A leak detector can pass its internal check while the complete test system still misses a defect. The chamber, valves, connecting lines and auxiliary pumps affect how much tracer gas reaches the instrument and how quickly it arrives. Validation therefore needs to reproduce the actual test configuration.
Define the measurand and acceptance condition
Record the permitted leak rate, units, tracer gas, concentration, pressure difference and direction of flow. A result obtained under one pressure or gas condition is not automatically equivalent to the operating leak rate of the product. Separate the requirement to locate a leak from the requirement to measure the total leakage.
Establish a stable background
Evacuate the clean system using the intended valve sequence. Record the background before introducing tracer gas. Residual helium from an earlier test can increase the baseline and recovery time. Changing the background subtraction or filtering during a comparison makes the results harder to interpret; retain the settings in the test record.
Place the reference source where it tests the system
A reference leak connected directly to the detector checks a short path. A suitable reference source at a remote chamber connection also tests transport through the system. Confirm that the reference is appropriate for the inlet and outlet pressures and that its assigned value and temperature conditions are known.
If an auxiliary pump removes part of the tracer flow, the detector may receive only a fraction of the total. Keep the pumping arrangement unchanged between validation and production testing. Do not assume that a direct-inlet calibration compensates for an unknown flow split.
Measure response and recovery
- Record the background with the reference source isolated.
- Introduce the reference flow using the intended connection and valve state.
- Record the time to the agreed response level and the stable signal.
- Isolate the source and measure the return to the accepted background.
- Repeat the cycle and compare the spread of the results.
The selected production dwell time must allow the relevant defect to be detected. A faster display update is not the same as a shorter gas transport time. Test the most remote or otherwise difficult location when the geometry creates substantially different paths.
Keep a reproducible validation record
Include instrument identification, reference-leak documentation, temperature, chamber volume, connection diagram, valve positions, auxiliary pumping, thresholds and filtering. Record both successful checks and any untested operating conditions. Repeat the relevant validation after changes to hoses, fixtures, pumping arrangements or the test recipe.
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