LEAKLAB · TESTING AND ENGINEERING
An evacuated object or a selected region is enclosed in a controlled tracer-gas atmosphere for an integral leak measurement.
Test arrangement
The evacuated object is connected to a helium mass-spectrometer detector and surrounded by a hood containing tracer gas. The hood and gas supply establish known exposure conditions. Helium entering the object is detected while concentration, exposure time and the covered boundary are controlled.
Scope and limitations
The result concerns the region actually covered. If the hood covers only part of the object, it does not establish the total leakage of unexposed areas. A subsequent local spray scan can help locate the source of an integral signal.
Gas concentration, pressure difference, temperature, object volume, line conductance, pumping and background recovery affect the measurement. The detector’s nominal sensitivity is not the detection limit of the connected test system. The applicable ASTM edition, acceptance criterion and full-system response are specified before testing.
Preparing and verifying the test
- Review the drawing, materials, internal volumes, test boundary and required result.
- Agree the document edition, allowable pressure difference, vacuum and temperature, acceptance criterion and required system sensitivity.
- Clean and dry the object, prepare fixtures and exclude leakage from the test connections.
- Check instrument metrological status and the working characteristics of the complete arrangement; use an appropriate reference response for the selected method.
- Perform the agreed scan or measurement cycle and record the actual conditions. Confirm suspected leaks by repeat tracer-gas exposure where applicable.
- Check system stability after the test and report the result against the agreed criterion.
What the customer receives
The agreed scope can include a test programme, operating or inspection instructions, measured results, a map of located leaks and a technical conclusion. The report identifies the object and tested regions, applicable programme, instruments and metrological status, pressure and temperature, response checks, observations and limitations.
Define your task
Send a drawing or sketch, material, dimensions and volume, working pressure, allowable vacuum and temperature, leak-tightness requirement, number of items, site and schedule. These inputs determine the method, fixture, equipment and reporting scope.
Discuss a test programme