The power required to drive the compressor will be determined by these volume and pressure considerations. A specifier will also want to think about system losses in determining compressor capacity: piping losses, pressure drops through dryers and filters, etc. Compressor buyers also have drive decisions to make such as motor belt- or direct-drive, engine gas- or diesel-drive, etc.
Compressor makers will often publish compressor-performance curves to enable specifiers to evaluate compressor performance over a range of operating conditions. This is especially true for centrifugal compressors which, like centrifugal pumps, can be sized to deliver different volumes and pressures depending on shaft speed and impeller sizing.
The Dept. of Energy is adopting energy standards for compressors against which some compressors makers are publishing data sheets. As more manufacturers publish these data, compressor buyers should have an easier time sorting through the energy usage of comparable compressors.
