Deck 8: Leak Detection, System Evacuation and System Clean-Up

Question 1

Moisture in a liquid state must be ____ before it can be removed with a vacuum pump.

A) vaporized
B) condensed
C) cooled
D) solidified

Answer 1

A

Question 2

When using a "standing pressure test" for leak-checking, ____________________ should never be used since an explosive mixture can be created.

Answer 2

air

Question 3

The oil in a vacuum pump should be changed after each time it is used.

Answer 3

True

Question 4

Noncondensable gases ____.

A) are desirable in a refrigeration system
B) are undesirable in a refrigeration system
C) condense readily under normal atmospheric conditions
D) help in pulling a vacuum

Question 5

Only two substances should be in the refrigeration system for proper operation. They are ____________________ and oil.

Question 6

A compound gauge ____.

A) indicates pressures above 14.696 psia
B) indicates pressures in inches Hg below atmospheric pressure
C) is one of two gauges on a typical gauge manifold
D) All of the above.

Question 7

Air entering a refrigerant system can eventually lead to compressor failure.

Question 8

At what pressure range does the technician valve off the vacuum pump when evacuating to a deep vacuum?

A) 200 to 100 microns.
B) 300 to 100 microns.
C) 300 to 200 microns.
D) 500 to 300 microns.

Question 9

Clearance tolerances are such that the ordinary clean refrigerant oil can be used satisfactorily in a vacuum pump.

Question 10

A micron gauge is used to measure ____.

A) atmospheric pressures at high altitudes
B) atmospheric pressures at sea level
C) absolute pressures below 1 mm Hg
D) high pressure in a refrigeration system

Question 11

The best method of leak checking is when the refrigeration system is ____.

A) in a vacuum
B) open to the atmosphere
C) operating with all fans activated
D) standing with dry nitrogen pressure of 150 psig in the system

Question 12

To pull a vacuum means to ____.

A) raise the pressure in a refrigeration system
B) lower the pressure in a refrigeration system below atmospheric
C) allow refrigerant to escape into the atmosphere
D) condense the gas in the system

Question 13

Which of the following represents the lowest vacuum?

A) 10 psia.
B) 5 in. Hg vacuum.
C) 5 psig.
D) 1000 microns.

Question 14

When moisture is present in a refrigeration system, it will react with the refrigerant and the oil to form ____.

A) carbon dioxide
B) acid
C) carbon monoxide
D) carbolic acid

Question 15

Sludge is produced when moisture, acid, and ____________________ are present in the system.

Question 16

The maximum recommended pressure for leak testing is 150 psig on the low-pressure side of the system.

Question 17

To insure accurate testing, the best material to use for connecting lines to the vacuum pump and gauge set is ____.

A) light flexible hose
B) heavy duty rubber gauge line
C) copper tube
D) garden hose

Question 18

While under a deep vacuum, any liquid water under the oil in the motor-compressor assembly can be removed by operating the compressor motor for several seconds without any adverse effect on the system.

Question 19

A multiple evacuation means that ____.

A) you connect three vacuum pumps simultaneously to a refrigeration system and pull a vacuum
B) you pull a vacuum on three different systems at the same time
C) you pull a vacuum on a refrigeration system more than once, allowing refrigerant or nitrogen into the system between each procedure
D) there must be more than one system operating before a vacuum can be pulled

Question 20

After repairing a system that has had an electrical motor failure (compressor burnout), it is good field practice to re-use the recovered refrigerant in that system.

Question 21

Why is refrigerant not used for a system standing pressure test?

Question 22

The electronic vacuum gage is attached to the system so it can measure the pressure ____________________ the system.

Question 23

A(n) ____________________ pressure could also mean refrigerant vapor is still seeping from the refrigeration system.

Question 24

A pressure of 100 microns has been reached with the vacuum pump operating. The pump is turned off and the gauge reading rises to 5,000 microns and stays there. What does this indicate?

Question 25

A pressure of 100 microns has been reached with the vacuum pump operating. The pump is turned off and the gauge reading rises to 500 microns and stays there. What does this indicate?

Question 26

A pressure of 100 microns has been reached with the vacuum pump operating. The pump is turned off and the gauge reading rises above 5,000 microns and keeps rising. What does this indicate?

Question 27

A deep vacuum involves reducing the pressure in a refrigeration system to a micron gauge reading of ____________________ or below.

Question 28

There are ____________________ microns in 1 mm Hg.

Question 29

Why is nitrogen considered a "noncondensable" gas?

Question 30

Micron gauge displays can be electronic analog, digital, or  ____________________.

Question 31

Explain why triple evacuations are not normally performed on large systems.

Question 32

Why is it a good idea to remove Schrader stems from service valves prior to evacuation?

Question 33

Why must all valves be opened when an evacuation is performed?