3B2 - Ch. 8 & 9

A kind of rotary compressor is _________________. a. a two lobe b. a cross - compound double cylinder c. sliding piston d. axial e. All of the above

a

A variable speed control regulates the speed of the _________ from air receiver pressure monitoring. a. driver b. compressor crankshaft c. compressor impellers d. compressor blades e. coupling

a

Adjustable diffuser vanes on centrifugal air compressors are implemented to ______________________________. a. change the operating characteristics of the compressor b. prevent back or reverse flow of air c. remove foreign particles from the air d. reduce the amount of air entering the compressor e. change the direction of the air flow to remove moisture

a

Air compressor inter and after coolers may be______________. a. water or air cooled b. oil or hydrogen cooled c. teflon lubricated d. electrically heated e. freon refrigerant cooled

a

Axial flow compressors are _______________________. a. a dynamic type of compressor b. a single acting compressor c. a rotary type of compressor d. centrifugal compressor e. All of the above

a

Cylinder arrangements of reciprocating air compressors may be: 1) Vertical or horizontal 2) Rotary or simplex 3) The V or Y type 4) An angle type 5) Twin impeller type a. 1, 3, 4 b. 1, 3, 5 c. 2, 4, 5 d. 1, 2, 3 e. 2, 3, 5

a

Internal lubrication of air compressors refers to: 1) The crankcase and crankshaft 2) Cylinder walls and pistons 3) Vanes and casing walls of some compressors 4) Impellers of a centrifugal compressor a. 2, 3 b. 1, 3, 4 c. 3, 4 d. 1, 4 e. 1, 2, 3

a

Output from a compressor using the constant speed control method must use some type of ______________ device. a. unloading b. uploading c. down loading d. start stop device e. variable speed

a

Reciprocating compressor valves are usually found in two common forms ____________________________. a. plate disc and channel type b. composition and rubber c. copper and aluminum d. angle and inverted e. ribbed and push rods

a

The item used to activate the inlet air unloader is ________________. a. a spring loaded pilot valve b. a torsion bar c. a bleed-off valve d. a compressor flywheel e. None of the above

a

The rotary screw compressor usually has the _____________________. a. male lobe driven b. male flute driven c. female flute driven d. female lobe driven e. female and male driven

a

To prevent surging, the capacity of the compressor must not be allowed to fall below the ___________. a. surge limit b. maximum volume c. rated point d. rated pressure e. set point

a

__________ of a compressor is known as free air delivered or free air capacity. a. Capacity b. Displacement c. Absolute pressure d. Efficiency e. Pressure ratio

a

___________ on centrifugal air compressors are provided in order to control the amount of air flowing to the impeller and thus control the capacity of the unit. a. Adjustable inlet vanes b. Adjustable diffuser vanes c. Variable frequency drive d. Moving and fixed blades e. Dummy piston

a

A double acting reciprocating air compressor __________________. a. must have at least two pistons b. receives and discharges air at both ends of the cylinder c. increases the pressure twice from inlet pressure value d. has one compression stroke for every crankshaft revolution e. None of the above

b

Four ways of dividing reciprocating compressors into types are: 1) Single or double acting 2) Method of compression 3) Number of impellers 4) Speed of prime mover 5) Method of drive 6) Cylinder arrangement a. 3, 4, 5, 6 b. 1, 2, 5, 6 c. 1, 3, 5, 6 d. 2, 3, 4, 6 e. 1, 3, 4, 5

b

In axial air compressors, the pressure rise per stage is ____________ therefore, for high pressures ____________ stages are required. 1) low 2) high 3) single 4) multi a. 1, 3 b. 1, 4 c. 2, 3 d. 2, 4 e. 2, 1

b

The stop and start system is best employed where ____________________________. a. the air demand is constant b. the air demand is low and infrequently demanded c. a large AC motor is used as the driver d. a diesel engine is used as the driver e. variable speed and start, stop

b

A good method of drying air before it goes into the receiver is to ____________. a. heat it b. pressurize it c. cool it d. increase the velocity e. decrease the velocity

c

An important advantage of a sliding vane compressor is that it ___________________________________. a. does not require internal lubrication b. has a high starting torque c. does not require inlet or discharge valves d. requires light nylon timing gears e. does not require a prime mover

c

Compressor connecting rods are constructed of _____________. a. cast iron b. stainless steel c. forged steel d. black iron e. brass

c

In a rotary lobe compressor one lobe is directly driven by the driving mechanism while the other lobe is driven by __________________________. a. intermeshing with the driven lobe b. a reduction gear c. means of timing gears d. speed increasing gears e. a belt

