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Block 3 > Compressors > Flashcards

Compressors Flashcards

Key information on compressors

1
Q

Zero degrees Kelvin is equivalent to what in celcius?

A

-273°Celcius

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2
Q

Zero degrees Rankine is equal to what in Fahrenheit?

A

-459°Fahrenheit.

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3
Q

What is atmospheric pressure?

A

14.7 psia

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4
Q

What are 3 devices for measuring pressure?

A

Barometer
Manometer
Bourdon Tube

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5
Q

“Pressure applied to a confined or static fluid is transmitted equally in all directions while being transmitted at right angles to the surface” is which law?

A

Pascal’s Law

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6
Q

“If the flow rate is constant, the sum of the kinetic and the potential energy at various points in the system is constant. Therefore, whenever the velocity (kinetic energy) of a fluid increases the (pressure potential) energy decreases” is what?

A

Bernoulli’s Principle

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7
Q

The law of conservation of energy states what?

A

This energy cannot be lost it has to go somewhere.

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8
Q

“if the temperature remains constant the volume changes inversely to pressure” is which law?

A

Boyle’s Law.

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9
Q

“if the pressure on a given volume of a gas is held constant the volume changes in direct proportion to the absolute temperature” is which law?

A

Charlie’s Law

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10
Q

“if the volume is constant the pressure exerted by the gas is directly proportional to the absolute temperature” is which law?

A

Gay-Lussac’s Law.

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11
Q

The combined gas law is a combination of which laws?

A

Boyle
Charles
Gay-Lussac

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12
Q

What are the two types of positive displacement compressors?

A

Rotary

Reciprocating

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13
Q

What does the term single acting mean?

A

That the compression happens on one side of the piston.

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14
Q

In a double acting compressor how many compression strokes are there for every rotation of the crankshaft?

A

Two.

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15
Q

What to reciprocating compressors that are suited to oil-free air delivery?

A

Labyrinth

Diaphragm

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16
Q

What are the properties of compressed air?

A

It can be compressed or reduced in volume.

Air will expand to fill any container.

Pressure in a confined, static fluid acts the same and equally in every direction. It always acts at right angles to the containing surface.

There must be a pressure change to create flow.

Air flows from high to low pressure areas.

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17
Q

What are the ways to increase pressure?

A

Reduce the volume to create more impact on a smaller wall area.

Introduce more air into the confined space.

Hit the air so the molecules travel faster and increase the intensity and the amount of impact on the same wall area.

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18
Q

What are compressors classified by?

A

Their principle operation and by their motion.

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19
Q

What are the methods of controlling the maximum air pressure of the compressor?

A

Throttling the intake.

Using a variable speed drive such as a gas or diesel engine power unit.

Using a pressure switch to start and stop an electric drive motor.

Unloading valve.

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20
Q

Which combination of rotors is for general use?

A

4 + 6
4 on the drive
6 on the driven

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21
Q

Which screw Combination is for high pressure, low volume?

A

6 + 8

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22
Q

Which screw Combination is for low pressure, high volume?

A

3 + 4

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23
Q

What is air slip?

A

The air returning to the inlet side past the sealing surfaces in a screw compressor.

24
Q

Where are water traps placed in a system?

A

Wherever compressed air is cooled and may fall below it’s dew point.

Low spots in the system
After the intercooler, after-cooler and air dryer

25
Q

A receiver can also act as what?

A

An after-cooler.

26
Q

The safety valve is usually set to what percentage above the systems maximum pressure?

A

5 to 10 %

27
Q

What are the two groups that industrial compressed air can be divided into?

A

Plant air and instrument air

28
Q

What are the four types of air dryers?

A

Delquescent
Regenerative desiccant
Refrigeration
Membrane

29
Q

What are the problems with the deliquescent dryers?

A

The chemicals must be replenished periodically and their disposal may be a problem.

30
Q

What is the desiccant used in regenerative dryers?

A

The solid desiccan is usually a silica gel activated alumina or molecular sieve.

31
Q

Which type of dryer requires you to switch Chambers for the other one to dry out?

A

Regenerative dessicant

32
Q

Refrigeration dryers use what to cool the air?

