Compressor, Blowers, Fans Review Flashcards
3 Examples of Positive Displacement ROTARY Compressors;
Vane
Liquid Ring (liquid piston)
Screw
What compressor will operate at the highest rpm?
Centrifugal
In a dynamic compressor the flow and the pressure attainable can be affected by:
-The smoothness of both the gas passages and the impeller
-The clearances within the compressor
-The speed of the impeller
Because of higher rotational speeds, ______, __________, and ___________ are areas of particular concern for dynamic compressor maintenance.
Seals, alignment, bearings
True or False;
In an axial compressor the air/gas passes radially along the compressor through alternate rows of stationary and rotating blades.
False
axially
True or False;
In an oil free screw compressor the female rotor is driven through a set of timing gears.
True
True or False;
In a vane compressor the air/gas is gradually compressed as the pockets get larger.
False
as the clearance gets smaller
Lobe Blowers produce __________ pressure, __________ flow(volume)
Low Pressure
High Flow(Volume)
True or False
Some rotary compressors can be used to create a vacuum by restricting the discharge.
false
Dynamic compressors convert velocity to pressure by:
Decreasing the gas velocity
Excessive discharge gas temperatures on a two stage dry screw compressor could be caused by:
Scaled up intercooler
In the case of centrifugal compressors, if the flow to discharge is low and a momentary reversal of flow occurs, the condition is called:
Surging
In both centrifugal and axial compressors when flow through the compressor becomes choked by either too high of a flow rate or speeds reaching sonic velocity, there is a condition called:
Stonewalling
The way the rotor’s radial position is set on large rotary vane compressors is by:
Shifting the bearing carriers and insert a dowel through the bearing carrier into the cylinder
There are three ways to arrange mechanical draft systems for boiler systems. What are they?
Induced, Forced, Balanced
What type of radial fan wheel is suitable for chunks of scrap material?
Open Wheel
Gas/air flow through a mechanical draft fan can be controlled by:
-Changing the fan blade angle
-Using shutters at the inlet
-Varying the speed of the fan
True or False;
Because liquid ring compressors deliver pulsation and oil free air, no separator is needed at the outlet.
False, needs to separate sealing fluid
When compared to a forced draft fan, an induced draft fan is usually:
Larger because it moves higher temperature gas
A vane compressor with excessive rotor slot wear would most likely:
Have increased vane wear and breakage
Sliding vane compressors do not need to be unloaded on a normal start-up because:
They use centrifugal force to move the vanes out and there is no seal to start compression until it is up to speed.
The balanced liquid ring compressor has:
A rotor that is centred in the casing
The method of capacity control that gives the most efficient unloaded operation of a rotary screw compressor is:
Geometry Control
The result of heating a gas in an enclosed space would be:
An increase in pressure
An example of a Dynamic compressor;
Axial
The radial journal bearing clearances in some centrifugal compressors can be changed by:
Shimming
If a liquid ring compressor was fed excess water for additional cooling, the most probable result would be:
A lower volume of gas would be discharged
What compressors used for oil free air, must have timing gears?
Dry Rotary Screw
Intercoolers can be located:
Between the 2nd stage and 3rd stage
intercoolers purpose - increase efficiency
An increased clearance volume in a rotary vane compressor:
Reduces the efficiency
If the minimum pressure valve on a sour gas service rotary screw compressor requires reseating, what safety precautions should be followed?
Lock and tag the prime mover
Purge all lines
Vent the compressor and lines
Oil pressure alarms on a compressor are set to work when:
Oil Pressure falls below a predetermined level
A pressure of one bar absolute is approximately equal to:
14.7 psia
How is the lobe tip to casing clearance set in a large rotary lobe blower?
Adjust the bearing carrier location and dowel to set the location
The seal oil pressure on a large dynamic compressor shaft seal must enter the seal at:
A pressure higher than the gas pressure it is trying to seal
Axial flow compressors have ______ on both the rotor and casing
Blades
The liquid ring compressor can be used to supply ____-_____ air:
oil-free
True or False;
Cycloidal blowers trap the air by meshing action of the lobes and flutes and deliver the gas along the flute to the discharge port.
