Key points
- Daily checks (oil, drain, gauges, leaks) take minutes and catch most problems before they become breakdowns.
- Service by running hours, not the calendar: filters around 1,000 h, motor bearings around 2,000 h, oil and separator at 4,000 to 8,000 h.
- Watch pressure drop: change the separator above 10 psid and line filters above 2 to 3 psid, even if the hours have not come up.
- Leaks can waste 20 to 30% of a compressor's output. A five-minute load and unload test tells you where you stand.
The checklist at a glance
This checklist is written for an oil-injected rotary screw compressor, the most common type in plants and workshops. Piston compressors share the daily and weekly checks; their hour-based services differ, so use the manual. Where the manual and this list disagree, the manual wins.
| When | Task | Source |
|---|---|---|
| Daily (every shift) | Check the lubricant level and top up with the lubricant the manufacturer specifies. | CAC Fact Sheet 5, Ceccato, Chicago Pneumatic |
| Daily (every shift) | Drain condensate from the air receiver, or confirm the automatic drain has discharged. | Chicago Pneumatic |
| Daily (every shift) | Read the controller or gauges: discharge pressure, discharge temperature, running and loaded hours. Note anything outside normal. | CAC Fact Sheet 5 |
| Daily (every shift) | Look and listen for oil leaks, air leaks, damage, unusual noise or vibration. | Chicago Pneumatic |
| Weekly | Check and clean the intake air filter, and check the intake vents are clear. | Ceccato, Chicago Pneumatic |
| Weekly | Inspect belts for wear and tension, and hoses for wear. | Ceccato, Chicago Pneumatic |
| Weekly | Check that automatic drain traps are not stuck open (leaking air) or stuck closed (holding water). Weekly is suggested; the source says periodically. | CAC Fact Sheet 5 |
| Every 400 hours | Examine and adjust belt tension. Tight belts wear bearings; loose belts slip and waste energy. | CAC Fact Sheet 5 |
| Every 1,000 hours | Replace the intake air filter element, sooner in dusty air. | Ceccato |
| Every 1,000 hours | Replace the oil filter. | Ceccato |
| Every 2,000 hours | Grease the motor bearings, following the motor nameplate. Do not over-grease. | Ceccato, CAC Fact Sheet 5 |
| Every 4,000 to 8,000 hours | Change the compressor lubricant. | Ceccato |
| Every 4,000 to 8,000 hours | Replace the air/oil separator element with the oil change, or sooner if its pressure drop exceeds 10 psid (0.7 bar). | Ceccato, CAC Fact Sheet 5 |
| By condition | Replace compressed air line filter elements when their pressure drop exceeds 2 to 3 psid (0.14 to 0.21 bar). | CAC Fact Sheet 5 |
| By condition | Clean cooler fins and heat exchanger surfaces when dust builds up. Dirty coolers lower efficiency and raise temperature. | CAC Fact Sheet 5 |
| Annually | Inspect every line filter element, whatever its pressure drop reads. | CAC Fact Sheet 5 |
| Annually | Run a leak test and survey: lines, joints, fittings, hoses, regulators, drains and tool connections. A well-maintained system loses less than 5 to 10% to leaks. | DOE Sourcebook, Fact Sheet 3, CAC Fact Sheet 5 |
| Annually | Benchmark power, pressure and flow against the figures recorded when the system was set up. Rising power at the same pressure and flow means efficiency is falling. | CAC Fact Sheet 5 |
| Annually | Water-cooled units: check water quality (pH and total dissolved solids), flow and temperature. | CAC Fact Sheet 5 |
| Annually | Test the safety valve and inspect the receiver as the manufacturer and your local pressure vessel rules require. | Manufacturer and local rules |
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Daily and weekly checks
These are operator checks. They need no tools and take a few minutes, and they are the ones most often skipped because nothing seems wrong.
- Lubricant level. In an oil-injected screw compressor the lubricant also seals the rotors and carries away most of the heat of compression, so a low level shows up as high temperature first. Top up only with the lubricant the manufacturer specifies.
- Drain the receiver. Water condenses in the tank and settles at the bottom, where it breaks down the coating and rusts the tank from inside. Chicago Pneumatic recommends draining daily, or fitting an automatic drain.
- Read the gauges. Write down discharge pressure, discharge temperature and the hour meter. One reading means little; a week of readings shows a trend, and the hour meter is what every service below is scheduled from.
- Look and listen. Oil on the floor, a new rattle, a hiss near a fitting. A noise that was not there yesterday is worth a work request today.
- Weekly: clean the intake filter and check the vents are clear, check belt wear and tension, and confirm the automatic drains are cycling. A drain stuck open leaks air all day; one stuck closed sends water downstream into tools and dryers.
