Oil-flooded rotary screw compressors are the workhorse of most Arizona facilities, and for good reason — injecting a fine mist of oil into the compression chamber cools the air, lubricates the rotors, and helps seal the compression process. It's a proven design.
But that oil has to stay where it belongs. When too much of it escapes into your compressed air supply — a problem called oil carryover — it can cause real damage downstream, and it's one of the more common issues we get called out for across Phoenix and Tucson.
Why Oil Carryover Matters
In general manufacturing, trace amounts of oil (under 3 ppm) are typically fine. But if your facility runs food and beverage, electronics, healthcare or semiconductor production, even that small amount can be too much — these applications demand oil-free or near-zero oil air.
Regardless of your industry, excessive oil carryover can lead to:
- Reduced air quality throughout your system
- Compromised end-product quality
- Damage to (or a shortened lifespan for) downstream equipment
- Higher maintenance and energy costs
- Unplanned downtime
What Causes Oil Carryover
A struggling air-oil separator. The separator's job is to pull oil mist out of the compressed air using centrifugal motion and mesh filtration. Once it clogs, airflow drops and energy consumption climbs — and oil starts slipping through.
Incorrect oil levels. Too much oil in the sump means more of it gets picked up in the airstream. Too little, and the separator can't do its job properly, letting oil vapor carry through.
Temperature out of range. Your compressor should run between 180°F and 200°F. Run hotter, and oil starts vaporizing. Run cooler, and you get condensation that interferes with proper separation.
Pressure out of range. High pressure forces more oil into the airstream. Low pressure keeps the separator from functioning the way it's designed to.
How to Prevent Oil Carryover
Stay on top of separator maintenance. Change spin-on separators every 4,000 hours, and drop-in separators every 8,000 hours or annually. Keep an eye on your pressure differential alarm, and replace the separator if the differential exceeds 10 PSI. Don't overlook your scavenge lines, either — clogged scavenge lines are among the top causes of oil carryover we see in the field.
Add the right downstream filtration. Coalescing filters remove oil aerosols, activated carbon filters handle oil vapor, and point-of-use filters can serve applications with specific requirements. Wherever air quality matters, follow the ISO 8573-1:2010 standard to determine the right filtration class (Classes 1–9) for your application. Replace inlet filters based on your supply air quality, and downstream filters every 4,000 hours or annually.
Handle the daily basics. A few habits go a long way: clear drains and return lines daily, check oil levels daily, keep discharge temperature within range, and make sure oil coolers stay clean and leak-free.
The Bottom Line
Oil carryover rarely comes from one single cause — it's usually a combination of a tired separator, an oil level that's drifted out of spec, and temperature or pressure running outside its ideal window. The good news is that all of these are preventable with a consistent maintenance routine and the right filtration for your application.
If you're not sure whether your system's oil carryover is within acceptable limits — or you're seeing signs of a problem already — it's worth having someone take a look before it turns into downstream equipment damage or a product quality issue.
Let C.A.P. Take a Look
Compressed Air Power has been keeping Arizona compressors running clean since 1984. As a locally owned, second-generation family business, our factory-trained technicians know how to track down the source of oil carryover fast — whether it's a separator overdue for replacement, an oil level that's off, or a system running outside its ideal temperature and pressure range.
We can inspect your separator, check your filtration setup against your industry's air quality requirements, and build a maintenance plan that keeps oil where it belongs — in the compressor, not in your air lines.
Noticing oil where it shouldn't be? Call our Phoenix team at 602-437-1266 or our Tucson team at 520-888-3266, or reach out online — we'll help you get it sorted out.
