Refrigeration Final Flashcards by allison d

If the head pressure of a reciprocating refrigeration compressor is excessive…

a. the relief valve should open before the high pressure cutout.
b. the relief valve should open and allow the excess refrigeration to flow to the receiver.
c. the high pressure cutout switch should operate before the relief valve opens.
d. you should close in on the suction valve.

c. the high pressure cutout switch should operate before the relief valve opens.

How well did you know this?

Not at all

Perfectly

The valve shown in illustration RA-0008 is installed on the suction side of the compressor. Which of the following statements about this valve is correct?

“E” is the inlet.
“D” is the backseat.
The valve is of the packless type.
All of the above.

“E” is the inlet.

Also, “D” is the front seat, “C” is the backseat, “B” is the charging port, and “A” is the cap.

How well did you know this?

Not at all

Perfectly

In preparing to remove the air from a refrigeration condenser for a large multibox water-cooled Type III system, all of the refrigerant in the system should be…

a. at a superheated temperature
b. pumped to the receiver
c. pumped to the evaporator
d. at a saturated temperature

b. pumped to the receiver

How well did you know this?

Not at all

Perfectly

R-12 has been a suitable refrigerant for use in high temperature applications with…

a. reciprocating compressors
b. rotary compressors
c. centrifugal compressors
d. all of the above

d. all of the above

How well did you know this?

Not at all

Perfectly

The temperature in a refrigerated space is controlled by adjusting the thermostat connected to the…

a. suction line solenoid
b. thermostatic expansion valve
c. liquid line solenoid
d. low pressure cutout switch

c. liquid line solenoid

How well did you know this?

Not at all

Perfectly

When replacing a thermostatic expansion valve sensing bulb, it is necessary to…

a. apply a light film of oil to increase heat transfer.
b. apply a light film of oil to prevent oxidation.
c. apply a heavy coating of grease to function as a heat sink.
d. carefully coat the device with silicone sealant to reduce the effects of convective cooling.

b. apply a light film of oil to prevent oxidation.

How well did you know this?

Not at all

Perfectly

High suction pressure to a refrigeration system compressor is caused by…

a. the expansion valve being insufficiently opened.
b. the expansion valve being open too wide.
c. the king valve being insufficiently opened.
d. a dirty dehydrator.

b. the expansion valve being open too wide.

How well did you know this?

Not at all

Perfectly

When a thermostatic expansion valve is installed in a container refrigeration system, the sensing bulb may not require insulation if the bulb is installed…

a. outside of the cooled air stream
b. in the cooled air stream
c. on the tail end of the condenser outlet
d. at the mid-horizontal level of a vertically run tail coil.

b. in the cooled air stream

How well did you know this?

Not at all

Perfectly

To correct the condition of slugging and flooding back in a refrigeration system, it may be necessary to…

a. readjust the discharge
b. pressure clean the expansion valve screen
c. add refrigerant
d. adjust the expansion valve

d. adjust the expansion valve

How well did you know this?

Not at all

Perfectly

The oil separator (oil trap) used in a large shipboard refrigeration system would be located between the…

a. compressor discharge valve and the condenser.
b. condenser and the receiver.
c. receiver and the king valve.
d. receiver and the expansion valve.

a. compressor discharge valve and the condenser.

How well did you know this?

Not at all

Perfectly

The heat required to change a substance from a solid to a liquid while at its freezing temperature is know as the latent heat of…

fusion

How well did you know this?

Not at all

Perfectly

Which statement about calibrating a newly installed thermostatic expansion valve is correct?

a. The procedure requires a refrigeration wrench and a digital thermometer to measure box temperature.
b. No special tools are required as long as the solid state circuit control panels are functioning properly.
c. The procedure is done at the factory with tools not available to a mariner.
d. An accurate thermometer and suction pressure gauge are essential to this process.

d. An accurate thermometer and suction pressure gauge are essential to this process.

How well did you know this?

Not at all

Perfectly

Refrigerant recovery cylinders are color coded…

yellow top and gray body

How well did you know this?

Not at all

Perfectly

How does a refrigeration solenoid valve differ from a modulating valve?

A liquid line solenoid valve is either COMPLETELY OPEN OR COMPLETELY CLOSED, whereas a modulation valve is positioned according to the strength of the applied electrical signal.

How well did you know this?

