PMI vs MTR for valves is not an either-or choice. Positive Material Identification (PMI) checks elemental composition at an identified test location, while a Material Test Report (MTR/MTC) documents the inspection evidence defined by its EN 10204 document type and stated scope. Type 2.1 contains no specific test results, Type 2.2 is based on non-specific inspection, and Types 3.1 and 3.2 cover specific inspection with different validation requirements. Buyers must connect both records to the supplied components through heat-number and marking-transfer traceability.

For EPC contractors, procurement teams and quality inspectors, the distinction matters because a technically acceptable certificate does not automatically prove the identity of every delivered component. Similarly, a successful PMI reading does not establish all mechanical properties or manufacturing requirements.

The objective should be a complete and auditable material verification record, not simply collecting more inspection documents.

1. What Is PMI Testing for Industrial Valves?

Positive Material Identification (PMI) is an analytical process used to identify or verify the elemental composition of metallic materials.

In valve manufacturing and inspection, PMI is commonly used to check whether selected metallic components are consistent with their specified alloy grades. It can help identify material mix-ups, incorrect substitutions and discrepancies between documented material grades and physical components.

PMI is particularly relevant when valves contain stainless steel, duplex stainless steel, nickel alloys or other materials where incorrect alloy selection could affect corrosion resistance, mechanical integrity or service suitability.

1.1 How Positive Material Identification Works

A PMI instrument analyzes the material at a selected test location and produces an elemental composition result. The measured composition is then compared with the applicable material specification, reference grade or approved acceptance criteria.

Depending on the equipment and method, PMI may be performed using:

• X-ray fluorescence (XRF).
• Optical emission spectroscopy (OES).
• Laser-induced breakdown spectroscopy (LIBS).

The methods do not have identical analytical capabilities. The appropriate method depends on the material, required elements, component geometry, surface condition and inspection specification.

For example, handheld XRF is useful for identifying many alloying elements in stainless steels and nickel alloys. However, standard handheld XRF analyzers cannot reliably determine carbon content in steel. If a grade distinction depends on carbon content, XRF alone is insufficient. Select OES or another validated method with demonstrated capability for the required element. Handheld LIBS capability is instrument- and application-dependent; confirm the analyzer model, calibration, detection limits and applicable material range before relying on it.

1.2 XRF, OES and LIBS: What Is the Difference?

Metodo	Useful for	Sample / field consideration	Limit to confirm
XRF	Rapid alloy identification and sorting for many stainless and nickel alloys.	Usually non-destructive and suitable for repeated checks on accessible surfaces.	Conventional handheld XRF does not reliably measure carbon; coatings, surface condition and geometry can affect results.
OES	Quantitative chemical analysis, including carbon when the instrument and calibration are suitable.	Spark OES normally requires suitable surface preparation and leaves a small test mark.	Confirm calibration, material matrix, sample geometry and required elements.
LIBS	Rapid elemental analysis; some validated handheld systems can measure light elements such as carbon.	Laser ablation is minimally destructive and may leave a small mark.	Carbon capability and accuracy are model-, calibration- and application-dependent; confirm demonstrated performance.

A buyer should not specify only the phrase “PMI testing” without defining the required analytical method. The inspection procedure should identify the material grades, elements of interest, acceptance criteria and any restrictions associated with the selected instrument.

Method-selection check: List the elements that must be verified before selecting the analyzer. If carbon distinguishes the specified grade, do not accept a conventional handheld XRF result as the carbon check; use OES or a validated LIBS method with documented capability for the relevant alloy.

1.3 What PMI Can and Cannot Verify

PMI can provide evidence that the tested location has an elemental composition consistent with a specified alloy grade within the capability of the selected method.

It does not automatically establish:

• Tensile strength or yield strength.
• Hardness.
• Impact toughness.
• Heat treatment condition.
• Grain structure.
• Complete material specification compliance.
• Original heat identity without supporting traceability records.
• Suitability for every pressure, temperature or corrosive service condition.

A PMI result should therefore be treated as one part of a material verification program rather than a complete material acceptance certificate. The result is meaningful only when the method is suitable for the required elements, the test location is identified, the instrument is controlled, and the acceptance basis is defined before testing.

2. What Is a Material Test Report (MTR/MTC)?

A Material Test Report (MTR), also commonly called a Material Test Certificate (MTC), is a commercial label often used for material inspection documentation; it does not, by itself, identify a formal inspection-document type or guarantee that test results are included. Where EN 10204 is specified, identify the required type separately from the material product standard and grade. Type 2.1 is a declaration of compliance without specific test results; Type 2.2 is based on non-specific inspection; Types 3.1 and 3.2 are specific inspection documents with defined validation requirements. The purchase order should state which type and which material records are required.

For metallic valve components, an MTR may include chemical composition, mechanical properties, material identification, heat or lot number, applicable material specification and relevant manufacturing or heat-treatment information. The exact content depends on the material specification, certificate type, manufacturing route and purchase requirements.

