1
Q
What are liquid ring compressors used for?
A
They handle saturated, explosive, dirty, and abrasive gases and process applications involving suspended solids.
They are particularly effective in situations requiring continuous operation with little maintenance.
1
Q
What aids in sealing the compressor in liquid ring compressors?
A
Water or process fluid.
This sealing method enables the operation of the compressor without rubbing parts.
1
Q
What is the flow capacity of liquid ring compressors in a vacuum situation?
A
20 to 23,000 cubic feet per minute (cfm).
These pumps can achieve vacuum levels of 29 inches of mercury (in Hg) or greater.
1
Q
What is a common application for liquid ring compressors?
A
Pulp and paper mills.
They are used to pull liquids out of pulp before the material is sent through dryers.
1
Q
What is the maximum flow and pressure for the compression side of liquid ring compressors?
A
Up to 2600 standard cubic feet per minute (scfm) at up to 130 pounds per square inch (psi).
Typically, the pressure is usually lower than 100 psi.
1
Q
What advantage do liquid ring compressors have regarding air or gas quality?
A
They deliver oil-free air or gas.
This feature is essential in chemical processing and refining applications.
1
Q
True or False: Liquid ring compressors require much maintenance.
A
False.
They can operate continuously in adverse conditions with little maintenance.
2
Q
Fill in the blank: The horsepower requirements for liquid ring compressors are much _______ than for a reciprocating compressor of the same size.
A
higher.
This is due to the rotor continually churning in a ring of seal liquid.
3
Q
What type of compressor is a liquid ring compressor?
A
An oil-free, positive displacement rotary compressor
4
Q
What components are mounted in a stationary cylinder in a liquid ring compressor?
A
A rotating impeller with a series of fixed, forward leaning blades
5
Q
Is there metal-to-metal contact between the rotating and stationary parts in a liquid ring compressor?
A
No
6
Q
What holds the specific clearances between the inlet and discharge cones and the rotor?
A
The bearings on the shaft
7
Q
How is the rotor shaft positioned in a liquid ring compressor?
A
Mounted off-centre
8
Q
What is the function of the liquid in the cylinder casing of a liquid ring compressor?
A
To seal the rotor tips
9
Q
What action carries the liquid around the inside of the cylinder?
A
The action of the rotating impeller
10
Q
What effect does the forward curve on the impeller vanes have on the liquid?
A
They try to pull the liquid into the centre
11
Q
What force causes the liquid to form a ring around the inside of the cylinder?
A
Centrifugal force
12
Q
What does the liquid ring do as the impeller turns in the eccentric casing?
A
Moves up and down the space between the rows of impeller vanes
13
Q
What happens to the volume of trapped air between the sets of fixed blades?
A
It varies depending on the relative position of the rotor to the casing
14
Q
Through what structure does air enter and exit a liquid ring compressor?
A
A set of cones (or port plates)
15
Q
Where does air enter in the liquid ring compressor?
A
Through one port in the cone
16
Q
Where is air discharged in the liquid ring compressor?
A
Through another port in the cone
17
Q
What is the relationship between the trapped air and the outer casing in a liquid ring compressor?
A
The air is trapped between the impeller vanes and never touches the outer casing
18
Q
What is saturated with seal liquid in a liquid ring compressor?
A
The gas leaving the compressor
This indicates that the gas contains vaporized liquid, which can affect performance if not managed properly.
19
What device is used to remove the liquid from the gas in a liquid ring compressor?
Baffle or cyclone separator
## Footnote
These devices help in separating the liquid from the gas before discharge.
20
What must the liquid from the compressor pass through before being fed back into the process?
Control valve
## Footnote
This valve prevents the compressed air/liquid mixture from venting to the atmosphere.
21
How often might a solenoid valve be closed to allow the receiver to fill?
20 seconds
## Footnote
This allows for an adequate filling time before the valve opens to drain.
22
For how long might the solenoid valve open to empty the receiver?
3 seconds
## Footnote
This is the time allotted for emptying the receiver based on the cycle described.
23
What can be adjusted if the cycle does not keep the main air receiver liquid-free?
Timer circuit
## Footnote
Adjustments can be made to improve the efficiency of liquid removal.
24
What is the effect of varying the amount of liquid passed through the unit?
It affects performance
## Footnote
While the quantity is not critical, it can influence the efficiency of the compressor.
25
What should seal liquid flow be regulated by?
Properly sized orifice or regulating hand valve
## Footnote
This ensures optimal performance by controlling the liquid flow.
26
What does not cause damage to the compressor according to the text?
