Pressure-Tightness Testing for Aluminum Castings: RFQ Methods and Acceptance Criteria

Pressure-tightness testing for aluminum castings is not one universal test. The correct method depends on the part, service medium, operating conditions, drawing requirements, machining stage, and the buyer's acceptance criteria. A useful RFQ therefore defines the test scope before suppliers compare tooling, casting, machining, and inspection cost.

This guide explains the decisions a buyer should document for pump housings, valve bodies, manifolds, coolant housings, and other castings with a sealed pressure boundary.

Start With the Functional Requirement

Before selecting equipment or a test medium, state what the casting must contain or exclude in service. Useful inputs include:

• •service medium, such as air, water, oil, coolant, or another project-defined fluid;
• •normal and maximum operating pressure;
• •whether the part also sees vacuum, thermal cycling, vibration, or pressure pulses;
• •which ports, sealing faces, machined bores, and wall zones form the pressure boundary;
• •whether testing occurs before machining, after machining, or at both stages.

These inputs let the supplier review casting route, wall thickness, gating, feeding, machining exposure, and inspection scope against the actual drawing.

Common Pressure-Tightness Test Methods

Several methods are used across industry, and none should be selected by name alone:

• •Pressure hold or pressure drop: the part is pressurized with a defined medium and monitored for a defined time.
• •Air-under-water or bubble observation: useful when the procedure defines pressure, dwell time, observation method, and allowable result.
• •Flow or pressure-decay measurement: provides a numeric result when equipment, part volume, stabilization time, and acceptance threshold are specified.
• •Hydrostatic testing: may be appropriate when the drawing or customer specification requires a liquid-pressure test.
• •Tracer-gas testing: helium-based methods exist in industry for applications that require a defined tracer-gas leak rate. If a buyer requires this method, the RFQ should identify the applicable standard, test setup, pressure, leak-rate unit, calibration, and acceptance threshold. It must not be assumed from a supplier's general pressure-testing capability.

Bohua Casting's confirmed in-house capability is a pressure-tightness testing workshop. The test method, medium, pressure, duration, and acceptance criteria are defined according to customer drawings and project requirements. Any buyer-specified tracer-gas method must be separately scoped and verified rather than inferred from general pressure-testing capability.

Define the Acceptance Criteria

"Leak test required" is not enough for a comparable quote. The RFQ should state:

• •test medium;
• •test pressure and any pressure ramp;
• •stabilization and hold time;
• •pass/fail threshold and measurement unit;
• •test temperature when relevant;
• •sealing fixture and plugged-port assumptions;
• •whether the result is recorded by batch, sample, or serial number;
• •whether retest, repair, or impregnation is permitted.

If the buyer has not finalized one of these fields, mark it as an open assumption and ask each supplier to propose a method separately from the base casting price.

Choose 100 Percent or Sampling by Project

Inspection frequency is also project-defined. Some safety-critical or sealing-critical characteristics may require testing on every part. Other characteristics may be controlled through an agreed sampling plan supported by process controls and first-article evidence. Bohua does not make an unconditional site-wide promise that every characteristic on every order receives 100 percent inspection.

The RFQ should identify:

• •first-article testing scope;
• •production sampling or all-part testing requirements;
• •reaction plan after a failed result;
• •traceability and record-retention expectations;
• •any customer-specific FAI or PPAP requirement. Bohua can provide PPAP documentation up to Level 5 according to project requirements.

Connect Testing to Casting and Machining Risk

Pressure-tightness cannot be guaranteed by a final test alone. Buyers should ask how the supplier will review:

• •fill and solidification risk;
• •wall transitions and hot spots;
• •machining stock and the risk of exposing subsurface discontinuities;
• •sealing-face flatness and surface finish;
• •heat treatment and surface finishing;
• •X-ray, CMM, material, and traceability records when the project requires them.

For specification planning, use the leak-test specification checklist, the quality-control overview, and the casting drawing requirements guide.

RFQ Checklist

Send the supplier:

• •2D drawing and 3D model with revision status;
• •pressure-boundary and sealing-interface notes;
• •service medium and operating conditions;
• •proposed test method or a request for recommendation;
• •pressure, duration, acceptance, and record requirements;
• •inspection frequency and traceability needs;
• •machining, heat-treatment, finishing, and approval scope;
• •prototype quantity, annual demand, destination, and timing.

Bohua Casting typically responds to complete RFQ packages within 1–2 business days, and sometimes faster depending on project complexity. Use the formal RFQ form to send the drawing package and open test assumptions for project-specific review.