We appreciate your time on our website. Please help us grow by sharing our site with your friends and colleagues. Thank you for helping us build a stronger community!
MCQ On Air Compressor | Marine Engineering
MAMQ & A
Marine Geek
6 min read
AIR COMPRESSOR
1. Single stage compressor
Provides air at high pressure
Therefore high compression temperature of the air
Heat produced in this fashion is waste of energy
all of the above
2. With respect to air compressor, the compression of this trapped air in the clearance volume causes effective loss of stroke due to which the volumetric efficiency of compressor drops.
TRUE
FALSE
N/A
N/A
3. In an air compressor, what is the effect due to less clearance volume
Very high pressure is developed
may result in piston banging or colliding to the cylinder head.
Very very high temperatures is developed
none of the above
4. An air compressor is equipped with an intercooler and an aftercooler to
inject water vapor into the compressed air
prevent overheating of first stage valves
increase compressor efficiency and economy
reduce the compressed air charge density
5. If there is a sudden drop in the capacity of a reciprocating air compressor, you should check for.
broken compressor valves
worn piston rings or cylinder liners
excessive compressor speed
6. In an air compressor, suction & delivery valves, late closing of v/v affects volumetric efficiency
TRUE
FALSE
N/A
N/A
7. Operating a reciprocating air compressor without an air intake filter can result in a/an
immediate piston damage
immediate clogging of the intake
possible explosion in the compressor
8. In an air compressor, which trip is never used on board ship.
Lubricating oil low pressure trip
Cooling water high-temperature trip
Motor overload trip and Motor overheating trip
All of the above are always used
9. If a ship service air compressor operating in intermittent service were failing to unload, the.
compressor would stop abruptly when power was secured
compressor would run continuously
air receiver indicated pressure would be shallow
compressor would require more than the normal amount of lubrication
10. Blower is a device working on its own to create positive pressure above atmospheric pressure or a vacuum.
TRUE
FALSE
N/A
11. If a ship service air compressor failed to unload the
compressor would run continuously
air receiver pressure would be shallow
belts could slip when starting
compressor would pump lube oil
12. Condensate must be drained periodically from the air compressor receivers to prevent.
second stage cylinder lockup
oil sump contamination
faulty operation of pneumatic valves
corrosion of air receiver baffles
13. Which of the following is most suited for a deck air compressor
Lobe type
Reciprocating type
Screw type
all of the above
14. A air compressor is designed for relatively low flow rates with a high differential pressure
TRUE
FALSE
N/A
15. What is meant by positive displacement compressor?
Wich draws in and increases the temperature of air in a chamber, then reduces the volume of the chamber to compress the air.
Wich draws in and captures a volume of air in a chamber, then reduces the volume of the chamber to compress the air.
Wich draws in and increases the volume of air in a chamber, then reduces the volume of the chamber to compress the air.
all of the above
16. Leaking valves in a low pressure, reciprocating, air compressor can result from
excessive compressor discharge pressure
operating the compressor at excessive speed
uneven piston stroke in the compressor
abrasion by dust and dirt
17. With respect to air compressors, Multi staging & Intercooling will result in
Compression work is reduced
Vol. efficiency and hence compressor capacity is increased
It approximates isothermal compression
all of the above
18. If the capacity of a reciprocating air compressor gradually drops off, the cause could be
leaking compressor valves
a clogged air filter
worn cylinder liners
all of the above
19. Unloading of a low-pressure, reciprocating, air compressor at start-up can be accomplished by.
holding the L.P. discharge valve open
the use of a precharged accumulator
using a permanently enlarged clearance expansion volume
temporarily discharging back to the compressor intake
20. Reciprocating air compressor bearing failure may result from
a misaligned crankshaft
overtightened drive belts
contaminated sump oil
all of the above
21. With respect to air compressor, as the pressure increases, more stages are required with inter-cooling due to the following disadvantages of single-stage compression:
Low volumetric efficiency
High air delivery temperature
Increased power input
all of the above
22. One cause of leaky valves in a low pressure air compressor may be attributed to.
running with an air filter element different from that required by the original manufacturer's
