AC&R
who approval is required for the use of self-contained air conditioning units?
NAVSEA
after completing the dehydration stage of moisture evacuation, what is used to remove the remaining moisture from the refrigeration system?
a vacuum pump
when you are renewing a leaky crankshaft seal, for which of the following reasons should you NOT attempt to pump the refrigerant out of the compressor?
air will be drawn into the compressor, causing the expansion valves to freeze
when you are evacuating and dehydrating a refrigeration system, as soon as the vacuum indicator shows 0.2-inch mercury absolute, where should you admit dry air through a chemical dehydrator?
at a point farthest from the pump
the high-speed compressor of multicylinder, reciprocating design found frequently on today's modern ships has its output controlled in which of the following ways?
automatically, by loading and unloading the cylinders only
to be properly reactivated, dehydrating agents should be heated (a) to what specific temperature and (b) for what length of time
(a) 300 degrees F (b) 12 hours
when you are installing a shaft seal, which of the following safety precautions should you observe?
-do not touch the bearing surface with your hand -rinse the seal in an approved cleaning solvent -dip the new seal in clean refrigerant oil just prior to installation
crankshaft seal failure on reciprocating compressors in a refrigeration system may be caused by which of the following factors?
-faulty lubrication -moisture -dirt or foreign material
the refrigerant water regulating valve is set to maintain what system discharge pressure?
125psig
refrigerant bottles should never be exposed to what maximum temperature
130 degrees F
the water failure switch should be set to cut in at what pressure, in pounds per square inch gauge?
15
high speed centrifugal refrigerant compressors operate at what speed?
1500rpms
when using a dehydrator to move moisture during system evacuation the air should be heated to what temperature?
240 degrees F
cooling coils should be defrosted before the frost reaches what maximum thickness?
3/16
what is the best overall range of relative humidity for human comfort and health?
30% to 70%
when reactivating the dehydrator drying agent it is heated for 12 hours at what temperature?
300 degrees F
refrigerant TXV valves are set to maintain a superheater range of what?
4 - 12 degrees F at cooling coil outlet
what relative humidity range is best for health conditions during cold weather?
40% to 50%
what relative humidity range is best for health conditions during warm weather?
50% to 60%
what NSTM contains information pertaining to refrigeration?
516
what is the operating range, in pounds per square inch gauge, of a high pressure switch?
60 to 350
before handling refrigerant bottles you should read what NSTM?
670
under normal operating conditions, how full should the receiver of a properly charged refrigeration system be when the compressor stops?
85%
what is the operating differential range, in pounds per square inch gauge, of the low pressure switch?
9 to 30
what is the ordinary average body temperature of a person
98.6 degrees F
which of the following laws state that the volume of any dry gas varies inversely with its absolute pressure, provided the temperature remains constant?
Boyle's law
aboard navy ships, which of the following fans are used primarily to exhaust explosive or hot gasses?
centrifugal
what type of fan is used primarily to exhaust explosive or hot gases?
centrifugal
which of the following is the purpose of the collection tray on the spot cooler?
collects the moisture condensed out of the air
what component is a refrigeration system is essentially a pump?
compressor
what type of heat gain comes from objects with which the body comes in contact?
conduction
what type of heat gain comes only from currents of heated air?
convection
refrigerant piping in modern naval installations is made of what material?
copper
what condition is the first indication of a shaft seal failure?
excessive oil leaking at the shaft
in a centrifugal refrigeration plant, what valve releases the refrigerant to the chiller?
float
what type of lube oil system is found on a high speed refrigerant compressors?
force-feed lubricating type
what can cause reduced cooling capacity, low compressor suction pressure, and a tendency for the compressor to short cycle?
frost on cooling coils
what unit of measurement is used for absolute humidity?
grains
when installing a new refrigerant shaft seal, care should be taken to never do what?
handle the seal with yout fingers, surgical gloves should be used for seal installation
what term best describes the vapor content of the atmosphere?
humidity
which of the following is a true statement regarding r-134a refrigerant?
if r-134a concentration becomes excessive, unconsciousness or even death bay result
in a space where refrigerant may be present in the atmosphere, for which of the following reasons should you leave the space immediately?
if you smell something unusual if you experience shortness of breath if you feel light-headed
the purge valve at the top of the condenser in a refrigeration system serves which of the following purposes?
it removes any air that may accumulate in the system
what type of heat is absorbed or given off by a substance while it is changing its physical state?
latent
what component is also known as a suction pressure control switch?
low pressure cutout switch
although the navy's air conditioning and refrigeration school teaches maintenance procedures, you should also refer to which of the following documents for details of the particular plants aboard your ship?
manufacturer's technical manual
what component contains a chemically treated element that changes color when there is an increase of moisture in the refrigerant?
moisture indicator
what item has a chemically treated element that changes color when there is an increase of moisture in the refrigerant?
moisture indicator
refrigerant usage logs must be reviewed at what frequency?
monthly
what switch is provided with high-speed compressors?
oil failure
what is the first indication of refrigerant shaft seal failure?
