Numerous factors play a role when selecting an appropriate compressor.

The required operating overpressure has to be determined to design the plant. At first, you have to comply with the consuming units’ demands. If different consuming units exist, the operating overpressure will be selected according to the highest required overpressure of all consuming units. Furthermore, the pressure loss should be included in the calculation of the overpressure. If high overpressure is expected then the plant should be adjusted to this higher demand.

Apart form the operating overpressure the demand for air should be determined. In this regard you have to add up the consumption of air of the individual consuming units.

Because of the fact that not all consuming units are operated simultaneously and permanently a “coincidence or an on-period factor” has to be taken into account which has to be estimated.
Reserves should be included in the calculation because losses (because of leakages, wear, etc.) might occur during operation.