2.1 What Information Should an MTR Contain?

A buyer reviewing an MTR should normally check the following fields when applicable:

MTR field	What the buyer should verify
Manufacturer identity	Whether the issuing manufacturer is identifiable.
Material specification	Whether the stated standard and grade match the purchase order.
Material description	Whether the product form is correct.
Heat number	Whether the material batch can be identified.
Composizione chimica	Whether reported elements meet the specified limits.
Mechanical properties	Whether required tensile, yield and elongation results are reported.
Hardness	Whether applicable hardness requirements are satisfied.
Heat treatment	Whether required treatment information is documented.
Inspection document type	Whether the certificate matches the specified EN 10204 type.
Authorized validation	Whether the required manufacturer or inspection representative has validated the document.

Not every document labelled MTR/MTC contains every field. The purchase specification, material product standard and inspection-document type determine what evidence is required and whether reported results are specific to the supplied product. In particular, do not expect specific test results from a Type 2.1 declaration, or assume that Type 2.2 results are specific to the delivered heat or lot.

2.2 Chemical Composition and Mechanical Test Results

Chemical composition and mechanical properties answer different questions. Chemical analysis identifies the reported elemental composition of the material sample. Mechanical testing evaluates properties such as tensile strength, yield strength and elongation under the applicable test requirements.

A material may have a chemical composition consistent with a specified alloy grade but still require additional verification of mechanical properties, hardness or heat treatment. This is why PMI cannot replace the mechanical test information or other material evidence required by the purchase specification and applicable inspection document.

2.3 Heat Number and Material Identification

The heat number is a key link between a material certificate and the material produced from a particular melting heat.

For valve buyers, the important question is not simply whether a heat number appears on an MTR. The question is whether the same material identity can be followed through:

1. Original material manufacturing.
2. Material receipt and storage.
3. Cutting and machining.
4. Marking transfer.
5. Component identification.
6. Valve assembly.
7. Final inspection and documentation.

If this chain is incomplete, an otherwise acceptable MTR may not adequately establish the identity of the material used in the delivered valve.

2.4 EN 10204 Types 2.1, 2.2, 3.1 and 3.2

BS EN 10204:2004 defines different types of inspection documents for metallic products. The standard distinguishes documents based on non-specific inspection from those based on specific inspection.

EN 10204 defines the type and validation of the inspection document; it does not replace the material product standard that defines the applicable grade, product form, test requirements and acceptance limits. The purchase order should identify both the material specification and the required inspection-document type.

Document type	General description	Buyer consideration
2.1	Declaration of compliance with the order	Does not provide specific test results.
2.2	Test report based on non-specific inspection	Results are not necessarily from the supplied product batch.
3.1	Inspection certificate validated by the manufacturer’s authorized inspection representative independent of the manufacturing department	Common requirement for project-specific material documentation.
3.2	Inspection certificate validated by the manufacturer’s authorized inspection representative and the purchaser’s authorized representative or an inspector designated by official regulations	Used when the purchase specification requires this additional validation.

Type 3.1 and Type 3.2 should not be treated as interchangeable. A third-party inspection visit does not automatically make a document an EN 10204 Type 3.2 certificate. The document must meet the applicable requirements for that certificate type.

Buyers should specify the required certificate type in the purchase order rather than assuming that all MTRs provide the same level of verification.

2.5 MTR Document Review: Minimum Buyer Checks

Use this sequence to review the document package against the purchase order and approved material list. It is a buyer review aid, not a substitute for issuer validation or the governing material specification.

• Document identity: identify the issuing organization, certificate number, issue date and the relevant purchase-order item or material line.
• Product and grade: confirm the product form, material specification, grade and any specified condition or heat-treatment requirement.
• Inspection-document type: verify that the submitted EN 10204 type matches the purchase requirement; do not infer Type 3.1 or 3.2 from the generic label “MTR”.
• Heat / lot reference: check whether a heat or lot number is stated and whether the document type and reported inspection scope support the level of batch-specific evidence required.
• Test scope and results: compare only the chemical, mechanical, hardness, impact or other results actually required and reported for that product and document type.
• Validation and document chain: check the required signatures or validation, and review intermediary or subcontractor records where needed to connect the original issuer’s document to the supplied material.
• Component linkage: reconcile the certificate reference and heat/lot identity with receiving records, marking-transfer records and the finished valve component register.

A document’s appearance or a printed heat number alone does not establish authenticity or prove that the delivered component is represented. Where document authenticity is in doubt, request confirmation through the issuing manufacturer or its controlled verification channel, where available.

3. PMI vs MTR for Valves: Key Differences for Buyers

PMI and MTR/MTC documentation serve complementary purposes. PMI provides an analytical result from the physical material; the document provides the declaration or inspection evidence defined by its actual type and scope. Neither should be used as a substitute for the other when the purchase specification requires both.