Not at all

Perfectly

A multiple evaporator coil unit is equipped with an evaporator back pressure regulating valve. This valve must be bypassed when pumping down the system for repairs because reduction of suction pressure would cause the valve to…

a. rupture
b. open
c. close
d. chatter

c. close

How well did you know this?

Not at all

Perfectly

Which can be considered as a drop-in replacement refrigerant?

No refrigerant could be considered a drop-in replacement since all require a lube oil change out and replacement with a different type of lube oil.

How well did you know this?

Not at all

Perfectly

If an evaporator or condenser coil of a container refrigeration system becomes dirty and requires cleaning, one of the suggested methods is the use a…

a. Binks gun with weak acid solvent
b. pressure wash or steam cleaning system
c. copper wire rotary brush
d. all of the above

b. pressure wash or steam cleaning system

How well did you know this?

Not at all

Perfectly

If a refrigeration system is overcharged with refrigerant, one result will be…

a. low suction pressure
b. higher than normal compressor head pressure
c. increased system operating efficiency
d. short cycling on the low pressure cutout

b. higher than normal compressor head pressure

How well did you know this?

Not at all

Perfectly

Each pressure vessel containing refrigerants which may be isolated shall be…

a. subject to annual hydrostatic tests to be performed in the presence of a marine inspector.
b. protected by a relief valve set to relieve at a pressure not exceeding 110% of the maximum allowable working pressure.
c. stored in an upright position in addition to being secured so as to prevent accidental release of the refrigerant within a confined space.
d. protected by a relief valve set to relieve at a pressure not exceeding the maximum allowable working pressure.

d. protected by a relief valve set to relieve at a pressure not exceeding the maximum allowable working pressure.

How well did you know this?

Not at all

Perfectly

When securing an oxyacetylene cutting outfit for an extended period, you should…

a. close the hand valves on the torch only
b. close the cylinder valves only
c. close the cylinder valves and torch valves with 4 to 5 pounds of pressure in the hoses.
d. close the cylinder valves and torch valves when pressure in the hoses and regulators is zero.

d. close the cylinder valves and torch valves when pressure in the hoses and regulators is zero.

How well did you know this?

Not at all

Perfectly

If the suction line between the evaporator and compressor is frosting up, the cause may be due to the thermal expansion valve…

a. thermal bulb coming loose from the suction line
b. needle valve being stuck closed
c. thermal bulb being in a cold air stream
d. all of the above

a. thermal bulb coming loose from the suction line

How well did you know this?

Not at all

Perfectly

A purge recovery system is used in a centrifugal air conditioning or refrigeration system to…

Purge non-condensable gases without losing refrigerant

How well did you know this?

Not at all

Perfectly

Where would you find the greatest amount of refrigerant superheat in an operating refrigeration system?

The compressor discharge

How well did you know this?

Not at all

Perfectly

If the discharge valves on a refrigeration compressor are leaking badly, the compressor will…

run continuously

How well did you know this?

Not at all

Perfectly

When welding with an oxyacetylene outfit... a. open the acetylene valve until the hose pressure is 26 psig. b. open the acetylene cylinder valve only 1/4 to 1/2 turn and leave the wrench on the valve stem. c. a leaking hose must be repaired by binding with tape. d. a flashback of flame into the hose is normal.

b. open the acetylene cylinder valve only 1/4 to 1/2 turn and leave the wrench on the valve stem.

R-12 is generally considered to be a safe, nontoxic, nonflammable and nonexplosive refrigerant. It can, however, become highly toxic when...

in contact with an open flame.

People familiar with ammonia refrigeration systems become accustomed to its odor and may forget that the vapors... a. in a low concentration can cause death. b. will dissolve in perspiration and cause caustic burns. c. will burn or explode. d. all of the above.

d. all of the above.

Noise in a refrigeration compressor can be caused by... a. worn bearings and piston pins. b. slugging due to flooding back. c. too much oil in circulation. d. all of the above

d. all of the above.

If a refrigeration compressor is short cycling on high head pressure, you should... a. purge the condenser if the waterside is dirty. b. check for proper water flow through the condenser. c. increase the high pressure cutout setting. d. reduce the cooling water flow.

b. check for proper water flow through the condenser.