Saturated vapor, entrained liquid, and occasional solids
## Footnote
These elements are small enough to pass through the impeller vanes without causing harm.
27
Where is lubrication required in a liquid ring compressor?
At the bearings
## Footnote
Bearings are located outside the casing to maintain an oil-free gas or air.
28
Why is it important to keep gas or air oil-free in refinery or chemical applications?
To prevent contamination or explosion
## Footnote
Oil contamination can compromise product quality and safety.
29
What can be used to cool and lubricate the stuffing boxes?
The liquid being moved or clean water from an external source
## Footnote
This option provides flexibility depending on the application.
30
What characterizes unbalanced liquid ring compressors?
Off-centre-mounted rotors
## Footnote
Balance refers to the radial loads applied to the bearings.
31
Where does the air feed into in a liquid ring compressor?
The inlet port on the port plate or the inlet cone
32
Why is the inlet port larger in a liquid ring compressor?
To allow a larger volume of air to pass through it
33
What happens to the air once it enters the inlet port?
It is trapped between the two vanes, the impeller shaft, and the inside surface of the working liquid
34
What causes a rise in pressure in a liquid ring compressor?
Reduction of volume in the enclosed space
35
Where is the outlet port located in a liquid ring compressor?
At the pre-determined discharge pressure location
36
At which position is the pressure greatest in an unbalanced liquid ring compressor?
At the 9 to 10 o'clock position
37
What is the pressure comparison between the 9 to 10 o'clock position and the 3 to 4 o'clock position?
Greater at the 9 to 10 o'clock position
38
What design consideration is necessary for unbalanced liquid ring compressors?
The shaft and bearings must be made heavier to handle the extra load
39
Fill in the blank: In a liquid ring compressor, the air is brought into the inlet because the volume between a set of impeller vanes starts small and _______.
[increases]
40
What design feature allows the balanced unit to cancel most of the pressure force load on the radial bearings?
Two intake and two discharge ports positioned 180° opposite each other.
## Footnote
This design helps to balance the pressure areas effectively.
41
How does the radial load on the bearings in balanced units compare to unbalanced units?
The radial load is very low in balanced units compared to unbalanced units.
## Footnote
Unbalanced units lead to higher radial loads due to smaller shafts and bearings.
42
Describe the shape of the casing design in balanced units.
The casing design is more elliptical than round.
## Footnote
This design helps in achieving a balanced liquid ring compressor.
43
How many intake and discharge ports does each impeller have in a balanced liquid ring compressor?
Two intake and two discharge ports for every chamber.
## Footnote
This is in contrast to unbalanced designs.
44
What is the primary function of a liquid ring compressor?
To raise the pressure of incoming gas or to remove air/liquids and reduce pressure in a process.
## Footnote
It can operate as either a compressor or a vacuum pump.
45
What is the maximum vacuum level a liquid ring can almost reach?
0 psia, which equals 29.94 inches of mercury column (in Hg).
## Footnote
This indicates a near-perfect vacuum.
46
Where is the vacuum typically measured in a liquid ring compressor system?
At the pump inlet using a vacuum gauge.
## Footnote
The vacuum reading may vary based on the location in the system.
47
True or False: The liquid ring compressor can only be used as a compressor.
False.
## Footnote
It can also function as a vacuum pump.
48
Fill in the blank: The pressure inside the vacuum pump is at a _______ compared to the pressure further back in the system.
more of a vacuum.
## Footnote
Fluids flow from high pressure to low pressure areas.
49
What is the purpose of the elliptical chambers in a balanced liquid ring compressor?
To facilitate the balanced operation of the compressor.
## Footnote
The design helps to maintain the radial balance of the unit.
50
What is the function of inlet ports in liquid compressors?
Inlet ports allow and direct air/gas into the impeller vane chambers
## Footnote
Inlet ports can be located on cones or flat wall porting plates.
51
What do outlet ports do in liquid compressors?
Outlet ports allow the trapped gas to be discharged by the liquid being forced into the vane chambers of the impeller
## Footnote
Outlet ports are also found on the cone or flat wall porting plate.
52
What is the purpose of the packing liquid supply in a liquid compressor?
To lubricate the packing and seal the rotating shaft to the stationary casing
## Footnote
The packing liquid should be clean fluid admitted through a pipe directly over the packing lantern ring.
53
What is mechanical packing used for in liquid compressors?
To prevent air from leaking into vacuum units or out of compressors
## Footnote
Mechanical packing is set within the stuffing box and may be replaced by mechanical seals.
54
What happens to the liquid inside the casing of a liquid compressor?
