General Tips and Tricks of Helium Leak Detection

12 General Tips and Tricks of Helium Leak Detection 

Probably the biggest problem with helium leak detector use comes from the construction material of the vacuum system or apparatus being tested. If the materials within the tested piece readily absorb helium, a false and/or confusing reading will exist for a considerable time afterward and will remain until the helium has left the piece. 

A second complication can come from materials that helium can easily permeate such as the elastomers used in O-ring connections. Helium readings from these materials can distract you from other true leak readings. Once an elastomer has become saturated with helium, it slowly desorbs the gas, which creates a large background noise. This background noise interferes with a helium leak detector s sensitivity and performance. All elastomers readily absorb, and slowly desorb, helium. Thus the fewer elastomers used within a system, the less of a problem there will be. Silicone tends to absorb helium the most, followed by nat- 

One additional complication with elastomers has to do with the connection between a vacuum system and a helium leak detector. If it is possible, connect the two with a nonelastomeric connection such as a stainless steel bellows. If this connection is not possible, the best elastomeric connection that you can use is a high-vacuum, thick-walled (V2 in I.D., 3/16 in. wall) vinyl tube of the shortest length possible. Do not use rubber or neoprene tubing. If you have several systems that may need leak detection, it is unlikely that one length of tube will accommodate all systems. It is best to have several connecting tubes, one for each system (or several systems) being tested, to allow you to select the shortest one that can be successfully used. 

Vinyl tubing connecting the vacuum system being tested to the helium leak detector 

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