Leak Testing the entire product
Integral leak test in chamber
A chamber test is used for integral leak testing. This means that the entire test object is tested for leaks. A chamber test will not tell you the location of the leaks, but can easily be combined with a leak locating test. Typical test objects are valves, heat exchangers, plastic containers, fluid bags and fuel systems parts. Depending on the leak rate, the size of the test object and the desired cycle time there are two ways of performing a chamber test. The leak test can be in atmospheric pressure which is very simple to set up, or it can be in a low pressure chamber which requires a bit more time and effort. Chamber tests are sometimes also called accumulation tests.
Chamber test /Atmospheric Pressure
A chamber test in atmospheric pressure is very simple to set up. All you need is a fixture with a very simple hood covering the test object. There is no need for an absolutely gas tight seal. A circulation unit, usually a fan, is connected to the air volume inside the hood, to ensure an even concentration of escaping tracer gas throughout the entire volume. A certain waiting time is needed to let the escaping tracer gas accumulate inside the hood. In an automated situation an automatic sampling probe takes a sample of the air inside the hood. The operator or the system controller is then informed by the detector about the total leakage from the test object. In a manual situation a simple hand probe can be inserted under the hood to get a reading.
Chamber test / Low Pressure (patented)
For test objects that are larger, have a difficult geometry and/or a very small acceptable leak rate, the method of using a low pressure chamber test is sometimes preferred. The basic principle is to create a low pressure under the hood, so that escaping tracer gas concentration increases quicker than in atmospheric pressure. The less air there is to mix with, the quicker the concentration rises, the shorter the cycle time. This obviously demands a little bit more in terms of hood and fixture design and additional pumps and valves. The benefit of this method is to allow hydrogen leak testing on objects that would otherwise need a much more complicated and costly high vacuum based leak testing solution based on other tracer gases.
Testing critical points
A point test is used when you know you have a limited area where you suspect there might be a leak and locating the leak is no longer an issue. A point test is to verify if and how much a certain point is leaking. This might be a valve, a welded point, or even a limited welded seam.