CHAPTER 5 COMPRESSORS
1. Lobe compressors can be used in wet and dry gas service.
a. true
b. false
2. The suction and the discharge ports on a liquid ring compressor are located:
a. on the rotor
b. on the inlet and outlet side of the casing
c. suction on rotor, discharge on casing
d. discharge on rotor and suction on casing
3. Liquid ring compressors are primarily used in:
a. hazardous gases
b. toxic gases
c. hot gases and vapors
d. solvent recovery
e. all the above
4. Identify the main components of a liquid ring compressor.
a. casing b. large discharge port
c. impeller d. large suction port
e. small discharge port f. small suction port
g. inlet guide vanes h. rotor
i. curved vanes j. intercooler
k. piston rod l. air cavity
m. water or seal liquid n. suction eye
5. Select the basic parts of an axial compressor:
5-1. 5-5.
5-2. 5-6.
5-3. 5-7.
5-4. 5-8.
6. Describe two types of compressor layouts.
a. diffuser and stator
b. V and L
c. open and closed
d. parallel and multistage
7. Select the basic parts of a cylinder and piston reciprocating compressor:
7-1 7-7
7-2 7-8
7-3 7-9
7-4 7-10
7-5 7-11
7-6 7-12
8. If a lobe compressor is used for wet gas service the _________ rotation is
recommended.
a. upward
b. downward
c. is not used for wet gas service
d. a or b is OK
9. Lobe compressors can be utilized as vacuum units.
a. true
b. false
10. The most common type of reciprocating compressor is:
a. plunger
b. rotary screw
c. piston
d. diaphragm
11. Parallel cylinder arrangement occurs when:
a. one cylinder is lined up with two separate intakes and common discharge lines.
b. two cylinders are lined up with separate intakes and common discharge lines.
c. two cylinders are lined up with common intakes and separate discharge lines.
d. two cylinders are lined up with separate intakes and separate discharge lines.
12. What two items make up a stage in an axial compressor?
a. stator and rotor blade
b. diffuser and impeller
c. impeller and casing
d. piston and rings
13. Piston and cylinder lubrication is more important in:
a. safety design than actual application
b. c & d
c. a pump
d. a compressor
14. The higher the pressure the larger the volume.
a. true
b. false
15. Liquids compress as easily as vapors or gases.
a. true
b. false
16. Compressed gases will resume _______________ when released:
a. 50 % original volume
b. 71% original volume
c. 98% original volume
d. 100 % original volume
17. The principle of compression has a measurable relationship between the volume a set
weight of gas occupies.
a. true
b. false
18. Compressors are primarily designed to:
a. compress gases and small amounts of liquid
b. compress relatively dry gases
c. compress hot fluids
d. work in closed systems
19. An inlet valve unloader is:
a. a safety valve designed to prevent over pressuring the receiver.
b. a relief valve designed to prevent over pressuring the receiver.
c. term applied to gas movement between stages
d. a & b
20. A demister is:
a. a cyclone type device used to remove solids from gas
b. a cyclone type device used to remove moisture from gas
c. converts liquid into mist
d. a heat exchanger
21. A desiccant dryer is used to remove moisture from compressor gases as they are passed
over a chemical called desiccant.
a. true
b. false
22. The design and operation of a compressor can usually be classified into two groups:
a. positive displacement and dynamic
b. rotary and reciprocating
c. axial and centrifugal
d. piston and centrifugal
23. Select the major components of a sliding vane compressor:
a. off center rotor i. impellers
b. direct center rotor j. piston
c. crankshaft k. suction port
d. discharge port l. impellers
e. vanes m. casing and base
f. diffuser plates n. cooling water jacket
g. air cooled jacket o. discharge check valve
h. connecting rod p. cylinder
24. Centrifugal compressors operate by:
a. compressing the gases in a cylinder and releasing
b. accelerating the gas axially along the shaft
c. accelerating the gas and converting the energy to pressure
d. a & c
25. The type of compressor that uses two helical rotors to compress gases:
a. twin lobe design
b. liquid ring
c. rotary screw
d. piston- V layout
26. The internal lobes on a lobe compressor are designed:
a. not to touch
b. with a power lobe that pushes the idler lobe
c. with a few thousandths of an inch clearance between casing and lobes.
