Radiographic testing and liquid penetrant testing are not interchangeable ways to declare a casting defect-free. They examine different kinds of conditions and depend on different procedures, access and interpretation. Selecting an examination method starts with the part’s function and the type of discontinuity the inspection needs to address.

A purchase order that merely says NDT required leaves major decisions unresolved. The method, inspection region, extent of coverage, acceptance criteria and reporting requirements should be agreed before production. Otherwise two suppliers may quote different examinations while appearing to meet the same request.

Begin with the inspection objective

Ask whether the concern is a surface-opening discontinuity, an internal condition or another characteristic. The component’s geometry and alloy can affect which techniques are practical. A thin accessible flange presents a different inspection problem from a thick, complex intersection.

The SFSA overview of nondestructive testing distinguishes examination methods used for steel castings. It is a useful starting point for method selection. The detailed procedure and acceptance basis should come from the standards and engineering requirements applicable to the actual order.

Understand what penetrant testing can show

Liquid penetrant testing is used to reveal discontinuities that are open to the examined surface. Surface preparation and the inspection procedure matter to the result. It does not provide a general view through the interior of the casting.

A machined surface may expose a condition that was not accessible on the original casting skin. Therefore, the stage of penetrant examination can matter. Agree whether inspection is required before machining, after machining, after a particular heat treatment or at another defined point in the route.

Understand what radiography contributes

Radiography provides information about internal conditions through an image produced by penetrating radiation. Part thickness, orientation and geometry influence the examination arrangement and the visibility of relevant features. It is not a guarantee that every possible discontinuity will be detected in every orientation.

Request an agreed examination plan for the relevant regions. A statement that a casting was X-rayed is incomplete without knowing the coverage and acceptance criteria. The report should identify the examined part, applicable procedure and results in a form that the buyer can review.

Avoid a blanket inspection requirement

The highest possible inspection extent is not automatically the best purchasing specification. Requirements should reflect the part’s design and service. A critical region may need a particular examination while another region can be accepted through a different agreed method.

For an illustrative housing, the buyer might identify a pressure-containing region and a separate noncritical mounting feature. The responsible engineer should decide whether their examination requirements differ. The foundry can advise on feasibility and cost, but should not substitute an easier test for a required one without approval.

Connect indications to acceptance decisions

An indication is an examination finding; its acceptability depends on the applicable criteria and context. Avoid describing every visible indication as a rejectable defect before evaluation. Equally, a report marked acceptable should identify the criteria that support that conclusion.

If repair is permitted, define the approval and re-examination requirements. Keep the original finding and final disposition traceable. An undocumented repair followed by a pass report deprives the buyer of information that may be required by the order or service specification.

Put the examination plan into the RFQ

For steel investment castings, specify the required method, regions, coverage, acceptance level and report format. Identify the governing standard edition and any personnel qualification requirements imposed by the project. Avoid replacing these details with a generic request for certified quality.

Discuss those requirements with Hengke through the technical enquiry page before comparing prices. A meaningful quotation should make clear which examination is included and what additional information is needed to establish the final acceptance plan.