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Compressors Exam > Modern Chap 19/20 > Flashcards

Modern Chap 19/20 Flashcards

1
Q

Compressors are driven by an ______ motor

A

electric

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2
Q

Compressors that are driven by an external motor are called ___________ compressors

A

open drive

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3
Q

compressors that are driven by an integrated motor are called _________ compressors

A

hermetic

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4
Q

There are two ways of joining a motor to an open drive compressor ______ drive and _____ driven

A

direct drive and belt driven

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5
Q

A direct drive compressor is driven by a _______ connecting the shaft of an electric motor directly to the compressor shaft

A

coupling

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6
Q

On a _________ compressor, a belt connects a pulley on the drive motor to a pulley on the compressor shaft

A

belt driven

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7
Q

On most compressors, the compressor pulley is larger than the ______ pulley which causes the compressor to turn more slowly than the motor

A

motor

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8
Q

Refrigeration compressors can also be driven by ________________ engines

A

internal combustion

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9
Q

Fully hermetic compressors are built in sizes from ____hp to ___hp

A

1/6hp to 20hp

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10
Q

A ______ ring is a split metal ring that is installed in a groove that encircles the piston

A

piston

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11
Q

Name the two types of piston rings;

A

compression rings and oil rings

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12
Q

Upper piston rings are known as compression rings, their purpose is to prevent pressurized _________ from blowing past the piston

A

refrigerant

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13
Q

The lower oil ring is designed to help ________ the cylinder wall while simultaneously preventing excess lubricant from entering the cylinder

A

lubricate

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14
Q

__________ are metal cylinders that connect the pistons to the connecting rods

A

piston pins

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15
Q

Compressor cylinders are usually made of

A

cast iron

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16
Q

As the piston moves down it creates a ______

A

vacuum

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17
Q

Although the refrigerant in the intake manifold is at a low pressure, it is still a greater pressure than the _______ in the cylinder when the piston is moving down

A

vacuum

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18
Q

As the piston moves upward in the cylinder, the increased pressure ______ the intake valve

A

seals

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19
Q

Poppet valves are only suitable for ____ speed compressors because they operate slowly

A

low speed

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20
Q

The _______ head serves as a pressure plate, sealing the top of the cylinder so the refrigerant can be compressed

A

cylinder head

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21
Q

A cylinder head also provides ______ passages into and out of the compressor

A

vapour

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22
Q

The portion of the compressor housing that supports the crankshaft is called the _______

A

crankcase

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23
Q

The portion of the housing that contains the cylinders is generally called the ________ block

A

cylinder

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24
Q

Adding more cylinders increases the _______ capacity for each revolution of the crankshaft

A

pumping

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25
Q

Compressors can have from one to _____ cylinders

A

twelve

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26
Q

Name some different cylinder arrangements:

A

Vertical, V, X, Y, Z, or radial

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27
Q

In a ________ design there is no connecting rod

A

scotch yoke

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28
Q

Scotch yoke is popular in _____ high ______ compressors

A

small high speed

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29
Q

In a scotch yoke design the piston and cylinder are _____

A

long

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30
Q

A rotary compressor is a compressor in which vapour compression takes place in spaces between the __________ and sides of an off-centre rotor that spins inside the cylinder

A

cylinder wall

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31
Q

A _______________________ compressor uses an off centre rotor to turn vanes(blades) that create pickets between the rotor and cylinder wall

A

rotating-vane rotary compressor

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32
Q

In a rotating vane rotary compressor, the low pressure vapour from the suction line is drawn into the opening between vanes as the vanes revolve. The trapped vapour in the slace is compressed until it can be pushed into the ___________

A

discharge/exhaust line

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33
Q

_______ compressor is the name commonly given to the first compressor in a cascade system

A

booster

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34
Q

Rotating vane compressors are frequently used as the booster compressor in a _________ system

