Need a replacement air/oil separator, but not sure which one fits your compressor? Start with the part number. If that number is missing or hard to read, your compressor information, a few measurements, and clear photos can help narrow down the replacement. 

What Does an Air/Oil Separator Do?

In an oil-injected rotary screw compressor, an air/oil separator removes oil mist from the compressed air. The separator media brings small oil droplets together so the collected oil can return to the compressor's oil circuit.

This is a different part from the compressor's oil filter or a downstream compressed air filter. When searching for a replacement, make sure you are identifying the separator element inside the compressor or its external spin-on separator.

1. Start with the Existing Part Number

Look for a part number on the installed separator, its packaging, a previous invoice, or the compressor's parts manual. A clear photo of the label is helpful, especially when a number includes spaces, dashes, or a suffix.

Enter that number in the search bar at Filter Element Store. If it does not bring up a match, send us the number and compressor details so we can help check the cross-reference.

Keep the complete number. A similar-looking number is not enough to confirm compatibility, and a suffix may identify a different version.

2. Record the Compressor Model and Serial Number

If the separator number is unavailable, photograph the compressor's data plate. Include the manufacturer, full model number, and serial number. For some brands like Kaeser, we also need the air compressor part number. There are OEM's like Atlas Copco, and their sister company Quincy, who are very secretive with their information, but we may still be able to help. The parts manual or service records may provide additional information.

A brand name or horsepower rating alone is not enough to select a separator. Confirm the replacement against the parts information for your particular machine.

3. Check Dimensions and Mounting Details

Measurements are useful for checking a proposed replacement, particularly when the old element has no readable label. Record dimensions in inches and include the mounting features as well as the main body size.

• Outside Diameter: Measure the separator body. If the top and bottom differ, record both.
• Inside Diameter: Measure the opening and note whether one or both ends are open.
• Flange Outside Diameter: For a flanged separator, measure the flange separately from the body.
• Height: Record the overall height and confirm if your measurement includes the flange, gasket, or any projecting hardware.
• Mounting details: Note bolt holes, gasket locations, and any fittings. For a spin-on separator, confirm the thread specification and sealing arrangement.

Matching dimensions do not establish compatibility by themselves. The mounting design, seals, and application specifications also need to match. Use measurements to support a verified part-number cross-reference.

4. Send Photos When the Match Is Unclear

Photos helps a lot! Even if you see a very similar looking separator on our website. A side view plus photos of the top and bottom can help distinguish separators that look similar. Include close-ups of the label, flange, openings, and gasket surfaces.

If you have a drawing, send that too. Mark which dimensions refer to the body and which refer to the overall assembly so there is less room for confusion.

5. Confirm What Comes with the Replacement

Before ordering, check whether the listing includes the required gaskets, O-rings, or other service components. An individual separator element and a service kit may have different contents.

Follow the compressor manufacturer's installation instructions, including requirements for seals and any grounding or anti-static features. Follow the specified service interval and operating limits rather than assuming every separator has the same replacement schedule.

Need Help Identifying Your Separator?

Send Filter Element Store the existing part number, compressor model and serial number, and any available photos or dimensions. We can help check the replacement before you place an order.

Search Filter Element Store for your air/oil separator part number.