C4
In a refrigeration system, the amount of superheat absorbed by the refrigerant is adjusted at the _________.
Evaporator
Expansion valve
Compressor
Ondenser
2 Refrigerant is circulated through a refrigeration system by the ___________.
Expansion valve
Evaporator
Condenser
Compressor
3 Salinity cell is installed in the distilling unit to indicate the ____________.
Quantity of freshwater produced
Leaking tube
Quality of water produced
Amount of chemical to be added
4Which of the following statements regarding low pressure, reciprocating, air compressor valves is correct?
A relatively large cylinder clearance space is require
Due to the physical construction of the valves, a rel
Mechanical operating valve gear is required to ope
Only the suction valve requires a push rod and rock
5 In a low pressure air compressor, the loss of volumetric efficiency normally results from _____.
Heating of the air leaving the cylinders
Adiabatic compression in the intercooler
Inaccurate valve timing
Constant enlargement of the clearance expansion v
6An eccentric reducer, used as a transition piece between a centrifugal pump suction flange and the suction piping flange, must be installed with the eccentric portion below the suction pipe centerline to _____.
Allow sediment to settle on the bottom
Reduce vapour pressure of the water entering the p
Slope the suction line upward the pump
Prevent the formation of air pockets
7When renewing the shaft packing on a centrifugal pump equipped with an external liquid sealing supply, you should _____?
Always turn down the shaft in a lathe to ensure a sn
Check the stuffing box for irregularities with a dial I
Ensure that the lantern ring is aligned with the seali
Make sure the seal cage is always positioned at the
8When installing a new rotary pump, the suction piping should _____.
Be of same diameter as the pump suction connecti
Be at least one size larger than the pump suction co
Be the next size smaller than the pump suction con
Be sloped to the pump
9 To prevent air pockets from forming in a centrifugal pump suction line installed angled from normal, any gate valve should be installed with the _____.
Bonnet above suction pipe centreline
Stem pointing upward at right angles to the pipe
Stem horizontal or pointing downward below the pi
Centreline above the suction pipe centreline
D 10On a medium pressure, differential piston, reciprocating air compressor, lubrication of the pistons/cylinders is usually accomplished _____________.
With metering type cylinder lubricators
By the splash method
Gravity fed lubricators
11When air compressors are arranged for automatic operation, the cylinders can be unloaded during starting by _____.
Bypassing the discharge valves
Applying reduced voltage to the motor
All of the above
Fitting depressors which hold the suction valve plat
12 Cylinder inlet valve failure in a low pressure air compressor can be caused by ______.
Carbon buildup on the pistons from excessive lubric
Sticking valves due to carbon buildup on the seats
Compressor overspeeding due to mechanical failure
Valve pounding due to valve covers being excessivel
13 The static suction lift of a pump is the difference in elevation between the _____.
Centreline of the pump and the suction liquid level
Centreline of the pump and the level of the dischar
Liquid levels of the suction and discharge
Centreline of the pump and the level of the liquid in
14Why is the discharge pressure of a herringbone gear pump steadier than the discharge pressure of a simple spur gear?
One discharge phase begins before the previous dis
Clearance between the gear teeth and casing is sm
The gear teeth are smaller than those of the simple
The herringbone gear pump has four spur gears ins
15 If an air compressor is used to supply compressed air to outlets throughout the engine room and on deck of a vessel, the system is known as the _____.
Combustion control air system
Ships service air system
Supply air system
Low pressure air system
16 The capacity of a rotary pump, delivering a constant viscosity fluid, will decrease when the discharge pressure is increased, due to________.
Decreased suction pressure
Increased suction pressure
Reduced slippage
Increased slippage
17A recirculating, or bleed off line is installed on a centrifugal pump in order to _____.
Prevent the pump from overheating when operatin
Establish a back pressure at the labyrinth seal to eli
Equalize pressure on both sides of the suction valve
Decrease the net positive suction head
18 If a centrifugal pump operating with a positive suction head vibrates, or becomes noisy, the cause could be ____________.
Excessive pump speed
Worn wearing rings
Air leakage into suction line
Insufficient venting
19 If an air compressor is used to supply air primarily to the combustion control system and other pneumatic controllers, the entire system is known as the _____.
Control air system
Forced draft air system
Supply air system
Ships service system
20 It is possible to mount a double suction centrifugal pump impeller with the vanes facing the wrong direction. This would cause the pump _____.
Head capacity to improve
Efficiency to decrease
Discharge to be reversed
Slippage to decrease
21Which of the following statements is true concerning the overall efficiency of air compressors?
High pressure compressors are more efficient than
Mechanical efficiency divided by compressor efficie
Two stage compressors are generally more efficient
The volumetric efficiency is decreased in multistage
22A compressor operating with an accumulation of dust and grease on the surfaces of an intercooler would result in _________. I. A decrease in volumetric efficiency of the compressor II. higher volume of air to be discharged to the receiver
I only
II only
Both I and II
Neither I nor II
23A compressor operating with an accumulation of dust and grease on the surface of an intercooler would result in _____. I. A high consumption of lube oil II. Higher than normal air pressure in the reciever
I only
II only
Both I and II
Neither I nor II
24What would be the result of throttling the suction valve to the point where the flow was less than that recommended by a centrifugal pump manufacture? I. The discharge head would be reduced II. The pump would begin to cavitate
I only
Both I and II
Neither I nor II
II only
25What would be the result of throttling the suction valve to the point where the flow was less than that recommended by the centrifugal pump? I. The designed total net head would be reduced II. The pump would begin to cavitate
I only
II only
Both I and II
Neither I nor II
26 If a reciprocating air compressor has a knock occurring in frequency with its operating RPM, the cause is probably ____________.
