Air compressor annual maintenance checklist

Owner and air users told the outage window

Owner and the shops on plant air told when air goes down, and pneumatic controls or valves that depend on it put on their backup supply or made safe first.

Lock and tag applied before the annual teardown

Every feed locked and tagged by each worker, tried dead. Air or power checks use the temporary release: guards on, people clear, receiver repressurized, run, then re-locked and bled.

Receiver isolated from the plant and bled to zero

Discharge valve closed to the distribution, receiver bled through its drain until the gauge reads zero and left vented while the drain and crankcase are worked on.

Oil changed and crankcase checked

Old oil drained warm and volume noted, refilled to the sight-glass mark with the manufacturer's grade, no metal or sludge in the drained oil.

Oil sample drawn for analysis on lubricated units

Where the site runs oil analysis, a sample drawn warm before the drain, labeled with the unit and run hours, results compared with last year's. Oil-free units noted as such.

Safety relief valve manually lifted and reseated

Valve pulled by its ring against tank pressure, blows freely and reseats without weeping, and is replaced rather than left in service if it drips or won't lift.

Pressure switch cut-in/cut-out and unloader verified

Cut-in and cut-out read at the gauge against the switch setting, unloader bleeds head pressure at shutdown so the motor restarts unloaded.

Receiver gauge compared against a calibrated test gauge

Both gauges read at the same pressure, the unit gauge replaced if it is off by more than the manufacturer allows, so the switch setting is judged on a true reading.

Receiver tank and automatic drain serviced

Tank exterior checked for rust, pitting or bulging at the bottom seam and welds, automatic drain disassembled and cleared, drain valve reseated.

Aftercooler or air dryer serviced where fitted

Aftercooler fins cleaned and the coalescing or dryer element checked, dryer holding dewpoint and draining, no water carrying downstream to the shop drops.

Receiver nameplate rating matched to relief and cutout

Nameplate legible, relief valve set pressure and switch cutout both no higher than the receiver's rated working pressure, mismatches reported to the owner.

Receiver inspection certificate current where required

Where the jurisdiction or insurer requires a pressure vessel inspection, the inspector's certificate posted at the receiver is in date. Expired or missing ones reported to the owner.

Guards on, valves reset and locks removed by their owner

Belt guard fastened, drain closed and discharge valve reopened to the plant, tools cleared, lock and tag removed by the person who hung them.

Motor current read loaded at cut-out against the nameplate

Amps read as the unit nears cut-out under the site's energized-work procedure and its PPE, within the nameplate rating and compared with last year's reading.

Pump-up time timed on restart and the annual baseline filed

Fill timed with plant demand steady, a slow fill pointing to worn valves or rings; fill time, amps, gauge check, relief result and oil analysis filed as next year's baseline.