Techniques
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.

Leak Testing - Chamber test, Atmospheric Pressure, integral test INFICON

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.

Leak Testing - Chamber test, low pressure (patented) INFICON

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.

Manual point test

A manual point test is performed using the Sniffer Probe AP55 connected to the Hydrogen Leak Detector Sensistor ISH2000. The sniffer flow is activated with a push button and the probe is put on top of the suspected leak point. The detector will immediately tell the operator the size of the leak and also indicate if the leak was below or above the preset leak limit (accept/reject).

Leak Testing - Manual point test INFICON

Automatic point test

An automatic point test is usually performed using a customised local enclosure around the test point. These local enclosures are sometimes also called clamps or clam shells. Clamps are small local enclosures mostly designed to fit over a specific pipe joint. It consists of a small chamber cut in half so it can be opened and closed around a pipe joint. The enclosure of the clamp is connected to the end of the sniffing sample hose.

Leak Testing - Automatic point test INFICON
Clamps are efficient for testing refrigerator joints and similar. The clamp reduces the operator dependence as compared to manual point testing. You can take advantage of the small volume in several ways. Testing is fast but can also be made extremely sensitive. You can increase the sensitivity by letting the gas accumulate inside the clamp for some time before taking the sample. The concentration will increase fast thanks to the small volume.

Testing joints, seams and surfaces

Leak testing seams, linear joints and surfaces with the hydrogen method is best done with scanning. Welded seams, long joints, tubes and hoses are all good examples of objects that can successfully be scanned for leaks. The scanning probe needs to be customised to fit the test object but is simple and inexpensive to manufacture. It can either be passive or actively sniffing, depending on the application. The scanning probe is a tracer gas collector with a built-in sensor, or a sniffer hose leading to an automatic sampling probe.

Leak testing - Testing joints, seams and surfaces INFICON
Leak testing - Testing joints, seams and surfaces INFICON
Leak testing - Testing joints, seams and surfaces INFICON