for engineering students

2.  in rotary screw air compressors, the most
important part is the screw unit. For this reason
they are called as rotary screw.
 When compressor start running, firstly, it raises
the compressor’s inside pressure approximately
1-2 bar.

4.  It consist of two screws - one with convex
and the other with concave contour
mostly called male and female rotor
respectively.
 These two screws gets rotating by means
of gear trips there by sucking the air
through an inlet port in chamber and then
compressing the same.

5.  Thus compression begins and air is
discharged at the end of other side.
 There is no contact between male and
female rotors and casing. Hence no
lubrication require but oil may injected
for the purpose of cooling.

7.  The helix of the male and female rotor screw
is designed to permit complete charging of the
inter lobe space before the re-mesh.
 On completion of the filling operation the inlet
end of male and female lobes begins to re-
engage thus reduces the volume of air
continuously.

9.  There are many different types of rotary
screw air compressors based on :-
1. Stages
2. cooling method
3. drive type.
 COOLING METHODS :-
1. Oil-free compressors
2. Oil-Injected Compressors

10.  Advantages :-
 Screw air compressors are designed as quiet by
the manufacturers.
 More efficient than reciprocating compressors.
 Screw air compressors can reach high capacities
that piston compressors cannot.
 These compressors are the high technology
products.
 If services done completely, they are long lived.

11.  Disadvantages :-
 Screw air compressors are more expensive than
reciprocating air compressors.

12.  Did you know?
 Rotary screw technology is the same technology
utilized by superchargers in high-performance
engines !