A spare flange, valve or pipe spool can look identical in carbon steel, low-alloy steel or stainless steel. The paperwork and a few simple checks tell them apart. This article covers two tools buyers and plant engineers use:
- inspection documents under EN 10204;
- positive material identification (PMI).
EN 10204 in one paragraph
EN 10204:2004, Metallic products — Types of inspection documents, is a European standard. It defines the types of inspection document a supplier can provide with metallic products. It replaced the 1991 edition. The standard does not set the tests themselves. It defines what kind of document is issued, who issues it, and what it is based on.
The four document types
| Type | Name | Issued by | Based on |
|---|---|---|---|
| 2.1 | Declaration of compliance with the order | Manufacturer | Statement only, with no test results |
| 2.2 | Test report | Manufacturer | Non-specific inspection: results from the same grade, not necessarily from the delivered heat or lot |
| 3.1 | Inspection certificate | Manufacturer's authorised inspection representative | Specific inspection of the delivered product, with results traceable to its heat or lot |
| 3.2 | Inspection certificate | Manufacturer's representative, co-signed by an independent inspector (third-party or purchaser's) | Specific inspection, witnessed and co-signed |
What this means in practice
- 2.1 and 2.2 are useful for low-risk items. They do not prove that the actual part is the right material.
- 3.1 is the common minimum for pressure-retaining parts, alloy materials and anything in hazardous service. It links test results to the heat number stamped on the part.
- 3.2 adds an independent witness. It costs more and takes longer, so specify it where the risk justifies it.
The purchase order must state the type required. If the order is silent, do not expect a 3.1 to arrive.
Checking a 3.1 certificate
When a 3.1 arrives with the goods, check:
- Heat number. It should appear on the certificate and on the part marking.
- Material grade and standard. These should be the ones ordered, including the edition where it matters.
- Chemistry and mechanical results. They should be within the limits of the material standard.
- Heat treatment condition. It should be stated where the material standard requires it.
- Signature. It should come from the authorised inspection representative, with a reference to EN 10204 type 3.1.
- Quantities and sizes. They should match the delivery.
A certificate without a heat number, or a heat number that does not appear on the part, does not provide traceability.
Positive material identification (PMI)
Paperwork can be wrong, and parts can be mixed up in a store. PMI checks the actual alloy of the part in hand.
API RP 578, Guidelines for a Material Verification Program for New and Existing Assets (3rd edition, 2018), gives guidance on verifying alloy materials. It covers materials bought directly by the owner and those supplied through distributors, fabricators or contractors.
Common PMI methods
- X-ray fluorescence (XRF). Portable, non-destructive and fast. It cannot measure carbon, so it cannot always separate grades that differ mainly in carbon content.
- Optical emission spectroscopy (OES). Can measure carbon. It slightly burns the surface, so it may need a hot work permit on an operating plant.
- Laser-induced breakdown spectroscopy (LIBS). Handheld, minimally destructive and fast. It can detect carbon. It was added in the 2018 edition.
When PMI is worth it
- Alloy parts in corrosive, high-temperature or hydrogen service
- Spares received from a distributor rather than direct from the mill
- Mixed stores, or legacy stock without clear marking
- After a failure where the wrong material is suspected
Building it into procurement
- State the EN 10204 type on every purchase order line.
- State whether PMI is required, by whom, and at what sampling level.
- Require heat-number marking that survives handling.
- Hold goods in quarantine until documents and PMI results are accepted.
- File certificates against the tag number of the installed item.
Summary
EN 10204 tells you what kind of evidence came with the material. PMI checks the material itself. For critical spares, specify a 3.1 certificate as a minimum, check traceability on arrival, and use PMI where the wrong alloy could cause a failure.
General guidance only. The authority having jurisdiction and the official text govern.
- BSI, BS EN 10204:2004 Metallic products — Types of inspection documents (published 25 Oct 2004; replaces the 1991 edition): knowledge.bsigroup.com
- Project Materials, "EN 10204 2.1 vs 2.2 vs 3.1 vs 3.2" (summary of document types): blog.projectmaterials.com
- Inspectioneering, "What to know about the 3rd edition of API RP 578", 19 Nov 2019 (API RP 578, 3rd ed., Feb 2018; XRF, OES, LIBS): inspectioneering.com
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