Compressed-Air Leak Load and Annual Cost (Load/Unload Test)

With production off, the fraction of a cycle the compressor runs loaded (t_load / (t_load + t_unload), the DOE Compressed Air Challenge method) times the rated capacity is the leakage flow, converted to kilowatts at the system specific power (18-22 kW per 100 cfm) and to dollars at the run hours and rate. A neglected system loses 20-30 percent of its air to leaks, a well-run one under 10, and the difference is thousands a year on the plant's most expensive utility. Needs no flow meter. An estimate from a stopwatch test, not a metered audit.

leak_fraction = load_min / (load_min + unload_min); leak_cfm = compressor_cfm x leak_fraction; leak_kw = leak_cfm x specific_power / 100; annual_kwh = leak_kw x run_hours; annual_cost = annual_kwh x rate_kwh.

The US DOE Compressed Air Challenge load/unload leak test (leak fraction = t_load / (t_load + t_unload), leak flow = fraction x compressor cfm) and the compressed-air specific-power convention (18-22 kW per 100 cfm at 100 psig for a rotary-screw system), by name; the relations are public.

The DOE Compressed Air Challenge load/unload method and the specific-power convention are public; the DOE compressed-air tip sheets and sourcebook are free at energy.gov.

Estimate. AHJ and licensed professional govern.

Field names used by the API: compressor_cfm, load_min, unload_min, specific_power, run_hours, rate_kwh, leak_fraction, leak_cfm, leak_kw, annual_kwh, annual_cost

• Leak fraction the loaded fraction of the load/unload cycle with production off, t_load / (t_load + t_unload)US DOE Compressed Air Challenge
• Leak flow the leak fraction times the compressor's delivered capacity at the operating pressureUS DOE Compressed Air Challenge
• Specific power the whole system's wire-to-air kW per 100 cfm (18-22 at 100 psig, rotary screw)compressed-air specific-power convention