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Reducing air leaks in your plant can save thousands of dollars annually. The home user of compressed air can, too, shave quite a few dollars off the electricity bill by being careful of their compressed air home usage.
Compressed air is one of the most costly forms of energy you can use. Of more importance to the user is that it's one of the most versatile, fast and strong types of energy to do work too.
When it's "quiet time" in the plant, wander around the machinery and listen.
Air will be leaking from many air fittings, unions, from broken or split polyethylene air lines, and you will often hear the gentle (or perhaps not so gentle) hissing of air escaping from the exhaust port of your air valves.
Compressed air exiting your air valve's exhaust ports and "chewing up your dollars" as it wafts to atmosphere can be muted if your valves have mufflers in the exhaust ports, but nevertheless, it can be heard.
If your plant doesn't have a "quiet or down-time" which would enable you to actually hear the leaks yourself as you wander the shop floor, there are commercially available ultra-sonic compressed air leak detectors on the market. Investing in an ultrasonic leak detector can bring substantial payback in energy savings.
Now back to our valves. What to do if air is bleeding from the exhaust port(s)? While an air valve and cylinder are doing work of course there will be air being exhausted continuously from the exhaust ports.
It's when the machine is down, when it's doing no useful - and hopefully money generating work for you - that air should not be escaping through the valve exhaust ports. At this point that loss of compressed air is just that; loss - of profits - of your money.
Usually you'll have one air valve connected to each air cylinder, and usually that cylinder will be a double acting type - which means that it will have two air lines running to it from the air valve, and as the air valve shifts back and forth in normal operation, air will alternately flow to the cylinder through one line or the other. When it's flowing into one line to the cylinder, the other line is allowing the air at the other end of the cylinder to flow through the valve to exhaust.
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In the graphic, the piston / rod assembly are shown in purple to identify them.
Inside, the two ends of the cylinder are separated by a piston. The piston is what drives the rod out and back as the cylinder cycles.
Around that piston will be an air seal that "crunches" between the side of the piston and the inside of the cylinder barrel, effectively stopping air from flowing by (bypassing) the piston.
In time that seal will wear, and air will start bypassing into the other side. This means that this air now has an open path from the supply side down the other air line to the valve, and thence to the exhaust port. And a gentle (or not so gentle) hiss occurs as your compressed air dollars exhaust to atmosphere.
Or....inside your air valve there is, too, a series of seals that normally prevent air from getting from the air supply side into the exhaust side of the valve, and then out the exhaust port. And that air, as it gently (or not so....etc. ) is pouring your compressed air dollars from the plant air supply.
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So, which is it that's leaking; the seal(s) around the piston in the cylinder, or the seal(s) inside the valve that stops the incoming air from getting across to the exhaust port without going up to the cylinder?
Have a look at your cylinder. If the cylinder rod is out (extended) air will be entering the air port at the rear of the cylinder. If the cylinder rod is in - retracted, the air will be coming into the cylinder port at the rod end.
Locate the air line to the cylinder that is charged, that is, the air line that is supplying air to the cylinder at that time, and crimp it. Many air lines are made of polyethylene or polypropylene, and it's quite easy to make a bit of a bend in the air line, effectively shutting off air to the cylinder.
Listen at the valve. If the air has stopped escaping the valve's exhaust port, then it has to be the seal(s) in the air cylinder that's letting air by-pass to get to the exhaust line.
If, after ensuring that the air to the cylinder is completely stopped, air continues to exhaust from either or both of the exhaust ports of the valve, then it's the seal(s) inside the air valve that are letting air get by.
Regardless of which is the culprit, the air valve or the cylinder, get it fixed....fast! Compressed air costs a bundle. You sure don't want to waste it.
Try to get your plant to be one of those that don't rack up the industry average of 10% of compressed air lost to wastage. How many dollars would drop to your “bottom line” if you reduced your compressed air electricity cost by 10%?
It’s worthwhile chasing down and eliminating those leaks.
Here's some more info on leak detection.
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