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Flashcards in Compressed Air System Deck (80):
1

An air compressor is equipped with an intercooler and an after cooler to __________.

increase compressor efficiency and economy

2

For any given volume of compressed air produced by a multistage air compressor, interstage cooling will __________.

decrease the power required for compression

3

The usual method of unloading a low pressure air compressor at start-up is accomplished by __________.

holding the suction valve open

4

The cylinders and intercoolers of most low pressure air compressor's are cooled by __________.

air

5

The unloading system on an air compressor will __________.

allow the motor to turn the compressor opposed only by friction

6

If an air compressor is used to supply air primarily to the combustion control system and other pneumatic controllers, the entire system is known as the __________.

control air system

7

When the compressed air reservoir is placed in line with an air compressor and is used as an after cooler, the reservoir must be __________.

frequently drained of condensed water

8

A viscous film of oil collected between the valve face and seat of a low pressure reciprocating air compressor will __________.

retard the opening and closing of the valve

9

Operating a reciprocating air compressor without an air filter will cause

excessive wear on valves and cylinder liners

10

Carbon deposits forming on the discharge valves of an air compressor are caused by oil deterioration under high pressure. The first step in reducing these deposits would be to __________.

reduce the discharge temperatures with intercoolers

11

Excessively low air pressure occurring in the intercooler of a reciprocating air compressor is caused by __________.

leaky discharge valves on the LP cylinder

12

Leaking valves in an air compressor can be a result of __________.

abrasion, dust, and dirt

13

After coolers are used with air compressors to __________.

reduce the temperature of compressed air

14

The device shown in the illustration GS-0029 is used to __________.

unload the cylinders of an air compressor

15

The air charge leaving an intercooler, or after cooler of an air compressor can be expected to be __________.

at or below the dew point

16

Which of the listed valve types is typically used for suction and discharge valves on modern low pressure air compressors?
A Sliding
B Rotary
C Reed
D Poppet

C Reed

17

In order to distribute the side pressures over a wide area of the cylinder walls and liners, which of the listed types of pistons are used in modern low pressure air compressors?

Trunk

18

Which of the following compressors would be used for a cold-ship start-up of a ship's service diesel generator on a motor ship?
A Ship's service air compressor
B Starting air compressor
C Topping air compressor
D Emergency air compressor

D Emergency air compressor

19

Which of the following compressors on a motor ship would most likely operate at approximately 100 psig?

Ship's service air compressor

20

If an air compressor is fitted with a hand-off-auto (H-O-A) control station, what statement concerning operation is true?

In the hand mode, the compressor will run continuously with unloading.

21

If the drive belts on an air compressor were squealing during startup, you should __________.

check the operation of the unloaders

22

If one drive belt on an air compressor is found to be worn you should __________.

replace all the belts

23

The main bearings of a reciprocating air compressor are tapered roller bearings. When mounted, these bearings are given a 'cold' end clearance to __________.

allow for longitudinal expansion of the crankshaft as the unit warms up

24

After disassembly, the safest way to remove carbon deposits from air compressor inlet and discharge valves is to use __________.

diesel oil

25

When checking the oil level on a reciprocating air compressor fitted with a dipstick, under what conditions should the oil level be checked?

With the compressor in the off mode incapable of starting.

26

As an indication that an air compressor air intake filter needs to be replaced or cleaned, what statement is true?

For a given air demand, the compressor would run for longer periods and the air intake pressure as measured between the filter and the compressor inlet would be more negative than with a clean filter.

27

Which of the following problems would be the probable cause for the faulty operation of a reciprocating air compressor suction valve?

Faulty operation of a cylinder unloader.

28

In a low pressure air compressor, the loss of volumetric efficiency normally results from __________.

heating of the air leaving the cylinders

29

Which of the following causes would most likely result in excessively high belt-driven reciprocating air compressor drive motor running current draw?

Excessive belt tension.

30

If a reciprocating air compressor was operating at a compression ratio that exceeded its design parameters, what would be the effect?

Higher than normal discharge pressure and lower than normal displacement capacity.

31

If a belt-driven reciprocating air compressor is operating at a lower than design displacement capacity (in cubic feet per minute), which of the following would be a cause?

Insufficiently tensioned drive belts.

32

If a reciprocating air compressor has cylinder suction or discharge valves that fail to properly seat, what statement is true concerning the result?

The compressor would have longer running periods at lower displacement capacity between operating cycles.

33

Overall heat transfer processes often involve two or more modes of heat transfer. Specifically, when heat is being transferred from one side of an air compressor cylinder wall to the opposite side, what mode of heat transfer is associated with that particular part of the overall process?

Conduction

34

In addition to the main starting air compressor, another air compressor, driven by a separate power source, is installed to __________.

supply a backup source of starting air

35

Intercoolers installed on starting air compressors, reduce the possibility of __________.

lube oil carbonization

36

The unloading system on an air compressor will __________.

allow the motor to turn the compressor opposed only by friction

37

The air compressor shown in Illustration GS-0119, when used aboard a vessel is typically operated as __________.

a constant capacity unit

38

air compressors are NOT permitted in which space(s) on a tank barge carrying grade A cargo?
A A space in which cargo hose is stored
B A cargo handling room
C An enclosed space containing cargo piping
D All of the above

D All of the above

39

A person may operate an air compressor in which of the following areas on board a tank barge?
A Pump room
B A space adjacent to a cargo tank
C A space two meters from a cargo valve
D Generator room

D Generator room

40

What is the most probable cause of reduced capacity in a reciprocating air compressor?