Which of the following refrigerants will normally require water-cooled compressor components? a. R-134 b. Ammonia c. R-22 d. all of the above

b. Ammonia

Refrigeration system compressor crankcase sweating is an indication of... a. insufficient lube oil circulating through the system. b. excessive circulation of lube oil through the system. c. insufficient refrigerant in the system d. overworked compressor

b. excessive circulation of lube oil through the system.

Which of the listed statements is a characteristic of the liquid charged power element used with thermostatic expansion valves? a. at the designed operating temperature, the liquid refrigerant charge has changed to a vapor. b. the liquid refrigerant tends to collect at the bellows or diaphragm and reduces the valve sensitivity. c. the sensing bulb is empty of liquid refrigerant charge at the designed operating temperature. d. the sensing bulb is never emptied of liquid refrigerant under normal operating conditions.

d. the sensing bulb is NEVER emptied of liquid refrigerant under normal operating conditions.

Moisture is removed from CFC-12 using a recycler by what means?

a dehydrator cartridge

All refrigerant recovered from burned out small appliances must be...

sent to a designed reclamation facility for processing.

Refrigerant leaving the metering device in a refrigeration system is in what state? a. sub-cooled liquid b. sub-cooled vapor c. saturated liquid/vapor mixture d. saturated liquid

saturated liquid/vapor mixture

if your skin comes in contact with liquid ammonia refrigerant, you should immediately...

flush the affected area with water.

When hot-gas defrosting a refrigeration system, one way to overcome the possibility of a large slug of liquid refrigerant entering the compressor suction is to use the installed... a. sub-cooler b. liquid extractors c. re-evaporator d. drain lines

c. re-evaporator

If a liquid line strainer (such as the one in illustration RA-0010) becomes clogged to the extent that it should be cleaned, this will be indicated by...

loss of refrigeration effect in the space being cooled.

An excessive charge of refrigerant in an air-cooled refrigeration system can cause... a. oil foaming in the compressor. b. higher than normal suction and discharge pressures with a higher box temperature. c. higher than normal discharge pressure with a normal box temperature. d. the compressor to run continuously.

c. higher than normal discharge pressure with a normal box temperature.

To correct the condition of slugging and flooding back in a refrigeration system, it may be necessary to... a. readjust the discharge pressure b. clean the expansion valve screen c. add refrigerant d. adjust the expansion valve

d. adjust the expansion valve

Industrial process and commercial CFC-type refrigeration equipment with annual leak rates of 35% or more require leak repair of the system if it contains a refrigerant charge of more than...

50 pounds

Which refrigerant is considered as a suitable replacement for R-11?

R-123

Compared with CFC-11, CFC-12 and HFC-134a, HCFC-22 operates at the... [highest/lowest] system pressure with the [highest/lowest] boiling point.

highest system pressure with the lowest boiling point.

If a refrigeration compressor crankcase is sweating, the trouble could be caused by... a. excessive superheat b. a minor amount of air in the system c. normal oil circulation with the refrigerant d. the expansion valve being stuck open

d. the expansion valve being stuck in the open position

What copper alloy is commonly used in heat exchangers and possesses a high resistance to corrosion?

Cupro-nickel

In a refrigeration system, the condenser cooling water regulating valve is directly controlled by the...

compressor discharge pressure

When taking readings at the suction service valve of an operating refrigeration compressor, what readings are required and why?

The pressure and temperature readings are both required as the refrigerant at the compressor suction is superheated.

The chemical formula for ozone is represented as...

Technicians servicing small refrigeration appliances can employ what type of recovery equipment? [Active/passive/either]

Either active or passive

Which of the valves listed should be closed when adding ammonia to a refrigeration system? a. master valve b. suction valve c. discharge valve d. king valve

d. KING valve

When air contains the maximum amount of moisture for a given temperature, the air is said to be...

saturated.

Overfilling a refrigerant container is extremely dangerous because of the high pressures generated by the...

hydrostatic pressure of the expanding liquid.

On ships equipped with refrigeration units of 20+ cubic feet... a. a gas mask or SCBA must be provided. b. it is the sole responsibility of the chief engineer to familiarize all crew with the use of gas masks and SCBAs. c. spare charges shall be carried for at least 50% of each size and variety of gas mask and SCBA. d. all of the above

a. a gas mask or SCBA must be provided.

