Pressure and Leak Tests for Custom Fittings: Write a Clear Specification

Identify the question the test must answer

A pressure integrity test and a leakage test can serve different purposes. One may examine structural resistance under a defined load, while another detects an unacceptable flow path under specified conditions. State the required outcome before asking the supplier to “pressure test” a fitting. The product’s design authority should choose the applicable standard and acceptance requirements for the service, including any regulatory obligations.

Specify the assembled test boundary

Identify which ports are connected, capped or open, and which seals and mating components form the test boundary. Fixture leakage can be mistaken for a part defect, while an overly forgiving fixture can hide a problem at the production interface. Use a drawing or controlled fixture reference to remove ambiguity. Record whether the part is tested before or after the final cleaning, coating or assembly operation.

Control the conditions that affect the reading

Document the medium, pressure, temperature, stabilization period, measurement interval and allowable result as required by the approved method. Pressure-decay readings can be influenced by temperature change and trapped volume, so a numerical threshold needs context. Do not transfer a threshold from a different fixture or volume without validation. Qualified personnel should establish the safe test arrangement and operating procedure for the stored energy involved.

Prove the measurement system works

Select equipment with suitable sensitivity and resolution for the acceptance criterion. Calibration establishes part of the evidence; routine verification with an appropriate reference or controlled check can show that the assembled test system is functioning. Define the reaction to a failed verification. A display showing zero is not meaningful evidence if the method cannot resolve the leakage level that matters to the product.

Make the release record useful

Tie results to part or lot identity, test procedure revision, equipment and the relevant conditions. Define the required coverage and how rejected parts are segregated and investigated. If rework is permitted, identify the authorized process and retest requirement. The report should distinguish an initial failure from a passing retest so trends are not hidden by recording only the final disposition.

Approval checklist and evidence

Worked review example

Illustrative scenario: a small fitting and a large housing are tested with the same pressure-decay limit, although the enclosed volumes differ. The apparent pass/fail comparison is therefore incomplete. The engineering review validates a suitable method for each setup and records volume, stabilization and measurement conditions. No test pressure or acceptance rate in this article should be treated as a production instruction; those values belong in the approved product-specific procedure.

Information for the engineering review

• Integrity or leakage objective
• Boundary, seals and fixture revision
• Medium and controlled test conditions
• Sensitivity and system verification
• Traceable results and retest rules

Discuss this requirement with KEC Tour using the controlled drawing, the relevant mating interfaces and the review information above. Identify the decision that needs confirmation and the acceptance evidence expected with the first parts.

Sources and further reading

• Parker O-Ring Handbook
• NIST measurement traceability

Frequently asked questions