Q3 2020

Compressed Air Systems, Part  3 by Bruce Grossman

By Bruce Grossman

In my long career troubleshooting and maintaining drycleaning and laundry equipment by far the largest cause of machine failure has been the condition of the compressed air reaching the machinery. Valves and regulators directing the flow of compressed air are wonders of modern manufacturing technology with close tolerances requiring the compressed air to be as free from particulates and moisture as possible.

During the air compression process moisture, compressor oil, debris and other materials which from now on I’ll call contaminants, are blown into the compressor tank (sometimes called the receiver). To prevent most of these contaminants from reaching the machinery, several methods are used. The first of these methods, and the subject of this article is the piping itself, and any installed components.

This issue’s article will address two physical forces employed to aid in removing water and debris from the compressed air stream. Gravity, we all know what that is; and inertia, which is the tendency of objects to keep moving in a straight line at constant velocity. Follow along using the accompanying illustration.


  1. GRAVITY- Notice first that the large pipe called a header is connected at each machine by branches which are called drops, used to supply compressed air to each individual machine. When designed properly the drops are taken off the top of the headers. Since water is much heavier than air it runs along the bottom of the header, pushed along by the flow of the air while the air flows along the top. Thus, gravity provides a very effective additional stage of separation. I’ve seen many installations where the drops were taken off at the bottom of the headers literally capturing and forcing water and other contaminants down into the machinery; a very unhappy situation, causing machine performance nightmares. At the end of the airline it is always beneficial to have what is known as a “drip leg”. A drip leg in its simplest form is nothing but a vertical piece of pipe used to collect and retain water and debris entrained in the compressed air system.


  1. INERTIA- Any remaining contaminants entrained in the compressed air are moving rapidly along through the headers and drops. Because of inertia they want to keep moving in a straight line. An abrupt change of direction in the drop is created by inserting a tee and piping the air flow to the machine from the side of the tee. The lighter compressed air makes the 90 degree turn out of the tee while the contaminants continue moving in a straight line and are captured in the drip leg. A combination of components after the tee provide the remaining pathway conducting the compressed air to the machinery. A ball valve is used to shut off the compressed air flow from the drop to the machine for maintenance and a combined filter/regulator provides another stage of contaminant removal along with filtration and air pressure regulation. Draining the drip legs can be done manually with a simple ball valve or automatically using a device known as a “drip leg drain.” I use an inexpensive air filter purchased from Harbor Freight, Item #68279 plugged at the outlet side as a drip leg drain.


I’m aware that in almost all cases the piping for the machinery already exists and you’re not going to get into replacing it because of this article. However, look at the diagram in the lower right of the illustration. It is very easy to just re-pipe the section at the end of the drop to the machine. Use soft copper tubing and compression fittings from the drop to the machine. Just having this section done properly will eliminate a great many problems.




That’s it for now, next issue’s article will be about removing moisture from the compressed air system. Call me at (702) 376-6693 if you have any suggestions, I’m always delighted to hear from a reader.


Bruce Grossman is the Chief of R&D for EZtimers Manufacturing. EZtimers is the manufacturer of the new EZ Level return tank water level control. To prevent boiler scaling and other damage the EZ Level  return tank water level control replaces that troublesome ball float valve in the condensate return tank. For saving money on handling waste the SAHARA and DROP IN THE BUCKET line of high purity separator water mister/evaporators provide a thrifty, legal method to get rid of the separator water generated by your dry-cleaning machine. See our Ad in this issue and for further information on EZtimers products visit  www.eztimers.com   Please address any questions or comments for Bruce to  bruce@eztimers.com  or call (702) 376-6693.

© 2020 by BRUCE GROSSMAN all rights reserved under International and Pan American copyright conventions.


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