The definition of gas leakage is that gas enters the interior of a vacuum system through the path of leakage from the outside of the system. According to this definition, any vacuum system has air leakage, and in practical applications, this definition does not determine whether the vacuum system has air leakage.

The condition for no air leakage in the vacuum system

Since it is impossible for a vacuum system to be absolutely leak free, it can be considered leak free if the following conditions are met: the final pressure of the vacuum system can reach the operating pressure range of the vacuum system within a reasonable time, and can be achieved and maintained within a reasonable time.

Ways of leakage

The definition of gas leakage refers to the pathway through which gas enters the interior of a vacuum system from the outside, which should be related to the materials and manufacturing processes that make up each part of the vacuum system.

This mainly includes: material manufacturing and processing, small holes, cracks, weld cracks, texture of material processing, properties of the material itself, micropores of porous materials, and penetration of molecular or crystal gaps.

Method for determining gas leakage

The commonly used method for determining false and true leaks is to stop pumping the vacuum system. The commonly used method for determining false and true leaks is to stop pumping the vacuum system, that is, to close the isolation valve between the pumping vacuum pump and the vacuum system.

Leak detector for leak detection - helium leak detector

Helium leak detector is currently the most widely used leak detector. In fact, the helium leak detector is a small gas mass spectrometer specifically designed to measure helium gas.

As it is a mass spectrometer, it must operate in a high vacuum range, so a vacuum pump is required to maintain the high vacuum of the instrument. The traditional helium leak detector uses a small diffusion pump and its front pump to draw high vacuum, but due to the lack of cooling water sources in the usage site, it uses air-cooled cooling.

Therefore, liquid nitrogen must be used to prevent the oil vapor from the pump from flowing back to the mass spectrometer. The new helium leak detector uses a turbo molecular pump and its front pump to draw high vacuum, so there is no problem of oil vapor reflux.

It should be noted that this new type of helium leak detector must be prevented from contaminating the turbine molecular pump when used for leak detection in contaminated vacuum systems. If the turbine molecular pump blades are leaked, they must be prevented from being contaminated. Cleaning the turbine molecular pump blades is difficult, and continued use without cleaning can damage the pump.