The vacuum system is required to obtain and maintain the vacuum state. If there is a serious air leakage, it is a major defect of the system. Therefore, the relevant vacuum leak detection is needed.
Breathability and leaky is different in nature. Breathability is the process of gas infiltration, diffusion, passage and escape from a side with a high density to a side with a small density. Any material has certain permeability. Leakage is a phenomenon in which gas molecules flow from the high pressure side to the low pressure side due to defects in the material itself or poor sealing portions. In another case, leakage does not occur at room temperature, but the difference in thermal expansion coefficient at the time of temperature change may also cause leakage. Fig.1 is a schematic diagram of the source of gas that affects the vacuum system.
Fig.1 Schematic diagram of the gas source that affects the system vacuum
Strictly speaking, any vacuum system has air leakage, and air leakage is absolute. A certain leak rate can be tolerated for different vacuum systems. For the current vacuum technology, the allowable leakage rate of the ultra-high vacuum system is ≤ 1.33×10 -11 Pa.m3/s.
Vacuum leak detection has become an indispensable part of the production and use of vacuum systems. The method of vacuum leak detection is varied, and the most representative methods are the helium mass spectrometer leak detection and quadrupole mass spectrometer residual gas analysis.