specifications
excessive operating hours without carrying out preventive maintenance
23. Blower simply displaces a volume of air from the inlet side to the discharge side without pressurizing it at all
TRUE
FALSE
N/A
N/A
24. Incorporating inter-cooling and or after-cooling to improve efficiency and reduce weight.
TRUE
FALSE
N/A
N/A
25. If a reciprocating air compressor has a knock occurring in frequency with its operating RPM, the cause is indicated by
Misalignment or worn-out main bearings
Insufficient cylinder lubrication
Defective or poorly fitted valves All
26. The energy in the compressed air can be stored while the air remains pressurized.
TRUE
FALSE
N/A
N/A
27. With respect to air compressors, Multi staging & Intercooling will result in
Vol. of air delivered is reduced; as a result, reduced size of cylinder, piston and delivery pipes is required
Reduced air delivery temp gives less thermal &mechanical loading and better lubrication of piston & cylinder
Due to less temp, suc. & del. valves remain clean
all of the above
28. In an air compressor, suction & delivery valves, excessive valve lift causes impact & v/v breakage
TRUE
FALSE
N/A
29. The unloading of an air compressor may be provided by I) holding the intake valve off of its seat II) temporarily relieving air in the intercooler to the atmosphere
I only
II only
Both I and II
Neither I nor II
30. With respect to air compressors, a lower Compression Ratio Per Stage will result in
Lower Air Temperatures
Reduced Carbon Build Up
Increased Valve Life
all of the above
31. With respect to air compressors, Volumetric Efficiency is affected by
Excessive piston end clearance (bump)
Defective valves
Piston/ring leakage
all of the above
32. With respect to air compressor, which statement is correct
This extra pressure due to heat is of no use but demands greater power from the prime mover while pushing the piston upward in the compression stroke.
Isothermal compression is a solution to this problem? but impossible to achieve in practice
Compressing the air to the same desired pressure in more than one stage and cooling the air in between the stages will take us close to isothermal compression
all of the above
33. Why should a person performing maintenance on an air compressor secure with a wire and tag all the system valves closed?
To prevent the unexpected.
To protect the equipment.
To protect the operator performing the maintenance.
Each of the above is correct
34. With respect to air compressors, Volumetric Efficiency is affected by
Restriction in discharge lines
Free air is air at atm. pressure and at 15 deg C
Vol.eff. always refer to low pressure pistons
all of the above
35. When air compressors are arranged for automatic operation, the cylinders can be unloaded during starting and stopping by
bypassing the discharge to suction
fitting depressors which hold the suction valve plates on their seats
step unloading the cylinders in a multi-cylinder machine
all of the above
36. In an air compressor, before taking suction, the air trapped in the clearance volume must expand below the suction pressure
TRUE
FALSE
N/A
37. A compressor operating with an accumulation of dust and grease on the surfaces of an intercooler would result in. I. the motor to run warmer than usual II. lower density air discharged to the receiver
I only
II only
Both I and II
Neither I nor II
38. With respect to air compressor, which statement is correct
The heat generated due to single-stage compression produces a resultant rise in pressure.
This pressure rise is apart from rise in pressure due to action of the piston.
This hike in pressure will be lost as soon as air is cooled down.
all of the above
39. When air compressors are arranged for automatic operation, the cylinders can be unloaded during starting.
bypassing the discharge valves
fitting depressors which hold the suction valve plates on their seats
step unloading the cylinders in a multi-cylinder machine
40. When air compressors are arranged for automatic operation, the cylinders can be unloaded during starting by.
bypassing the discharge valves
fitting depressors which hold the suction valve plates on their seats
step unloading the cylinders in a multi-cylinder machine
all of the above
41. With respect to air compressor, bumping clearance is provided for
thermal expansion
to control the air temperature
to give cushioning effect
to slow down the piston speed in TDC region
42. A reciprocating air compressor is running roughly and vibrating excessively, indicating that the.
compressor is overloaded
motor is overloaded
foundation bolts are loose
belts are too tight
43. If the capacity of a reciprocating air compressor gradually drops off, the cause could be
leaking compressor valves
a clogged air filter
worn cylinder liners
all of the above
44. A leaking suction valve in the second stage of a two-stage, high pressure, air compressor can cause excessively high
second stage discharge pressure
first stage discharge pressure
pressure in the aftercooler
compressor final discharge temperature
45. To obtain maximum efficiency, two stage air compressors are usually
horizontally mounted
never fitted with intake filters
fitted with intercoolers
operated in an unloaded condition at all times