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
An automatic purge unit is required on units:
With centrifugal compressors
Containing low pressure refrigerants
Absorption systems
Double indirect open spray systems
Containing low pressure refrigerants
An RMO notices that the diameter of the suction line is 36” and the diameter of the discharge line is 18”. What can we determine from this statement?
The unit is piped wrong because the diameters should be opposite
The cold refrigerant vapor needs less space than a hot vapor
The high pressure line needs more diameter to handle the pressure
The higher the vapor pressure is, the less volume is needed
The higher the vapor pressure is, the less volume is needed
Shaft glands on a steam turbine are located:
Front and rear of turbine
Wherever the shaft emerges from the casing or steam could leak
Wherever air could leak out of the turbine
Wherever oil can leak from the lubrication system
Wherever the shaft emerges from the casing or steam could leak
While inspecting the machine room, the compressor is cycling on and off, what is causing the compressor to cycle on and off?
Refrigerant overcharge
Refrigerant undercharge
Compressor valves problems
Non condensables in the system
Refrigerant undercharge
When looking at a large semi-hermetic reciprocating compressor, you would expect to find:
Suction and discharge lines parallel to each other
Suction and discharge lines perpendicular to each other
Depends on the amount of cylinders
Suction on top and discharge off the bottom
Suction and discharge lines perpendicular to each other
If the temperature outside drops b 8 deg.C, what is the equivalent drop in def.F?
4 deg.F
40 deg.F
14 deg.F
8 deg.F
14 deg.F
If the temperature outside drops by 8 deg.C, the equivalent drop in def.F can be calculated using the formula: def.F = (9/5 * deg.C) + 32. Plugging in the value of -8 deg.C, we get def.F = (9/5 * -8) + 32 = 14 deg.F. Therefore, the correct answer is 14 deg.F
The medium/mediums for cooling in an evaporative condenser is/are:
Air only
Refrigerant and water
Water and air
Glycol and air
Water and air
What is the most used regulation book in the U.S. used by the RMO?
NFPA
USEPA
Federal Regulation book
NYC building code
USEPA
You are the RMO of a facility which contains a 750 ton centrifugal Trane chiller. The chief ask you to order extra refrigerant for the upcoming season. If the machine charge is determined to be 1500lbs, how much refrigerant can you store without being in violation of the code?
Whatever the chief engineer deems safe
Whatever can be tied down and stored safely
200lbs of refrigerant
330 lbs of refrigerant
330 lbs of refrigerant
There are two refrigerating systems. System “A” operates with a suction pressure of 18 PSIG and a speed of 230 RPM. It is absorbing 800 BTUs per minute in its evaporator. The second system “B” is operating with a suction pressure of 22 PSIG and a speed of 300 RPM. It is absorbing 600 BTUs per minute from a brine tank. From the data given it can be said that:
“A” is producing three tons and “B” is producing for tons
“A” is producing four tons and “B” is producing four tons
“A” is producing four tons and “B” is producing three tons
“A” is producing three tons and “B” is producing three tons
“A” is producing four tons and “B” is producing three tons
1 ton of refrigerant is = 12000 BTU’s per hour
What is the diaphragm of the power assembly of a TEV made of?
Copper
Flexible rubber
Flexible steel
N/A
Flexible steel
You notice that the second stage compressor on your reciprocating chiller has foaming in the oil sight glass. As an operator you should check for:
Excessive charge
Burnt out crankcase heater
Moisture in the system
Too much oil
Burnt out crankcase heater
An automatic oil trap is installed in the high side of a refrigeration system. When the float of the traps lifts it allows:
Hot oil to defrost the coils
Hot oil to go through the stuffing box
Oil to drain off into the receiver reservoir
Oil to leave the trap and return to the compressor
Oil to leave the trap and return to the compressor
A valve that will not provide continuos flow of refrigerant through the circuit is the:
Globe valve
Service valve
Solenoid valve
TXV
Solenoid valve
The recirculation valve on a surface condenser is controlled by the:
Hot well level control
The condensate pumps
pneumatic controller
Oil pump pressure
Hot well level control
Why is it important to minimize moisture in the inlet steam to a turbine?
Prevent damage to turbine blades
It takes longer to warm up with moisture
Acids can form in the surface condenser
Moisture has no effect, steam is heated moisture
Prevent damage to turbine blades
What is the state of the refrigerant as it enters and exits the compressor?
Low temperature liquid in and high temperature liquid out
Low temperature vapor in and high temperature vapor out
Low temperature in and high temperature out
Low pressure in and high pressure out
Low temperature vapor in and high temperature vapor out
After condensate water leaves the recirculation valve, where does it go?
Back to the boiler
Down the drain back
Back to the hot well for priming
Back to turbine
Back to the hot well for priming
Which one of the following will connect to the middle port on a gauge manifold?
