1
Q
what is the one major moving part in a centralfugal compressor
A
rotor theon witch the impeller or impeller attach
2
Q
What is the main function of centrifugal compressors?
A
Centrifugal compressors convert velocity into pressure.
3
Q
What components do centrifugal compressors and pumps have in common?
A
Both use diffusers, a volute casing, or a combination.
4
Q
What is a single-stage centrifugal compressor?
A
It consists of a single impeller attached to an extended motor shaft.
5
Q
How is the volute housing of a single-stage compressor mounted?
A
It is flange-mounted to the motor casing.
6
Q
What is the common application of single-stage centrifugal compressors?
A
To deliver large amounts of air at low pressure.
7
Q
What is the purpose of diffuser vanes in a single-stage compressor?
A
To increase the efficiency and capacity of the compressor.
8
Q
What effect does increasing the speed of a single-stage compressor have?
A
It increases the volume and can achieve higher compression ratios.
9
Q
What is multi-staging in centrifugal compressors?
A
Adding additional impellers to increase volume and overall pressure ratio.
10
Q
How are the impellers arranged in a multi-stage centrifugal compressor?
A
In line along the rotor shaft.
11
Q
What is the maximum number of stages (impellers) that can be present on a single rotor?
A
As many as 12 stages.
12
Q
Fill in the blank: Centrifugal compressors are very similar in operation and construction to _______.
A
centrifugal pumps.
13
Q
True or False: A single-stage compressor is more complex than a multi-stage compressor.
A
False.
14
Q
What is the arrangement of impellers in an alternate design for multi-staging?
A
Four or five individual impellers with their volute casings arranged around a central bull gear
15
Q
What is the purpose of the arrangement around a central bull gear in multi-stage compressors?
A
Allows intercooling to occur between each stage
16
Q
What is the initial action that occurs when gas enters a centrifugal compressor?
A
Gas draws into the eye of the impeller
17
Q
What happens to the gas as it accelerates through the impeller?
A
Centrifugal force and velocity energy impart to the gas
18
Q
What occurs when the gas discharges from the impeller?
A
It flows into the diffuser or volute and decelerates
19
Q
What does the deceleration of gas in the diffuser transform into?
A
Pressure energy
20
Q
How does the pressure ratio of multi-stage compressors compare to single-stage compressors?
A
Higher pressure ratio
21
Q
Fill in the blank: The process in a multi-stage compressor repeats through every stage, resulting in a _______ for multi-stage compressors than for single-stage compressors.
A
higher pressure ratio
22
Q
true or false sectional casing are usually on small units with low pressure ratios and small volumes
A
true
23
Q
where are sectional compressors used
A
supply low pressure air for aeration in sewage plants
combustion air for engines
vacume pumps
24
Q
what can you inspect on horizontal split casing when you remove the upper section
A
rotor,impellers, bearings, seals ,
25
the casing splits along the centre line on a horizontal split casing true or false
true
26
sealing on horizontal split casings is metal to metal which presents a problem for higher pressures for this reason what are split casings limited to for pisg?
less then 1000psig
27
horizontally split casing are can be manufactured from what
grey cast iron , nodular iron , steel
28
name 3 compressor casings
sectional
horizontal
vertically split
29
what is the most important part of a compressor
impeller ,provides acceleration velocity for the conversion into gas pressure
30
what casings are used for high pressure applications of unto 10,000 psi and are made of a cylindrical or barrel casing
vertically split casings ,can be 5" thick upto 8 feet in diameter
31
what casing has a removable front cover and is sealed by an o-ring
vertically split casing
32
shaft speeds can exceed what rpm
50,000 rpm
33
during assembly how is the rotor shaft balanced
dynamically balanced
34
what impeller is the simplest design , is usually single stage and may be cast or fabricated
open impellers , used in rough service environments and dirty gases need to be moved
34
3 types of impeller vane designs
open
semi closed
closed
35
what controls and directs the gas flow into the compressor or from one stage to the next ?
guide elements
36
what is a diaphragm
it separates the impellers in the compressor casing ,
37
diaphragms can be casted into the casing or removable , forming the volute where the velocity converts into pressure true or false
true
38
how do you control internal leakage in the diaphragm assembly ?
labyrinth seals minimize internal leakage
39
arranging the impellers back to back reduces ?
axial thrust do this when you require high pressure rise within a single casing
40
what does the double flow arrangement do
doubles maximum flow of the compressor and reduces discharge pressure
41
what seal would u use when you encounter high pressures
interlocking labyrinth seal
42
What is a key feature of closed impellers?
