Power Engineering 3B2 - Chapter 9

When a compressor is stopped, the cooling water supply should: a. Run for 5 minutes afterward. b. Run for 10 minutes afterward. c. Be shut off. d. Be left on. e. Have the flow cut in half.

C

A type of rotary compressor that is suitable for high speeds and may have a speed increasing gear implemented with an electric motor drive is: a. A screw type b. A sliding vane type c. A rotary lobe type d. An axial flow type e. A radial flow type

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

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

Air compressor lubrication oil should have: a. A high flash point. b. A low flash point. c. A high carbon content. d. Synthetic additives given to them. e. An ability to absorb moisture.

A

Air hand tools are usually lighter than electric hand tools because: a. Air tools don't have a heavy armature. b. Air is lighter than copper wire. c. Air tool casings are made of thin aluminum. d. Air tools do not have any internal moving parts. e. Air is lighter than electricity.

A

Air transmission piping is _____ and _____ to install than electrical wiring. 1. More costly 2. Less costly 3. As costly 4. More difficult 5. Less difficult 6. As difficult a. 1, 4 b. 2, 5 c. 3, 6 d. 1, 5 e. 2, 4

A

Compressed air machinery may be used in explosive atmospheres without hazard because they: a. Are free from sparking contacts b. Absorb flammable gases c. Run at lower RPM d. Require no lubrication e. Run hotter than electric motors

A

Detrimental effects of moisture in an air compression system are: 1) It may cause corrosion 2) It may cause water hammer 3) It will reduce compressor capacity 4) It will cool the air below the dew point 5) It may wash carbon off the valves 6) It may freeze in the air lines a. 1, 2, 3, 6 b. 3, 4, 5, 6 c. 1, 2, 3, 4, 5, 6 d. 2, 4, 5, 6 e. 1, 2, 3, 4, 5

A

If there is a shut-off valve between the aftercooler and the receiver, the aftercooler must also be fitted with a ________. a. safety valve b. pressure gauge c. thermometer d. fusible plug e. vacuum breaker

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

The four principle driving methods for reciprocating compressors are by: 1. Electric motors 2. Water wheel 3. Internal combustion engines 4. Steam turbine 5. Wind power 6. Steam engine a. 1, 3, 4, 6 b. 1, 2, 4, 5 c. 2, 4, 5, 6 d. 2, 3, 4, 6 e. 3, 4, 5, 6

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

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

To prevent surging, the capacity of the compressor must not be allowed to fall below the: a. Surge point b. Maximum volume c. Rated point d. Rated pressure e. Set point

A

When starting up a compressor, ensure the manual block valves in the suction and discharge lines are ______________. a. both wide open b. both closed c. both valves throttled back d. suction valve wide open and discharge valve closed e. suction valve closed and discharge valve wide open

A

When the load is to great, the compressed air machinery simply _____. 1. Slows down 2. Increase the air supplied 3. Stops 4. Decreases the air supply a. 1, 3 b. 1, 2 c. 3, 4 d. 2, 4 e. 1, 4

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 _____ is used to activate the inlet air unloader by monitoring receiver pressure. a. Solenoid valve. b. Spring loaded pilot valve. c. Spring. d. Lever. e. Camshaft.

B

A typical air dryer type consists of a pressure vessel containing a chemical known as a ____________. a. drying agent b. desiccant c. moisture eliminator d. dryer e. silica

B

Air carrying the maximum amount of water at a certain temperature and pressure is said to be: a. Superheated. b. Saturated. c. De-superheated. d. Balanced. e. Humidified.

B

Air receivers should be inspected regularly and then ______________. a. pneumatically tested b. hydrostatically tested c. dismantle and cleaned d. tested for explosive gases e. shipped to a pressure vessel tester

B

Air tools are preferred over steam driven tools because: 1. There is less chance of being burned. 2. Less equipment is required. 3. Air tools require less lubrication. 4. Air tools are quieter than steam driven equipment. a. 1, 3. b. 1, 2. c. 3, 4. d. 2, 4. e. 1, 4.

B

An advantage of driving a compressor with a steam engine is that it can be operated _____ at lower speeds. a. Without supervision. b. More efficiently. c. Less efficiently. d. With high pressure. e. With unqualified personnel.

B

An air compressor will require more power to compress the air if an intercooler is implemented. a. True b. False

B

Barrel type casings in centrifugal air compressors are for: a. Storing high-pressure air. b. Pressures above 6900 kPa. c. Inducing rotation to the air. d. Cooling during compression. e. Changing pressure to volume.