In a refrigeration system, the component installed downstream of the thermal expansion valve is the...

evaporator.

If the temperature of ammonia gas in the discharge piping and condenser of a refrigeration system remains above 266*F, the vapor will...

cease to condense.

One function of the thermal expansion valve is to regulate...

the amount of refrigerant flow to the evaporator coil.

The compressor is a water-cooled refrigeration system is short cycling on the high pressure cutout switch. One reason could be... a. system is low on refrigerant. b. high pressure cutout switch is improperly adjusted. c. discharge valves are leaking slightly. d. discharge valves are leaking excessively.

b. high pressure cutout switch is improperly adjusted.

The compressor in an air-cooled condensing refrigeration system is short cycling on the high pressure cutout switch. One reason could be... a. system is overcharged with refrigerant. b. system is low on refrigerant. c. discharge valves are leaking slightly. d. discharge valves are leaking excessively.

a. system is overcharged with refrigerant.

Which of the following statements is true concerning Illustration RA-0001?

Gauge #7 would be classified as a compound gauge (pressure and vacuum), which would usually be colored blue.

The FIRST thing to do to ensure that a refrigeration unit will not start while undergoing repairs is to...

secure and tag the electrical circuit. Lock out - tag out.

A sight glass is installed in the liquid line to indicate the condition of the refrigerant charge and may also indicate...

moisture in the system.

The process of removing refrigerant from a system and storing it without testing or processing is known as...

recovering.

A refrigerant with oil in solution has... a. higher boiling temperature for a given pressure than does a pure refrigerant b. lower boiling temperature for a given pressure than does a pure refrigerant. c. boiling pressure equal to that of a pure refrigerant at a given pressure. d. no effect on boiling point.

a. higher boiling temperature for a given pressure than does a pure refrigerant

A small obstruction at the thermostatic expansion valve inlet will result in what condition?

suction pressure fluctuations

Under normal conditions, ammonia refrigerants should be added at the...

high side of the system.

A refrigeration system is equipped with a reciprocating compressor and a water-cooled condensing unit. If the system is overcharged, the resulting high head pressure will be caused by...

refrigerant flooding the condenser.

The thermostatically-controlled solenoid valve in the liquid line is operated in response to the...

temperature of the box.

The receiver used in a refrigeration system serves what function?

Storing liquid refrigerant

Which piping material is recommended to be used in extra heavy duty sizes in ammonia refrigeration system construction?

Steel

To service a 60-ton air conditioning package, the easiest way to determine the type of refrigerant used is to...

look at the unit name plate.

The watch engineer finds the cargo refrigeration compressor has blown the shaft seal. In this situation, they should...

secure the compressor at once and close the suction and discharge valves.

Expansion valve maintenance should include which of the following procedures? a. cleaning of in-line filters. b. ensuring that the thermal bulb is in good contact with the suction line. c. checking that the thermal bulb is in the proper location. d. all of the above.

d. all of the above.

Moisture in the refrigerant may... a. freeze on the expansion valve seat and reduce the flow of liquid refrigerant. b. emulsify the oil in the condenser. c. freeze in the king valve. d. clog the oil trap.

a. freeze on the expansion valve seat and reduce the flow of liquid refrigerant.

The rate of heat transfer from a hot region to a cold region is affected most by the...

temperature difference between the regions.

An acetylene pressure regulator should never be adjusted to maintain pressures exceeding 15 psig because...

the gas becomes extremely unstable under this condition.

If the head pressure of a reciprocating refrigeration compressor is excessive...

the high pressure cutout switch should operated before the relief valve opens.

Which of the following statements represents the last step to be followed when replacing the power element of the device shown in Illustration RA-0007? a. replace all removed shrouding b. calibrate sensing bulb c. measure evaporator tail coil superheat d. remove all excess capillary tubing

c. measure evaporator tail coil superheat

If you know that a refrigeration system is leaking refrigerant, you would first...

look for traces of oil.

When checking the oil level in a refrigeration compressor, the most accurate reading is obtained...

after shutdown following a prolonged period of operation.

What is the best accepted method for testing a thermostatic expansion valve?

Place the sensing bulb in ice water and then warm by hand. Observe flood-through and temperature change at the suction line.

A compound gauge is used to measure...

pressure and vacuum.

When opening or closing compressor service and line valves on a typical refrigeration system, you must first remove the...

seal cap.