c

It is advisable that ________ is fitted between the aftercooler and air receiver. a. a gauge glass b. pressure gauge c. a moisture separator d. an air filter e. temperature gauge

c

Reciprocating compressors are suitable for_________________. a. low pressure service b. only high pressure service c. all ranges of pressure d. single stage only e. None of the above

c

Single-acting compressors having the bottom of the cylinder open to the crankcase will have lubrication provided by _________________________. a. a pressure lubricator b. a force fed oil pump c. a splash system d. an oil ring e. None of the above

c

The prime purpose of water cooling or air cooling of air compressors is to ______________________________. a. cool the air b. help increase moisture and volume of the air c. keep the cylinder at a reasonable temperature d. prevent fire from occurring in the receiver e. prevent operator injury

c

The reasons for cooling the air in an air compression system is to: 1) Remove water vapor and oil vapor from the air. 2) Make cylinder lubrication more effective. 3) Decrease the amount of power required to compress the air. 4) Remove fixed carbon from the value s. a. 2, 4 b. 1, 4 c. 1, 2, 3 d. 1, 2, 3, 4 e. None of the above

c

A compressor driven by a constant speed driver has its output varied by _____________________________. a. a stop and start switch b. a solenoid valve c. a mercury switch d. some type of unloading device e. a safety relief valve

d

A free piston air compressor _____________________________. a. has a spare or free piston for air compression b. uses one steam cylinder to drive two compression pistons c. has a common intake and discharge valve system d. has a cushion cylinder that acts as a flywheel e. has two crankshaft

d

A method of unloading a reciprocating compressor is to ________________________. a. hold the discharge valve closed b. hold the discharge valve open c. place a check valve in the discharge line d. hold the inlet valves in the open position e. unloading a cylinder

d

A reciprocating compressor can deliver oil-free air if it ________________________________ . a. uses an oil separator at the compressor discharge b. uses an oil filter before the compressor inlet c. implements a charcoal filter at the compressor discharge d. implements carbon or Teflon piston rings e. uses an intercooler to increase the oil viscosity

d

Air compressor pistons are constructed of: 1) Steel 2) Cast iron 3) Brass 4) Aluminum 5) Copper alloy a. 1 b. 1, 2 c. 3, 4, 5 d. 1, 2, 4 e. 2, 3, 4, 5

d

Axial flow compressor advantages are similar to those of centrifugal air compressors, they have an added advantage of ______________________. a. being lower in cost b. being a shorter machine c. being corrosion and erosion free d. being approximately 10% more efficient e. solid forged rotor

d

Centrifugal compressors are commonly used for ___________________. a. low volume, high pressure applications b. low speed, high pressure applications c. high humidity, low volume applications d. large volume, low pressure applications e. large volume, low speed

d

Compressor valves are usually automatic and open and close by _________________________________. a. action of a poppet valve b. movement of the piston covering or uncovering ports c. operation of an air solenoid valve d. a pressure difference e. a camshaft

d

Each pair of moving and fixed blades in an axial air compressor constitutes a/an _______________. a. pressure drop b. temperature decrease c. program of air d. stage e. obstacle

d

For changing the air ____________ in centrifugal air compressors to ______________, volute casings and diffuser vanes are implemented. 1) pressure 2) volume 3) velocity 4) temperature a. 1,2 b. 2,4 c. 4,1 d. 3,1 e. 4, 2

d

In a compressed air system, if water vapour is not removed from the air then it may collect in pipelines and cause: 1) Increase in pressure 2) Water hammer 3) Gurgling noise 4) Damage from freezing a. 1, 3 b. 3 c. 1, 4 d. 2, 4 e. 1, 2, 3

d

In a multistage reciprocating compressor the highest pressure stages may be_______________________. a. remote controlled b. poppet valve regulated c. double lobe d. single acting e. free piston

d

In the ________ compressor, the male rotor has convex lobes and the female rotor has concave flutes. a. lobe type rotary b. axial flow c. sliding vanes d. rotary screw e. free piston

d

In the variable speed control method the compressor output is regulated by _______________________. a. adjustment of clearance pockets b. a rheostat c. a safety relief valve d. a driver that can be throttled e. only small receivers are available

d

Lubricating oil is necessary in an air compressor in order to perform the following functions: 1) Provide sealing 2) Remove heat 3) Reduce friction 4) Eliminate water cooling 5) Reduce corrosion 6) Remove carbon 7) Prevent wear a. 1, 2, 3, 4, 5 b. 1, 2, 3, 4, 5, 6, 7 c. 1, 3, 4, 6 d. 1, 2, 3, 5, 7 e. 1, 2, 4, 5