B

Compressed air can be used for _____ in boiler furnaces. a. Cooling b. Soot blowing c. Ventilation d. Purging e. Cleaning

B

Effective intercooling will reduce weakening of parts due to high temperatures, and reduce possibility of ___________. a. compressor explosions b. water hammer c. compressor implosions d. compressor leaks e. corrosion

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 the 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 an air dryer desiccant is used to _________________. a. fill the empty space in the air dryer b. absorb moisture c. prevent corrosion in the receiver d. add moisture to the air e. heat the air

B

Of all the positive displacement compressors, the _____ compressor can deliver the highest discharge pressure. a. Sliding vane b. Reciprocating c. Rotary lobe d. Radial flow e. Axial flow

B

Positive displacement compressors may be divided into two general types of compressors: 1. Reciprocating 2. Centrifugal 3. Rotary 4. Axial a. 1, 2 b. 1, 3 c. 1, 4 d. 2, 3 e. 2, 4

B

Surging of dynamic air compressors can produce severe shock to the system and may be violent enough to damage the: a. Driver and casing. b. Impeller or piping. c. Dummy piston. d. Bearings and gearing. e. Casing and foundation.

B

The clearance pocket method of unloading an air compressor uses: a. Clearance pockets at each end of the cylinder. b. The variable volume principle. c. Slide valve unloader. d. Hydraulically controlled inlet vanes. e. Hold the inlet valves in the close position.

B

The four major purposes of an air receiver is to: 1) Act as a reservoir or storage vessel 2) House fittings such as safety valve, pressure gauge, and fusible plug 3) Dampen the pulsations of a reciprocating compressor 4) Act as a compressor output control reference point 5) Allow moisture and oil particles to settle out 6) Allow further heating of the air before going to the use a. 1, 2, 5, 6 b. 1, 3, 4, 5 c. 1, 2, 3, 6 d. 2, 3, 4, 5 e. 2, 4, 5, 6

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

The term dynamic describes those compressors that use _____ to give velocity then pressure to the air. a. Turbulence. b. Blades or vanes. c. Pistons. d. Screws. e. Lobes.

B

The specifications for an air receiver must conform to the A.S.M.E. section _____. a. I b. VI c. IV d. VII e. VIII

E

A compressor with _____ is known as an angle compressor. a. A "V" type cylinder arrangement b. A "Y" type cylinder arrangement c. One cylinder on the horizontal axis and the other on the vertical axis d. Horizontal cylinder arrangement e. 45 degree type cylinder arrangement

C

A disadvantage of an electrical hand tool over an air powered hand tool is: a. It is constant speed b. After prolonged use it becomes magnetized c. There is a chance of electric shock d. An electric hand tool cannot be reversed e. A source of power is more readily available

C

A fusible plug is required on the air receiver shell to: a. Remove unwanted moisture and oil. b. Vent air if the discharge temperature of the air compressor is too high. c. Vent the air from the receiver in the event of a fire occurring in the vicinity of the air receiver. d. Vent off air if the receiver pressure is up. e. Release the air pressure should ice be formed.

C

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

A reciprocating compressor that employs clearance pocket as an unloading, method has the crank end inlet valve open and the clearance pocket closed. What capacity is the compressor working at? a. 0%. b. 25%. c. 50%. d. 75%. e. 100%.

C

After an air receiver is opened up it should be thoroughly ventilated because of the chance of it containing: a. Oil. b. Water. c. Carbon monoxide. d. Carbon dioxide. e. Hydrogen.

C

Air compressors should be automatically unloaded ______________. a. by the operator b. during the shutting-down period c. for the start-up period d. at all times of compressor output e. if there is no cooling water for the aftercooler

C

An advantage of dynamic compressors and some rotary compressors as compared to reciprocating compressors is that they can: a. Be quickly shut down b. Be opened for internal inspection c. Deliver oil free air d. Effectively use low speed drivers e. Have no moving parts

C

Centrifugal compressor impellers are usually made form steel and are: 1. Cast. 2. Machined. 3. Forged. 4. Made by welding. 5. Galvanized. a. 1, 2, 3. b. 1, 4, 5. c. 1, 3, 4. d. 2, 3, 5. e. 3, 4, 5

C

Control systems can use compressed air as a _____ medium and also to power actuating devices such as air cylinders. a. Heating b. Drying c. Signaling d. Cooling e. Lubricating

C

In positive displacement compressors the air is compressed by: a. Increasing the velocity b. Changing velocity to pressure c. The pushing action of pistons, vanes or lobes d. Changing vacuum to pressure e. Multiple stages

C

Positive displacement compressor types include: 1. Sliding vane 2. Axial flow 3. Internal gear 4. Volute casing 5. Rotary screw 6. Multi lobe a. 1, 3, 4, 6 b. 2, 4, 5, 6 c. 1, 3, 5, 6 d. 1, 2, 4, 5 e. 2, 3, 4, 6

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 valves. a. 2, 4 b. 1, 4 c. 1, 2, 3 d. 1, 2, 3, 4 e. None of the above

C

The variable speed control is best suited to a driver that can be _____. a. Utilize with clearance pocket and inlet valve unloader. b. Unloaded. c. Throttled. d. Start and stop controlled. e. Monitored.

C

To avoid air compressor explosions the system should be provided with: a. Maximum cooling water possible. b. Maximum oil possible to prevent overheating. c. Minimum oil necessary for adequate lubrication. d. Having the cylinder walls well insulated. e. An aftercooler.

C

Two general types or designs of dynamic air compressors are: a. Rotary and reciprocating. b. Single stage and multistage. c. Axial flow and centrifugal. d. Sliding vane and internal gear. e. Rotary and axial flow.

