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3
Classification of Compressors
Compressors are classified in the same way as pumps.
The chart in Figure 3.1 shows
the most common types. Compressors that are not used on the ADGAS plant are
shaded in grey.
The same two main groups are used for compressors as for pumps:
• positive displacement
•
dynamic
ADGAS does not use rotary compressors on the plant and axial compressors are only
found in the gas turbine used for electrical power generation.
Figure 3.1: Compressor Classification Chart
Compressors
Positive
displacement
Dynamic
Reciprocating
Rotary
Centrifugal
Piston
Lobe
Vane
Screw
Axial
Now try
Exercise 1
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4 Positive
Displacement Compressors
Positive displacement compressors include those shown in that part of the
classification
chart repeated in Figure 4.1.
All positive displacement compressors draw in a volume of gas that depends on the
size of the
fluid chamber. They trap this gas in a space formed between the
compressing element, a piston
or rotor, and the compressor casing. The gas volume is
reduced and its pressure increased. It is then displaced by the compressing element as
it is pushed out of the discharge port.
Although the volume of gas discharged is less than the
volume entering from the
suction port, because the capacity is measured
as if the pressure and temperature
were fixed at 1.1013bara and 15
o
C, the capacity of these compressors
depends only
on their size and speed.
Positive displacement compressors do not give a steady discharge of gas.
They are usually driven by electric motors, directly or through a gearbox.
Figure 4.1: Positive Displacement Compressors
Positive
displacement
Reciprocating
Rotary
Piston
Lobe
Vane
Screw
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