PM checklist
Screw air compressor: a preventive maintenance checklist
A screw air compressor fails in a few repeatable ways: oil level, dirty filters, hot discharge air, water in the lines, and a separator that was left past its hours. This checklist is a starting point for those jobs. Change every interval from the OEM manual and from your own breakdowns. The wider method is in the preventive maintenance guide.
Key takeaways
- Most compressor downtime is oil, filters, heat or water, not a mystery inside the airend.
- Daily checks are looking and listening. The parts changes follow running hours, not the calendar alone.
- Write the limit next to the check. "Oil OK" is not a record. The level, the temperature and the hours are.
- Treat the OEM hour interval as the start, then shorten it if you find dirt, heat or water early.
- A compressor that feeds the whole shop is an A-critical asset. Its PM should not slip because the line is busy.
Daily and weekly checks
These are operator or technician rounds. They take minutes. Skipping them is how a small leak becomes a hot shutdown.
| When | Check | What to record | Act when |
|---|---|---|---|
| Every shift | Oil level in the sight glass | Level against the marks | Below the low mark, or oil where it should not be |
| Every shift | Unusual noise, vibration or a new smell | A short note if anything changed | A new noise that was not there yesterday |
| Every shift | Discharge temperature and pressure | The numbers, not "normal" | Temperature climbing toward the OEM trip point |
| Daily | Condensate drains | Did the drain pass water, or was it stuck open or shut | Water downstream, or a drain that never cycles |
| Weekly | Intake filter condition | Clean, dirty, or changed | Filter loaded with dust, or the gauge the OEM specifies is past its mark |
| Weekly | Leaks you can hear at fittings, hoses and the receiver | Location of each leak | Any leak on a line that feeds production |
| Weekly | Cooler fins and the cabinet filter | Clean or blocked | Dust mat on the cooler, or the cabinet running hot |
Lock the machine out before you open a panel or change a filter. The lockout tagout procedure is the sequence. A running compressor is stored energy.
Running-hour service
These jobs follow hours, because a compressor on three shifts ages three times faster than the same machine on one. Use whichever comes first: the OEM hours, or a calendar cap so a lightly used machine is still opened.
| Job | Usual trigger | What "done" looks like |
|---|---|---|
| Change oil, oil filter and air filter | OEM running hours | Hours at change, oil grade, filter part numbers, and a photo of the old filter if it was damaged |
| Change the separator element | OEM hours, or when differential pressure rises | Hours, the pressure difference before and after, and the part fitted |
| Service the inlet valve and the minimum-pressure valve | OEM hours, or if the machine is slow to load | What was found: sticking, wear, or nothing |
| Check belt or coupling, if fitted | OEM hours | Tension or alignment, and whether it was adjusted |
| Test safety valves and the pressure switch | OEM or your statutory interval | Test date, result, and who witnessed it |
| Sample the oil if the OEM or your reliability plan asks for it | On the service interval | Lab result attached to the job, not left in an inbox |
A worked example from a typical plant
Worked example (illustrative)
A fabrication shop runs one 75 kW screw compressor that feeds every line. It is on two shifts, about 4,000 hours a year. Last year it stopped twice: once for a separator left 800 hours past due, once because a drain failed and water reached a plasma cutter.
The planner writes two schedules. A weekly round covers oil level, drains, intake filter and leaks, with number tasks for discharge temperature. A usage schedule fires the oil, filter and separator change at the OEM hours, or at 12 months, whichever comes first. Both jobs carry the checklist above. All figures here are illustrative, not a result from a MaintenanceIQ customer.
The weekly round is what would have caught the stuck drain. The hour schedule is what would have changed the separator before it collapsed. Neither replaces the OEM manual.
Common mistakes
- Changing oil on a calendar while the machine runs three shifts. The hours arrive first.
- Writing "checked" with no temperature. Next month you cannot see the climb.
- Ignoring small leaks because air feels free. The U.S. Department of Energy sourcebook treats leaks as one of the largest compressed-air losses.
- Opening the cabinet while it is running. Isolate, lock, and release pressure first.
- Copying this list onto a machine the OEM maintains under a different service plan. The manual wins when they disagree.
How to put this list to work
Pick one compressor, not every utility on site. Copy the shift checks into a one-page round and the hour jobs into a second schedule. Walk it for a month before you add tasks. If a check never finds anything and never will, drop it. If a failure happens that the list would not have seen, add that check.
Keep the OEM manual next to the list. Where the manual gives an hour figure, use that figure. This page only tells you which failures are common enough to deserve a line on the round.
Sources
- Improving Compressed Air System Performance: A Sourcebook for Industry (opens in a new tab), U.S. Department of Energy, Compressed Air Challenge
- Maintenance of work equipment (opens in a new tab), Health and Safety Executive (HSE), UK
Frequently asked questions
How often should a screw compressor be serviced?
Follow the OEM hour intervals for oil, filters and the separator. Add a short daily or weekly round for oil level, drains, heat and leaks. Use whichever comes first if the machine sometimes sits idle and sometimes runs hard.
What readings are worth keeping?
Discharge temperature, discharge pressure, oil level, hours at each service, and whether the drains passed water. A tick with no number is not a trend.
Can operators do the daily checks?
Yes, if the checks are looking, listening and recording, and if opening a guard or changing a filter is reserved for people trained to isolate the machine.
Does this checklist replace the OEM manual?
No. It is a starting list of the failures plants actually see. Where it disagrees with the manual for your model, follow the manual.