Rotating impeller vanes throw the liquid outward against the elliptical casing, forming a liquid ring
## Footnote
This liquid ring surrounds the inside of the casing.
55
Fill in the blank: The _______ allows and directs air/gas into the impeller vane chambers.
[inlet ports]
56
True or False: Mechanical seals can replace mechanical packing in liquid compressors.
True
57
What do inlet ports on liquid compressors do?
Allow and direct air/gas into the impeller vane chambers
## Footnote
Inlet ports can be located on the cones or flat wall porting plate.
58
What is the function of outlet ports in liquid compressors?
Allow the trapped gas to be discharged by the liquid being forced into the vane chambers of the impeller
## Footnote
Outlet ports are also located on the cone or flat wall porting plate.
59
What is the purpose of the packing liquid supply in liquid compressors?
To lubricate the packing and seal the rotating shaft to the stationary casing
## Footnote
The packing liquid should be clean fluid admitted through a pipe over the packing lantern ring.
60
What does mechanical packing do in liquid compressors?
Prevents air from leaking into vacuum units or out of compressors
## Footnote
Mechanical packing is set within the stuffing box and may be replaced by mechanical seals.
61
How do rotating impeller vanes function in a liquid compressor?
Throw the liquid inside the casing outward against the elliptical casing, forming a liquid ring
## Footnote
This liquid ring is essential for the operation of the compressor.
62
Fill in the blank: The _______ directs air/gas into the impeller vane chambers.
[inlet ports]
63
True or False: Mechanical seals can replace mechanical packing in liquid compressors.
True
64
What components are involved in the liquid compressor parts?
Inlet ports, outlet ports, packing liquid supply, mechanical packing, rotating impeller vanes
## Footnote
These components work together to ensure efficient compressor operation.
65
What do inlet ports on liquid compressors do?
Allow and direct air/gas into the impeller vane chambers
## Footnote
Inlet ports can be located on the cones or flat wall porting plate.
66
What is the function of outlet ports in liquid compressors?
Allow the trapped gas to be discharged by the liquid being forced into the vane chambers of the impeller
## Footnote
Outlet ports are also located on the cone or flat wall porting plate.
67
What is the purpose of the packing liquid supply in liquid compressors?
To lubricate the packing and seal the rotating shaft to the stationary casing
## Footnote
The packing liquid should be clean fluid admitted through a pipe over the packing lantern ring.
68
What does mechanical packing do in liquid compressors?
Prevents air from leaking into vacuum units or out of compressors
## Footnote
Mechanical packing is set within the stuffing box and may be replaced by mechanical seals.
69
How do rotating impeller vanes function in a liquid compressor?
Throw the liquid inside the casing outward against the elliptical casing, forming a liquid ring
## Footnote
This liquid ring is essential for the operation of the compressor.
70
Fill in the blank: The _______ directs air/gas into the impeller vane chambers.
[inlet ports]
71
True or False: Mechanical seals can replace mechanical packing in liquid compressors.
True
72
What components are involved in the liquid compressor parts?
Inlet ports, outlet ports, packing liquid supply, mechanical packing, rotating impeller vanes
## Footnote
These components work together to ensure efficient compressor operation.
73
What is the function of the rotor in a liquid vane compressor?
The rotor revolves at high speed and results in a continuous liquid ring following the contour of the casing while sealing the tips of the impeller vanes.
74
What is continuously supplied to the pump in a liquid vane compressor?
A small quantity of liquid.
75
What is the purpose of the liquid supplied to the pump?
To take up the heat of compression.
76
What happens to the surplus liquid in a liquid vane compressor?
It is discharged from the pump with the gas and removed from the gas by a baffle or cyclone separator.
77
What is used to cool the seal water in a liquid vane compressor system?
A heat exchanger.
78
What does the pressure switch on the air receiver operate?
A solenoid unloader.
79
What is the purpose of the solenoid unloader in the system?
To prevent buildup of excessive air pressure and recirculate higher-pressure air in a bypass fashion.
80
Fill in the blank: The _____ is used to remove the surplus liquid from the gas.
[baffle or cyclone separator]
81
True or False: The hot condensed water is recirculated back into the system.
False.
82
What type of gas is processed in a liquid ring compressor?
Wet gas.
83
Fill in the blank: The liquid ring compressor uses _____ to maintain operational pressure.
[pressure switch]
84
What is the role of the cool seal water in the compressor system?
It is recirculated to maintain effective sealing.
85
What should you consult for specific preventative maintenance guidelines for liquid ring compressors?