oil leakage
which of the following conditions is an early indication of crankshaft seal failure?
oil leaking at the shaft in large amounts
what actuates the compressor capacity control valve?
oil pressure
what is your body continuous source of heat?
oxidation of foodstuffs and other chemical processes
what color shows excessive moisture of water damage to the moisture indictor element and that is must be replaced?
pink
what type of fan is used aboard ships for ventilating holds and cofferdams?
portable
which of the following refrigerants are used in centrifugal vapor compression units?
r-114 or r-11
what refrigerant is tetrafluoroethane (C2H2F4)?
r-134a
which of the following is a type of refrigerant is used by the navy?
r-134a
what component acts as a temporary storage space and surge tank for the liquid refrigerant?
receiver
what component acts as temporary storage space and surge tank for the liquid refrigerant?
receiver
what unit of measure is used for the amount of heat removed?
refrigeration ton
what term best describes when air contains the maximum amount of moisture that is can hold at a specific temperature and pressure?
saturation
testing of refrigerant system for leaks is accomplished IAW PMS at what periodicity?
semi-annually
what type of heat is absorbed or given off by a substance that is NOT in the process of changing its physical state?
sensible
what component helps prevent damage to the compressor from foreign matter
strainer
what component is used to avoid damage to the compressor from foreign matter?
strainer
during plant operation, which of the following symptoms will indicate a clogged refrigerant liquid line strainer?
temperature of the tubing on the inlet side of the strainer will be much warmer than the tubing on the outlet side
the term frosting back means what?
the appearance of frost on the suction line extending as far back as the compressor
the compressor capacity control valve is located were?
the compressor crankcase cover
if the TXV is misadjusted and gives an excessive temperature range, what detrimental effect will occur?
the cooling-coil will become starved and will operate at reduced efficiency
what is the load on the air conditioning plant determined by?
the desired chill water temperature
the refrigerant liquid strainer is designed to protect what?
the solenoid valves and TXV
what action must be taken if the refrigerant compressor indicates a temperature of the liquid leaving the receiver is more than 5 degrees F lower than the temperature corresponding to the discharge pressure?
the system must be purged
which of the following is a definition of the term dewpoint of air?
the temperature at which the air is saturated with moisture
when the thermostatic valve is operating properly, how does the temperature at the outlet side of the valve compare with the temperature at the inlet side?
the temperature is much lower at the outlet side only
what controls the capacity of refrigerant compressor?
the unloading and loading of the cylinders
what procedure is used to remove moisture remaining in a refrigeration system after preliminary dehydration?
the vacuum pump suction line is connected to the charging connection, the system is closed to the atmosphere, and the charging connection is open to the vacuum pump
what component regulates the a mount of refrigerant to the cooling coil?
thermostatic expansion valve (TXV)
what component regulates the amount of refrigerant to the cooling coil?
thermostatic expansion valve (TXV)
in the duct system of navy ships, axial-flow fans are used instead of centrifugal fans for what reason?
they require less installation space
in testing condenser tube for leakage, why should you hold the exploring tube of the leak detector at one end of each condenser tube for about 10 seconds before driving a cork into each end of the tube?
to draw fresh air through the tube
what is the purpose of refrigeration?
to maintain spaces at low temperatures
liquid refrigerant may flood from the evaporator back to the compressor if the thermostatic expansion valve is adjusted in what manner?
too low a degree of superheat
what type of fan is low-pressure and usually installed without duct work?
tube-axial
when refrigerant is being charged into a refrigeration system, what total number of persons must be present?
two
what types of fans are high-pressure fans, and generally installed in duct system?
vane-axial
the lithium bromide unit operates on the absorption cycle. what is used as the primary refrigerant?
water
what switch stops the compressor in the event of failure of the circulating water supply?
water failure
what component controls the quantity of circulating water flowing through the refrigerant condenser?
water regulating valve
excess water accumulated in heavy seas is automatically sealed out of waterproof ventilators by what means?
weight of the water in the bucket
when the exterior surfaces of the tubes and fins on an air cooled condenser become dirty and restrict air circulation, the finned surfaces should be cleaned by which of the following methods?
with a stiff-bristled brush
when checking compressor suction valves for proper operation, what is an indication that they are working satisfactorily?
with the line stop valve shut the compressor can hold a minimum of 20 inches of vacuum
why are refrigerants considered to be deadly?
because of halocarbons
what types of fans are used in hot weather to provide local circulation?
bracket
if you do not have a tank-type cleaner, show should you clean an refrigeration system?
by inserting a hard wool felt filter in the suction
how is the unloader mechanism of the compressor operated?
by oil pressure from the capacity control valve
how are refrigerant leaks detected?
by use of an electronic tester or by soapsuds test method
if compressor discharge valves become defective, which of the following actions should you take?
entire discharge valve assembly should be replaced
suppose a refrigerant compressor has been pumped down to 2 psig and the suction and discharge stop valves are closed. what is indicated by a discharge pressure drop at a rate of 3 psi per minute and a suction pressure increase?
discharge valve is leaking
