A precise PMI and NDE schedule connects each inspection to a useful procurement question: material identity, a relevant discontinuity or an assembled-valve test. Define the component, method and acceptance basis so each record supports the intended decision.
PMI addresses material identity using a defined analytical method. NDE is a broader group of examinations with different capabilities. Neither an alloy reading nor a generic NDE stamp proves every aspect of valve quality.
ZGV's published component and material tables make it easier to identify the parts an inspection plan should address. Link each PMI or NDE requirement to the proposed material schedule, then agree the method, coverage, records and witness points in the technical quotation.
Separate the questions before selecting the methods
Material mix-up, a surface-breaking crack, an internal discontinuity and leakage across an assembled seat are different concerns. One method cannot be assumed to detect or approve all of them.
PMI can form part of a nondestructive inspection programme, so PMI and NDE are not necessarily mutually exclusive categories. The useful comparison is between the specific questions and methods, rather than a claim that one replaces the other.
| Question | Possible evidence to specify | Boundary to keep visible |
|---|---|---|
| Is this the required alloy? | Suitable PMI method and traceable results | The instrument's elemental capability and surface condition matter |
| Are relevant discontinuities open to the surface? | Qualified penetrant examination where applicable | Closed internal discontinuities are outside that method's capability |
| Are relevant surface/near-surface discontinuities present in a suitable material? | Magnetic particle examination where applicable | Requires a ferromagnetic material and a suitable procedure |
| Is volumetric examination required? | Appropriate UT/RT procedure and coverage as specified | Geometry, material and access affect capability |
| Does the assembled boundary meet a pressure-test requirement? | Applicable shell or closure test record | This is a different verification from identifying alloy chemistry |
The table is a planning aid. The governing product code, purchase specification and qualified examination procedure determine the actual methods and acceptance.
What handheld XRF can leave unresolved
Evident's PMI application note describes XRF as a near-surface elemental measurement and identifies carbon as an element it does not directly measure. Paint, plating or contamination can also affect what is measured.
This matters when a buyer needs to distinguish grades whose important difference includes carbon. A grade name displayed by an instrument should not be used to claim that an unmeasured element has been verified. Select a suitable analytical method and procedure for the required discrimination.
PMI also does not, by itself, establish heat treatment, impact properties, tensile results or complete manufacturing traceability. Request those records separately when they form part of the order. A useful report identifies the part, test location, method, equipment and result so the reading can be connected to the actual assembly.
Surface examination has its own limits
ASNT's penetrant-testing primer explains that penetrant examination depends on a discontinuity opening to the surface and on suitable surface preparation. It cannot reveal a fully enclosed internal discontinuity.
ASNT separately describes magnetic particle testing for surface and near-surface discontinuities in ferromagnetic materials. Specifying MT indiscriminately for every stainless component ignores the material and method requirements.
An indication is also not automatically a rejectable defect. Evaluation needs the governing acceptance criteria, component zone and qualified interpretation. Ask for the result and disposition, not only a line saying inspected.
Define coverage instead of asking for 100% inspection
The phrase 100% can mean all valves, all selected components, every accessible surface or a specified examination volume. Those are different scopes.
A clear inspection line identifies:
- The component and material to examine.
- The stage and surface condition at examination.
- The selected method and procedure.
- The zone, area or volume and any inaccessible regions.
- The acceptance standard and edition.
- Personnel qualification, reporting and witness requirements as specified.
Record limitations openly. An inaccessible region should not disappear behind an unrestricted passed label. If another method is proposed, obtain engineering approval of the changed coverage and capability.
An illustrative inspection-plan correction
Consider a fictional purchase note: “100% PMI, PT/MT, all valves.” The supplier cannot tell whether the buyer expects every wetted part, body/bonnet only or a sample from each batch. It also fails to define how PT and MT apply to different materials.
Rewrite the note as a component schedule. The responsible engineer identifies the required parts, method and coverage for each, then names the acceptance criteria. The supplier returns a procedure and record format, with any limitation or alternative visible before the work starts.
This can avoid paying for a broad phrase while leaving a critical component outside the actual inspection scope. The aim is a test that answers the required question, rather than the largest number of inspection acronyms.
What a component schedule can look like
The following is an illustrative planning extract, with no examination acceptance limits assigned:
| Component/question | Proposed review route | Still to agree |
|---|---|---|
| Stainless body: alloy identity | Suitable PMI method on identified locations | Required elements, surface preparation, coverage and acceptance |
| Nonporous stainless surface: open discontinuities | PT where the material and surface are suitable | Procedure, stage, examination area and evaluation criteria |
| Carbon-steel part: surface/near-surface discontinuities | MT where the part is suitably ferromagnetic | Procedure, coverage and evaluation criteria |
The same part may need more than one row because chemistry and discontinuities are different questions. This schedule makes the scope visible without inventing a universal test package or a rejectable-indication threshold.
Build the inspection plan around the offered ZGV configuration
ZGV's 2519 metal-seated ball valve table includes different material configurations. A schedule for one column should not be applied silently to a different offered build. Surface treatment can also be relevant when selecting and interpreting an examination.
Ask ZGV for the material schedule and inspection scope for the engineering model offered. Agree testing availability, any additional cost and required witnessing in the quotation, with the records matched to the components that matter to your project.
The record should preserve method limitations and the evaluator's disposition of relevant indications. Do not replace a qualified assessment with an instrument's automatic grade match or an unexplained no defects stamp. Both the observation and its acceptance basis need to remain reviewable.
Submit the component-specific inspection requirements with the service and product reference. Approve the methods, coverage and acceptance basis together so each result has a clear meaning.
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