The maintenance manual
## Footnote
Each liquid ring compressor has a specific maintenance manual that provides detailed guidelines.
86
What is the maintenance schedule for liquid ring compressors?
Periodic maintenance
## Footnote
Maintenance scheduling guidelines help check for various compressor conditions.
87
What inspections should be performed every six months on a liquid ring compressor?
* Clean and refill the drive coupling with oil or grease
* Inspect compressor bearings for roughness
* Replace dirty or broken down bearing grease
* Re-lubricate the drive motor bearings
## Footnote
Follow the coupling manufacturer's instructions for lubrication.
88
What inspections should be performed every twelve months on a liquid ring compressor?
* Inspect compressor bearings for wear and lubrication
* Repair bearings and replace lubricant if necessary
* Replace stuffing box packing
## Footnote
Follow manufacturer's instructions for packing replacement.
89
How are compressors with grease-packed bearings lubricated after shipment?
They need no further lubrication until the first six-month scheduled check
## Footnote
This is due to initial lubrication before shipment.
90
What are the steps to check the bearings of a liquid ring compressor?
* Remove the bearing caps
* Inspect the condition and quantity of grease
* Replace the bearing caps if grease is satisfactory
* Replace or add grease if contaminated or low
## Footnote
Use a clean, lint-free cloth to wipe out old grease.
91
What should be done if the bearing grease is contaminated or low?
* Replace or add grease
* Use a clean putty knife to pack the bearings with recommended grease
* Pack bearing caps ¼ to ⅓ full with grease
## Footnote
Ensure the grease is flush with the edge of the inner and outer races.
92
What is important to maintain when replacing bearing caps?
The original thickness of gaskets and shims
## Footnote
This thickness affects the shaft axial position.
93
What should you consult for specific preventative maintenance guidelines for liquid ring compressors?
The maintenance manual
## Footnote
Each liquid ring compressor has a specific maintenance manual that provides detailed guidelines.
94
What is the maintenance schedule for liquid ring compressors?
Periodic maintenance
## Footnote
Maintenance scheduling guidelines help check for various compressor conditions.
95
What inspections should be performed every six months on a liquid ring compressor?
* Clean and refill the drive coupling with oil or grease
* Inspect compressor bearings for roughness
* Replace dirty or broken down bearing grease
* Re-lubricate the drive motor bearings
## Footnote
Follow the coupling manufacturer's instructions for lubrication.
96
What inspections should be performed every twelve months on a liquid ring compressor?
* Inspect compressor bearings for wear and lubrication
* Repair bearings and replace lubricant if necessary
* Replace stuffing box packing
## Footnote
Follow manufacturer's instructions for packing replacement.
97
How are compressors with grease-packed bearings lubricated after shipment?
They need no further lubrication until the first six-month scheduled check
## Footnote
This is due to initial lubrication before shipment.
98
What are the steps to check the bearings of a liquid ring compressor?
* Remove the bearing caps
* Inspect the condition and quantity of grease
* Replace the bearing caps if grease is satisfactory
* Replace or add grease if contaminated or low
## Footnote
Use a clean, lint-free cloth to wipe out old grease.
99
What should be done if the bearing grease is contaminated or low?
* Replace or add grease
* Use a clean putty knife to pack the bearings with recommended grease
* Pack bearing caps ¼ to ⅓ full with grease
## Footnote
Ensure the grease is flush with the edge of the inner and outer races.
100
What is important to maintain when replacing bearing caps?
The original thickness of gaskets and shims
## Footnote
This thickness affects the shaft axial position.
101
How often should the packing in a continuous process system be scheduled for tightening and replacement?
Annually
## Footnote
More frequent change out may be required for severe service applications.
102
What should be recorded when removing packing rings if lantern rings are used?
Position and number of packing rings on each side of the lantern ring
## Footnote
This helps in reassembly and maintenance tracking.
103
What are some signs of mechanical problems that may develop over time?
Increase in noise, heat, and vibration
## Footnote
These symptoms indicate potential operational issues with the unit.
104
What should be checked if the V-belt tension is not up to specification?
Retighten the belts and check belt alignment
## Footnote
Proper alignment is crucial to prevent high vibration symptoms.
105
What operational checks should be performed if the unit is not operating correctly?
Check liquid flow rate, shaft direction of rotation, rated rpm, discharge piping for obstructions, and gas inlet line restrictions
## Footnote
Each check helps identify the source of the operational issue.
106
True or False: Altering the amount of liquid in the compressor affects the amount the compressor delivers.
True
## Footnote
Liquid is used to displace trapped gases within the compressor.
