Compressed Air Filters

Filters; this is page two of information about compressed air filters. Page one on compressed air filters is here.

This continues the information about compressed air filters, and, if you have a question about filters, you can post it at the bottom of this page.

The items numbered in the filter graphic are described in the accompanying text.

6) Filter Bowl

The filter bowl of your air filter may thread into the cap housing, or it may be connected to the cap via bayonet-like mount.

Installing the filter bowl with the bayonet style of mount requires pushing the filter bowl up against the cap, rotating it a short distance, and letting the lugs on the bowl slide down into the receptacles in the cap.

Remember, force equals pressure times area.

You've got at least 3 or 4 square inches of surface area inside the bowl itself, and if your air-line is charged with 100 PSI of air pressure, then there's three or four hundred pounds of force pushing down on the bowl.

If you somehow manage to get the bowl un-bayoneted or unscrewed from the filter cap against that pressure, the filter bowl will likely and unfortunately blow itself right out of your hands, smashing itself into bits and pieces on the floor, and possibly injuring you or a colleague with flying debris from the impact!

Does this sound like something I am really familiar with? You bet! (Insert rueful chuckle here!)

Sometimes the bowls of the air filter are plastic with a metal shroud, or are completely metal construction. That being the case, why use metal or metal shrouded bowls filter bowls?

7) Filter Quiet Zone

Inside of almost every air filter bowl there will be a device that separates the bowl, horizontally, into two sections. This barrier, often made of a plastic or plastic composite, is usually installed hanging from the bottom of the filter element inside the bowl.

It has the purpose of blocking the cyclonic incoming air and preventing that fast moving compressed air from reaching the puddle of debris, water and oil that the filter is collecting in the bottom of the filter bowl.

The barrier creates a quiet zone in the filter bowl, allowing the contamination that collects onto the sides of the bowl to flow down, out of the cyclonic air stream, and to remain - without getting entrained or re-entrained back into the same air stream, until the waste liquid can be expelled from the drain at the bottom of the bowl.

8) Drain

All industrial compressed air filters will have a drain of some sort in the bottom of the filter bowl.

These drains may be manual, a float type, or can be electronic auto drains. They need to be opened regularly to allow collected water and debris to escape from the filter bowl.

Failure to drain the filter bowls often enough will mean that the water and debris in the quiet zone will fill past the barrier, and once there, be entrained into the cyclonic air stream, onto, and sometimes even through the filter element.

In some cases debris and water from a full filter bowl will flood the element so badly that it seems to become almost no filter at all, and is actually contributing a steady stream of crud downstream, to damage the air components, and choking your air supply to death.

What size of compressed air filter will you need?

Here is information on compressed air filter sizes.

Here are the generally accepted symbols for drawing compressed air filters in your circuit schematic.

If you have any questions about compressed air filters, please submit them here.