Result

Continuous devices such as valve positioners consume air constantly and usually dominate the total, while solenoid valves draw air only when they actuate, so their demand is averaged from volume per cycle and cycle frequency. The diversity factor matters: assuming every intermittent device fires simultaneously oversizes the compressor, while a realistic factor gives sensible peak sizing — but set it conservatively for critical systems. The margin then covers leakage, future additions and receiver recovery. Reference-library values are typical figures only; confirm actual consumption against each device datasheet, since a leaking positioner alone can consume far more than expected. Finally, capacity is not the whole story — instrument air must also meet a dryness, particulate and oil-content class per ISO 8573-1 (a common target is roughly Class 2 oil, Class 3 particulate, with a dew point well below the lowest ambient temperature), because wet or dirty air damages instruments regardless of how much of it you have.