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Temperature and leakage

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Temperature effects on the test gas (air) and / or to the test volume during the test phase for the result and the reproducibility of the results of leak testing have a very negative influence. As seen in the "General Gas Law" does, here is the gas temperature in the calculation. In most test systems, which work according to the method of pressure drop / rise in pressure method, the actual gas temperature is considered constant and not very often measured. Moreover, as the test gas is always assumed normal air pressure.

Gas law

The practice of the leak test has also shown that the gas temperature has not the primary influence on the outcome.

Much stronger influences make themselves felt from the outside, acting on the test volume during the test and the test facility. In this case, that an increase in temperature lead to an increase in pressure and a reduction in temperature to a pressure drop. If this effect takes place during the testing phase, can not detect the test system without extra effort, whether the change in pressure comes from a leakage and / or a temperature effect. In the worst case may cause a small leak outside through a temperature of influence to ensure that no pressure change is measured.

A further complication is that the different test volumes also have very different temperature transitions from outside to inside. In addition, the testing machines (eg warm test volume) recording a temperature of the parts. I.e. it is not without the prior studies to predict how much impact a temperature influence on the outcome.

These effects can be caused by some measures appear to meet:

  • Constructively to ensure that the plant and the parts are not exposed to fluctuating temperatures
    (no drafts, no sunlight, no heater, etc.)
  • Intend, perhaps, a cooling line is useful (e.g., after washing streets)
    (the best inspection results are achieved without additional compensating measures) 
  • The partial absorption thermally from the equipment and the test volumes decouple
    (e.g., plastic absorption obstructs)
  • A temperature compensation bring to the application
    (On this occasion, the partial temperature and ambient temperature is measured. The difference
    is dragged as a reference variable to the compensation near. The necessary compensation
    table must be determined empirically.)