A

cascade

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35
Q

In a stationary-blade rotary compressor the blade is stationary instead of the _______ like in a rotary vane

A

rotor

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36
Q

A ______ compressor produces vapour compression between the walls of a fixed scroll and an orbiting scroll

A

scroll

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37
Q

As two high-pressure pockets are discharging, new low-pressure pockets are formed at the outer edges of the _____

A

scroll

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38
Q

The suction from the outer portion of the scroll and the discharge from the inner portion are ________

A

continuous

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39
Q

In a screw compressor the male rotor has ____ lobes and the female has ____ interlobe spaces

A

male 4

female 6

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40
Q

In a screw compressor the ______ rotor meshes with and drives the male rotor

A

female

41
Q

In a screw compressor the male rotor rotates ____% faster than the female rotor because they’re are four lobes on the male rotor and six meshing grooves

A

50%

42
Q

Unloader mechanisms provide a unique feature of screw compressors: their ability to control capacity through _______ _________ unloading which allows for smooth accurate control

A

infinitely variable

43
Q

A _________ compressor is a compressor consisting of a rotor operated impeller with radial blades inside a volute casing

A

centrifugal

44
Q

The force that throws the vapour outward during the impeller stage is called

A

centrifugal force

45
Q

Centrifugal compressors are more efficient when operating at ____ speeds and are designed to be

A

high

46
Q

The ______ in a centrifugal compressor is the casing in which the impeller rotates

A

stator

47
Q

The stator is a volute design meaning that it is _______ shaped

A

spiral

48
Q

There is no vapour trapping pockets in a _________ compressor

A

centrifugal

49
Q

How to attach gauges when there are no service valves?

A

use special tapping valves that pierce the lines

50
Q

_________ reduce noise that may be caused by gas pulsation

A

mufflers

51
Q

The heat must be removed from a compressor to prevent loss of ________ and to maintain the lubricating qualities of the oil

A

efficiency

52
Q

_______ is a fluids resistance to flowing

A

viscosity

53
Q

______ oils have a viscosity that is best for refrigeration temperatures and refrigerant

A

mineral

54
Q

Reciprocating compressors may be lubricated by either a ______ or ________ (force feed) system

A

splash or pressure

55
Q

In the _____ system, the crankcase is filled with the correct oil up to the bottom of the main bearings or to the middle of the crankshaft bearing. Each revolution the crank throw is dipped and splashes oil everywhere

A

splash system

56
Q

_________ lubrications systems use a small oil pump to force oil to the main bearings.

A

pressure

57
Q

Since the oil pump delivers oil, under pressure, to all bearing surfaces, a _______________ system provides better protection than splash

A

pressure lubrication

58
Q

An _________ is a mechanism that temporarily reduces the pressure in the compressor during start up

A

unloader

59
Q

An unloader may be operated ; (3)

A

electrically , mechanically, or hydraulically

60
Q

An unloader may also be used to vary the ________ capacity in certain compressors wbu h is useful when there is a changing heat load like an air conditioner

A

pumping

61
Q

_______ devices are used throughout the compressor wherever a gap between components puke allow refrigerant or pressure to escape

A

sealing

62
Q

Name three types of sealing devices

A

gaskets , O rings, shaft seals

63
Q

On open drive and semi hermetic compressors, mating surfaces of the cases are usually sealed with ______

A

gaskets

64
Q

O rings are used when there may be some ______ between the assembled parts

A

motion

65
Q

A _______________ is a device that warms up the compressor crankcase to evaporate any liquid refrigerant trapped in the oil

A

crankcase heater

66
Q

During the off cycle, refrigerant will migrate to the coolest part of the system which is the

A

compressor

67
Q

Crankcase heaters may be operated during the off cycle or they may be ____________ controlled

A

thermostatically

68
Q

Crankcase heaters are required on compressors that operate in ambient temperatures ______ than the _________ temperatures

