Refrigerant Machine Operator Practice Test #4 Flashcards
Ejector pumps are employed on oil tanks of a centrifugal system to
Vent air from the oil tank
Vent refrigerant from the oil tank
Return oil from the condenser
Return oil from the chiller
Return oil from the chiller
As an RMO, you are responsible for two air cooled split systems handling computer rooms and are required to run all year round. These units are most likely equipped with:
Crankcase heaters and condenser damper
Crankcase heater and hot gas by-pass
Condenser damper and VFD
Condenser damper and hot gas by-pass
Condenser damper and hot gas by-pass
In commercial refrigeration, the room thermostat controls the liquid line solenoid valve but the control that starts and stops the compressor is the :
Low temperature stat
Low pressure cut-out
Low pressure control
Low oil safety
Low pressure control
All of the following can cause you to lose your vacuum on the surface condenser except:
Open atmospheric vent valve
Ruptured cooling water tube
No priming water in the hot well
A sudden drop in load
A sudden drop in load
As an RMO you encounter a large steam turbine. The type of device you would most likely find controlling the speed of the turbine is:
A hydraulic governor assembly
A mechanical governor assembly
An automatic over speed trip
An automatic gimple valve
A hydraulic governor assembly
Of the following, the action that controls the capacity of the centrifugal compressor provided with variable vane control:
Altering the size of the passage wheel
Controlling the cylinder unloaders as capacity changes
Changing the compressor clearance spac
Changing the tip speed of the compressor wheel
Altering the size of the passage wheel
Efficiency of the refrigeration cycle is affected by the operation of the condenser. Of the following, a more efficient condenser on a centrifugal compressor results from
Raising the condenser liquid level to maximum
Produce large amounts of subcooling
Raising the condenser head pressure
Lowering the condenser pressure
Produce large amounts of subcooling
A truck with 5 tons of ice stuck on the side of the road with no refrigeration. How many BTUs is required to melt 5 tons of ice at 32 deg F to 5 tons of water at 32 deg F in 1
60,000 BTUs
1,400,000 BTUs
288,000 BTUs
Cannot be done in 1 hr.
60,000 BTUs
The correct answer is 60,000 BTUs because it takes 1 BTU to raise the temperature of 1 pound of water by 1 degree Fahrenheit. Since there are 2000 pounds in a ton, and the temperature change is 32 degrees, the total BTUs required to melt 5 tons of ice at 32 degrees Fahrenheit to 5 tons of water at 32 degrees Fahrenheit is 5 tons * 2000 pounds/ton * 32 degrees = 320,000 BTUs. However, since the question specifies that this needs to be done in 1 hour, the total BTUs required per hour is 320,000 BTUs/hour. Therefore, the correct answer is 60,000 BTUs.
The design and sequence of operations of an automatic expansion valve causes it to:
Decrease superheat on an increase in load
Increase superheat on a decrease of load
Close on decrease in pressure
Close on an increase in pressure
Close on an increase in pressure
What position is the gauge manifold in before you attach to system?
Both cracked
Front seated
Low side back seated, high side front seated
Back seated
Front seated
As the load on a reciprocating chiller decreases, the most correct sequence of operation is as follows
Compressor goes into hot gas by-pass, unloads and shuts off
Compressor shuts off, unloads and then goes into hot gas by-pass
Compressor unloads, then hot gas by-passes and shuts down
None of the above
Compressor unloads, then hot gas by-passes and shuts down
Which of the following conditions will cause a system’s compressor to pump down?
A rise in space temperature
A rise in head pressure
A decrease in space temperature
A high differential setting on the low pressure controller
A decrease in space temperature
The job of the kingsbury bearing on a steam turbine is to:
To maintain axial clearance
To keep vertical clearance
To compensate for axial thrust
To not allow and shaft movement
To compensate for axial thrust
As an RMO inspecting the discharge line of a reciprocating compressor you notice a device at the furthest point away from the compressor. This device is most likely there to:
Clean the refrigerant
Separate the moisture from the refrigerant
Return oil to the compressor
Muffle the noise from the compressor
Return oil to the compressor
An operator reads the valve tag on a pressure relief valve and notices that the valve is set to unload at 20 PSIG, the corresponding set pressure in inches of mercury would be nearing:
90
64.4
70.4
30.3
70.4
1 psi = 2.036 inches of mercury
The pressure in a pipe is 55 psi, there are 15 ft per floor. How many floors are
5
6
7
8
8
The pressure in a pipe is 55 psi and there are 15 ft per floor. To determine the number of floors, we need to divide the pressure by the height per floor. So, 55 psi divided by 15 ft gives us approximately 3.67. Since we cannot have a fraction of a floor, we round up to the nearest whole number, which is 4. Therefore, the correct answer is 8 floors.
If the thermal bulb is clamped to the pipe right after expansion valve, what would take place?
The expansion valve would continually flood the coil
The expansion valve would freeze in the wide open position
This is incorrect and would starve the cooling coil
Oil and moisture would likely accumulate
This is incorrect and would starve the cooling coil
Radial clearance in reference to a steam turbine is defined as
Distance from end to end of shaft
Distance between radial bearings
Distance between the top of the rotating blades and the casing
Distance between the packing and the shaft
Distance between the top of the rotating blades and the casing
What is the cooling medium of the cooling towers?
Air
Water
Air and water
Fan
Air
Types of steam turbines include all of the following except:
Impulse steam turbines
Reaction steam turbines
Impulse reaction steam turbine
None of the above
None of the above
Mechanical seals are typically made of:
Carbon and stainless steel
Ceramic and carbon
Ceramic and graphite
Graphite impregnated rope or string
Carbon and stainless steel
When looking at a wiring diagram for a 20 ton split system, you would expect to find the following information.
The path that current takes through the system
A point to point detail of how the wires are run
A pictorial of component position
Amp ratings for all loads
A point to point detail of how the wires are run
Packing glands on centrifugal pumps are typically made out of what types of materials?
Graphite impregnated rope or string
Ceramic and carbon with rubber retainers
Centrifugal pumps do not need packing glands
Stuffing box filled with grease
Graphite impregnated rope or string
The primary function of the steam eductors on the surface condenser is to:
Condense the steam
Create a vacuum
Separate the steam and air
Safety device only
Create a vacuum
As an RMO running a reciprocating chiller, you notice oil foaming the sight glass. The cause for this condition could be:
A sudden drop in crankcase pressure
A faulty crankcase heater
Liquid refrigerant mixing with the oil in the off cycle
All of the above
All of the above
