SOURCING STAINLESS STEEL | SUPPLY CHAIN
Complex specifications For most industries stainless steel is specified by grade, product form (plate, sheet, pipe etc) and size. Many nuclear engineers also define the maximum level of cobalt and other elements. This combination of technical specifications covering cobalt content, alloy and product form vary widely between projects. As a heavily regulated industry, only a few grades of
stainless steel are permissible under nuclear codes in critical areas. In the US ASME system, these include grades 304 and 316, together with low-carbon “L” versions; similar steels exist in European standards and the French RCC-M code. Duplex grades are sometimes used where high strength is needed. When it comes to technical specifications, the percentage
content of cobalt and other trace elements varies between different plant designs and the component location within the plant. French RCC-M standards typically set a maximum of 0.20% of cobalt, but lower contents of 0.10 or 0.05% can also be requested. Another requirement is the stringent qualification
requirements set by nuclear authorities. These mean that production can only take place at steel mills with proven experience under agreed production methods and the correct quality certifications to ensure production standards, material traceability and nuclear safety culture are followed to the letter. A final complicating factor is that engineering,
procurement and construction (EPC) contractors need to order material in multiple product forms and sizes. These include heavy plate for large tanks and heat exchangers, thin sheet for small process vessels or to line cooling ponds, and tubes and fittings in a variety of sizes for pipework.
Balancing requirements with batch size Combining these project-specific technical requirements can mean a batch of steel is tailored to one specific project.
This can create a major procurement challenge, especially as the low-cobalt requirement is almost unique to the nuclear industry and its influence is larger than it seems at first glance. The difficulties are even more apparent in smaller projects, such as repairs or replacement of components in existing plants but can also be present in new build plant if an individual fabricator is procuring material for a small part of an overall package of work. When it comes to ordering material, a fabricator may
need to procure 5, 10 or 20 tonnes of 316L material spread across several product forms such as plate, sheet and tube. However, bulk steelmaking typically produces material in melt quantities of around 50-100 tonnes. With this in mind, an order of, for example, 20 tonnes
of grade 316L with less than 0.2% cobalt, creates a set of commercial choices for the steelmaker. They could produce a full 80 tonne melt of specialist low cobalt steel to satisfy the 20 tonne requirement. However, there’s no guarantee of further orders for the same grade with the same trace element content. This may leave the balance of 60 tonnes in stock for years, tying up cashflow. