The QC review stops when the supplier rejects liquid penetrant testing of the hard-faced 410 stainless steel plug and seat ring, even though PT appears in the agreed inspection and test plan. Resolve this by separating three questions: the minimum examination required by ASME B16.34, the scope of the purchaser’s additional requirements, and the examination method applicable to the actual surface.
NDE requirement paths
| Requirement path | What determines examination | Application to this valve |
|---|---|---|
| ASME B16.34 Standard Class minimum | Standard Class does not make NDE of cast valve bodies mandatory under the cited basis. | This establishes only the code minimum. It does not cancel purchaser-specified PT. |
| ASME B16.34 Special Class minimum | Additional examination under Clause 8 supports the higher pressure-temperature ratings assigned to Special Class valves. |
Apply this path only when the valve is ordered and rated as Special Class. A class number by itself does not establish that status. |
| Purchase specification or agreed inspection plan | The specified component, examination method, examination stage, acceptance criteria, and records define the supplier’s contractual scope. | The agreed plan lists PT, so process it as a project requirement unless both parties formally revise the plan. |
| Material or product specification | A separately invoked specification may add material-specific examination requirements. | Require the supplier to identify the document, edition, paragraph, component, and acceptance criteria behind its claimed distinction between 410 SS and 316 SS. |
The recommended disposition is to retain PT of the specified hard-facing area. The supplier’s two arguments address different matters and neither removes an agreed inspection-plan operation. Standard Class status addresses the minimum B16.34 examination of the valve body. The requested PT concerns hard-facing on the plug and seat ring. The claim that PT applies to 316 SS but not 410 SS needs a separate cited requirement; it is not the stated B16.34 rule.
Requirement hierarchy and scope
Before anything else, confirm which document actually requires PT and exactly what it covers. Record the purchase order, valve data sheet, project specification, approved drawing, and inspection plan by revision. An agreed inspection plan converts the examination from an optional code supplement into a defined project hold, witness, or review activity according to that plan’s status.
Do not merge the body and trim into one NDE decision. The reported construction contains an A216 WCC cast body and a 410 SS plug and seat ring with a hard-facing area. The B16.34 statement cited for Standard Class concerns cast valve bodies, while the requested PT location is on trim hard-facing. A body-examination exemption cannot automatically be extended to deposited hard-facing, machined trim surfaces, or another component.
Establish the governing order of precedence from the purchase documents. Where the inspection plan explicitly calls for PT, obtain a written concession or approved revision before deleting it. A supplier comment on the document does not revise an accepted requirement. The disposition should identify whether PT remains required, is replaced by another method, or is deleted, together with the technical and contractual authority for that decision.
Standard Class and Special Class distinction
Special Class is a rating category, not a synonym for high pressure. Under the cited B16.34 framework, additional examination permits a Special Class valve to receive a higher pressure-temperature rating than the corresponding Standard Class valve. The applicable ratings are tabulated in ASME B16.34, and the additional examination requirements are addressed in Clause 8.
A nominal pressure class does not answer the classification question. For example, B16.34 can identify a valve as Class 150 Standard Class or Class 150 Special Class; both retain the Class 150 designation but use different ratings. Apply the same decision logic to the reported Class 600 valve: read the ordered class description and the applicable rating table rather than inferring Special Class from the number.
Likewise, a class of 3500 or above would not become Special Class merely because the number or service pressure is high. Determine the category from the specified B16.34 rating basis. The decisive records are the purchase description, valve data sheet, manufacturer’s rating documentation, and applicable B16.34 pressure-temperature table. Do not move on until those records consistently identify Standard Class or Special Class.
PT applicability to 410 SS hard-facing
Liquid penetrant examination detects discontinuities that are open to a clean, nonporous surface. Its basic applicability does not depend on the component being 316 SS. Surface condition, coating, contamination, geometry, examination procedure, and the acceptance criteria control whether PT can produce a valid result.
The base trim material and deposited hard-facing must be treated as separate variables. The examination request is for the hard-facing area, so review the hard-facing specification, deposition procedure, heat-treatment sequence, machining sequence, and drawing notes. Identify whether PT is required after deposition, after final machining, or at both stages. Examination before the final operation does not automatically satisfy a requirement written for the finished surface.
Magnetic-particle testing may be technically considered when the examination surface is ferromagnetic, but that does not authorize substituting MT for specified PT. The hard-facing alloy and its magnetic response have not been identified. Confirm method suitability on the actual examination surface and obtain purchaser approval before changing methods.