d. a & c
27. The stator blades in axial compressor can be arranged in all the following designs
except:
a. fixed
b. individually adjustable
c. stator-rotor impeller
d. continually variable
28. A 23,000 horse power axial compressor produces as efficiently as a comparable
_________ horse power centrifugal compressor.
a. 30,000
b. 20,000
c. 25,000
d. 23,000
29. The typical compressor system most closely resembles the following:
a. compressor, dryer, air receiver, gas header
b. compressor, air receiver, dryer, gas header
c. compressor, gas header, air receiver, dryer
d. gas header, compressor, dryer, air receiver
30. List two dynamic compressors:
a. dynamic & rotary
b. rotary & reciprocating
c. centrifugal & axial
d. axial & centronic
31 Gas volume does not vary with temperature and pressure.
a. true
b. false
32. Liquids are considered to be:
a. non-compressible
b. compressible in low pressure operations
c. compressible during high pressure operations <500 psig
d. compressible in a PD compressor operation
33. What type of equipment is an aftercooler or intercooler?
a. air cooled heat exchanger
b. water cooled heat exchanger
c. refrigeration expansion valve
d. a or b
34. Gases and vapors are non-compressible.
a. true
b. false
c. depends on molecular structure of gas or vapor
d. directly proportional to temperature
35. The rapid compression of a gas or vapor:
a. moves molecules closer together
b. generates heat
c. produces a cooling effect
d. a & b
e. a & c
36. Compressed gases produce heat because of molecular friction.
a. true
b. false
37. In a sliding vane compressor the gas inlet port is positioned so gas flows into the vanes
when they are:
a. fully extended and the largest air pocket is formed
b. 50% extended and the air pocket is half formed
c. 25% extended and the air pocket is just forming
d. the vanes are always fully extended on a sliding vane compressor because the
rotor is positioned “direct center.”
38. Lobe compressors are characterized by the:
a. close clearances between the casing and impellers
b. two kidney bean shaped impellers
c. use of timing gears
d. all the above
39. If the compression ratio for a 3 stage compressor is 3.2. What is the final pressure?
a. 481.7 psia
b. 212.3 psig
c. 67.4 psia
d. 180.5 psia
40. If the compression ratio for a 4 stage compressor is 3.6. What is the final pressure?
a. 850 psia
b. 989 psia
c. 1,890 psig
d. 2,469 psia
41. If the compression ratio for a 6 stage compressor is 4.0. What is the final pressure?
a. 235.2 psia
b. 3,763.2 psia
c. 60211 psia
d. 15,052.8 psia
42. Rotary screw compressors operate at speeds between:
a. 200 and 1000 RPM
b. 425 and 1250 RPM
c. 850 and 1600 RPM
d. 1750 and 3600 RPM
43. A rotary screw compressor has a capacity rating:
a. 4,500 CFM
b. 8,000 CFM
c. 12,000 CFM
d. 16,000 CFM
44. Rotary screw compressors deliver pressures between:
a. 35- 55 psig
b. 65- 90 psia
c. 100- 130 psia
d. 120- 160 psia
45. Reciprocating compressors typical discharge pressure range from:
a. 0- 30,000 psi
b. 0- 20,000 psi
c. 0- 10,000 psi
d. 0- 7,500 psi
46. On a centrifugal compressor the part of the impeller vane that comes into contact with the
gas first is called the:
a. wear ring outlet
b. suction eye
c. impeller shroud
d. suction vane tip
47. What is the first step in starting up a compressor:
a.
48. A liquid ring compressor can produce a vacuum of:
a. 12-16 inches of Hg
b. 27- 29 inches of Hg
c. 16- 22 inches of Hg
d. 22- 26 inches of Hg
49. List the devices used in a reciprocating compressor to provide smooth gas flow, reduce
vibration, and prevent under/ overloading:
a.
b.
c.
Answer Key Chapter Five Compressors
