Cylinders comprise the working chambers, the compressor valves and the cylinder cooling.
The design of the cylinder is adapted to the specific pumping duty.
The number and size of the working chambers is defined by the thermodynamic function of the compressor. Several working chambers can be fitted within one cylinder.
The arrangement of the cylinder axes influence the design of the crank shaft and the mechanical stresses of the compressor. In a compressor with in line cylinders the axes of the cylinders are parallel and are at right angles to the crankshaft. In general the axes are in a vertical plane, therefore also called a vertical piston arrangement (fig. a)
If the cylinders are arranged in two opposite groups the compressor is of the boxer type (balanced opposed piston). The axis of the cylinders are then mostly in a horizontal plane (fig. b).
If the cylinders are arranged in two planes which are at an angle to each other it is called a V design (fig c).
A V-angle of 90 degrees is favourable for the balance of the mass forces. A special case is the arrangement of both vertical and horizontal cylinder axis (vertical / horizontal design fig. d).