3.1 Side-by-Side Comparison

Punto di confronto	PMI	MTR/MTC
Primary purpose	Identify or verify elemental composition at the tested location	Provide the declaration or inspection evidence defined by the actual document type
Evidence type	Physical analytical result	Manufacturer’s material / inspection document
Composizione chimica	Measured at tested location, within method capability	May report chemical results; document type and scope determine whether results are specific to the supplied product
Mechanical properties	Not established by routine PMI	Only where required and included in the applicable inspection results
Heat treatment	Not established by routine PMI	May document required treatment when included in the material records
Heat number	Cannot independently establish original heat identity	May identify a heat or inspection unit; the component link still requires traceability records
Component identification	Requires test-location identification	Requires marking and document linkage
Manufacturing history	Not established	May include relevant manufacturing information, depending on document scope
Material substitution detection	Useful for identifying alloy discrepancies at tested locations	Depends on document review, document type and traceability
Final material compliance	Not established alone	Not established without complete verification of the applicable requirements

3.2 Which Evidence Is Stronger for Material Verification?

Neither is universally stronger because the two methods answer different questions.

Consider a stainless steel valve body specified with a particular material grade. A Type 3.1 or 3.2 inspection certificate, when required and correctly linked to the supplied material, may report the material specification, chemical analysis, tensile and yield strength, heat number and required heat-treatment information within its scope. A Type 2.1 declaration does not provide specific test results, while a Type 2.2 report is based on non-specific inspection. A PMI test on the actual valve body may independently identify its alloy composition at the selected test location.

If the PMI result is inconsistent with the specified grade, the discrepancy requires investigation even if the submitted MTR appears acceptable. Conversely, if PMI passes but the MTR is missing required mechanical properties, the material documentation remains incomplete.

The buyer therefore needs both documentary evidence and physical verification when both are specified.

3.3 Why Neither Can Replace the Other

MSS SP-137-2025 is directly relevant because it addresses PMI of metal valves, flanges, fittings, pressure-boundary parts of valves and other piping components. Its published scope describes semi-quantitative analysis for material-grade identification and cautions that the procedure may not be suitable for certifying the accuracy of material test reports. API RP 578, Fourth Edition (2023), “Material Verification Program for New and Existing Assets,” provides recommended-practice context for owner/operator material verification programs; its current title and scope should not be confused with the earlier title referring to alloy piping systems or treated as a valve-specific PMI product standard. The purchase specification, applicable valve-specific practice and approved ITP remain controlling for the project.

• PMI is not a substitute for the original material test report.
• An MTR is not a substitute for physical material identification.
• Traceability is required to connect the evidence to the actual supplied component.

4. What Does Each Method Actually Prove?

Understanding the evidence boundary is essential when reviewing valve supplier documentation.

4.1 What an MTR Proves

A document labelled MTR/MTC provides only the declaration or inspection evidence defined by its actual type, stated scope and supporting records. Where EN 10204 is specified, the distinction is material:

• Type 2.1: a declaration of compliance with the order; it does not provide specific test results.
• Type 2.2: a test report based on non-specific inspection; its results are not necessarily from the supplied product or heat.
• Type 3.1: specific inspection results validated by the manufacturer’s authorized inspection representative who is independent of the manufacturing department.
• Type 3.2: specific inspection results with the additional validation required from the manufacturer’s representative and the purchaser’s authorized representative or an inspector designated by official regulations.

A Type 3.1 or 3.2 document can support review of the reported chemical composition, mechanical properties or other specified tests within its scope. Heat-specific evidence still depends on the document identifying the relevant heat or inspection unit and on traceability records connecting that material to the supplied valve component. Do not infer test results, heat identity or component linkage from the generic label “MTR/MTC”.

EN 10204 distinguishes inspection documents based on non-specific inspection from those based on specific inspection. The purchaser should specify the required type and test scope in the purchase order and verify the submitted document against that requirement.

4.2 What PMI Proves

PMI provides analytical evidence about the elemental composition of the material at the tested location. For example, an appropriately selected PMI method can help distinguish between certain stainless steel and nickel alloy grades.

It can identify discrepancies such as:

• A component containing an unexpected alloy.
• An incorrect material substitution.
• A mismatch between a specified grade and measured composition.
• Potential material mixing during manufacturing or storage.

However, PMI does not automatically establish the original manufacturing heat, the authenticity of an MTR, mechanical test compliance, required heat-treatment condition, hardness or impact performance, or complete conformity with a product specification.

PMI should be evaluated against the specified material grade and the analytical capability of the selected instrument.

The result is also limited to the tested point and the selected method’s validated elemental range. It does not automatically verify the full component volume, adjacent weld metal, an underlying base metal, or untested components. The inspection map must identify exactly where each reading was taken.

4.3 What Remains Unverified Without Traceability?

The central weakness occurs when test results and material records cannot be linked to the actual valve components.

Consider this example: a supplier submits an acceptable MTR for a stainless steel heat and a PMI report showing an acceptable alloy composition. However, the PMI report does not identify the valve tag number, component location or heat number. The two documents may individually appear acceptable, but the buyer cannot establish that the tested component is the component represented by the submitted MTR.

This is a traceability gap. The correct response is to request supporting identification and manufacturing records rather than automatically accepting the documentation package.

5. Material Traceability Gaps in Valve Manufacturing and Supply

Material traceability is the ability to maintain an identifiable connection between material origin, manufacturing records, individual components and the finished equipment.

For industrial valves, this process can become more complicated because a finished assembly may contain multiple materials, product forms, manufacturing heats and subcontracted components.

5.1 Missing or Mismatched Heat Numbers

A material certificate may identify a heat number, but the physical material or finished component may have a missing, unreadable or inconsistent marking.