In a refrigeration system, a shortage of refrigerant is indicated by...

bubbles in the sight glass.

If the thermostatic expansion valve fails, what will occur?

The valve will move toward the closed position. (It will fail closed thereby shutting off flow to the system.)

You run tests to discover why a compressor is running excessively. The refrigerated space temperature is normal, the suction pressure is slightly above normal, and the head pressure is low. What do you suspect?

Leaking door gaskets.

In a refrigeration system, the amount of refrigerant admitted to the evaporator is directly related to...

The superheat of the refrigerant in the tail coil (where the TXV sensing bulb is located).

Overcharging an air-cooled refrigeration system will cause the compressor to...

short cycle.

Foaming of the oil in a compressor crankcase is caused by...

refrigerant boiling out of solution from the lube oil.

Air trapped in a refrigeration system using a water-cooled condenser is usually indicated by...

usually high head pressure (when compared to the existing temperature of the liquid refrigerant).

Ammonia is lighter than air and if a leak should occur its concentration will be...

of minimum importance during venting procedures.

Constant superheat is maintained at the evaporator outlet of a refrigeration coil by a...

thermal expansion valve (sensing bulb).

When using a gauge manifold to add refrigerant to a system, which hose connection should be connected to the refrigerant cylinder?

The center (yellow) one.

When recovering R-12 from a small appliance with a working compressor, using a recovery device manufactured after 1993, what percentage of the remaining charge must be removed from the system?

90%

The water regulating valve installed in a refrigeration system is operated by the...

compressor discharge pressure

During the operation of a large, multi-box refrigeration system using a fixed capacity compressor, only two of the five boxes are in the process of actively being cooled. If two additional boxes were to be brought into the cooling process simultaneously, what would happen to the low side pressure?

Low side pressure would temporarily increase.

If an expansion valve is adjusted for too low a superheat value, what might happen?

Too much liquid would be passed back to the compressor.

Alkylbenzene ISO 32 cSt refrigerant oil is miscible and suitable to use with which refrigerant?

R-22

An increasing head pressure, without any corresponding change in the cooling water inlet temperature, would probably be caused by...

air and non-condensable gases in the condenser.

What device is the safest to use when locating ammonia leaks?

litmus paper

The refrigeration piping component shown in Illustration RA-0002 is primarily used to...

reduce noise and vibration from traveling along piping which could ultimately damage the distant down steam equipment.

A compound gauge is typically installed on the...

suction side of the compressor. | Pressure-vacuum

The transfer of heat within a solid, caused by the application of thermal energy, is called...

conduction.

An important consideration in selecting a lubricating oil for use in a refrigeration compressor is for the oil to have what quality?

Have a low pour point. | It will still flow at lower temps.

What device indicates the proper operation of a refrigeration system dryer?

Moisture indicator

In a refrigeration system, the heat normally producing the flash gas at the thermostatic expansion valve is obtained from...

the portion of liquid refrigerant which does not flash.

The thermal expansion valve reacts directly to the temperature of the...

evaporator coil outlet.

If you find an extremely large refrigerant leak while using a halide torch, your flame will...

probably go out.

Excessive oil foaming in the crankcase of a refrigeration compressor can result in overheated...

compressor bearings.

The valve shown in Illustration RA-0007 is used to control what?

Superheat at the coil outlet

Refrigerants referred to as CFC's are... a. fully halogenated b. partially hydrogenated c. fully carbonated d. completely filled with hydrogen atoms

a. fully halogenated!

When liquid reaches the compressor of a refrigeration system through the suction line, the condition is called...

flooding back, or slugging.

An obstructed expansion valve may be indicated by an incompletely cooled evaporator and ______ at the evaporator inlet.

frosting.

What chemical symbol represents ammonia?

NH3

Disposable refrigerant cylinders may contain a maximum amount of refrigerant of ___ pounds.

Inhalation of high concentrations of CFCs may have which of the following effects? a. drowsiness b. loss of concentration c. cardiac arrhythmia d. all of the above

d. all of the above

The safety heads of most large reciprocating compressors used in refrigeration systems are held in place by...

heavy coil springs.

Persons recovering refrigerant from small appliances must be certified as a...

Type I or Universal technician.