A

lower than the evaporator temperatures

69
Q

If the refrigerant gets to the compressor and condenses then the ref/oil mix will begin to foam when the compressor starts. This causes the oil charge to pump out of the compressor , a condition know as ________

A

oil slugging

70
Q

Slugging of oil or liquid refrigerant can cause ; (3)

A

broken valves, damaged pistons, and broken head gaskets

71
Q

A heating coil keeps the crankcase coil up to ___ degrees warmer than system temperature to ensure the oil will be warm enough to mix with refrigerant and prevent _________

A

30F warmer

prevent oil slugging

72
Q

Which is the most expensive; compressor, condenser, evaporator, metering device?

A

compressor

73
Q

______ slugging can damage compressor valves, pistons, scrolls, and vanes

A

liquid

74
Q

All mechanical compressors require two basic elements; ______ oil for lubrication and _____ free vapour refrigerant for cooling

A

clean oil and liquid free vapour refrigerant

75
Q

Name three safety devices that ensure compressors do not run during periods of excessive heat or pressure?

A

internal overloads, external overloads, pressure switches

76
Q

What are some important variables that a safety device may monitor;

A
  • Current draw on compressor motor
  • temp of the discharge line
  • head pressure
  • temp of compressor dome
77
Q

Motors and other current drawing electrical devices require __________ protection

A

overcurrent

78
Q

______ current can damage conductor insulation and lead to a short circuit or a ground fault

A

high current

79
Q

How is overcurrent protection provided?

A

circuit breaker or fuses

80
Q

A ________ overload is a type of diodes or protection device that is mounted to the compressor shell near the compressor motor terminals

A

thermal overload

81
Q

thermal overloads use a bimetal disc that opens and closes a set of electrical contacts based on ________

A

temperature

82
Q

Where are internal overloads located in a compressor?

A

wired into the motor windings at the manufacturer

83
Q

What is a CPR?

A

crankcase pressure regulator

84
Q

what is LRA?

A

locked rotor amperage

85
Q

A ______________ regulator is a valve with an adjustable pressure setting that prevents crankcase pressure from exceeding preset safe value

A

crankcase pressure regulator

86
Q

Where is a discharge pressure switch installed? between the ________ and the __________

A

compressor and the condenser

87
Q

What is a discharge line pressure switch?

A

shuts compressor off if head pressure gets too high

88
Q

Another way to protect against high discharge pressure is a discharge line ________

A

thermostat

89
Q

A _______line ________ senses discharge line temperature and opens on a rise in temperature to turn off the system and protect the compressor

A

discharge line thermostat

90
Q

An accumulator consists of a tank with a reservoir on the bottom for __________ refrigerant and an inlet and outlet on top for the flow of _________ refrigerant

A

liquid refrigerant

vapour refrigerant

91
Q

An ____ separator is a system component that removes oil from high pressure refrigerant vapour as both refrigerant and oil leave the compressor

A

oil

92
Q

An oil separator is placed in the _______ line between the compressor and condenser

A

discharge line

93
Q

An ___ reservoir is a storage vessel that holds an oil supply for a compressor or a group of compressors

A

oil

94
Q

Oil trapped by the _____________ is returned to the oil reservoir until it is needed

A

oil separator

95
Q

An ____ ______ regulator is an oil control device that regulates the level of oil within a compressor using a float mechanism

A

oil level regulator

96
Q

What happens when the float drops in an oil level regulator?

A

oil level is low so the regulator opens to allow oil to flow from the reservoir

97
Q

oil _______ control is a form of control that will shut off electrical power to the compressor of the net oil pressure or oil level drops beeline normal for a certain amount of time

A

safety

98
Q

A __________ absorber is a flexible line of tubing that carries refrigerant but also reduces or dampens any vibration or physical motion

A

vibration

99
Q

Vibration absorbers should be installed in both the _______ line and ________ line as close to the compressor as possible

A

suction line and discharge line

Compressors Exam (9 decks)

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