C

The specifications for an air receiver must conform to the ASME Section: a. I. b. VI. c. IV. d. VII. e. VIII.

E

When first starting a compressor operate the cylinder lubricator by hand to _______________. a. take some load off the pressure lubricator b. make sure it works for duration of compressor operation c. supply some oil to the cylinder for start-up d. to ensure that there is oil in the crankcase e. All of the above

C

When starting up a compressor, make sure: 1) No one is still working on the unit 2) The suction and discharge valves are closed 3) To check the system for oil leaks 4) It is unloaded a. 1, 2, 3 b. 1, 2, 4 c. 1, 3, 4 d. 2, 3, 4 e. 1, 2, 3, 4

C

_____ can be started by use of a compressed air starting motor or applied high pressure air directly to starting cylinders. a. Gas turbine engines b. Steam turbine engines c. Large diesel engines d. Gasoline engines e. Centrifugal pumps

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 The water separator is often fitted directly t the outlet of the aftercooler. When it's not integral to the aftercooler, it's installed as close as possible

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

Air transmission piping is _____ than electrical wiring. a. Longer. b. Lighter. c. Smoother. d. More expensive. e. Less expensive.

D

An air filter on an air compressor inlet pipe is used to ___________________. a. reduce the air velocity b. keep out the moisture c. purify the air by removing exhaust process gases d. prevent dust and other particulate from entering the compressor e. increase the air velocity

D

Compressed air is not used for: a. Starting large diesel engines. b. Soot blowing for boiler furnaces. c. Mixing of agitating materials for a process. d. Cooling and aerating the steam in a steam condenser. e. Instrumentation and controls.

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

The presence of ________ in the air may later result in the compressed air piping being subjected to water hammer. a. oil b. corrosion c. dirt particles d. nitrogen e. moisture

E

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

Once the compressor is started and running at rated speed and all conditions are satisfactory, it is recommended to load the compressor up __________. a. quickly to 100% load b. quickly to 75% load c. quickly to 50% load d. gradually e. slowly to 10% load and stop

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

Since a _____ operates at a relatively high speed, as a driver for a reciprocating compressor a speed reducing arrangement must be used. a. Steam turbine b. Steam engine c. Internal combustion engine d. Electric motor e. Gas turbine

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 inlet pipe to the compressor must be _________________. a. larger that the compressor intake b. twice as large as the compressor intake c. smaller than the compressor intake d. at least as large as the compressor intake e. at least as large as the compressor discharge

D

The two main classifications of compressors are: a. Single acting and double acting b. Reciprocating and rotary c. Centrifugal and axial d. Positive displacement and dynamic e. Rotary and dynamic

D

Transmission losses are less with air than with steam since none of the air could _____ in the pipe, as is the case with steam. a. Evaporate. b. Expand. c. Explode. d. Condense. e. Lubricate.

D

When air is compressed its: 1. Volume decreases. 2. Pressure increases. 3. Specific heat increases. 4. Velocity decreases. 5. Temperature increases. a. 1, 2, 3, 4, 5 b. 3, 4, 5 c. 1, 3, 4, 5 d. 1, 2, 4, 5 e. 2, 3, 4, 5

D

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

A truly adiabatic air compression system would not have any _____ given or taken from the cycle. a. Temperature. b. Oil. c. Pressure. d. Lubrication. e. Heat.

E

Aftercoolers should be fitted with _______________. a. pressure gauges b. thermometers c. possibly a safety valve d. water separator e. All of the above

E

An advantage of air driven hand tools over electric had tools is that they do not become _____ after extensive use. a. Dull b. Greasy c. Heavy d. Smoky e. Hot

E

An air receive is a pressure vessel which is used: 1) As a reservoir 2) To dampen pulsation of reciprocating compressor 3) To allow moisture and oil particles to settle out from the air a. 1 b. 2 c. 3 d. 1, 2 e. 1, 2, 3

E

Dynamic compressors are _____ compressors: a. Positive displacement b. Double acting c. Reciprocating d. Single acting e. Centrifugal or axial flow

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 axis of an air receiver may be: 1) Vertical 2) 45° from vertical 3) Horizontal 4) 30° for vertical a. 1 b. 2 c. 3 d. 4, 2 e. 1, 3

E

The discharge pipe of an air compressor: a. Larger than the compressor discharge. b. Twice as large as the compressor discharge. c. Smaller than the compressor discharge. d. At least as large as the compressor intake. e. At least as large as the compressor discharge.

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

Use of the start and stop air compressor output control in conjunction with the constant speed control system: a. Conserves the motor life. b. Reduces high amperage draw therefore saving electricity. c. Gives a flexible control life. d. Conserves the compressors life. e. All of the above.

E

_____ compression is preferable because of the lesser amount of power required to carry out the compression. a. Adiabatic. b. Positive displacement. c. Dynamic. d. Unloaded. e. Isothermal.

E

_____ compressors are more efficient than other positive displacement types. a. Rotary screw. b. Sliding vane. c. Rotary lobe. d. Axial flow. e. Reciprocating.

E