Possible causes include:

• Material identification lost during cutting.
• Incorrect marking transfer.
• Mixed batches during storage.
• Incorrect component identification during machining.
• Incomplete records from subcontractors.

Verification: Compare the original material certificate, receiving inspection record, marking-transfer record and component identification. A PMI reading alone cannot reconstruct an undocumented original heat identity.

5.2 Material Marking Transfer Errors

During manufacturing, original material markings may not remain on every finished component. For example, a forging may be cut into several components and machined into valve parts.

The manufacturer needs a controlled marking-transfer process to preserve the connection between the original material identification and the finished components.

The inspection record should identify:

• Original material heat number.
• Parent material identification.
• Transferred marking.
• Finished component identification.
• Relevant manufacturing record.

If this process cannot be demonstrated, the material traceability chain is incomplete.

Engineering scenario — marking transfer after cutting: A parent forging is cut into several valve components and its original heat mark is removed during machining. The gap is not repaired by a later PMI reading alone. Verify the cutting map, controlled transfer record, component IDs and final material register before the parts are released.

5.3 Mixed Material Grades or Uncontrolled Substitution

Material mixing can occur during storage, machining or subcontracted manufacturing. Potential examples include different stainless steel grades stored together, similar-looking alloy components mixed during production, an unapproved material substitution, or incorrect bolting supplied for an assembly.

PMI can help identify certain alloy discrepancies, but the result must be interpreted using the required analytical method and acceptance criteria. The supplier should also provide the applicable nonconformance and material disposition records if a discrepancy is identified.

5.4 MTRs That Cannot Be Linked to Individual Components

A supplier may submit several MTRs for a valve package without clearly identifying which certificate belongs to which component. This is particularly important for valves with multiple pressure-containing and metallic trim components.

A document register should connect:

• Valve tag number.
• Component description.
• Material grade.
• Heat number.
• MTR reference.
• PMI report reference, when required.

Without this mapping, reviewing a collection of certificates does not necessarily establish traceability.

Engineering scenario — one valve, several material heats: A package may contain a body, bonnet, stem, closure member and bolting made from different specified materials. A body MTR cannot be treated as evidence for the stem or bolting. Reconcile each bill-of-material item to its own grade, heat or lot reference, certificate and required PMI record.

5.5 PMI Records Without Component Identification

A PMI report may contain chemical composition results but omit the identification of the tested component. For example, a report might show several acceptable stainless steel readings without recording which valve bodies or stems were tested.

The buyer should request a test report containing identifiable component references and sufficient information to reproduce or audit the inspection.

5.6 Incomplete Traceability Through Machining and Assembly

Material identification must be maintained through the manufacturing stages required by the project. A complete review may include:

1. Original material receipt.
2. Incoming inspection.
3. Storage and segregation.
4. Cutting and marking transfer.
5. Machining.
6. Component inspection.
7. Assembly.
8. Final identification.
9. Documentation compilation.

For complex valve assemblies, the manufacturer should be able to demonstrate how the applicable material records remain linked to the finished valve through component-level material traceability.

6. PMI and MTR Requirements for Different Valve Components

Not every valve component has the same material verification requirements. The appropriate documentation and inspection scope depend on the valve design, component function, material specification, service conditions and purchase order.

6.1 Valve Body, Bonnet and Pressure-Boundary Components

The valve body and bonnet are commonly important items in a material verification program because they form part of the pressure-containing structure.

Buyers should review:

• Applicable material specification and grade.
• Casting or forging identification.
• MTR and heat number.
• Required mechanical properties.
• PMI requirements, where specified.
• Traceability to the finished component and valve tag.

For alloy pressure-boundary components, PMI may provide useful additional evidence that the physical material is consistent with the specified grade.

6.2 Ball, Disc, Gate and Other Closure Components

Closure components may use different materials from the valve body. For example, a valve may have a carbon steel body with stainless steel or special-alloy closure components.

The verification plan should identify each material separately. The buyer should not assume that a body PMI result establishes the material identity of the ball, disc or gate.

6.3 Valve Stem and Metallic Trim

Stem and trim materials may have specific requirements for strength, corrosion resistance, hardness or wear resistance. PMI can help verify alloy composition where appropriate.

However, additional mechanical testing, hardness verification, heat-treatment records or other specified inspection may be necessary. An acceptable PMI result does not independently prove stem strength or hardness.

6.4 Bolting, Welds and Weld Overlays

Bolting should be reviewed against the applicable material specification, certificate requirements and component identification.

Welded areas and weld overlays require particular care. The base material and deposited weld metal may have different material specifications and verification requirements.

A PMI procedure should therefore define which material is being tested, whether the target is base metal or deposited weld metal, appropriate test locations, method capability and surface preparation, and acceptance criteria for the relevant material.

A reading taken from an exposed weld overlay should not automatically be interpreted as proof of the underlying base material.

Where both overlay chemistry and base-metal identity are specified, define separate test locations and methods that can distinguish the deposited layer from the substrate. Surface preparation and the analytical depth of the method should be considered in the approved procedure.

