Technology Modules: Leak Test Instruments

When special purpose machinery requires a leak test to be carried out the best solution is to integrate a leak test instrument.  

A process may requirement the automatic assembly of a number of parts and then the final assembly may need to be tested.  Leak test instruments can be easily combined into any special purpose machine and can be integrated with the machine control to automatically signal pass and fail results so that the next process is carried our correctly, for example if a part fails a leak test then the control system would ensure no further function are carried out and the parts is rejected (or may a reject mark is applied).

There are 6 main areas of leak test instrumentation that can be considered

Absolute or gauge pressure transducers

    • When pressure drop is large relative to the sensitivity of the transducer, one can use a simple pressure transducer or pressure meter.

Differential pressure leak test instruments, vacuum and overpressure

    • There are a range of leak test instruments available from a number of suppliers most of whom TQC have worked with. These instruments can sometimes come with additional pneumatic and/or electrical input/output capabilities for leak test fixture control. The use of differential pressure transducers significantly increase the sensitivity of the test over the use of gauge pressure measurement.

Flow instruments

    • These usually work by maintaining a constant pressure whilst measuring the flow. They are generally used for flows and larger allowable leaks.

Hydrogen sniffing instruments

    • Hydrogen sniffing uses tracer gas hydrogen in less than 5% concentration (below the explosive limit). This is used extensively in the telecoms and aerospace industries for locating leaking joints.

High vacuum leak testing

    • High vacuum leak testing can be used by using a high vacuum pumping system and transducers with a tuned sensing range close to absolute vacuum. This method can be used for checking sealed liquid containers where the leaking liquid vaporizes hindering the ability of the high vacuum pumping system to get to low vacuum.

Helium leak testing

    • The use of helium mass spectrometers to test for leaks gives a capability of testing very small leaks typically less than 1,000th of the techniques outlined above. This is the most sensitive leak testing technique.

Get in touch with us to discuss your requirements and we will be happy to offer our professional advice and visit you at your site.

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