Determining Leak Rates
Zero Leakage sounds ideal, but nothing made by man can be considered to be absolutely leak tight. Even in the absence of minute porosity, the permeation of certain gases through metals, crystals, polymers, and glasses still occurs. Therefore, specifications for leakage should always be expressed in maximum allowable leak rate, or maximum tolerable leak rate.
Dimensions of Leakage Units: A leak is always measured in terms of mass flow, i.e., a given volume of gas or liquid for a specified time interval, such as oz/yr, grams/yr, gallons/hour, drops/min, cc/sec, etc.
The formula for determining the rate of gas leakage is:
Pressure x Volume / Time, at a given temperature.
In leakage work, mass flow is typically in Atm–cc/sec at 25 deg. C.
Reasons for Leakage Testing
Rapid, nondestructive methods for the detection of gas and liquid leakage in sealed systems are of great industrial and commercial importance. The operational reliability of such systems are greatly increased when considerable attention is paid to the leak testing of individual components as well, as that of the final assembly.
Leak testing is performed for four basic reasons:
1. To prevent material loss by leakage.
2. To prevent contamination, creation of hazardous conditions, short product life or disfigurement by leakage.
3. To detect faulty components and control the reliability of the product.
4. To reduce warranty cost.
Please see this link for the most current Popular Tracer Gases Leak Rate Summary