6.5 Non-Metallic Seats, Packing and Gaskets

Conventional metallic PMI methods are not the normal verification approach for non-metallic components.

For PTFE, elastomers, graphite and other non-metallic sealing materials, buyers should define appropriate documentation requirements. These may include material grade or compound identification, manufacturer’s material certificate or declaration, batch or lot number, relevant physical or chemical test results, temperature and media compatibility information where required, and supplier traceability records.

The inspection approach should match the material rather than applying metallic PMI requirements indiscriminately.

Valve Component Verification Matrix

Componente	MTR / Material Document	PMI Consideration	Additional Verification
Corpo	Applicable casting/forging certificate	As specified	Mechanical properties
Cassa	Applicable material certificate	As specified	Tracciabilità
Ball / disc / gate	Component material certificate	As specified	Surface and coating requirements
Stelo	Certificato materiale	As specified	Hardness / mechanical properties
Metallic trim	Material-specific documents	Risk and specification dependent	Dimensional / surface checks
Viteria	Applicable bolting certificates	According to project scope	Grade and mechanical properties
Sovrapposizione saldata	Base and weld consumable/deposit records	Specific procedure required	Weld inspection
Seats / packing	Non-metallic material documents	Conventional metallic PMI not applicable	Batch and compatibility records

Scope note: This is a planning reference, not a universal mandatory inspection matrix. The approved BOM, project material specification and ITP take precedence.

7. How to Combine PMI and MTR in a Valve Inspection Plan

An effective material verification process should connect document review, physical inspection and component traceability. The following workflow provides a practical approach for valve manufacturers, purchasers and third-party inspectors.

Step 1 – Review the Purchase Specification

Before manufacturing or inspection begins, identify the required materials and documentation. Confirm valve body and bonnet material, closure and stem material, metallic trim requirements, applicable ASTM/ASME/EN specifications, required MTR/MTC certificate type, PMI method and inspection extent, applicable acceptance criteria, and required ITP witness and hold points.

Unclear requirements should be resolved before material procurement.

Step 2 – Verify Material Certificates

Review each certificate against the purchase order and approved material specifications. Check the material grade, product form, heat number, chemical composition and required mechanical test results.

Where EN 10204 is specified, confirm that the submitted document type matches the purchase requirement. If an intermediary or subcontractor supplies the material, review the supporting documentation needed to establish the connection to the original manufacturer.

Step 3 – Confirm Physical Markings and Heat Numbers

Compare the physical markings on the material or component with the corresponding material records. Check heat number, material grade, manufacturer identification where required, component identification and marking-transfer records.

Any mismatch should be recorded and resolved before acceptance.

Step 4 – Perform PMI According to the Approved Scope

Where PMI is required, use the approved inspection procedure. The procedure should define testing method, applicable material grades, required elements, test locations, inspection extent, acceptance criteria, instrument identification and calibration status, and reporting requirements.

For critical grade distinctions involving carbon, an appropriate OES or validated LIBS method may be necessary instead of conventional handheld XRF.

Step 5 – Reconcile Inspection Results

PMI results should be compared with the relevant material specification and MTR. For every tested component, the inspection records should identify:

• Valve tag number.
• Component name.
• Material grade.
• Heat number, where traceability is required.
• MTR reference.
• PMI report reference.
• Actual test result.
• Acceptance status.

A passing PMI result should not automatically close a discrepancy in the original material documentation.

Step 6 – Compile the Final Material Documentation Package

The final documentation package should contain the records required by the purchase order and approved ITP. Depending on project scope, this may include:

1. Material certificate register.
2. Applicable MTR/MTC documents.
3. PMI procedure.
4. PMI inspection reports.
5. Material marking-transfer records.
6. Component traceability matrix.
7. Nonconformance and disposition records.
8. Third-party inspection reports, where required.
9. Final valve identification and documentation index.

The purpose is to allow the purchaser or inspector to trace the supplied material evidence back to the relevant finished valve components.

For broader inspection context, buyers can also review the general industrial valve inspection and ITP requirements and the documented stages in the processo di produzione valvole. These resources provide related manufacturing and inspection context; they do not replace the project-specific material verification plan.

8. PMI, MTR and Third-Party Inspection: What Should the ITP Specify?

The Inspection and Test Plan (ITP) should define the material verification requirements before manufacturing starts. A common procurement mistake is specifying only “MTR required” or “PMI required” without defining the inspection scope.

8.1 PMI Inspection Extent and Acceptance Criteria

The PMI inspection extent should be established by the applicable purchase specification, owner requirements, material verification program and approved ITP.

ITP item	Requirement to define
Component scope	Which valve components require PMI.
Inspection extent	Percentage, quantity or specific components.
Test method	XRF, OES or LIBS.
Inspection stage	Incoming, in-process or final inspection.
Criteri di accettazione	Required material grade and applicable limits.
Preparazione della superficie	Requirements for reliable measurement.
Controllo dello strumento	Calibration and verification requirements.
Reporting	Component identification and measured results.
Witness points	Purchaser or third-party inspection involvement.

There is no universal rule requiring 100% PMI on every industrial valve. Some projects may require full PMI coverage for designated components, while others may define sampling or risk-based inspection. The approved project requirements determine the correct approach.