The statement that 410 SS needs no PT while A276-316 does needs a traceable basis. Request the exact material or product specification, edition, paragraph, and acceptance table. Then check whether it applies to raw material, finished trim, deposited hard-facing, or the completed valve. A raw-material requirement does not necessarily govern fabrication discontinuities introduced during hard-facing or machining.
Document-review procedure
- Freeze the document basis. List the current revisions of the purchase order, data sheet, material specification, drawing, approved inspection plan, NDE procedure, and applicable B16.34 edition. Confirm that the inspection plan still contains PT before evaluating the supplier’s request.
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Identify the valve category. Compare the ordered designation and rating documentation with the Standard Class and Special Class tables in B16.34. Record the table used and the resulting category. Do not infer the category from
Class 600alone. -
Map every examination to a component. Create separate rows for the
A216 WCCbody,410 SSplug, seat ring, and hard-facing. For each row, state the examination method, stage, extent, acceptance criteria, and record required. - Separate code minimums from additions. Mark each operation as required by B16.34, another invoked specification, or the purchaser’s inspection plan. This prevents the Standard Class body rule from being incorrectly applied to trim hard-facing.
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Challenge the alloy-based rejection. Ask the supplier for the exact clause supporting different PT treatment of 410 SS and
A276-316. Verify the clause’s component and manufacturing-stage scope rather than accepting a material designation alone. - Confirm the PT procedure. Check that the approved procedure covers the surface material, hard-facing condition, surface preparation, examination stage, technique, evaluation, acceptance criteria, personnel qualification basis, and report format. Read required process values from the approved procedure; do not insert generic values into the inspection plan.
- Resolve conflicts formally. If the supplier still proposes deleting or replacing PT, process the change through the project’s deviation or concession route. Retain PT until an authorized disposition revises the requirement.
Examination execution controls
| Control point | Required confirmation | Reason |
|---|---|---|
| Component identity | Plug and seat ring identities match the drawing and material records. | Prevents a report for unrelated trim from being accepted. |
| Examination surface | The report identifies the hard-facing area and its examination extent. | A generic reference to trim PT does not establish coverage. |
| Process stage | PT occurs at the stage stated in the inspection plan or drawing. | Later machining or deposition can remove or create surface indications. |
| Surface condition | The surface is prepared as required by the approved procedure. | Contamination, roughness, or inaccessible geometry can mask relevant indications or create nonrelevant indications. |
| Evaluation basis | The report cites the approved acceptance criteria. | Performing PT without a defined disposition rule does not close the inspection point. |
| Traceability | Valve, component, drawing, procedure, examiner, date, and result are linked. | Traceability connects the examination result to the supplied valve. |
When an indication is found, evaluate and disposition it under the invoked acceptance criteria. Do not create acceptance limits from the valve’s class, the 410 SS designation, or general workshop practice. If repair is permitted, record the approved repair method, repeat the required manufacturing steps, and re-examine the affected area using the specified method and criteria.
Final acceptance verification
- Verify that the valve is documented as Standard Class or Special Class using the applicable B16.34 rating table, not the pressure-class number alone.
- Verify that the inspection matrix keeps body NDE separate from PT of the plug and seat-ring hard-facing.
- Verify that any claimed 410-versus-316 rule includes a traceable specification, edition, paragraph, scope, and acceptance criteria.
- Verify that an authorized concession exists if the agreed PT requirement was deleted or replaced.
- Verify that the final PT report identifies the examined hard-facing area, procedure, examination stage, acceptance basis, component traceability, results, and any repair re-examination.
Frequently asked questions
Can I require PT on a Standard Class valve?
Yes. Standard Class defines the cited B16.34 minimum for cast-body examination; it does not prevent the purchaser from specifying additional PT. If PT is in the agreed inspection plan, retain it until an authorized revision or concession changes the requirement.
Does Class 600 mean the valve is Special Class?
No. The class number alone does not identify Standard Class or Special Class. Compare the ordered designation and rating documentation with the applicable ASME B16.34 pressure-temperature table.
Can I omit PT because the plug and seat ring are 410 SS?
Not on that statement alone. Verify the exact specification and clause claimed for the alloy distinction, then confirm that it applies to the finished hard-facing area; finally, accept the valve only when the required PT report or an authorized concession closes the inspection-plan item.