Which of the following is not part of the high side of a refrigeration system? a. condenser b. receiver c. accumulator d. liquid line

c. accumulator | Located on the low side, after the evaporator outlet.

HCFC-123 presents health threats to service technicians, which may include its... a. flammability as a liquid b. freezing in the compressor c. toxic threat d. being caustic and strong offensive odor

c. toxic threat

In Illustration RA-0005, the liquid line strainer is located between the...

receiver and solenoid valve only.

Latent heat can be define as the heat which must be added to a substance in order for it to change ______.

phase. Solid to liquid, liquid to vapor, etc.

To add refrigerant to the low side of an air conditioning system, the refrigerant should be introduced through the [suction/discharge] service valve as a [liquid/vapor].

suction service valve as a vapor.

The temperature of the refrigerant in the evaporator coil depends mostly upon the ______ in the _______.

refrigerant pressure in the evaporator.

All refrigeration systems must be protected with a.... a. high pressure cutout b. refrigerant receiver c. pressure relief device d. low pressure cutout

a. high pressure cutout

In a multi-evaporator refrigeration system, a solenoid valve is installed in the liquid line before...

each expansion valve.

The refrigeration system low pressure cutout switch is actuated by...

pressure changes in the suction line.

The heat identified by only a change in temperature is known as ______ heat.

sensible

The compressor is short cycling on high head pressure when the sea water cooling temperature is 72*F. In this situation, you should... a. check for sufficient cooling water flow through the condenser. b. purge non-condensable gases from the receiver. c. reset the thermostatic expansion valve. d. completely purge the high pressure side of the system.

a. check for sufficient cooling water flow through the condenser.

If a compressor were short cycling on the low pressure cutout switch, the probable cause for this might be the... a. system was overcharged with refrigerant b. high pressure switch was improperly adjusted c. expansion valve strainers were fouled d. suction valves were leaking slightly

c. expansion valve strainers were fouled

When it becomes necessary to repair a refrigeration system using R-134a and the system will be open for more than a few minutes, the open ends of the system should be...

plugged.

If the suction pressure for an operating refrigeration compressor is below normal, the cause may be... a. an excess of liquid refrigerant b. the expansion valve overfeeding c. a fouled compressor suction strainer d. the compressor short cycling

c. a fouled compressor suction strainer

Which refrigerant is an interim retrofit replacement for R-11?

R-123

Rather than design an infinite variety of valve sizes for use as thermostatic expansion valves, some manufacturers use...

internal restrictors of different sizes.

Soft solders have relatively low melting points and consist mainly of...

lead-based alloys.

When a compressor motor fails to start, the FIRST thing that should be checked for is a...

blown fuse in the motor circuit.

Ammonia, when used as a refrigerant, is valuable because of its high efficiency. However, it is... a. toxic b. flammable c. explosive d. all of the above

d. all of the above

Excessive oil foaming in the crankcase of a refrigeration compressor is most likely to occur when the compressor...

states after a long idle period.

Short cycling of a refrigeration compressor refers to...

frequently starting and stopping.

Which method of heat transfer takes place when two substances of different temperatures are in physical contact with each other?

Conduction

The pressure in a high pressure refrigeration system about to be opened for repair should be...

0 psia.

Standard driers used in many container type refrigeration systems may contain ______ or silica gel.

activated alumina

When the relief valve opens on a refrigeration compressor discharge line, it discharges high pressure refrigerant vapor to the...

suction side of the compressor. | It loops back.

When using the test set up shown in Illustration RA-0004 to find a leak in an evaporator coil, it is important to remember that...

the refrigerant is heavier than air and will be detected below the leak.

Some refrigeration systems have chemical moisture indicators installed in conjunction with the sight glass in the liquid line. If excess moisture is present in the system, the indicator will...

change color.

A constant hissing sound at the thermal expansion valve will always indicate...

a lack of refrigerant.

Oil separators installed in refrigeration systems serve to...

return oil entrained in refrigerant vapor back to the compressor crankcase.

In an oxyacetylene welding outfit, each cylinder has a regulator and two pressure gauges. One pressure gauge indicates cylinder pressure and the other gauge is used to indicate...

hose pressure.

Leaking suction valves in a refrigeration compressor (internal leak) are indicated by...

higher than normal suction pressure.

Tubing is sized by...

outside diameter.

Refrigeration Final Flashcards

(149 cards)