What are the marking and traceability requirements for A106 A106M steel pipe?

When an inspector, a welder, or an EPC engineer picks up a length of seamless carbon steel pipe in a refinery, a power plant, or a high-temperature steam line, the first thing they need to confirm is not the diameter or the wall thickness — it is what is written on the pipe. A small painted stencil, a die-stamped code, or a printed tag on a bundle of pipe is often the only link between a piece of steel and its full quality history. For products manufactured to ASTM A106/A106M, that link is not optional: the specification sets out detailed marking and traceability requirements that every shipment must satisfy before it can be accepted at the receiving dock.

This article walks through those requirements in a practical way — what must be marked, where it must appear, how marking changes when the pipe is hydrostatically tested, eddy-current tested, or both, and how the manufacturer, the heat number, and the supplementary requirements together form the traceability chain that allows every length of A106 A106M steel pipe to be traced back to its heat, its test results, and its compliance documents.

Why Marking and Traceability Matter for A106/A106M Pipe

A106/A106M covers seamless carbon steel pipe for high-temperature service, in sizes from NPS 1/8 through NPS 48, used in pressure tubes, process piping, refinery headers, boiler systems, and structural applications such as structure works and pipeline works. Because the pipe is often installed in safety-critical services — including power generation and petrochemical facilities — purchasers and third-party inspectors must be able to confirm, at any point in the life of the pipe, that it really is the grade, heat, and lot that the mill test certificate claims it is.

Marking is how that claim is verified in the field, while traceability — the supporting documentation, heat numbering, and cross-references between physical product and paperwork — is what makes the marking meaningful. Without proper marking, even a perfectly made pipe cannot be positively identified. Without traceability, the marking has nothing to refer to.

What Must Be Marked on Each Length of A106/A106M Pipe

Under A106/A106M (most commonly cited as the -15, -18, or -22 edition), the manufacturer is required to apply a set of identifying marks to every length of pipe. The minimum marking content typically includes:

• Manufacturer's name or trademark (for example, the EZ Steel Industrial brand, or a recognized brand mark approved by the purchaser)
• The standard designation, marked as "A106" or "A106/A106M" depending on the edition being referenced
• The grade letter (A, B, or C), since the same specification covers three grades with different tensile and yield strength levels
• The size (nominal pipe size and either schedule or nominal wall)
• The heat number, which links the pipe to a specific heat of steel and to its chemical and mechanical test results
• A symbol or code indicating the type of non-destructive examination the pipe has been subjected to, when applicable

When supplementary hydrostatic or NDE requirements are invoked by the purchase order, the marking is expanded to record the test status. Table 4 in A106/A106M defines the marking combinations that correspond to whether the pipe has been hydrostatically tested, NDE-tested, or both:

This compact four-row table is the single most important reference for inspectors. It removes any ambiguity: when you read the marking on a length of A106 A106M steel pipe, you can immediately tell whether that specific length was hydrostatically tested, eddy-current or ultrasonic tested, both, or neither, and you can compare that to what was ordered.

Where the Marking Has to Appear

A106/A106M allows some flexibility in where the marks are applied, but not in whether they are applied. The standard permits the full set of required marks to be placed either on each individual length of pipe, or on a tag attached to each bundle, provided the bundle is the unit of shipment. If marks are placed on the bundle tag, every required mark must appear on the tag; individual lengths inside the bundle are not required to carry the full set, though they usually carry at least the manufacturer, grade, and heat number for in-process and yard handling.

For big diameter steel pipe and for orders shipped as individual lengths, marking is almost always applied to each length by one of three methods:

• Stenciling with paint or ink — common for large-diameter seamless pipe, where there is a flat, accessible surface on the pipe end or outside surface
• Die-stamping — used for small-diameter pipe where stenciling would be illegible, and for pipe that will be hot-dip galvanized (where paint marking would be removed)
• Adhesive labels or tags — permitted for bundle shipments, with the standard allowing total footage to be on the bundle tag rather than on each length

When the purchase order invokes Supplementary Requirement S5 (marking of pipe with the customer's identification), the customer-specific mark is added to the standard required marks, not used in place of them. This is a common source of confusion at receiving: a missing customer tag is not a reason to reject a shipment if the standard marking is intact, but a missing standard mark is never acceptable regardless of how complete the customer tag is.

Heat Numbers and the Traceability Chain

Traceability under A106/A106M is anchored on the heat number. A heat is a single melt of steel produced in an electric arc furnace, basic oxygen furnace, or other primary melting unit, and each heat is given a unique identifier by the steelmaker. That identifier is then carried through every subsequent operation: billet casting, pipe piercing, hot rolling or cold drawing, heat treatment, hydrostatic and NDE testing, and final inspection.

