Due to ageing of the compressors and inherent inefficiencies in the internal components, the free air delivered may be less than the design value, despite good maintenance practices. Sometimes, other factors such as poor maintenance, fouled heat exchanger and effects of altitude also tend to reduce free air delivery. In order to meet the air demand, the inefficient compressor may have to run for more time, thus consuming more power than actually required.
The power wastage depends on the percentage deviation of FAD capacity. For example, a worn outs compressor valve can reduce the compressor capacity by as much as 20 percent. A periodic assessment of the FAD capacity of each compressor has to be carried out to check its actual capacity. If the deviations are more than 10%, corrective measures should be taken to rectify the same.
The purpose of this assessment is to find out the present actual air compressor performance to be compared with design values for assessing the compressor efficiency.