A

Heat exchangers chilled by refrigerants

33
Q

Describe how a membrane dryer works.

A

They use a membrane that block nitrogen and oxygen molecules but a lot of water vapor to pass through.

34
Q

Describe the construction of a membrane dryer

A

The membrane is constructed of the thousands of fiber tubes through which the water vapors pass. The shell is constructed from plastic and aluminum to prevent corrosion.

35
Q

What are the ways contamination is produced in the system?

A

Construction assembly and maintenance debris.
Oil carried over from the compressor.
Operational wear particles, pipe scale, and rust generated within the line.

36
Q

Describe the filtering action of a filter.

A

Air enters and deflector plate swirls the air around the filter bowl and is directed around the bowl by a shroud so it doesn’t swirl around the element. This causes the larger particles to be thrown to the outside. The baffle below the filtering element creates a quiet zone then the air is forced through the filtering element which removes the smaller particles and clean air exits and enters the system.

37
Q

Coalescing filters are designed to remove all small particles as small as?

A

O.3 micrometers

38
Q

Describe the operating principles of a pressure regulator.

A

An adjusting screw preloads a spring on top of the piston there is a pilot passage open to the outlet Port this allows the pressure on the downside to control the piston as the downside pressure increases the piston rises along with the poppet and flow decreases.

39
Q

Where should lubricators be placed in a system?

A

Located downstream from any device that might be contaminated by lubricating oil such as paint sprayers.

40
Q

What are the types of lubricators?

A

Fog and mist

41
Q

Describe the operating principles of a lubricator.

A

Air enters and a predetermined amount is allowed through the Venturi, the remaining air is let through a bypass valve into the bowl and out the outlet port. The air pressure in the bowl forces oil up the capillary tube. The air in the Venturi creates a low pressure which allows the oil to enter the airstream. As oil enters the Airstream it is atomized into an airborne oil mist, fog which is carried to the pneumatic device.

42
Q

What does FRL mean?

A

Filter
Regulator
Lubricator

43
Q

How do you remember the order of which the filter regulator and lubricator need to go?

A

Never regulate your filter and never lubricate your regulator.

44
Q

How is pressure controlled in a compressor?

A

Through unloading valves.

45
Q

How is pressure controlled in Branch lines for specific applications?

A

Through pressure regulators.

46
Q

What controls the movement of the actuators?

A

Directional control valves.

47
Q

What controls the volume of the air to the actuator?

A

Flow control valves.

48
Q

Absolute zero is what?

A 
A perfect vacuum
- 459.69° F
0° Rankin
- 273.16° C
0° Kelvin
49
Q

Positive displacement compressors work on the principle of what?

A

Trapping a specific volume of air then reducing that volume to get a higher pressure.

50
Q

What are the eight major components that are critical for proper compressor function and operation?

A 
Frame
Crankshaft
Connecting Rod
Crosshead and Guides
Pistons
Cylinders
Valves
Distance Pieces
51
Q

What is inlet valve unloading?

A

When the output of a compressor is reduced by holding open one or more suction valves and allowing the air to flow in and out of the compressor cylinder through the valves. The suction valve was held open there is no compressed air to deliver and the compressor continues to run but delivers no air or partial air until the demand increases.

52
Q

Why should inlet valve unloading be done for short periods of time?

A

Because for long periods of time increases while temperatures so it is common to have the compressor shut down on a timer if it runs unloaded for too long.

53
Q

Where and when should a safety relief valve be placed?

A

Anytime there’s a possibility of an obstruction occurring like a valve left closed or the possibility that they could fail to work intercoolers and after coolers plugging off.

54
Q

What is the slope for an airline?

A

1-2 inches per 10 ft.

2.5-5 cm per 3m.

55
Q

What are the types of positive displacement compressors?

A

Rotary- sliding vane, liquid ring
Screw- single rotor, two rotor
Reciprocating- single acting, double acting, labyrinth, diaphragm.

56
Q

What are the types of non positive displacement compressors?

A

Dynamic- axial flow, centrifugal, ejector.

Block 3 (3 decks)

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