How to Change a Drop-In Oil Filter on a Rotary Screw Air Compressor

Here's How to Change a Drop-In Oil Filter on a Rotary Screw Compressor

Replacing a drop-in oil filter is a key part of maintaining your rotary screw air compressor and keeping it running at peak performance. In this guide, we’ll walk you through the full step-by-step process—from safety procedures to the final bolt—so you can change your filter with confidence.

Safety First

This guide shows how to change a drop-in oil filter on your rotary screw air compressor. Before beginning, you should always have the required personal protective equipment (PPE), and you should ensure the equipment is properly de-energized before performing any maintenance.

The procedures demonstrated in this guide are intended for trained and qualified air compressor maintenance technicians. This is for educational purposes only.

What You’ll Need

• New drop-in oil filter
• Oil pan
• Pig mat or oil absorption mat
• Molykote grease
• Adjustable wrench
• Ratchet wrench
• ⅝” socket
• New square o-ring
• Lockout/tagout mechanism

Step-by-Step Instructions

1. Clear the Area and Begin Lockout/Tagout

Ensure the work area is clean and free of hazards. Lockout/tagout is the first and most critical safety step. Only a qualified technician should perform this process.

When locking out the handle, our technician uses their right hand and turns to the left to avoid a possible arc flash. Always check to ensure the panel is locked securely. Then, isolate the air system by turning the supply handle to the OFF position.

2. Confirm Power is Disconnected

Attempt to power up the unit to confirm it is no longer connected to power. Also, check the control panel to verify everything is fully de-energized.

3. Relieve Air Pressure from the System

Use a wrench to loosen the sump pressure monitoring line. Tap the connection to ensure there's no remaining pressure. The pressure gauge should read zero before proceeding.

4. Remove the Saturated Oil Filter

Place the oil pan beneath the filter. Remove the bottom of the oil filter housing and use the drain plug to release the oil.

If the bottom is stripped or too tight to remove, you can remove the entire housing by loosening the top mounting bolts. In our example, the technician removes the housing due to a stripped plug.

Use a ratchet wrench with a ⅝” socket in a crisscross pattern to loosen and remove the housing bolts. Keep the bolts in a secure place. Support the housing with one hand as you remove the final bolt, then lower it carefully to the ground.

5. Discard the Old Filter and Prep the Housing

Pour out any residual oil and discard the used filter in your oil pan.

Grab your new drop-in filter. Apply Molykote grease to the inside seal of the filter. Apply a new square o-ring to the canister and grease that seal as well.

6. Prime and Install the New Filter

Partially fill the filter housing with oil to prime the filter. Insert the new drop-in filter into the housing and allow it to absorb the oil. Then fill the housing until it is about ¾ full.

Lift the housing and filter unit back into place. Support the bottom with one hand and hand-tighten one bolt to secure it. Then attach the remaining bolts in a crisscross pattern using the socket wrench.

7. Power the Unit Back On Safely

Once your new filter is in place, it’s time to bring the system back online.

Remove the lockout/tagout mechanism, again turning your body away from the panel as you power it on. Slowly turn the air supply valve to the ON position.

That’s It!

Your drop-in oil filter is now installed and ready to go. Remember—routine maintenance like this helps extend the life of your compressor and keeps your operation running smoothly.