QUICK ANSWER
What to Know First
Decide whether the task is leak location, total leakage measurement, acceptance testing or troubleshooting. Define pressure direction, safe object limits, acceptance criterion with units and conditions, accessible surfaces and fixtures. Then review method, tracer use, background, response, reference checks and reporting.
OVERVIEW
The Technical Context
Planning selects the method and the result that must be demonstrated. The preparation checklist then checks whether the selected object, fixtures, connections and equipment are ready. Keeping those stages distinct avoids choosing a test from a detector headline alone.
A pass/fail decision needs an engineering requirement. The provider and customer should agree the boundary, pressures, method, reference basis, deviations and acceptance authority before work starts.
- Define local vs integral objectives.
- State pressure direction and safe limits.
- Keep criterion, units and conditions together.
- Review system response and background.
ENGINEERING GUIDANCE
Define the Objective and Test Boundary
Leak location identifies where tracer crosses the boundary. An integral arrangement evaluates combined leakage under stated conditions. Acceptance testing applies an agreed decision rule. Troubleshooting may instead compare configurations to investigate a symptom.
Identify the object, drawing/revision, joints, seals, welds, ports and any excluded areas. Clarify whether temporary fixtures, caps, adapters and enclosure seals are included in the boundary or must be checked separately.
ENGINEERING GUIDANCE
Choose a Method from the Object and Required Result
| Arrangement | Basic approach | Planning questions |
|---|---|---|
| Vacuum spray | Evacuate the object; apply tracer outside. | Can the object safely withstand vacuum? Which surfaces are accessible? What response and background apply? |
| Pressurised sniffer | Introduce tracer above ambient; sample outside. | What overpressure/concentration are approved? Can the probe reach each area with a controlled scan? |
| Integral enclosure/hood | Use a defined enclosure to evaluate combined leakage. | How are enclosure volume, mixing, dwell, fixtures and background handled? |
ENGINEERING GUIDANCE
Make the Acceptance Criterion Complete
State leak-rate value and unit, gas or concentration, pressure difference/direction and reference conditions required by the specification. Distinguish the engineering criterion from a detector's minimum indicated capability.
Do not transfer a limit from another fluid, pressure or object without an approved basis. If the criterion is missing, identify the engineer or quality authority responsible for defining it before an acceptance test is proposed.
ENGINEERING GUIDANCE
Review Fixtures and System Response
Connections, volumes, pumping arrangement and probe/enclosure details influence how quickly tracer reaches the detector and how long the system takes to recover. A fast instrument does not automatically make a fast complete test.
Allow for stabilisation, tracer application, response, dwell and clean-up in the proposed sequence. An auxiliary or partial-flow pumping arrangement needs an appropriate reference/check method for quantitative interpretation.
ENGINEERING GUIDANCE
Control Background and Reference Checks
Excess helium in the surrounding area can increase background and delay recovery. Plan ventilation, tracer quantities, filling activities and separation of known-leak operations so the useful signal can be interpreted.
Follow the exact detector manual and approved procedure for warm-up, calibration/reference-leak checks, mode, units, background and validity. Record the reference device identity and condition; do not assume one check covers every later configuration.
ENGINEERING GUIDANCE
Set Safe Object and Tracer Conditions
Confirm the allowable vacuum and overpressure, fixture restraint, pressure regulation and handling before evacuating or pressurising the object. Helium is inert but can displace oxygen, and cylinders/pressure systems introduce stored-energy hazards.
Arrange competent site review, ventilation and gas/pressure controls. Once the method is agreed, use the preparation resource to review cleanliness, residue, accessible ports, blanking and transport or site needs.
ENGINEERING GUIDANCE
Agree the Record and Decision
The record should identify the object, revision, method, boundary, fixtures, pressures, tracer basis, instruments/reference devices, checks, background, results, acceptance rule and deviations needed by the approved procedure.
Agree how inconclusive or invalid results are handled and whether retesting is permitted after a change. ISO 20485 describes tracer-gas testing techniques; a reference to it does not by itself certify a particular test or provider.
PRACTICAL WORKSHEET
Helium Leak-Test Planning Worksheet
Use this before the readiness checklist so the proposed test has a clear engineering basis.
Objective and boundary
- Locate, measure total, accept/reject or troubleshoot
- Object identity, revision and included joints
- Temporary fixtures and exclusions
Criterion and pressure
- Leak-rate value, unit and reference conditions
- Pressure direction and approved safe limits
- Acceptance authority and decision rule
Method and response
- Vacuum, sniffer or enclosure arrangement
- Ports, fixtures, probe access and pumping
- Stabilisation, response, dwell and recovery
Equipment and environment
- Detector mode and reference-leak checks
- Background helium and ventilation
- Gas concentration, handling and site controls
Records
- Required report and traceable identification
- Test sequence and validity checks
- Deviations, retest and approval responsibilities
PRIMARY REFERENCES
Technical Sources and Further Reading
These references support the general technical explanation. Always use the current instructions and approved procedure for the exact equipment and task.