Misalignment or worn main bearings
Insufficient cylinder lubrication
Defective or poorly fitted valves
All of the above
27When renewing spiral packaging in a centrifugal pump stuffing box, after the packing is firmly seated, the packing gland nuts should be _____.
Left in that position
Loosened until the gland clears the stuffing box
Loosened, and then retightened until they are only f
Tightened an additional 10% to compress the packi
28 To prevent overheating and scoring of the shaft after repacking the stuffing box, which of the following procedures should be carried out?
Lubricate the lantern ring with cylinder oil before in
Tighten the packing in small increments while the p
Tightening the gland in all the way and then backin
Operating the pump slowly and applying oil freely t
29An advantage of a helical gear pump over a simple gear pump is that the helical gear pump is capable of _____.
Maintaining a steadier speed
Delivering liquids over greater distances
Operating for longer periods of time
Producing a smoother discharge flow
30Which of the following statements is correct with regards to the operation of a centrifugal cargo pump?
Oil is discharged from the center of the impeller thr
The discharge capacity varies directly with the spee
Gravity causes the oil to flow toward the discharge.
The self‐priming feature of the centrifugal pump en
31 The function of the spring used with channel or plate‐type valves for reciprocating air compressors is to _____.
Open the valves during downward stroke
Reduce compressor discharge pulsations
Reduce air intake and exhaust pulsations
Provide positive closing of the valves
32A first stage unloader installed in a low pressure air compressor is unable to completely retract. This will result in _____.
An abnormally low intercooler pressure
Overheating of the discharge valve
Loss of moisture in the air charge in the receiver
Frequent lifting of the intercooler relief valve
33 Liquid is kept from leaking out of the shaft ends of a helical gear pump by _____.
Overlapping spaces between gear teeth
A roller bearing
The use of shaft end caps
A stuffing box
34 In a centrifugal pump, the seal piping directs liquid from the discharge side of the pump to the _____________________.
Packing gland
Wearing ring
Stuffing
Lantern ring
35Which of the listed conditions can lead to cavitations in a centrifugal pump?
Rough casing volute surfaces
Vapor pockets formed in the suction flow stream
Worn wearing rings
Partial restriction in the discharge valve
36 The leakage of air into the pump casing by way of the packing gland of a condensate pump, is prevented by_____.
A water seal line to the packing gland
Special packing in the stuffing box
An air seal line from the compressed air line
The vacuum in the pump suction
37 The net positive suction head of a boiler centrifugal feed pump should be calculated over and above the _____.
Speed of the impeller
Pump capacity in GPM
Impeller ratio in the pump
Feedwater vapor pressure
38Which of the listed parts is used in a lobe‐type rotay pump to allow for wear on the lobe edges?
Replaceable gib inserts
Spur gear adjusters
Casing gear thrust bearings
Replaceable liner plates
39An unloader is installed on an air compressor to _____.
Bypass the high pressure stage to the intercooler
Prevent excessive interstage pressure buildup
Remove the compression load as the compressor co
Control compressor discharge pressure
40Which of the following statements describes the function of an air compressor intake filter?
Protects against the damaging effects of airborne s
Protects against suction valve float.
Provides a positive pressure on the air inlet valves.
Prevents lubricating oil contamination of the compr
41What would probably occur if excessive misalignment existed between a centrifugal pump and its power source?
Pump cavitation will increase
Shaft bearing will overheat
Power consumption will be reduced
Flashing will occur at the impeller eye
42 The initial unloading (at start‐up) of the device shown in the illustration is accomplished by ____________.
Discharging the compressed air to the receiver with
Temporarily discharging the compressed air to the a
Holding open the high pressure stage reed‐type suc
The use of an intercooler relief device
43 Two individual centrifugal pump impellers of the same diameter, width, and rotating speed are to be compared, one is cast with straight vanes, the other with curved vanes. Which of the following statements is correct?
The straight vane impeller always develops a higher
The curved vane impeller is less likely to develop ca
The straight vane impeller always has a greater cap
The curved vane impeller will be easier to balance
44How can we quickly reduce high water level in a steaming boiler?
By the used of bottom blow valve
By the used of safety valves
By the used of water column valve
By the used of surface blow valve
45 If the discharge valve is closed before the drive motor is stopped, which type of pump will most likely be damaged?
Reciprocating pump
Gear pump
Centrifugal pump
Turbine pump
46One of the main functions of wearing rings, as used in a centrifugal pumps, is to _____.
Maintain radial alignment between the pump impel
Absorb all impeller shaft end thrust
Prevent water leakage to the atmosphere
Allow for economical replacement of worn internal
47A centrifugal pump operating against a closed discharge valve has a/an _____.
Capacity of 100%
Efficiency of 0%
Internal slippage of 0%
Shut off horsepower rating of 100%
48 The function of a centrifugal pump double volute casing is to _____.
Double the liquid velocity through the pump when
Reduce radial thrust on the impeller
Reduce hydraulic end thrust
Provide the effect of multi‐staging
49Which of the following changes in pump operating parameters will lead to pump cavitation in a centrifugal pump that is operating in an open system?
Steadily decreasing pump speed
Steadily increasing pump suction pressure
Steadily increasing pump discharge pressure
Steadily increasing pump inlet temperature
50What should be done if localized scoring is discovered on a pump shaft sleeve during routine maintenance inspection?
Reassemble the pump and provide more water leak
Check for parallel alignment of sleeve radial face to
Reassemble the pump and set the governor to obta
Correct the cause of scoring and install a new shaft
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