water and chemical mixture is corrosive.

40
Q

What is this?

A

Deliquescent Dryer

41
Q

Label this.

A
42
Q

What are the three purposes of a receiver?

A
  • Store Compressed Air
  • Take Up Fluctuations In Demand
  • Allow The System To Vary Within Reasonable Limits
43
Q

What is this?

A

Safety Relief Valve

44
Q

What is the last line of defense in a compressed air system?

A

Safety Relief Valve

45
Q

Safety Relief Valves must be installed where?

A

On all components of a compressed air system.

46
Q

What does CFM stand for?

A

Cubic Feet Per Minute

47
Q

What is the most common standard adopted by the compressor industry on standard cubic foot.

A
  • ASME: Temperature = 68F
  • Pressure = 14.7psia
  • Relative Humidity = 36%
48
Q

What is Volumetric Efficiency?

A

The ratio of Compressor Capacity compared to the Calculated Displacement expressed as a percent.

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