Leak Test Method                          <more details please download PDF file>

Bell Jar method - Hood test

As in the vacuum hood test the overpressure hood test is an overall leak test. A test set-up similar to the vacuum test is used. A vacuum chamber is used for the hood, which can be evacuated by an auxiliary pump and to which the leak detector is connected. The helium search gas which is escaping through leaks in the test object is indicated by the leak detector. The use of a helium leak detector allows detection of extremely small leaks and is suitable for automatic leak detection.

Sniffer method - Sniffer test/Detector probe

At this type of test the suspected areas of the test object are carefully explored by means of a detector probe, a "sniffer", which is connected to the leak detector. The object to be tested is under helium search gas overpressure. The sensitivity of the method of the method and the accuracy of localizing any leaky points depend on the nature of the search gas, the design of the sniffer and the time constant of the actual leak testing device.

Bombing method - Bombing test

The bombing test is a pressure/vacuum method of leak detection used for testing of hermetically sealed components containing a cavity which can be gas-filled or evacuated. The objects to be tested get in a pressure chamber exposed to the helium search gas. During an exposure time of up to several hours at a high helium pressure, the helium will penetrate through any leaks present in the test object. This is the part referred to as the "bombing". After the pressurization or bombing the objects are tested for helium emission in a vacuum vessel, following the same procedure as in the hood test. This test permits detection of the smallest leak rates and is especially used for objects which can not be gas-filled by other means.

Vacuum spraying method - Tracer probe test

At the tracer probe test the same set-up as used for the hood test is applied, but without the hood. A spray probe is used to spray a fine jet of helium search gas at areas suspected of leaking. Again the helium enters through leaks present at the evacuated test object and the detector connected to it. The detector indicates if a leak is present at the area the helium search gas is exposed to.

Vacuum hood method - Hood test

The Hood Test is an overall leak test. The evacuated test object is covered with a hood. The space between the test object and the hood is filled with Helium from the search gas reservoir so the total outer surface of the test object is exposed to the Helium search gas. The helium enters through all leaks present at the evacuated test object and thus the detector connected to it. The detector now indicates the total leak rate.