Recently I’ve been asked on more than one occasion to help a medical device manufacturer to determine where and how much their device is leaking. Both of those questions can be answered with great precision—but not at the same time or by using the same processes.
Originally published on European Medical Device Technology, December 2011:
Recently I’ve been asked on more than one occasion to help a medical device manufacturer to determine where and how much their device is leaking. Both of those questions can be answered with great precision—but not at the same time or by using the same processes.
Old-fashioned bubble testing, where a device is submerged underwater, will identify the leak site immediately. Taking it a step up in sophistication, you can use trace gas testing to get an approximate idea of how much leakage there is at various sites in a device.
However, if the function of your device has very specific tolerances for overall leakage, the leak rate will need to be determined with great accuracy. Test methods such as pressure decay and mass flow are example of techniques that make decisions on overall leak rates. These leak detection methods will tell you exactly how much your device leaks, but not where those leaks are occurring.
An assembly with a fair number of parts may have many potential leak sites--porous materials, badly made joints and so forth--and may need a combination of measurement and location test techniques. In this case, production line testing is most expediently done by pressure decay or flow test measurement, and only those parts that do not satisfy the overall test criteria are then tested by a location search technique.
Companies such as Uson, which I work for, have leak detection equipment that can respond to both scenarios and will provide no-cost consultations on how to use one or another method for audit testing or testing of all production units and when. Typically these detailed application analyses take 48 hours to complete in fine detail and at no charge. You just need to know if you want a best-match system for finding leaks or measuring them, or how to marry two leak test solutions to achieve both.
---Dave Selin, European Sales Manager, Uson (www.uson.com)