a) According to number of stages:- i) Single stage: - Delivery pressure up to 10 bar ii) Multistate:- Delivery pressure above 10 bar.

b) According to number of cylinder:- i) Single cylinder ii) Multi cylinder.

c) According to method of cooling:- i) Air cooled ii) Water cooled.

d) According to action of air:- i) Single acting ii)Double acting.

e) According to capacity:- i) Low capacity ii) Medium capacity iii) High capacity.

f) According to drive:- i) Steam engine drive ii) Steam turbine drive iii) Electric motor drive iv) Internal combustion drive.