Ask a mill for pipe and you receive steel with a row of characters stamped or painted on it. Most buyers check the grade, confirm the size and move on. That is a mistake, because on a properly marked pipe almost every character carries a contractual meaning, and several of them tell you whether the pipe was tested at all.
What SA-999 puts on every pipe
SA-999/SA-999M clause 26.1 is the floor every other pipe specification sits on. Each length of pipe shall be legibly marked with the manufacturer’s name or brand, the specification number and the grade. Marking shall begin approximately 12 in. [300 mm] from the end of each length. For pipe smaller than NPS 2 and under 3 ft [1 m], the information may instead be marked on a tag attached to the bundle or box.
Three neighbouring clauses change how you read a stencil that looks unusual. Clause 26.4 requires pipes weld repaired in accordance with 17.1 to be marked WR, so a repair mark is a disclosure, not a defect. Clause 26.2 requires that when pipe marked as specified is rejected, the ASTM designation shall be cancelled. Clause 26.3 is easy to miss: for austenitic steel pipe, the marking paint or ink shall not contain detrimental amounts of harmful metals or metal salts, such as zinc, lead or copper, which cause corrosive attack on heating.
Clause 26.5 explains the letters X, Y and Z. Where certain requirements of an ASME specification are to be completed by the purchaser on receipt, the manufacturer shall indicate that not all requirements have been completed by a letter such as X, Y or Z immediately following the specification number. The letter may be removed after completion, and clause 25.4 requires the test report to carry an explanation of it.
What each specification adds on top
| Specification | Marking elements required beyond the A999 baseline | Clause |
|---|---|---|
| SA-999/SA-999M | Manufacturer’s name or brand, specification number, grade. Marking begins approx. 12 in. [300 mm] from the end. Below NPS 2 and under 3 ft [1 m], a bundle or box tag is permitted. Weld repaired pipe marked WR. Rejected pipe has the ASTM designation cancelled. For austenitic pipe the paint or ink shall not contain detrimental zinc, lead or copper | 26.1 to 26.5 |
| SA-312/SA-312M | NPS or outside diameter and schedule number or average wall thickness, heat number, and NH when hydrotesting is not performed, plus ET for eddy-current or UT for ultrasonic testing. Private identifying mark, the 12.3 marking if applicable, and whether seamless (SML), welded (WLD) or heavily cold-worked (HCW). For the H grades also the heat number and heat-treatment lot identification. Weight on pipe larger than NPS 4 if the order so specifies | 17.1 |
| SA-312, supplementary | Radiographically examined double welded pipe marked RT after the specification and grade. Minimum wall pipe marked S8 | S5.1, S8.1 |
| SA-790/SA-790M | Private identifying mark and whether the pipe is seamless or welded. Weight on pipe larger than NPS 4 if the order so specifies | 16.1 |
| SB-829, seamless nickel and nickel alloy | Name or brand of the manufacturer, name of the material or UNS number, the letters ASTM, product specification number, heat number, class if applicable, and nominal size, on each piece 3/4 in. (19.0 mm) outside diameter and larger and lengths over 3 ft (914 mm), by a method that will not result in harmful contamination. SB-775 applies the same list to welded nickel alloy pipe on each piece 1/2 NPS and larger | 14.1.1, 14.1.2 |
| SA-182/SA-182M | QT for quenched and tempered low alloy or martensitic stainless forgings. W for repair welded forgings, WNS where a repair welded austenitic forging has not been postweld heat treated per Table 4. Dual marking permitted where a part meets more than one class or grade. Plugs and bushings to ASME B16.11 need not be marked. F 91 additionally marked with the appropriate Type | 19.1.1 to 19.1.6 |
| SA-961/SA-961M | Product specification number, grade or marking symbol, class, certifying organization’s name or symbol, heat number or heat identification, size, and service rating if applicable, in a position not to injure the usefulness of the forgings. Tags or box labels where size or shape prevents full marking. MSS SP 25 marking followed, except the word steel shall not be substituted for the specification grade | 20.1 to 20.3 |
The certificate has to agree with the stencil
SA-999 clause 25.1 requires a certificate of compliance stating that the product was manufactured, sampled, tested and inspected in accordance with the specification, including the year-date, the supplementary requirements and any other requirements designated in the purchase order. A signature or notarization is not required, but the document shall be dated and shall clearly identify the organization submitting it, and clause 25.1.1 makes the certifying organization responsible for the contents whether or not it is signed.
Clause 25.2 lists what the test report must carry: heat number, heat analysis, product analysis if specified or required, tensile properties, bend and flattening test results, hydrostatic test pressure, nondestructive electric test method, impact test results, and anything else the applicable product specification requires. A heat number on the pipe that does not appear on the report means the traceability chain is broken at the first link.
Where the letters NH, ET, UT and RT come from
These four marks change what you are buying, and each traces to a specific clause. SA-312 clause 12.3 applies to pipe whose dimensions equal or exceed NPS 10: the purchaser, with the agreement of the manufacturer, is permitted to waive the hydrostatic test requirement when in lieu of that test the purchaser performs a system test, and each length of pipe furnished without the completed manufacturer’s hydrostatic test shall include with the mandatory markings the letters NH. So NH is not a defect marker and not an abbreviation of the grade. It states that the hydrostatic test was waived and a system test is the substitute. That is why SA-312 clause 16.1 requires the certification to state whether or not the material was hydrostatically tested. ET and UT record which non-destructive method was used, and RT on double welded SA-312 pipe records full radiographic examination under supplementary requirement S5.
One requirement has a scheduling consequence. Because SA-312 clause 17.1 requires the heat-treatment lot identification on the marking for the H grades, a pipe ordered in one heat-treatment lot cannot be split across lots without the marking changing. Where a project needs mixed heats, say that in the purchase order before ordering.
Forgings and flanges carry a second marking language
SA-182 clause 19.1 adds to the SA-961 marking, and the repair marks matter most for a piping order. A W mark means the forging was repair welded, and WNS means it was repair welded without the postweld heat treatment that Table 4 calls for.
Acceptance checklist
1. Grade and UNS number agree.
2. The heat number on the pipe appears on the test report.
3. Size and schedule are on the marking, not only on the packing list.
4. Test status is explicit. Look for NH, ET, UT or RT and read them against clause 12.3, clause 16.1, supplementary requirement S5 and the certification.
5. Repair and heat-treatment flags are present.
6. Rejected material is cancelled, not returned unmarked and forgings are not marked steel, with QT, W, WNS and Type marks present where the grade and fabrication route require them.
7. Any X, Y or Z letter is explained on the test report
Stencils are free to read once you know the vocabulary, and the cost of learning it is a short conversation before the order is placed rather than a claim after the pipe has been fabricated into a system. If you want the marking requirements for a specific specification and grade checked against an order you are about to place, send us the specification, the grade, the size and the quantity. If you want the marking requirements for a specific specification and grade checked against an order you are about to place, send us the specification, the grade, the size and the quantity. Our seamless pipe and tube range is supplied with full material certification, and the nickel alloy seamless pipe page sets out the grades we hold. Request a quotation through the contact page or on WhatsApp at +86 186 2137 7760.
