Limitations of leak testing using the pressure change method

 

With regard to increasing environmental limitations, the tightness requirements for parts and components become more stringent. This is why many users apply testing methods based on the pressure change method for their processes. But these methods have limitations.

Colloquial expressions such as “technically tight“, “gas tight“, “virus tight“, “bacteria tight”, “water tight“ and “liquid-tight“ are not sufficient to describe a tightness requirement. The limitations of the pressure change method can easily be illustrated with an example of the expression “liquid tight” with a leakage rate in the range of 10^-6 mbar l/s. In a container with a volume of 5 liters, such a leakage causes a pressure loss of 2.0 · 10^-7 mbar per second. This would be 1.2 · 10^-5 mbar per minute, 7.2 · 10^-4 mbar per hour, 1.7 · 10^-2 mbar per a day, and 6.3 mbar per year. The instruments in use must therefore be able to resolve these pressure changes.