Air Receiver Pump-Up and Pump-Down Time

A receiver is a buffer, and the two numbers that describe it are how long the compressor takes to fill it and how long the plant can draw from it before pressure falls to the cut-in. Both come from one relation, which is just the ideal gas law in shop units: the free air stored is the volume times the pressure band in atmospheres, and 14.7 converts psig to atmospheres. THE CONSEQUENCE PEOPLE MISS IS THAT A RECEIVER'S USEFULNESS DEPENDS ON THE BAND YOU ARE WILLING TO GIVE UP, NOT ON THE TANK. Widening the cut-in to cut-out band from 20 to 40 psi doubles the usable storage out of the same vessel -- free capacity, paid for in slightly lower minimum pressure. That is what makes the draw-down form the useful one. A shop with a sandblaster or a large intermittent tool does not need a compressor that covers the peak; it needs a receiver big enough to cover the peak's DURATION while the compressor catches up between uses, and sizing that way is far cheaper than sizing the compressor to the peak. A 120 cu ft receiver on a 35 psi band supplying a tool that draws 30 scfm more than the compressor makes gives 9.52 minutes of cover -- so a tool that runs two minutes at a time is amply covered, and only about 25 cu ft of tank would have been needed for it. The receiver-sizing form is the same relation the air receiver calculator uses, rearranged, so the two cannot disagree. This is ideal-gas arithmetic at constant temperature. Real filling heats the air, so a receiver that reads its cut-out pressure hot will fall back as it cools and the compressor will restart -- pump-up times run slightly optimistic for that reason. It does not size the compressor, evaluate the piping between compressor and receiver, or address the drain, relief valve, and pressure vessel code requirements that a receiver carries; an air receiver is a pressure vessel with inspection obligations in most jurisdictions. It does not account for the storage in the distribution piping itself, which on a large system is real and sometimes substantial. The compressor and receiver manufacturers' data and the applicable pressure vessel code govern.

pump-up time = V (p2 - p1) / (14.7 x compressor scfm); draw-down time = V (cut-out - cut-in) / (14.7 x net demand); usable free air = V x band / 14.7; receiver required = duration x 14.7 x net demand / the band.

The receiver storage relation as standard practice, by name: the ideal gas law in shop units, with 14.7 converting psig to atmospheres. The receiver-sizing form is the SAME relation the air receiver calculator uses, rearranged, so the two cannot disagree. Constant temperature assumed. The compressor and receiver manufacturers' data and the applicable pressure vessel code govern.

Ideal-gas arithmetic on a volume and a pressure band; no manufacturer table is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: receiver_volume_ft3, fill_start_psig, fill_end_psig, compressor_scfm, cut_out_psig, cut_in_psig, net_demand_scfm, required_cover_minutes, pump_up_minutes, draw_down_minutes, draw_down_seconds, usable_free_air_ft3, receiver_required_ft3

• Constant temperature assumed real filling heats the air and the pressure falls back as it coolscompressed air practice
• An air receiver is a pressure vessel with drain, relief and inspection obligations not addressed herethe applicable pressure vessel code
• Piping storage is not counted on a large system it is real and sometimes substantialcompressed air practice