Assignment Review

Question 1

Two Classifications of Dynamic Compressors

Answer 1

Centrifugal and Axial

Question 2

How do Dynamic Compressors create pressure?

Answer 2

Converting gas velocity energy into pressure

Question 3

How is gas directed from one stage to the next in a single-shaft multi-staged design?

Answer 3

Through a diffuser

Question 4

Which centrifugal compressor casing has the lowest pressure capabilities?

Answer 4

Sectional Casing

Question 5

Which centrifugal compressor impeller design used extensively for multi-stage designs is capable of higher pressure ratios?

Answer 5

Closed impeller

Question 6

What causes axial thrust in a dynamic compressor?

Answer 6

Pressure differential acting on the impeller’s surfaces

Question 7

What is used to control axial thrust in a dynamic compressor?

Answer 7

Thrust bearings

Question 8

What is the name of the cast sections that form the diffusers or volutes in single- shaft machines?

Answer 8

Diaphragms

Question 9

Which type of seal used on centrifugal compressors has rotating speed limitations?

Answer 9

Mechanical seals

Question 10

What is the simplest method of controlling axial compressor output?

Answer 10

Variable Speed

Question 11

Where does fouling primarily occur in Axial compressors?

Answer 11

Stator blades

Question 12

What is the name for the condition where high discharge pressures and corresponding low flow rates result in flow reversal?

Answer 12

Surging

Question 13

What is the name for the condition where maximum flow has been reached at low discharge pressures?

Answer 13

Stonewalling

Question 14

How is surging prevented in single-speed dynamic compressors?

Answer 14

Opening the recycle valve

Question 15

How are vibration levels monitored in dynamic compressors?

Answer 15

Measuring rotor position continually with proximity probes

Question 16

What units of measurement do manometers use to indicate relative pressures?

Answer 16

inches of water

Question 17

What pressure is measured when one end of a manometer is inserted perpendicular (90°) to duct air flow and the other end is open to atmosphere?

Answer 17

Static Pressure

Question 18

What pressure is measured when one end of a manometer is facing into the duct air flow and the other end is perpendicular (90°) to the air flow?

Answer 18

Velocity Pressure

Question 19

Which of these describes ‘Total pressure’ ?

Answer 19

Velocity pressure plus static pressure

Question 20

What is used to prevent static electrical charges from causing harm to equipment or personnel?

Answer 20

Installation of grounding straps, brushes and holders

Question 21

What is the name of the draft arrangement in which a fan is located between the boiler and chimney?

Answer 21

induced draft

Question 22

Which centrifugal fan wheel is suited for handling high particulates or materials in the air stream?

Answer 22

Straight Radial

Question 23

Which centrifugal fan wheel is suited for residential heating systems because of the low operating speeds and noise levels?

Answer 23

forward curved

Question 24

Whose principle indicates that converging ducting will increase velocity pressure, while diverging ducting will increase static pressure?

Answer 24

Bernoullis

Question 25

How is the capacity of a fan controlled?

Answer 25

Inlet guide vanes, inlet/outlet dampers, Variable operating speeds

Question 26

If a fan is located at the top of a cooling tower and draws air upward through the tower, it is known as a(n):

Answer 26

Induced draft fan

Question 27

Under what conditions will a dynamic compressor reach its stonewall or choke point?

Answer 27

High flow, low pressure

Question 28

__________blades in some _________compressors can be used to control flow through the machine:

Answer 28

Stator / Axial

Question 29

Which of the following is used to prevent compressor surging?

Answer 29

Recycle / Bypass Valve

Question 30

Fans are:

Answer 30

Low pressure / high volume machines

Question 31

Centrifugal blowers operate on the same principle as:

Answer 31

Centrifugal compressors

Question 32

What is used to control axial compressor capacity?

Answer 32

Adjust operating speed or stator blade pitch

Question 33

A fan drawing flue gas from a boiler furnace would:

Answer 33

Require high maintenance because of heat, moisture and contaminants

Question 34

The correct order of installation for the following air-line accessories is:

Answer 34

FRL! Filter, regulator, lubricator

Question 35

Pressure in a confined, static fluid acts the same and equally in every direction, and always acts at right angles to the surface. This statement is known as:

Answer 35

Pascals Law

Question 36

What is necessary in order for fluids to flow from one area to another?

Answer 36

A Pressure Differential

Question 37

Why would it be advantageous to use a two-stage inter-cooled compressor over a single-stage if both put out 100 CFM?

Answer 37

Inter-cooled compressors are more efficient

Question 38

How are dynamic compressors classified?

Answer 38

Direction of air or gas through rotating components

Question 39

Which of the following is a tool used to inspect internal components without disassembling a compressor?

Answer 39

Borescope

Question 40

What can be used to reduce thrust in a dynamic compressor?

Answer 40

Balance drum or piston

Question 41

Which compressor can be cleaned by feeding crushed walnut shells into an operating unit?

Answer 41

Axial Compressor

Question 42

Which of the following methods is not used to control the flow through centrifugal fans?

Answer 42

Varying the blade pitch

Question 43

Which style of centrifugal compressor housing would be used for extremely high pressure applications?

Answer 43

Barrel type (vertically split)

Question 44

The wet seals used on some dynamic compressors require that seal oil enters the seal:

Answer 44

At a pressure higher than the gas pressure to be sealed