8.2 Document Review and Witness Points

The ITP should distinguish between document review and physical inspection.

Inspection activity	Possible ITP classification
MTR review	Review
Incoming material identification	Witness / Review
Marking transfer	Surveillance / Witness
PMI testing	Witness / Hold / Review
Nonconformance disposition	Review / Approval
Final documentation review	Review

These are illustrative classifications. The actual inspection points must be agreed by the purchaser, manufacturer and relevant inspection parties.

8.2.1 PMI Report: Minimum Fields to Review

The approved ITP or PMI procedure should define the report content for the project. As a practical buyer review, check whether each record identifies the following information where applicable to the specified inspection scope:

• Valve tag or serial number, component description and exact test location.
• Specified material grade and governing material specification.
• Heat or lot number and corresponding MTR reference, where traceability is required and available.
• PMI method, analyzer make/model and instrument identification or serial number.
• Instrument verification or calibration check required by the approved procedure.
• Surface preparation or test conditions that could affect the reading, where relevant.
• Actual elemental readings or recorded analytical output, not only a generic “PASS” statement, when required by the procedure.
• Acceptance criteria, procedure/specification revision, inspection extent and sample identification.
• Inspection date and operator identification, plus witness, retest or nonconformance references where applicable.

This is a review checklist, not a universal mandatory report format. The purchase specification, selected method, instrument capability and approved ITP determine the required fields and acceptance basis.

8.3 Third-Party Inspection and EN 10204 Type 3.2

Third-party inspection and EN 10204 Type 3.2 certification are related but not identical concepts. A third-party inspector may witness PMI testing, review MTRs, verify component markings or inspect manufacturing activities.

However, witnessing an inspection does not automatically establish Type 3.2 certification. Type 3.2 requires the applicable validation by both the manufacturer’s authorized inspection representative independent of the manufacturing department and the purchaser’s authorized inspection representative or an inspector designated by official regulations.

Buyers should define the required certificate type, inspection responsibilities and witnessing scope in the purchase order.

8.4 Nonconformity and Material Discrepancy Handling

If PMI results do not match the specified grade or the MTR, the discrepancy should be treated as a material nonconformity requiring investigation.

A reasonable response includes:

1. Identify and segregate the affected component.
2. Record the actual PMI result and test location.
3. Review instrument condition and testing procedure.
4. Confirm material specification and acceptance criteria.
5. Check the corresponding MTR and heat number.
6. Perform additional analysis using an appropriate method if necessary.
7. Obtain an approved technical disposition before release.

Do not simply repeat PMI testing until a passing result appears. Repeated testing should follow an approved investigation procedure and preserve the original results.

8.5 Material Evidence Disposition Matrix

When reviewing a supplier’s material package, do not reduce the decision to “PMI passed” or “MTR received.” Evaluate the relationship between the certificate, physical component identification, PMI result and purchase requirements.

Finding	What it means	Recommended buyer action
MTR matches the specified grade; heat number and component link are complete; required PMI is consistent	The reviewed evidence is aligned for the checked scope.	Record the review against the applicable PO and ITP. Continue other required inspection; do not infer that unrelated requirements are satisfied.
PMI result conflicts with the MTR or specified grade	Possible material mix-up, wrong test location, surface issue, instrument/method limitation or documentation error.	Place the affected component on hold, preserve the original result, verify the test method and location, check the MTR/marking chain, and obtain confirmatory analysis and approved disposition.
PMI grade appears consistent, but the required MTR is missing	Elemental composition at the tested point may be consistent; mechanical test results, heat identity and required manufacturing evidence remain unverified.	Request the required material certificate and traceability records. Do not use PMI as a substitute for missing certificate evidence.
MTR is complete, but component marking or heat-number transfer cannot be linked	The certificate may describe a material heat, but its connection to the delivered component is not demonstrated.	Request receiving, segregation, cutting and marking-transfer records. Maintain a documentation hold until the traceability gap is resolved.
PMI report lists readings but no valve tag, component ID or test location	The results cannot be reliably assigned to the supplied valve components.	Request a revised, traceable report or controlled reinspection. Retain the original report in the audit trail.
XRF is used where carbon content is required to distinguish the grade	The selected method may not measure a decisive element.	Use OES or another validated method with proven capability for the required element and material. Confirm the method in the approved procedure.
PMI passes, but required hardness, tensile, impact or heat-treatment evidence is absent	PMI does not establish those properties or conditions.	Request the specified mechanical test, hardness or heat-treatment records. Assess each requirement independently.

Disposition boundary: “Hold,” “review” and “accept” must be assigned under the contract, approved ITP and purchaser’s quality procedure. This matrix is a review aid, not an independent acceptance code.

8.6 Component-Level Certificate Reconciliation Template

A useful material register links every required certificate and PMI result to the valve tag and the component actually inspected. The following fields can be copied into a supplier document register or inspection tracker.