Enclosure of the vane allows for higher pressure ratios
## Footnote
Closed impellers can be used extensively in single and multi-stage units, up to 12 stages, and in axial compressors as the last stage.
43
How do closed impellers contribute to efficiency?
Minimize leakage due to close tolerances
## Footnote
This design feature results in higher efficiencies in compressor systems.
44
What types of blades can semi-closed impellers have?
Straight radial, backward leaning, forward leaning, or a combination
## Footnote
The choice of blade type depends on compressor design requirements.
45
In what configurations can closed impellers be used?
Single-stage and multi-stage units, and as the last stage in axial compressors
## Footnote
Closed impellers are capable of supporting up to 12 stages.
46
What are guide elements?
Guide elements control and direct gas flow into the compressor or from one stage to the next
## Footnote
They may be stationary or movable inlet guide vanes or stationary or adjustable diffusers.
47
What is the function of inlet guide vanes in a compressor?
Inlet guide vanes control compressor output and increase efficiency
## Footnote
They regulate the gas flow entering the compressor.
48
How is the outlet of a compressor controlled?
The outlet is controlled by throttling the inlet gas flow
## Footnote
This can be achieved with a linkage system.
49
What regulates the position of the guide vanes in a compressor?
A control drive regulates the position of the guide vanes
## Footnote
The position can vary from fully open to fully closed based on system requirements.
50
Fill in the blank: Guide elements may take the form of stationary or movable _______ or stationary or adjustable _______.
inlet guide vanes; diffusers
51
What is axial thrust in dynamic compressors?
Axial thrust is the result of the differential pressure between the impeller front and the back shroud surfaces.
52
What happens to the thrust load as the area or pressure differential increases?
The thrust load increases.
53
In which direction does a single impeller or a series of impellers generate thrust load?
In the direction of the suction end of the compressor.
54
What methods can be used to minimize or eliminate thrust loads in compressors?
The following methods may be used individually or in combination:
* Balance Pistons
* Balance Drums
55
How does a balance piston minimize axial thrust?
A balance piston provides a surface area on which the full discharge pressure acts, creating an opposite acting force.
56
Where is the balance piston installed in a compressor?
At the discharge end of the compressor immediately behind the last impeller.
57
What does the balance piston allow regarding discharge gas?
It allows discharge gas to leak into a chamber formed by the back of the impeller and the face of the balance piston.
58
True or False: The balance piston acts with the discharge pressure to minimize axial thrust.
True.
59
Fill in the blank: Axial thrust is minimized by the installation of a _______ at the discharge end of the compressor.
[balance piston]
60
What is the purpose of the thrust collar in a compressor?
To control and maintain axial thrust and rotor location
61
Where is the thrust collar usually located in a compressor?
At the suction end of the compressor
62
What components control axial movement in relation to the thrust collar?
Thrust bearings, which can be either pivoting shoe or fixed land
63
What is the relationship between the thrust collar face and the bearing surface?
Controlled by close tolerances and oil film
64
What can result from contact due to shaft movement in a compressor?
Instant compressor failure
65
What are the two types of thrust bearings mentioned?
* Pivoting shoe
* Fixed land
66
Fill in the blank: The thrust collar is _____ and can be replaceable.
[replaceable]
67
What happens due to high rotational speeds and close clearances in compressors?
Any contact results in instant compressor failure
68
true or false the shaft seal has a slight interference fit and set screws hold it in place
true
69
where are carbon ring seals used
low pressure differentials
they are self lubricating
70
true or false carbon rings are often used in conjunction with labyrinth seals as a final sealing element
true
71
when are mechanical seals used
where the shaft speed is slow ,they cause friction and heat
72
what does beam refer to
rotor supported by bearings on both ends
73
you can achieve lubrication on compressors with anti friction bearings or journal bearings if you use ?
oil bath ,oil feeder, pressurized lube system
74
75
What is the primary function of bearings in a compressor?
Provide support and ensure the correct location of the rotor
## Footnote
Bearings are critical for the operation of compressors, affecting performance and efficiency.
76
What types of support bearings are used in compressors?
Anti-friction or plain journal bearings
## Footnote
The choice depends on size and rotational speed.
77
In which type of compressors are plain journal bearings typically used?
Larger multi-stage compressors
## Footnote
They are better suited for high rotational speeds.
78
What type of bearings can be used for oil-free compression?
Magnetic bearings with dry gas seals
## Footnote
These provide a solution for applications requiring oil-free operation.
79
What is the purpose of thrust bearings in a compressor?
Control axial thrust and ensure correct rotor location
## Footnote
Thrust bearings are crucial for maintaining rotor stability.
80
What type of thrust bearings are commonly used?
