Technical insight
Helium Leak Testing for Vacuum Parts: Define Acceptance Before Ordering
For a vacuum-component order, ask the responsible engineer to approve both the acceptance limit and the conditions under which it will be assessed. Use the purchasing checklist below to resolve the test boundary before comparing quotations. It is editorial guidance, not a test procedure or a universal leak-rate limit.
By Geetai Precision
- Published
- Updated
Replace a vague pass statement with a defined requirement
Leybold explains that an acceptance specification needs a stated leak rate under defined conditions; the acceptable value depends on the application. A bare claim of zero leakage is not an adequate acceptance basis.
Editorial recommendation: identify the delivered item and the sealed boundary in a marked drawing. Name the ports, temporary closures, seals and joints included in the assessment. Have the purchaser and testing provider agree which fixture interfaces are excluded and how fixture leakage will be checked.
Choose between locating a leak and assessing the whole boundary
Pfeiffer describes spraying tracer gas onto an evacuated part and sniffing around a pressurized part as leak-localization methods. Its integral methods enclose the part so gas crossing the defined boundary can be assessed collectively.
| Purchase question | Request in the quotation |
|---|---|
| Where is the suspected leak? | A named local method and a record of the areas examined. |
| Does the complete specified boundary meet its limit? | An agreed integral method covering that boundary, not only a list of sprayed locations. |
| Can two quotations be compared? | The same limit, units, gas basis and documented conditions; list any differences before comparing prices. |
Do not select overpressure or evacuation from this table alone. Require the responsible engineer and testing provider to confirm the suitability of the part and fixture for the proposed pressure differential.
Attach a short test schedule
- Item identity: drawing revision, part or assembly identifier, delivery condition and included sealing hardware.
- Gas conditions: tracer-gas identity and concentration, pressure on each side, pressure direction and any required temperature condition.
- Measurement sequence: agreed stabilization and exposure periods, background assessment and response-time check for the actual setup.
- Acceptance record: limit and units, measured value or stated reporting threshold, method reference, date and item identity. Do not replace an instrument threshold with a claim of zero.
Pfeiffer describes calibration with a test leak producing a known gas flow under defined conditions. It also discusses external test leaks for setups using auxiliary pumps and for checking response time.
Request the reference-leak identification and calibration record applicable to the agreed setup. If a fixture, connection or pump arrangement changes, ask the testing provider whether the setup check must be repeated before acceptance.
Keep component acceptance separate from system commissioning
For example, if a machined housing is assessed with temporary port covers, ask for those covers and seals to be identified in the report. Treat later assembly with different hardware as a separate acceptance question; do not silently extend the component sign-off to the completed instrument.
Related review paths
References
- What is a leak and how to measure the leak rate in vacuum systems — Leybold. Accessed 2026-09-21T05:14:35.000Z.
- How to Find a Leak with Tracer Gas — Pfeiffer Vacuum. Accessed 2026-09-21T05:14:35.000Z.
- 7.2 Leak detection with tracer gases — Pfeiffer Vacuum. Accessed 2026-09-21T05:14:35.000Z.