Services by running hours
A compressor wears with running hours, so its services are scheduled on the hour meter. The figures below are the ones Ceccato (an Atlas Copco brand) publishes for its screw compressors, with the belt interval from the Compressed Air Challenge. They nest: at 2,000 hours you do the 2,000 hour service and everything the 1,000 hour one includes.
| Every | Service |
|---|---|
| 400 h | Check and adjust belt tension |
| 1,000 h | Replace the air filter and the oil filter |
| 2,000 h | Grease the motor bearings |
| 4,000 to 8,000 h | Change the lubricant and the air/oil separator together |
Why the oil interval is a range: lubricant life depends on the lubricant type, the operating temperature and how clean the intake air is. A compressor running hot in a dusty room sits at the short end. Your manual or an oil analysis tells you which end you are at.
More on why that matters: setting preventive maintenance intervals.
Change by pressure drop, not only by hours
Filters and separators clog at the rate the air dirties them, not at the rate the hour meter turns. Every element you can fit with a differential pressure gauge gives you a better trigger than the calendar.
| Element | New | Change at |
|---|---|---|
| Air/oil separator | 2 to 3 psid at full load | About 10 psid (0.7 bar) |
| Line filters (particulate, oil removal) | Per manufacturer | 2 to 3 psid (0.14 to 0.21 bar), and inspect at least yearly |
Both thresholds are from the Compressed Air Challenge, which also notes that changing the separator earlier can pay for itself when electricity is expensive: the compressor has to push every bar of pressure drop.
The leak test you can run today
According to the U.S. Department of Energy's compressed air sourcebook, leaks sometimes waste 20 to 30% of a compressor's output, a plant that has not been well maintained typically leaks about 20% of its capacity, and proactive leak repair brings that below 5 to 10%. If your compressor has load/unload or start/stop control, you can measure where you are in a few minutes:
- Choose a time when nothing uses air: all tools and air-powered equipment off.
- Let the compressor run. Leaks alone will make it load and unload.
- Time several cycles: minutes on load (T) and minutes off load (t), and average them.
Leakage (%) = (T × 100) / (T + t)
Worked example (invented figures): the compressor runs loaded for 2 minutes, then idles for 8. Leakage = 2 × 100 / (2 + 8) = 20%, one fifth of its output going nowhere. That is the number to bring down, and the one to measure again after the repairs.
Start the hunt where the sourcebook says leaks usually are: couplings, hoses, tubes and fittings, pressure regulators, open condensate traps and shut-off valves, pipe joints, disconnects and thread sealants.
Safety before you start
- Isolate the electrical supply and lock it out, and vent the compressor and receiver to zero pressure before opening anything. A screw compressor can restart automatically.
- Let it cool. Lubricant and discharge pipework run hot enough to burn.
- Do not clean yourself or the machine with full line pressure. In the US, OSHA 1910.242(b) allows compressed air for cleaning only below 30 psi, and only with chip guarding and protective equipment.
- Leave the safety valve alone except to test it as the manufacturer and your local pressure vessel rules require. Never plug or reset it to stop it lifting.
Turn the checklist into a schedule
A paper checklist tells you what to do; it does not tell you when the 2,000 hour service is due on the third compressor. For that you need three things on record: each compressor's hour meter, the last service done and at what reading, and the plan itself.
- Register each compressor once, with its make, model and hour meter.
- Enter the services above as a preventive maintenance template, one interval per row, with the parts each one uses.
- Read the hour meters on a routine. The schedule is only as current as the last reading.
- Keep the daily and weekly checks as a short inspection the operator ticks on a phone, so a failed check becomes a work order instead of a note.
Solmex does all four, and it is free to start: preventive maintenance schedules each service from the hour meter on fixed milestones, and inspections turn a failed check into a finding with a work order behind it.
Sources
Every interval and threshold on this page was read in the source below. Intervals vary by make and model, so check them against your own manual.
- Compressed Air Challenge, Fact Sheet #5: Maintenance of Compressed Air Systems for Peak Performance (May 2026, Rev. 1)
- U.S. Department of Energy and Compressed Air Challenge, Improving Compressed Air System Performance: A Sourcebook for Industry, Third Edition, Fact Sheet 3: Compressed Air System Leaks
- Ceccato (Atlas Copco Compressors Australia), Air Compressor Maintenance Tips
- Chicago Pneumatic, The importance of screw compressor maintenance schedule
- Chicago Pneumatic, How many times a month do we have to drain the water from our compressor
- OSHA, 29 CFR 1910.242: Hand and portable powered tools and equipment, general