True
True or False;
The natural draft system uses both forced draft and induced draft fans.
False;
no fans
Within a lobe blower system, the pressure increase takes place:
In the discharge piping
The correct order of installation for the following air line accessories is:
FRL
Filter, Regulator, Lubricator
Blowers may be positive displacement or dynamic. The dynamic blower operates on the same principle as:
Centrifugal compressors
What centrifugal compressor parts converts velocity to pressure?
Diffuser, Volute
Pressure in a confined, static fluid acts equally and undiminished in all directions at right angles to the surface. This statement is known as:
Pascals Law
Receivers must have what 3 components installed on them?
Pressure Gauge
Relief Valve
Moisture Drain
A perfect vacuum is equal to:
-14.7 psig
To measure the deepest vacuum in a system, install the vacuum gauge:
Near the inlet port of the vacuum pump
Capacity of a centrifugal compressor can be controlled by:
Controlling the flow of air to the inlet
Centrifugal compressors produce_____ flow.
Radial
Filters placed directly in the air line, after the receiver, are designed to trap:
Solid contaminants, oil and water vapour
What is the advantage of using a two-stage compressor instead of a single-stage if both put out 100 CFM?
The two-stage would be more efficient
For the same horsepower driver, what are the advantages of a screw compressor over a reciprocating compressor?
Higher volume
More compact
Less vibration
An oil separator would be found on what type of compressor systems?
Rotary wet screw compressor
The dewpoint of air or gas is:
The temperature at which the water vapour will condense
When discharge gauge pressure reads 50 psig, how would you convert this reading to psia?
Add 14.7 psi to get psia reading
Absolute zero is equal to:
-273 Celcius
As a rule of thumb, the atmospheric pressure change for every 1,000 feet of altitude gain will cause on a column of mercury.
A drop of 1 inch
What is necessary for air or gas to flow?
Create a Pressure Differential
high pressure will flow to low pressure
The type of vibration isolation used on a fan depends primarily on:
The weight and vibration characteristics of the fan
Vibration monitoring of large industrial, dynamic compressors is done by?
Continuously using proximity probes
Large, single-suction, centrifugal fans are generally mounted using what bearings?
Double row spherical roller bearings
Rotary screw compressors usually have thrust bearings on the:
Output end of both rotors
When doing an installation on any compressor mounted with plain journal bearings, it is important to:
Avoid touching the bearing or journal surfaces with your bare fingers
oily finger skin is acidic
What happens when the airflow through a compressor piping system is throttled from a six-inch line down to a three-inch line?
Velocity increases and pressure decreases
When discharge gas is being recycled in a dynamic compressor, it goes through the aftercooler before reentering the compressor. What would occur if the aftercooler water jacket became scaled up?
The air temperature would increase
How can axial forces be balanced on a multi-stage centrifugal compressor?
Balancing drums
From a design standpoint, internal leakage (slip) in a dry screw compressor can be decreased most easily by:
Increasing the rpm
The cold installed clearances between the rotors and the bearing carriers on a rotary screw compressor are usually held:
Tighter on the discharge end
Discharge pressure at a screw compressor outlet port is not dependent on:
The speed of rotation
The purpose of a minimum pressure valve in a sliding vane compressor is to:
Keep a minimum pressure for lubrication on start-up
The most common maintenance on a dry sliding vane compressor is:
Replacing the vanes
In a sliding vane compressor, which valve is opened by direct oil pressure from the sump?
Servo valve
On oil flooded sliding vane compressors, what prevents pressure from leaking back from the compressor to the air inlet filter?
The non-return portion of the inlet throttle valve
A rotary liquid ring compressor operating at sea level would have what pressure in the inlet cone?
Less than 14.7 psia
