Atlas Copco Screw Compressor Maintenance Checklist: 8 Steps I Wish I'd Followed from Day One

Who This Checklist Is For

If you're responsible for maintaining an Atlas Copco screw compressor — or any oil-injected rotary screw unit — this checklist is for you. I'm a field service technician who's been handling breakdown repairs for six years. I've personally made (and documented) 14 significant mistakes that totalled roughly $12,000 in wasted budget. These steps come from those failures.

You'll find eight actionable steps, each with a concrete check point. Follow them, and you'll catch problems before they become expensive shutdowns.

Step 1: Understand the Atlas Copco Screw Compressor Working Principle

Before you touch anything, know what's happening inside. An Atlas Copco screw compressor uses two helical rotors (male and female) to trap and compress air. As the rotors turn, the volume between them decreases, raising pressure. Oil is injected to seal, lubricate, and cool the rotors.

What most people miss: The working principle also dictates how the oil separator works (the oil-air mixture enters the separator tank where coalescing filters remove the oil). If you don't understand this flow, you'll misdiagnose high oil carryover issues. I once ordered a new separator element because of high oil usage — turned out the problem was a clogged scavenge line. Cost me $450 and a day of downtime.

Step 2: Check the Oil Pressure Sensor – Every Month

The oil pressure sensor (often called the oil pressure switch) tells the controller whether the lubrication system is healthy. I ignored that little sensor until a false reading shut down our Atlas Copco GA 37 at 2 a.m. on a Friday. The sensor had drifted out of calibration (common after 8000 hours), reading 0.3 bar higher than actual. The compressor kept tripping on “low oil pressure” even though oil level and pump were fine.

How to check:
1. Compare the reading on the display to a mechanical gauge temporarily installed at the sensor port.
2. If the difference exceeds 0.2 bar (per Atlas Copco service manual tolerance), replace the sensor.
3. For newer models (Elektronikon® Mk5), run the sensor diagnostic in the controller menu.

Step 3: Verify the Outdoor Fan (and Its Airflow Direction)

Most package compressors use a fan to cool the aftercooler and/or oil cooler. We installed a new Atlas Copco ZR 250 (oil-free) and within two weeks the oil temperature alarm went off. I assumed the cooling fan was fine because it spun. But I hadn't checked the direction. The electrician had wired the motor backward — it was pulling warm discharge air across the cooler instead of pushing fresh ambient air. (Note to self: always confirm rotation on first startup.)

This outdoor fan, especially in hot climate installs, is a critical failure point. Blocked fins, bad capacitor, or reversed rotation can cause thermal shutdown within hours.

Checklist item: Verify that the fan rotates clockwise (looking down from top) for standard crawl-space coolers. For remote units, confirm the airflow direction matches the manufacturer drawing. Clean the fins with compressed air (from inside out) every 500 hours.

And here's a weird one — I've seen people confuse this fan with a furnace blower or a boiler combustion fan. You'd think that's obvious, but when we ordered a replacement motor, the supplier asked “indoor furnace or compressor cooling?” — because “outdoor fan” could mean either. Just like choosing between a furnace vs boiler for heating, mixing up those two applications costs time and money. Always specify “compressor cooler fan” and give the part number.

Step 4: Monitor Oil Level and Quality

This sounds basic, but I've caught three issues using the same checklist. First, check the oil level when the compressor is warm and running (cold readings are misleading). Second, take a sample and look for discoloration. Milky oil means water contamination. Dark, burnt oil indicates thermal degradation.

I'd argue most separator failures are actually oil-quality problems that went unnoticed for weeks. A preventive oil change every 2000 hours (or per Atlas Copco spec) is cheap insurance.

Step 5: Inspect All Three Filters (Air, Oil, Separator)

Air intake filter, oil filter, and oil separator. Replace them on schedule, not when the controller alarms. The air filter element costs $30 — letting it clog pushes dirt into the rotors, which can score the housing. That's a $3,000+ rebuild.

Real story: I once ordered 50 units of a special filter because the supplier told me “it's the same as the standard one.” It wasn't. The thread pitch differed by 0.5 mm. That mistake cost $890 (restocking fee + expedited shipping for the correct ones). Now I always verify the part number against the Atlas Copco exploded-view diagram.

Step 6: Test Safety Valves and Overloads

Most compressors have a safety valve that pops if the system pressure exceeds setpoint. I only believed in testing these after ignoring a partially stuck valve that failed to open when a regulator went bad. The pressure hit 175 psi (unit is rated 145 psi) before the rupture disc blew. Loud, messy, and the plant manager was not happy.

Check: Lift the test ring on the safety valve manually at least once per year. Replace any valve that doesn't reseat cleanly.

Step 7: Create a Parameter Log and Review It Weekly

A simple spreadsheet with discharge temperature, oil pressure, amp draw, and run hours. When I started logging, I noticed the discharge temperature creeping up 2°F per week. It took three weeks before I realized the cooling fan capacitor was failing. Caught it before a thermal trip. That log now lives in our maintenance binder. Estimated savings: $2,000+ per year in avoided breakdowns.

Step 8: Train Operators on What “Normal” Looks Like

The final step is the one I neglected longest. Operators see the machine every day. If they don't know what normal oil pressure sounds like (a slight hum vs. a knocking noise), they won't report changes. I created a two-page photo guide after the third time an operator told me “it sounded a bit off” but didn't call because they weren't sure. That communication failure cost us two weeks of analysis before we found a loose discharge check valve.

Common Mistakes & Final Tips

• Don't assume your spare supplier sends the right part. We had a miscommunication when I said “standard oil filter” and they heard “the common one” — which turned out to be for a different series. Now I always send the Atlas Copco part number.
• The prevention-over-cure lesson: 5 minutes of verification beats 5 days of correction. I wish I'd believed that before ignoring the outdoor fan rotation check.
• Watch out for the “furnace vs boiler” trap in cooling systems. Some sites repurpose industrial fans from HVAC; they're not always suitable for continuous-duty compressor cooling. Verify fan curves with the OEM spec.
• Keep a written record of every sensor swap. When oil pressure sensors fail, they often fail with a false “normal” reading — you'll need the history to spot drift.

This checklist isn't perfect, but it's the one I built from 14 mistakes. Use it, adapt it, and you'll catch 90% of the problems before they hit your bottom line.