The end result is that the heat number marked on a length of pipe can be cross-referenced to:

• The chemical composition report, showing the actual C, Mn, P, S, Si, Cr, Cu, Mo, Ni, and V values for that heat
• The mechanical test report, including tensile, yield, elongation, and (where specified) Charpy impact results
• The hydrostatic test record, including the test pressure and the duration of the hold
• The NDE report, identifying the method, coverage, sensitivity, and acceptance criteria
• The mill test certificate (MTC) issued under EN 10204 type 3.1, which consolidates the above into a single signed document

For projects that bundle pipe with fittings, flanges, gaskets, and stud bolts, the same heat-traceability principle is extended. Fittings are matched to the pipe heat (or qualified as a separate heat with its own documentation), and gaskets and stud bolts are matched to the corresponding pressure class and material specification. On a packaged pipeline works shipment, the bundle tag, the MTC, the packing list, and the heat number stencil on the pipe are all designed to be checked against one another before installation.

Special Marking Cases: Galvanized, Cold-Drawn, and SMLS Pipe

A106/A106M is the specification for seamless pipe, but the same marking principles apply to related products. Three cases come up often in practice:

Hot-dip galvanized A106 pipe. When A106 pipe is subsequently galvanized, the standard paint stencil is typically removed by the acid pickling step. The manufacturer is required to remark the pipe after galvanizing, usually by die-stamping the marks into the zinc coating or by reapplying a paint stencil designed to adhere to the galvanized surface. Inspectors should never assume that the absence of a paint mark means the pipe is unmarked — a die-stamp is equally valid under the standard.

Cold-drawn pipe. Cold-drawn A106 pipe is often supplied with tighter dimensional tolerances than hot-finished pipe, and is frequently used in heat-exchanger and boiler service as pressure tubes. Marking requirements are unchanged, but the smaller diameter and thinner wall often mean that die-stamping is the only practical option. The standard explicitly allows low-stress die-stamping that does not impair the serviceability of the pipe.

Structural applications. When A106 pipe is used in structure works — for example, as steel tubular piles per ASTM A252, where A252 is the structural piling standard but A106 is sometimes accepted for combined pressure-plus-structural service — the marking on the pipe still references A106, not A252, because the pipe itself was manufactured to A106. The structural use is described in the project specification, not in the pipe marking.

How to Verify Marking and Traceability at Receiving

A consistent receiving-inspection routine will catch most marking and traceability issues before pipe enters the warehouse. The following sequence works well in practice:

1. Confirm the manufacturer's name or trademark on the pipe or tag matches the manufacturer named on the MTC.
2. Confirm the specification designation and grade (for example, "A106 Grade B") matches the purchase order.
3. Confirm the size and schedule match the purchase order, both on the marking and on the MTC.
4. Read the heat number on the pipe or tag, and check that the same heat number appears on the MTC. For bundle shipments, the heat number on the bundle tag is the controlling identifier.
5. Read the test marking (Test pressure, NDE, NH, or Test pressure/NDE) and confirm it matches what the purchase order specified for that item.
6. For bundle shipments, confirm the total footage stated on the bundle tag is consistent with the quantity invoiced.
7. For orders with supplementary requirements, confirm any additional marks (for example, customer identification under S5, or impact-test marking under S3) are present as required.

Any discrepancy between the marking on the pipe and the documentation is a non-conformance and must be resolved before the pipe is released for installation. Most discrepancies are clerical (a missing character in a heat number, a transposed digit in a test pressure), and they are usually resolved by the manufacturer reissuing corrected documentation. Physical re-marking is required only when the mark itself is missing, illegible, or wrong.

Working with a Manufacturer That Manages the Documentation for You

Because the marking and traceability chain is a long one — from steel mill to pipe mill to warehouse to site — the practical risk to a buyer is not that any single document is wrong, but that a small inconsistency is missed because the documentation was assembled by hand at the end of the run. A manufacturer that issues MTCs electronically, ties the heat number on each length to a unique pipe ID in its production system, and ships a consolidated traceability package with the order reduces that risk substantially.

When sourcing A106/A106M pipe for a refinery turnaround, a power-plant retrofit, or a long-distance pipeline works project, it is worth asking the supplier three specific questions before placing the order:

• How is the heat number applied, and is it visible after the pipe is coated, galvanized, or bundled?
• What test marking (Test pressure, NDE, NH, or both) will appear on the pipe for the specific supplementary requirements in the purchase order?
• How are heat numbers cross-referenced between the pipe, the bundle tag, the MTC, and the packing list?

A supplier that answers those three questions clearly and consistently — and that can show you a recent MTC package with the corresponding marked pipe — is much more likely to deliver pipe that passes receiving inspection without delay, and that remains traceable through decades of service.