Tilting pad type thrust bearings
## Footnote
They can be incorporated with journal bearings in the housing arrangement.
81
What is the element that drives the compressor called?
Prime mover
## Footnote
The choice of prime mover affects compressor performance and operation.
82
What factors influence the choice of a prime mover?
* Speed range
* Available power
* HP requirements
* Economic considerations
* Customer preference
## Footnote
Each factor plays a role in determining the most suitable prime mover for a specific application.
83
What is the most widely used driver for single-stage, low horsepower compressors?
Electric motors
## Footnote
These may be directly driven or driven through a speed increasing gearbox.
84
When are steam turbines used as prime movers?
Where excess process steam is available from plant operations
## Footnote
They can be directly coupled or driven through a gearbox.
85
What type of prime mover is common in the gas processing industry?
Gas turbines
## Footnote
The gas from the process plant powers the turbine and is conveyed through the compressor.
86
What are the two (2) major classifications of dynamic compressors?
Centrifugal and Axial
87
How do dynamic compressors produce pressure?
They convert velocity into pressure using diffusers, volute casing, or a combination of the two.
88
What can be done to increase the efficiency of a single-stage compressor?
Diffuser vanes fit to the inside of the housing.
89
What has to be done to increase the volume and overall pressure ratio of a centrifugal compressor?
Add additional impellers (each called a stage) to the rotor shaft.
90
Name the three (3) casing designs in dynamic compressors.
* Horizontally split
* Vertically split
* Sectional casing
91
Which casing design do you use for high-pressure applications (10,000 psig)?
Vertically split casing
92
Name the three (3) styles of impellers in centrifugal compressors.
* Open
* Semi-closed
* Closed
93
Which impeller design provides the highest pressure ratio?
Closed impeller
94
What is the purpose of the guide vanes?
Control or convert the gas flow into the compressor or from one stage to the next.
95
What causes axial thrust in a dynamic compressor?
Differential pressure between the impeller fromt and back shroud surfaces.
96
What are three (3) ways that you can axial thrust?
* thrust bearings
* balance piston or drums
* opposing gas flows
## Footnote
Axial thrust refers to the force acting along the axis of a rotating shaft in a compressor.
97
What is one of the most commonly used seal types in dynamic compressors?
Labyrinth seal
## Footnote
Labyrinth seals are designed to minimize leakage and are widely used due to their effectiveness.
98
How does the most common seal prevent leakage?
It allows small pressure drops at each stage.
## Footnote
This pressure drop helps maintain control over the flow of gas within the compressor.
99
What three (3) other types of seals can you find in dynamic compressors?
* Labyrinth gas seals
* Carbon ring seals
* Oil or wet seals
## Footnote
Different seal types are used to manage leakage and maintain efficiency in dynamic compressors.
100
List the five (5) factors that influence the selection of a prime mover.
* Speed range
* Available power
* Hp requirements
* Economic considerations
* Customer preference
## Footnote
These factors are critical for ensuring the prime mover meets operational needs and economic viability.
101
What type of compressor has aerodynamically shaped blades?
Axial compressor
## Footnote
Axial compressors utilize blades designed to efficiently move air or gas along the axis of the compressor.
102
What is the simplest way to control the compressor output?
With a variable speed drive
## Footnote
Variable speed drives allow for flexible control over compressor performance based on demand.
103
What other method is available for compressor control?
Varying the position of stator blades
## Footnote
Adjusting the position of the stator blades can optimize performance across different operating conditions.
104
Which instrument can you use to inspect the internal components without removing the casing covers?
Borescope
## Footnote
A borescope allows for visual inspection of internal components, aiding in maintenance and troubleshooting.
105
What do you call flow reversal in a compressor?
Surge
## Footnote
Surge is a condition where the flow of gas in a compressor reverses, which can lead to operational issues.
millwright level 3
flashcards
Decks in class (25)
# Cards
-
millwright Manuel chapter 257
-
gas laws and coefficient of linear expansion63
-
cross dial alignment20
-
laser shaft alignment16
-
alignment trade science test38
-
fans58
-
dynamic pumps89
-
postive displacement pumps0
-
hydraulics168
-
hydraulic valves74
-
hydraulic pumps90
-
fluid accessoires and seals65
-
seals part b42
-
trouble shooting and maintenance35
-
compressor fundamentals and b85
-
screw compressors and lobe blowers72
-
liquid ring compressors143
-
dynamic compressors106
-
vane compressors33
-
compressor crankshaft and frame components153
-
compressor cylinder components part b38
-
compressor auxiliary systems28
-
compressor valves13
-
pneumatic system30
-
gas and air dryers10
