As requirements for meeting the oil and gas industry standards have become stricter, materials manufacturers need to acknowledge early changes in the industry and adapt.
By Marcus Hillbom
The oil and gas offshore industry is often exposed to some of the most challenging working conditions in the world, so the materials used to support this sector must be manufactured to the highest industry standards.
As products, processes, and materials for the offshore industry evolve, and the focus on safety and performance continues to increase, developing standards to mirror these advances is a continuous journey.
Not long ago, meeting ASTM, EN-norm, and NORSOK standards was the critical benchmark. However, times have changed, and requirements have become even stricter. The ever-increasing list of new standards and customer demands includes increased reduction ratio, tighter chemical specifications, and extra testing. In addition to meeting common offshore standards, operators now face additional test-ing requirements to certify materials for aggressive conditions.
In recent years, significant new standards developed are influencing the manufacturing of bar materials for the oil and gas offshore market segment.
Setting the standards
Two such important examples of standards recently introduced are ISO 17781 and 17782. These will essentially be extensions of existing NORSOK standards.
ISO 17781 specifies quality control testing methods and test conditions for the characterisation of microstructure in relation to relevant properties in ferritic/austenitic (duplex) stainless steel components. These components are supplied in the solution annealed condition and fabrication welds in the as-welded condition.
ISO 17782 establishes a procedure for verifying that the manufacturer of special materials for the petroleum, petrochemical and natural gas industries has sufficient competence and experience to manufacture materials in the required shapes and sizes with acceptable properties.
At the end of last year, the NORSOK M-650 and M-630 standards were released in their final editions and will be replaced in the future by the previously mentioned ISO standards.
Another significant standard, first released in 2016, is IOGP S-563 for piping and valve components. IOGP S-563 was developed as a result of a joint industry project (JIP) with some of the major end-user and engineering companies within the oil and gas industry. The purpose of the JIP was to harmonise demands and testing within the industry and to set one material standard that both material manufacturers and component producers could follow.
Adapting early to new standards
The challenge for materials manufacturers in meeting the range of more stringent standards has been to acknowledge early changes in the industry and adapt accordingly.
A major consideration for materials producers has been responding to increased impact strength requirements as part of the new standards. We acknowledged this change in the industry back in 2016 and started to see how we could meet these more stringent standards.
Previously, materials were required to surpass acceptance criteria of an average 45J and a single 35J impact in longitudinal and transverse directions. However, the new ISO 17781 standard includes two quality classes (QL I and QL II) that require improved performance.
QL II sets the acceptance criteria at an average of 65J and a single of 50J in a longitudinal direction, recommended for most applications within the industry. QL I is the highest quality class, with acceptance criteria of average 85J and single 65J. For both quality classes, acceptance criteria for transversal direction are an average of 45J and 35J.
This significant increase in acceptance criteria for impact testing is especially important when producing large dimension bars above 200mm or 8 inches. The mechanical strength has an opposite relation to the dimension of the bar, meaning the larger dimension of the bar, the less the mechanical strength. This is mainly because the larger material dimensions have a larger grain size, which is related to the power of the forging press and heat treatment procedures.
The laws of physics make this challenge difficult to mitigate, but there are ways to improve the outcome.
Raising the bar in material solutions
The changes in standards meant that manufacturers had to reconsider their materials offer to ensure it meets both regulatory and market demands.
Sandvik Materials Technology, soon to be renamed Alleima at the end of August 2022, is one such company that has undergone a reassessment of its product portfolio. In 2017, the company began designing a new generation of duplex materials to increase mechanical strength and corrosion resistance and to meet all other relevant demands of the offshore industry.
The change involved starting from scratch for a range of materials, redesigning the chemical composition, and many parts of the manufacturing steps.
One of the most recent developments from the company is the introduction of the duplex stainless steel SAF™ 2205+, which has been pre-engineered to comply with the toughest demands of the oil and gas offshore industry.
“A major consideration for materials producers has been responding to increased impact strength requirements as part of the new standards. We acknowledged this change in the industry back in 2016 and started to see how we could meet these more stringent standards.”
Unlike other stainless steels, the grade is pre-approved to the latest IOGP S-563 and ISO 17781 standards, so operators do not have to wait weeks to comply with new tests. With highly improved mechanical properties and weldability, the material has been tested to withstand extreme corrosion. It is certified to meet the latest subsea requirements, such as avoiding hard-to-detect pitting corrosion and other types of general corrosion in pumps and valves.
Analysis of produced bars demonstrates that SAF™ 2205+ provides a significant increase (up to 50%) in the level of impact strength compared to the machinability-improved version of the grade, Sanmac® 2205. This enables the material to comply with QL II in a wide size range of dimensions up to 260mm, or 10.2 inches.
Furthermore, austenite spacing testing has been introduced to ensure performance in HISC (hydrogen-induced stress cracking) related applications under cathodic protection and other environments.
Another recent development has been the addition of super alloy Sanicro® 625 bar to the growing family of high-performing nickel alloys. The bar, which has an ASTM classification of Grade 1, will be used to machine advanced components exposed to acids, alkalis, seawater, and other wet, corrosive conditions in both cryogenic environments and temperatures up to 593°C (1100°F).
The chemical composition includes 62% nickel, 21% chromium, and 8.5% molybdenum, ensuring high resistance to pitting and crevice corrosion. The addition of 3.5% niobium creates a stiffening effect with the molybdenum and provides good stabilisation against intergranular corrosion. Ductility and toughness are also very high, and the material is approved by all key relevant standards (including ISO, ASTM, ASTME, and EN).
The introduction of Sanicro® 625 bar follows the launch in 2021 of Sanicro® 825 bar, and two new high-strength grades in the pipeline (Sanicro® 718 and Sanicro® 925) for release in the coming year.
Looking ahead
As technology evolves and applications become more advanced, the material design comes under increased pressure to perform better. Tougher times call for tougher materials, and the development of increasingly stricter standards means material manufacturers must respond accordingly.
This will involve companies upgrading their existing bar portfolio where appropriate and continuing to provide new materials to the market. As oil and gas offshore projects enter increasingly challenging environments, operators will rely more heavily on material manufacturers to deliver high-performance options for their critical applications.
About the author
Marcus Hillbom is the Technical Marketing Manager at Sandvik Materials Technology. Marcus has worked extensively for over 20 years with tooling and machining solutions within Sandvik, including at Sandvik Coromant, a global leader in machining technology. Today his focus and passion are to increase technical knowledge within the organisation to better support customers with new product development.
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