Valve tag	Componente	Specified grade	Heat / lot ID	MTR reference	PMI report / point	Stato della revisione
[Tag]	[Body]	[Grade / spec]	[Heat ID]	[MTR No.]	[Report / point]	[Open / accepted / hold]
[Tag]	[Bonnet]	[Grade / spec]	[Heat ID]	[MTR No.]	[Report / point]	[Open / accepted / hold]
[Tag]	[Stem / closure]	[Grade / spec]	[Heat ID]	[MTR No.]	[Report / point]	[Open / accepted / hold]
[Tag]	[Bolting / trim]	[Grade / spec]	[Heat / lot ID]	[MTR No.]	[Report / point]	[Open / accepted / hold]

Expand the register for the actual bill of materials. Do not assume that one body certificate or one PMI reading covers the bonnet, closure member, stem, bolting, weld overlay or other separately specified materials. For non-metallic seats, packing and gaskets, use the applicable batch and material-document fields rather than metallic PMI.

9. Valve Material Verification Checklist for RFQ and Purchase Orders

For procurement teams, the best way to avoid material documentation gaps is to define requirements before issuing the purchase order. The following checklist can be used when preparing valve RFQs or evaluating technical bids.

Material Specification

• Specify body and bonnet material grades.
• Identify ball, disc, gate and stem materials.
• Specify metallic trim and bolting materials.
• Identify applicable ASTM, ASME or EN specifications.
• Define any additional heat-treatment or hardness requirements.

MTR / MTC Requirements

• Specify the required EN 10204 certificate type.
• Require applicable chemical composition results.
• Require specified mechanical test results.
• Require heat number identification.
• Define document validation requirements.
• Require supporting records for material traceability.

PMI Requirements

• Define which valve components require PMI.
• Specify the inspection extent.
• Specify acceptable PMI methods.
• Define required elements and acceptance criteria.
• Address carbon verification where necessary.
• Define testing stage and witness requirements.
• Require identifiable PMI reports.

Traceability Requirements

• Maintain heat number identification.
• Document marking transfer.
• Link MTR references to individual components.
• Link PMI results to tested components.
• Maintain material segregation records.
• Define nonconformance and material substitution approval procedures.

Final Documentation

• MTR/MTC package.
• PMI procedure and inspection reports.
• Material traceability matrix.
• Component identification records.
• Approved ITP and inspection records.
• Nonconformance records, if applicable.
• Final documentation index.

9.1 Suggested RFQ / Purchase Order Wording

The following is a starting clause for technical clarification. It must be edited to match the project specification, applicable material standards, component list and approved ITP before it is issued as a contractual requirement.

Material documentation and verification – editable procurement clause

The supplier shall submit the inspection documents required for the valve components identified in the approved material list. Each document shall identify the applicable material specification and grade, product form and heat or lot reference where required by the specified document type and purchase specification. Chemical, mechanical and other test results shall be provided where required by the material product standard, specified EN 10204 document type and purchase specification. Where EN 10204 is invoked, the required inspection document type shall be [insert Type 2.1 / Type 2.2 / Type 3.1 / Type 3.2, as applicable].

PMI shall be performed on [identify components] to an extent of [insert percentage / quantity / component list], using [insert approved method] and the acceptance criteria stated in [insert specification / procedure]. The PMI report shall identify the valve tag, component, test location, material grade, measured result, instrument identification and applicable report reference. Where carbon or another element outside the selected instrument’s validated capability is required, an appropriate alternative analytical method shall be used.

The supplier shall maintain heat-number identification and marking-transfer traceability from material receipt through machining, component inspection and final assembly. MTR references and PMI results shall be cross-referenced to the relevant valve tags and components. Any discrepancy, material substitution or missing traceability record shall be reported for purchaser review and written disposition before release.

This sample is not a universal standard clause. Define the component scope, method, extent, certificate type, acceptance criteria and witness/hold points in the contract documents.

9.2 Technical Bid Normalization Questions

When comparing quotations, ask every bidder to respond to the same material-verification basis. A low-priced offer may exclude PMI, provide a different certificate type, or limit traceability to selected components. Record these as technical deviations rather than assuming that the offers are equivalent.

Bid comparison item	Bidder response to request	Evidenza da richiedere	Deviation to record
Ambito dei materiali	List of body, bonnet, closure, stem, bolting and trim grades	Approved BOM / material schedule	Missing or substituted grades
Certificate type	EN 10204 type or other specified document	Sample certificate / document index	Lower or unclear document level
PMI extent	Components and percentage/quantity covered	PMI procedure / ITP	Excluded components or sampling differences
PMI method	XRF, OES or LIBS and measurable elements	Method statement / instrument capability	Method cannot verify a required element
Tracciabilità	Heat/lot and marking-transfer controls	Traceability matrix / sample records	Unlinked MTRs or component IDs
Inspection involvement	Review, witness and hold points	ITP / inspection schedule	Different third-party or purchaser scope
Dossier finale	List of records supplied at handover	Documentation index	Missing reports or late-submission exclusions

Procurement recommendation: Do not write only “PMI and MTR required” in the purchase order. Specify the material scope, certificate type, inspection extent, acceptance criteria and required traceability records.

