Assignment Review Flashcards
Two Classifications of Dynamic Compressors
Centrifugal and Axial
How do Dynamic Compressors create pressure?
Converting gas velocity energy into pressure
How is gas directed from one stage to the next in a single-shaft multi-staged design?
Through a diffuser
Which centrifugal compressor casing has the lowest pressure capabilities?
Sectional Casing
Which centrifugal compressor impeller design used extensively for multi-stage designs is capable of higher pressure ratios?
Closed impeller
What causes axial thrust in a dynamic compressor?
Pressure differential acting on the impeller’s surfaces
What is used to control axial thrust in a dynamic compressor?
Thrust bearings
What is the name of the cast sections that form the diffusers or volutes in single- shaft machines?
Diaphragms
Which type of seal used on centrifugal compressors has rotating speed limitations?
Mechanical seals
What is the simplest method of controlling axial compressor output?
Variable Speed
Where does fouling primarily occur in Axial compressors?
Stator blades
What is the name for the condition where high discharge pressures and corresponding low flow rates result in flow reversal?
Surging
What is the name for the condition where maximum flow has been reached at low discharge pressures?
Stonewalling
How is surging prevented in single-speed dynamic compressors?
Opening the recycle valve
How are vibration levels monitored in dynamic compressors?
Measuring rotor position continually with proximity probes
What units of measurement do manometers use to indicate relative pressures?
inches of water
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?
Static Pressure
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?
Velocity Pressure
Which of these describes ‘Total pressure’ ?
Velocity pressure plus static pressure
What is used to prevent static electrical charges from causing harm to equipment or personnel?
Installation of grounding straps, brushes and holders
What is the name of the draft arrangement in which a fan is located between the boiler and chimney?
induced draft
Which centrifugal fan wheel is suited for handling high particulates or materials in the air stream?
Straight Radial
Which centrifugal fan wheel is suited for residential heating systems because of the low operating speeds and noise levels?
forward curved
Whose principle indicates that converging ducting will increase velocity pressure, while diverging ducting will increase static pressure?
Bernoullis
How is the capacity of a fan controlled?
Inlet guide vanes, inlet/outlet dampers, Variable operating speeds
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):
Induced draft fan
Under what conditions will a dynamic compressor reach its stonewall or choke point?
High flow, low pressure
__________blades in some _________compressors can be used to control flow through the machine:
Stator / Axial
Which of the following is used to prevent compressor surging?
Recycle / Bypass Valve
Fans are:
Low pressure / high volume machines
Centrifugal blowers operate on the same principle as:
Centrifugal compressors
What is used to control axial compressor capacity?
Adjust operating speed or stator blade pitch
A fan drawing flue gas from a boiler furnace would:
Require high maintenance because of heat, moisture and contaminants
The correct order of installation for the following air-line accessories is:
FRL!
Filter, regulator, lubricator
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:
Pascals Law
What is necessary in order for fluids to flow from one area to another?
A Pressure Differential
Why would it be advantageous to use a two-stage inter-cooled compressor over a single-stage if both put out 100 CFM?
Inter-cooled compressors are more efficient
How are dynamic compressors classified?
Direction of air or gas through rotating components
Which of the following is a tool used to inspect internal components without disassembling a compressor?
Borescope
What can be used to reduce thrust in a dynamic compressor?
Balance drum or piston
Which compressor can be cleaned by feeding crushed walnut shells into an operating unit?
Axial Compressor
Which of the following methods is not used to control the flow through centrifugal fans?
Varying the blade pitch
Which style of centrifugal compressor housing would be used for extremely high pressure applications?
Barrel type (vertically split)
The wet seals used on some dynamic compressors require that seal oil enters the seal:
At a pressure higher than the gas pressure to be sealed