d

Oil free air may be provided by reciprocating air compressors by _______________________________. a. use of a porous filter b. use of an oil filter c. nylon and brass piston rings d. carbon or Teflon piston rings e. use of an intercooler

d

One method to prevent surging in dynamic compressors is to ___________________. a. sue variable frequency drive b. use vanes c. install a recirculation line d. open a discharge line blow-off valve to atmosphere e. use a safety valve

d

Reciprocating air compressors are best suited to _____________________. a. high speed, low volume applications b. low pressure, high volume applications c. low pressure, low volume applications d. high pressure, moderate volume applications e. high speed, high volume applications

d

Rotary lobe compressors have their elements ________________________ . a. lubricated by graphite b. enclosed by an aluminum casing c. as spring loaded vanes d. revolving in opposite directions e. lubricated by oil

d

The aftercooler is used in an air compression system to _____________________. a. cool the air after the first stage of compression b. cool the lubricating oil of large axial compressors c. cool the air after it leaves the receiver d. cool the air after the last stage of compression e. cool the air before being compressed

d

The operating speed of a typical two-stage sliding vane compressor ranges up to _____________. a. 250 rpm b. 5000 rpm c. 1800 rpm d. 3000 rpm e. 2000 rpm

d

Water cooling by water jacketing of air compressor cylinders is preferred over air cooling because _________________________. a. the construction of the compressor is cheaper than the finned type b. there is less piping involved c. the construction is fairly simple d. more efficient cooling is obtained e. the air temperature can not be controlled

d

A centrifugal air compressor may have ________ for multi-staging. a. two or more pistons b. two or more impellers on separate shaft c. two or more compressors d. two or more diffuser vanes e. two or more impellers on same shaft

e

A reciprocating compressor is suited for all ranges of ______ . a. discharge air temperatures b. speed c. oil lubrication d. cooling water temperatures e. pressures

e

Axial flow compressor blades are subject to greater ________ and ________ than there is in a centrifugal compressor. 1) fouling 2) erosion 3) corrosion 4) cleaning a. 1, 3 b. 1, 4 c. 2, 1 d. 3, 4 e. 2, 3

e

Centrifugal air compressors are used for __________________ pressure applications. a. changing b. low volume, high pressure c. low volume, low pressure d. high volume, high pressure e. high volume, low pressure

e

Compressor lubrication may be divided into two main sections __________ lubrication and __________ lubrication. 1) peripheral 2) internal 3) splash 4) external 5) pressure a. 1, 2 b. 3, 5 c. 3, 4, 5 d. 2, 3, 4 e. 2, 4

e

If _____________ is used then the cylinder is constructed with integral cast fins, which provide increased radiating area. a. water cooling b. water jacket c. glycol cooling d. sliding vane compressor e. air cooling

e

In multistage compression, the high-pressure cylinders are __________ because the volume is __________ and the pressure is __________than the lower pressure stages. 1) smaller 2) larger 3) higher 4) lower 5) more 6) less a. 2, 5, 4 b. 1, 5, 4 c. 2, 4, 6 d. 2, 5, 6 e. 1, 6, 3

e

The ________ control method can be used when the compressor is driven by a steam engine, a turbine, or an internal combustion engine. a. constant speed b. start and stop c. dual d. start and stop in conjunction with constant speed e. variable speed

e

The flow of air from a compressor must be _______ to suit load requirements and to maintain constant pressure in the system. a. increased b. decreased c. dampened d. interrupted e. regulated

e

The impellers of a _________ compressor maintain their relative positions with each other by the use of timing gears. a. siding vane b. free piston c. axial flow d. angle types e. lobe type rotary

e

The lobe type compressor runs at speeds up to about _________ Rev/min. a. 1550 b. 1600 c. 1650 d. 1700 e. 1750

e

Three different designs of rotary compressors are: 1) Sliding vane 2) Rotary screw 3) Axial flow 4) Volute centrifugal 5) Rotary lobe 6) Diffuser vane centrifugal a. 2, 4, 6 b. 1, 2, 3 c. 3, 4, 6 d. 1, 3, 5 e. 1, 2, 5

e

_______ and carbon rings can be used in reciprocating air compressors to deliver oil free air. a. Brass b. Aluminum c. Titanium d. Ceramic e. Teflon

e

________ positive displacement compressors require intake and discharge valves. a. Rotary b. Centrifugal c. Sliding vanes d. Rotary lob e. Reciprocating

e