10. Frequently Asked Questions

10.1 Is PMI Testing a Replacement for an MTR?

No. PMI verifies elemental composition at the tested location, while an MTR/MTC label may refer to different inspection-document types. Under EN 10204, Type 2.1 does not provide specific test results, Type 2.2 is based on non-specific inspection, and Types 3.1 and 3.2 provide specific inspection results with defined validation. PMI does not independently establish mechanical properties, heat treatment or original heat identity. Specify the required document type and PMI scope in the purchase specification.

10.2 Does an MTR Prove the Actual Material Used in a Valve?

A document labelled MTR/MTC provides the declaration or inspection evidence defined by its actual type and stated scope. However, it does not automatically establish that every finished valve component corresponds to that document. The supplier must maintain appropriate material identification, marking-transfer and manufacturing traceability records.

10.3 Is 100% PMI Required for Every Industrial Valve?

No universal 100% PMI requirement applies to every industrial valve. The required inspection extent depends on the project specification, applicable material verification program, component criticality and approved ITP. The purchaser should define the required coverage before manufacturing begins.

10.4 What Is the Difference Between EN 10204 Type 3.1 and Type 3.2?

Both are inspection documents based on specific inspection. Type 3.1 is validated by the manufacturer’s authorized inspection representative independent of the manufacturing department. Type 3.2 additionally involves validation by the purchaser’s authorized inspection representative or an inspector designated by official regulations. Type 3.2 should be specified when the project requires this additional verification.

10.5 Can Handheld XRF Verify 316L Stainless Steel?

Handheld XRF can identify many alloying elements in stainless steel, including chromium, nickel and molybdenum. However, conventional handheld XRF cannot reliably measure carbon content. Because carbon content is important for distinguishing 316L from certain other 316 grades, XRF alone is insufficient when this distinction must be verified. An appropriate OES or validated LIBS method should be considered when carbon measurement is required.

10.6 Should Valve Buyers Request Both PMI and MTR?

When the purchase specification requires both, yes. The specified MTR/MTC document provides the declaration or inspection evidence defined by its document type, while PMI independently checks elemental composition at selected physical locations. The two should be connected through component identification, heat-number records and a documented traceability system.

Conclusion: Build a Complete Valve Material Verification Record

For valve procurement, PMI vs MTR for valves is a question of complementary evidence, not an either-or choice. The certificate establishes only the inspection evidence defined by its document type and scope; PMI checks elemental composition at the tested point.

Neither closes the material-verification loop unless the records are linked to the actual body, bonnet, closure, stem, bolting and other specified components through controlled heat or lot identification.

Before placing the order, define the required certificate type, component-level material schedule, PMI method and extent, acceptance criteria, marking-transfer controls, ITP points and final dossier index. That gives bidders a common technical basis and gives inspectors an auditable route from the material record to the delivered valve.

Request Testing and Documentation Scope

For a project-specific review, provide the valve datasheet and tag list, body and trim material grades, required MTR/MTC document type, PMI method and inspection extent, and the applicable ITP or third-party witness requirements. The scope and acceptance basis must be confirmed against the purchase specification.

For product context, review the gamma di prodotti di valvole industriali e sulla Raymon Valve company profile.Request Testing and Documentation Scope

Engineering Note: Scope and Assumptions

• Scopo: Explain the complementary roles of PMI, material inspection documents and component-level traceability for industrial valve procurement and inspection.
• Assunzione: The purchase order, approved material specification, bill of materials and ITP define the actual component scope, certificate type, inspection extent and acceptance criteria.
• Limit: This article does not approve a material grade, certify a valve, establish compliance for a specific model, or replace project-specific metallurgy, welding, corrosion or quality review.
• Method boundary: Instrument capabilities vary by model, calibration, sample condition and target element. Confirm the method’s demonstrated capability before testing.
• Author / reviewer: Raymon Valve Technical Content Team. No individual engineer or professional credential is claimed.

Technical References

Use the current applicable edition and the project purchase specification when establishing inspection requirements. These references provide general technical context and do not certify any specific Raymon Valve product.

• MSS – SP-137-2025, Quality Standard for Positive Material Identification of Metal Valves, Flanges, Fittings and Other Piping Components. The publisher’s announcement identifies the PMI methods and the standard’s material-grade identification scope.
• API – Digital Standards Catalog: API RP 578, Fourth Edition (2023), Material Verification Program for New and Existing Assets. This is recommended-practice guidance for owner/operator material verification programs; verify the current edition and project applicability when preparing the PO.
• BSI – BS EN 10204:2004, Metallic products: Types of inspection documents. BSI lists this edition as Current and describes the standard’s distinction between documents based on non-specific and specific inspection. Use the standard and purchase order to define the required document type.
• British Stainless Steel Association – EN 10204 inspection certificate types. Supplementary industry explanation of the 2.1, 2.2, 3.1 and 3.2 document distinctions; the standard and contract remain controlling.
• ASTM – E1476-04(2022), Standard Guide for Metals Identification, Grade Verification, and Sorting. A general guide to nondestructive metal identification and sorting methods.
• Hitachi High-Tech – LIBS, XRF and OES method comparison. Manufacturer technical background only; verify performance against the actual instrument model and approved procedure.

General guidance only. The applicable material specification, purchase order, approved ITP and project requirements govern final inspection scope and acceptance.