Solenoid valve
King valve
Vacuum pump
Suction or discharge service valves
Vacuum pump
When considering the rate of BTUs rejected by the condenser, an important point for the operator to remember is:
Will increase if you oversize the tower
Will decrease as the water temperature goes down
Will increase as the velocity goes up
Will show no difference as long as the water temperature is the same
Will increase as the velocity goes up
On a water cooled chiller, the heat that is absorbed by the chilled water is:
Rejected to the ambient air as sensible heat
Rejected as latent and sensible heat heat to the ambient air
Minimal in comparison to the volume of water
Rejected by the compressor
Rejected as latent and sensible heat heat to the ambient air
It has been determined that the oil level in a particular refrigeration system is low, additional oil should be charged into the system by
Pumping it through the suction service valve
Pumping it into the compressor crankcase
Pumping it into the king valve
Using the gauge manifold to draw through both service valves simultaneously
Pumping it into the compressor crankcase
Solenoid valves are characterized by an electromagnet. Which of the following will take place when a normally close solenoid is energized?
Valve disc will rotate 180 degrees
Valve will meter flow of refrigerant to evaporator
Valve plunger will lift off the seat
Magnetic force will close contact
Valve plunger will lift off the seat
What is the minimum required times that the RMO needs to perform rounds on equipment and fill out the log book, per NYC Fire Dept.
Once per shift
Once a day
Every two hours
Every hour
Once per shift
A systems condenser water pump has been shut down for service. When it is turned back on, it is discovered that it is not moving water. What should the RMO do?
Check the shaft bearings for grease
Check the contacts with the voltmeter for correct voltage
Open the petcock and bleed air from volute
Bleed excess water pressure from the bottom plug
Open the petcock and bleed air from volute
As and RMO in charge of a refrigeration machine in your building controlling the capacity of the machine, how does the solenoid valve unloader get activated?
With spring pressure
With pneumatic pressure
With electric current in a coil causing the plunger to lift
None of the above
With electric current in a coil causing the plunger to lift
An RMO is inspecting a centrifugal pump and he notices excessive water leaking from the mechanical seal. The RMO should:
Tighten evenly to get a steady drip
This is normal for a mechanical seal
Shut down the pump, turn on the standby and call for pump service
Order a new pump because mechanical seals cannot be replaced
Shut down the pump, turn on the standby and call for pump service
Oil that has been separated from the refrigerant is returned to the compressor and tied into the
Oil charging valve
Discharge service valve
Oil pump suction
Compressor crankcase
Compressor crankcase
When conducting a routine tour of the plant, an RMO notices a significant increase in superheat for a reciprocating compressor. Of the following, the most likely cause of this would be?
Scale particles lodged in the TEV
Unraveling of the insulation covering the thermal bulb of the TEV
Overcharge of refrigerant
Noncondensables in the system
Scale particles lodged in the TEV
After completing repair to a refrigeration system, you leak check the system with your electronic leak detector. After no leaks are found, proper disposal of the R-22 and nitrogen mix to :
Separate refrigerant from nitrogen and vent
Recover the mixture and mark to be destroyed
Vent the mixture to the outside air
You cannot use R-22 for this purpose
Vent the mixture to the outside air
The use of oil in the refrigeration machine is to
Mix the oil with liquid refrigerant
Add non condensables to refrigerant
Reduce friction in the compressor parts
None of the above
Reduce friction in the compressor parts
Which of the following statements should be imprinted on the body of a fusible plug?
Temperature at which the fusible member melts
Date manufactured
Busting pressure
Maximum operating pressure
Temperature at which the fusible member melts
What is the most common metering device on a reciprocating system?
Thermostatic expansion valve
Automatic expansion valve
Orifice
Capillary tube
Thermostatic expansion valve
If the city water is too expensive, you can use water from:
Well
Lake
All answers are correct
River
All answers are correct
If R134 contact your skin, what would you do?
Nothing, it is HFC
Use body oil on skin
Flush with water until removed
Make sure you have proper air movement over skin to evaporate
Flush with water until removed
The orifice plate meters the refrigerant. What else can be said about the vessel that contains the orifice plate?
It is a vapor recycler
It cleans the refrigerant
It economizes
It acts as a condenser for subcooling
It economizes
The sole refrigeration engineer on duty in a building is permitted to leave the building refrigeration system is in operation only when
Lunch or dinner occur
System is in automatic operation
Relieved by another licensed refrigeration engineer
The assistant provides coverage or supervision
Relieved by another licensed refrigeration engineer
When changing water to ice, what must be removed?
Specific heat
Latent heat
Sensible heat
N/A
Latent heat
Vice-President of operations comes in on a cold winter day and ask the RMO to go shovel snow. What should he do?
Obey the manger and go out and shovel snow with radio communication
As long as you check in every 45 minutes
Do not go out and shovel snow until another licensed engineer relieves you
Call the union shop and fill out a report, but shovel snow
Do not go out and shovel snow until another licensed engineer relieves you
