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A well-soldered system may operate for an extended time — perhaps even 20 years — without needing a charge. But, because no system is perfect, the equipment still has leaks. Those leaks may not be enough to affect performance or even read on a gauge. They can be as small as 1 oz per 20 years or as large as 1 oz per hour.
Every joint, seam, or weld has a “fault” of some kind. Some may be too small to detect even with the best leak-detection instruments. Given enough time under the stress of vibration, temperature, and pressure, the faults grow into detectable leaks.
Some leaks come and go as they plug up and reopen under particular conditions. The escaping gas may not even be leaking at the time of the test.
A leak could be the result of several different faults — solder impurities, a speck of dirt on a gasket or gasket surface, a microscopic scratch, weld fracture, etc. A look under an electron microscope would readily reveal more information.
In measuring the performance of leak-finding devices, their sensitivity — or their ability to measure different levels of leaks — comes into play. Soap bubble testing, for example, would be rated as low sensitivity because only large (above 6 oz per year) leaks in a favorable location can be detected.
The emergence of electronic sensing devices has proven that microscopic leaks not only exist, but in fact can be measured down to 1/10 of what soap bubbles can measure.
The low sensitivity of soap bubbles can lead to problems for the technician. When using soap bubbles to confirm and pin down a small leak site detected by electronics, the leak may be so small that no bubbles form.
So, did the electronic device give a false reading? A great many of the bubble solutions fail the sensitivity test because of their composition — shampoo, bubble bath, or dish washing soap with a variety of additives. However, the recent emergence of several new bubble leak detectors has significantly lowered the detection threshold to the point where they can be used to verify electronically detectable leaks.
Bubble leak detectors are now available in a non-hazardous, non-toxic, non-residue formulae containing no ethylene glycol. They can be used on equipment containing most gases — air, natural gas, all refrigerants, ammonia, S02, etc. They come in different temperature ranges and some are oxygen compatible.
Best of all, leaks down to 1 micron can be easily detected, as some have fluorescent qualities that make the bubbles sparkle under light.
An understanding of the different types of leaks will help technicians locate them.
TYPES OF LEAKSAll of us will have experienced searching for the following leaks at some point in our careers.
A quick review of the most commonly used tools would at least include the following:
Publication date: 02/05/2001