How to Change an Air/Oil Separator on a Rotary Screw Compressor

Preparing Your Workspace and Tools

To begin, ensure that your workspace is clear of hazards and that you have the following materials ready:

• Gloves
• Clean cloths
• Oil pan
• Lockout/tagout mechanism
• Molykote grease
• Comprehensive tool kit (we’ll specify tools as we use them)

Step 1: Safety First with Lockout/Tagout

Safety is always the top priority. The first step in this process is engaging the lockout/tagout (LOTO) mechanism to ensure the unit is fully powered down and won’t start unexpectedly.

Lock out the handle by using your right hand while turning away to the left. This is crucial to avoid potential exposure to an arc flash. After locking the handle, check that the panel is securely locked.

Next, isolate or turn off the air supply to the system. To verify the unit is fully disconnected, try to power up the unit. This ensures there is no electricity running to the compressor. Additionally, check the control panel to confirm that power is fully off.

Step 2: Releasing Pressure from the System

Once safety precautions are in place, use a wrench to loosen the sump pressure monitoring line. Tap the connection lightly to verify there is no pressure remaining in the system. Check the gauge to ensure it reads “zero” before proceeding.

Step 3: Removing the Old Air/Oil Separator

Now that the unit is powered down and safe to work on, it’s time to remove the old air/oil separator. Follow these steps:

• Disconnect the tubes, piping, and control lines from the top of the sump tank. You’ll be working with the check valve and other connected lines. We like to use a combination of a wrench and channel lock pliers.
• Remove the discharge pipe from the minimum pressure check valve by detaching the coupling. For this task, we like to use a ratcheting combination wrench in tandem with channel lock pliers.
• Remove the bolts from the sump tank lid using an impact driver. For bolts in hard-to-reach places, use channel lock pliers. Carefully remove the bolts by hand and set them aside.
• Disconnect the scavenge line from the top of the sump tank lid and remove it from the tank.
• Carefully remove the sump tank lid, making sure no dust or debris enters the tank.
• Remove the old, saturated separator. Be cautious during this step to ensure no dirt falls into the sump tank.

Step 4: Installing the New Separator

Now that the old separator is removed, it’s time to install the new one.

• Place the new separator into the sump tank carefully. Again, make sure no dirt or dust enters the tank during installation.
• Clean the sump tank and separator surfaces using a clean cloth to remove any residual oil or debris.
• Prepare the tank lid by cleaning it thoroughly with a cloth. Then, apply molykote grease to the O-ring before placing it into position.
• Replace the sump tank lid carefully, ensuring it aligns properly with the discharge pipe over the minimum pressure check valve.
• Insert the bolts into the top of the lid, hand-tightening them to start. Use a ratchet wrench to make the bolts snug.
• Using a torque wrench set to the correct torque specification for your sump tank, tighten the bolts in a star pattern. This ensures even distribution of force across the sump tank lid.

Step 5: Reconnecting and Finishing Up

After securing the lid, reconnect the various components:

• Reattach the discharge pipe to the minimum pressure check valve by tightening the clamp over the coupling.
• Reinstall the scavenge line and make sure the connection is secure on the top of the sump tank lid.
• Reconnect all air lines, blow-down valve, and control line valves to the top of the sump tank lid, ensuring all fittings are tight.

Step 6: Powering Up Safely

Before powering the unit back on, ensure everything is reconnected. This includes reconnecting the sump pressure monitoring line.

• Slowly turn on the air valve and check for any air leaks around the fittings on the sump tank lid.
• Remove the lockout/tagout mechanism safely by turning away from the panel as you power it back on.
• Finally, slowly turn the air supply valve to the “on” position and observe the unit as it comes back online.