107
What happens if there are obstructions in the discharge piping?
Reduces capacity, reduces vacuum level, or discharge pressure, and increases required horsepower
## Footnote
This can lead to inefficiencies in the compressor's operation.
108
What is the consequence of an undersized pipe or restriction in the gas inlet line?
Produces a higher vacuum at the pump than at the process connection
## Footnote
This can lead to loss of vacuum if the seal water is pulled faster than it can be supplied.
109
Fill in the blank: If the unit shows high vibration and is coupled through a mechanical coupling, ensure that the _______ alignment is well within misalignment limits.
shaft coupling
## Footnote
Proper alignment is critical for the unit's operation.
110
How often should the packing in a continuous process system be scheduled for tightening and replacement?
Annually
## Footnote
More frequent change out may be required for severe service applications.
111
What should be recorded when removing packing rings if lantern rings are used?
Position and number of packing rings on each side of the lantern ring
## Footnote
This helps in reassembly and maintenance tracking.
112
What are some signs of mechanical problems that may develop over time?
Increase in noise, heat, and vibration
## Footnote
These symptoms indicate potential operational issues with the unit.
113
What should be checked if the V-belt tension is not up to specification?
Retighten the belts and check belt alignment
## Footnote
Proper alignment is crucial to prevent high vibration symptoms.
114
What operational checks should be performed if the unit is not operating correctly?
Check liquid flow rate, shaft direction of rotation, rated rpm, discharge piping for obstructions, and gas inlet line restrictions
## Footnote
Each check helps identify the source of the operational issue.
115
True or False: Altering the amount of liquid in the compressor affects the amount the compressor delivers.
True
## Footnote
Liquid is used to displace trapped gases within the compressor.
116
What happens if there are obstructions in the discharge piping?
Reduces capacity, reduces vacuum level, or discharge pressure, and increases required horsepower
## Footnote
This can lead to inefficiencies in the compressor's operation.
117
What is the consequence of an undersized pipe or restriction in the gas inlet line?
Produces a higher vacuum at the pump than at the process connection
## Footnote
This can lead to loss of vacuum if the seal water is pulled faster than it can be supplied.
118
Fill in the blank: If the unit shows high vibration and is coupled through a mechanical coupling, ensure that the _______ alignment is well within misalignment limits.
shaft coupling
## Footnote
Proper alignment is critical for the unit's operation.
119
What is the first step in repairing the tapered cone from the head?
Remove the cone part from the head if required
120
What tool is used to check the impeller cone for localized wear?
Feeler gauge
121
What is the maximum acceptable depth of localized wear on the impeller cone?
0.030 of an inch (0.76 mm)
122
What can be done to damaged surfaces of the impeller cone?
Repair with a spray weld that can be re-machined to original dimensions
123
What should be considered if the pump operates at or near maximum capacity?
Localized wear greater than 0.030 of an inch may not be acceptable
124
What is the first step in repairing the tapered cone from the head?
Remove the cone part from the head if required
125
What tool is used to check the impeller cone for localized wear?
Feeler gauge
126
What is the maximum acceptable depth of localized wear on the impeller cone?
0.030 of an inch (0.76 mm)
127
What can be done to damaged surfaces of the impeller cone?
Repair with a spray weld that can be re-machined to original dimensions
128
What should be considered if the pump operates at or near maximum capacity?
Localized wear greater than 0.030 of an inch may not be acceptable
129
What is the liquid ring compressor able to handle?
Dirty abrasive
## Footnote
Includes suspended solids and process applications.
130
Why are the horsepower requirements for a liquid ring compressor much higher than a reciprocating compressor of the same size?
Rotor is continually churning in a ring of seal liquid.
131
What does the centrifugal force cause in a liquid ring compressor?
Causes the liquid to be thrown away from the center and forms a liquid ring around the inside of the cylinder.
132
How does the gas get into and out of the liquid ring compressor?
Set of cones ports or port plates.
133
How can a liquid ring compressor cause water vapour to condense out of the gas running through the compressor?
If the sealing liquid is cool enough, it causes water or other vapours to reach dew point.
134
How is an unbalanced liquid ring compressor identified?
Off-centered mounted rotors.
135
What is the purpose of a vacuum pump?
To remove air/liquids and reduce the pressure in the process to less than atmospheric pressure.
136
Why does the pressure of the air entering a vacuum pump (or any compressor) always have to be below atmospheric pressure?
Fluids flow from high pressure to low pressure.
137
How is the rotor set in the centre of the body?
Using shims (gaskets) between bearing caps and bearing housing on each end of compressor.
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
