One NACE method, four pass marks: sour service testing to Saudi Aramco, ADNOC, QatarEnergy and PDO specifications

A steel plate whose three HIC specimens average a crack length ratio of 12 per cent passes API 5L Annex H and passes Petroleum Development Oman's SP-2161. Under Saudi Aramco's 01-SAMSS-016 the same plate fails, because Aramco caps the ratio at 10 per cent. The test, NACE TM0284 in Solution A for 96 hours, is identical in all three. The operator's amendment is what decides the result.

• The method is shared: NACE TM0284 for hydrogen-induced cracking, NACE TM0177 and TM0316 for sulphide stress cracking, inside the NACE MR0175/ISO 15156 framework.
• The pass mark is not: each operator amends the method, and the amendments differ in acceptance limits, control samples, retests, hardness and inclusion rating.
• The binding constraint: reading the operator's specification, and its revision, before the specimens are cut. A programme run to the bare NACE method can pass every test and still be rejected.

Where the four specifications part company

TCR's corrosion and sour service laboratory in Mahape, Navi Mumbai, runs HIC and SSC programmes for steel mills, pipe makers, valve and vessel fabricators and EPC contractors supplying the Gulf operators. The clauses below are read from the specifications themselves.

Three of those rows catch suppliers more often than the rest.

The control sample. Every one of the four expects a control specimen of known susceptibility, average crack length ratio above 20 per cent, to go into the same solution as the production specimens. If the control does not crack, the solution did not do its job and the whole batch is void. A laboratory that cannot produce a control sample cannot run an Aramco, PDO or OQGN programme at all. TCR makes and holds its own control specimens.

The retest. Aramco allows a failed heat to be retested on two more plates from the same heat. PDO and OQGN do not. A mill that plans its schedule on Aramco's rule and then supplies to Oman discovers the difference when a heat is lost.

The inclusion rating. PDO SP-2347 and OQGN G14-PD-PL both require the pipe maker to order coil or plate with a maximum inclusion content measured to ASTM E45 Method D, severity level 1, stated on the mill certificate. ADNOC's specification calls for an ASTM E45 inclusion test as well. Inclusions are where hydrogen collects and where HIC starts, which is why operators now check them before the cracking test rather than after it fails.

What ADNOC adds to four-point bend SSC

ADNOC's Appendix A2 is the most prescriptive of the four on sulphide stress cracking, and it reads like a list of the ways a four-point bend test can be quietly made easier:

• three specimens transverse to the weld, with the weld bead at mid-length;
• the inner pipe surface and the internal weld reinforcement left as they are, unmachined, and the specimen never flattened;
• machined faces finished to Ra 0.8 micrometres or better, as-received faces cleaned only by fine glass-bead blasting;
• every specimen checked by visual and wet magnetic particle inspection before loading, so a pre-existing flaw is not reported as a crack;
• the inner supports at least the weld width plus 50 mm apart, and the stress confirmed by strain gauges, not calculated from deflection alone;
• acceptance: no surface-breaking crack deeper than 0.1 mm through the thickness, with pitting, laps, weld porosity and internal HIC-type cracks named as not failures; specimens that pass then go on to SOHIC evaluation under ISO 15156-2.

How TCR runs an operator programme

The sequence is the same whichever operator the purchase order names; the acceptance column changes. The corrosion bench is run by Manoj Prabhakar Singh, Department Head, Corrosion Testing.

1. Read the order. The specification and its revision, the product form, the heat treatment condition and every parameter the order alters. In a 2024 PDO line pipe programme, the order specified atmospheric pressure and a 5 bar H2S partial pressure in the same line, which cannot both be true; it went back for a ruling before a specimen was cut (case study).
2. Trace the specimens. Location, orientation and rolling direction recorded and hard-stamped, cut in TCR's own machine shop, thinnest and thickest plate of a heat tested where the specification asks for both.
3. Verify the environment. Solution pH at the start and end; hydrogen sulphide purity; H2S concentration by iodometric titration at saturation and at the end of the exposure, as 01-SAMSS-016 requires at 1 hour and 96 hours.
4. Expose for the full period. 96 hours for HIC and 720 hours for SSC, with no accelerated proxy.
5. Report to the operator's clause. CLR, CTR and CSR per section and per specimen, photographs of cracked sections, hardness, inclusion photomicrographs where cracking is found, judged against the operator's limits rather than the bare NACE method.

The same discipline runs to non-standard environments. In 2025 TCR qualified duplex stainless steel girth welds for a PDO pipeline contractor by four-point bend in an autoclave at 90 degrees Celsius, with 10 mbar hydrogen sulphide and 10 bar carbon dioxide in a brine of 170,000 ppm chloride, for 720 hours. The applied stress was set from hot and ambient tensile tests run in the same laboratory, as the ratio of the actual yield strength at 90 degrees to that at room temperature, applied to the 90-degree yield, and confirmed by strain gauges either side of the weld root. Acceptance was no visible crack and no pit deeper than 25 micrometres, with retesting prohibited.

Saudi Aramco, ADNOC, QatarEnergy and PDO in practice

• PDO and OQGN, Oman. TCR's laboratory is approved by Petroleum Development Oman for HIC and SSC testing, and has run line pipe programmes to SP-2347 and to OQ Gas Networks' G14-PD-PL.
• Saudi Aramco. 01-SAMSS-016 accepts HIC results only from laboratories Saudi Aramco approves, and the buyer holds the current list. TCR runs the 01-SAMSS-016 method and reporting set; the approval route for each order is confirmed with the buyer at enquiry. For material made in India, TCR's inspectors can also witness sampling and testing at the mill, the work Saudi Aramco's vendor inspection matrix lists as its own category (source and vendor inspection). Inside the Kingdom, the group works through TCR Arabia.
• ADNOC. Appendix A2 four-point bend SSC, SOHIC evaluation and the ASTM E45 inclusion test, run as one programme.
• QatarEnergy. QatarEnergy project specifications are read the same way: the purchase order names the specification and its revision, and the acceptance criteria come from it. The group is represented in Qatar through TCR Qatar; the testing is done in Navi Mumbai.

Every method in this article, NACE TM0284, TM0177 and TM0316, ASTM G39, EFC 16 and ASTM E45 Methods A and D, sits inside TCR's NABL ISO/IEC 17025:2017 accreditation, certificate NABLT0726MH18640, on the quality page. NACE International's India section named the laboratory its Best Laboratory for 2007, and the sour service bench has been in continuous use since. For hydrogen embrittlement that is not driven by hydrogen sulphide, such as hydrogen cylinder steels to ISO 11114-4 and plated fasteners to ASTM F519, see hydrogen embrittlement testing; for toughness after hydrogen charging, CTOD with H2S pre-charging. The industries this serves first are upstream oil and gas, pipelines and refining and petrochemicals.

This article was written and edited by the TCR Newsroom, the editorial desk of the TCR group, covering materials testing, inspection and asset integrity work across TCR’s laboratories in India and Saudi Arabia and its alliances in Qatar, Japan and beyond.