Header and Drop Installations
In my lengthy career troubleshooting and maintaining dry cleaning and laundry equipment, by far, the most significant 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, water, compressor oil, debris, and other materials, which from now on I’ll call contaminants, are blown into the compressor tank (sometimes called the receiver). Several methods are used to prevent most of these contaminants from reaching the machinery. These methods, the subject of this article is the piping itself and related installed components.
Two forces are employed in removing water and debris from the compressed air stream; gravity, which we all know, and inertia, the tendency of objects to keep moving in a straight line at constant velocity. Follow along using the accompanying illustration.
First, the large pipe called a header is connected at each machine by branches called drops, used to supply compressed air to each machine. When correctly designed, the drops are taken off the top of the headers. Water being much heavier than air, runs along the bottom of the header, pushed along by the movement of the air while the lighter air flows above the water. Thus, gravity provides a very effective stage of separation. I’ve seen many installations where the drops were taken off at the bottom of the headers, literally capturing then forcing water and other contaminants down into the machinery; a very unhappy situation, causing machine performance nightmares. At the end of the airline, having what is known as a “drip leg” is always beneficial. In its simplest form, a drip leg is nothing but a vertical piece of pipe used to collect and retain water and debris entrained in the compressed air system.
Any remaining contaminants entrained in the compressed air are pushed rapidly 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 airflow 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 provides the remaining pathway conducting the compressed air to the machinery. A ball valve shuts off the compressed air flow from the drop to the machine for maintenance. 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 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 usually 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 correctly will eliminate a great many problems.
COMPRESSED AIR CAN BE DANGEROUS!
BEFORE ATTEMPTING ANY MAINTENANCE ON COMPRESSED AIR SYSTEMS, BE SURE TO BLEED OFF ANY AIR IN THE COMPRESSOR OR PIPING UNTIL THERE IS NO AIR PRESSURE LEFT IN THE COMPRESSED AIR SYSTEM
That’s it for now; the next issue’s article will be about removing moisture from the compressed air system. Look for my AD on innovative products under EZtimers Manufacturing. Call me at (702) 376-6693 if you have any suggestions. I’m always delighted to hear from a reader.