Leaking air valves

41

A dirty intercooler on an air compressor will cause __________.

an increase in current flow to the motor

42

A squealing sound generated by a reciprocating air compressor upon starting may indicate __________ .

defective unloader

43

A reciprocating air compressor is running roughly and vibrating excessively, indicating that the __________ .

foundation bolts are loose

44

A knocking sound emitted from an unloaded air compressor is probably caused by __________ .

a loose piston

45

A squealing sound occurring from within an operating reciprocating air compressor is an indication of __________ .

tight compressor bearings

46

Air blowing from the intake air filter of an operating air compressor indicates __________ .

broken inlet valves

47

air compressor cylinder unloaders enable the compressor to __________.

start and come up to speed before air compression begins

48

air compressor receivers should be 'blown down' at least __________ .

daily

49

air compressors are equipped with unloading systems for the purpose of __________ .

removing all but the frictional load during starting

50

An air compressor can be unloaded at start-up by __________.

relieving the intercooler pressure to the atmosphere

51

An air compressor is equipped with an intercooler to __________.
I. increase the efficiency of the compressor, and/or
II. reduce the low pressure cylinder designed operating temperature

I only

52

An important point of consideration when replacing a dry type intake filter on an air compressor is to __________ .

select the proper size filter so that air flow is not restricted

53

An unloader is installed on an air compressor to __________.

remove the compression load as the compressor comes up to speed during starting

54

An unloader is installed on an air compressor to __________.

remove all but the frictional load during starting

55

Carbon deposits forming on the discharge valves of an air compressor are caused by oil deterioration under high pressure. The first step in reducing these deposits would be to __________ .

reduce the discharge temperatures with intercoolers

56

Compared to poppet and other mechanically operated valves, which of the following advantages is gained by using a thin plate (feather) low lift type valve in an low pressure air compressor?
A They improve compression efficiency.
B They operate with a minimum of noise.
C They are simple and easy to replace.
D All of the above.

D All of the above.

57

Condensate must be drained from the intercooler and aftercoolers of an air compressor because __________ .

water contamination causes erratic operation of pneumatic components

58

Condensate must be drained periodically from the air compressor receivers to prevent __________ .

faulty operation of pneumatic valves

59

Cylinder inlet valve failure in a low pressure air compressor can be caused by __________ .

mechanical failure in the unloader

60

Differential pistons used in some reciprocating air compressors, serve to provide __________ .

more than one stage of compression by each piston

61

Excessive lube oil consumption by a reciprocating air compressor can be caused by __________ .

carrying the oil level higher than normal

62

Excessive lube oil consumption in a reciprocating air compressor is an indication of __________ .

worn or broken piston rings

63

If a ship service air compressor failed to unload the __________.

belts could slip when starting

64

If a ship service air compressor failed to unload the __________.

circuit breaker may open on starting

65

If an electric motor driven air compressor fails to start, it may be due to a

tripped overload relay

66

If the capacity of a reciprocating air compressor gradually drops off, the cause could be __________ .
A leaking compressor valves
B a clogged air filter
C worn cylinder liners
D all of the above

D all of the above

67

If the intercooler of a low pressure air compressor becomes fouled either internally or externally, the __________ .

volumetric efficiency will be decreased

68

Intercooling of a multistage air compressor provides the advantages of reducing the work of compression on the succeeding stages, and __________ .
A condensing part of the original water vapor content
B reducing the maximum piston loads
C increasing the volumetric efficiency
D all of the above

D all of the above

69

On small, low pressure, air compressors, the cylinders are usually lubricated by the __________ .

splash method

70

One cause of leaky valves in a low pressure air compressor may be attributed to __________ .

excessive operating hours without carrying out preventive maintenance

71

The unloading of an air compressor may be provided by __________.
I. holding the intake valve off of its seat, and/or
II. temporarily relieving the the intercooler to the atmosphere

Both I and II

72

The volumetric efficiency of a reciprocating air compressor, is the ratio of the __________ .

actual amount of air discharged by the compressor, to the theoretical volume swept by the movement of the compressor?

73

One function of the air receiver in a compressed air system is to __________.

minimize the system's line pulsations

74

As demand on the device shown in illustration GS-0119 fluctuates in the pressure range of 100 to 110 psi, the output of the unit is controlled by __________.

the modulation of the opening of a butterfly valve located in the air intake

75

If all of the air charge has been lost from a ship service air receiver, the compressor mechanical unloading system will __________.

fail to function as designed, but the compressor having no load will start with little or no difficulty

76

Which of the routine maintenance procedures listed is required for starting air receivers?

Frequent draining of accumulated moisture.

77

Which of the following problems can occur if you continually fail to drain off condensate from a starting air receiver?

Corrosion and eventual failure of the tank.

78

What is the function of an air receiver in the compressed air system on a MODU?

Acts as an accumulator

79

In addition to a pressure gage and a relief valve, an air receiver should be fitted with a __________ .

drain connection

80

A dirty intercooler on the ship service air compressor will result in __________ .

higher than normal power consumption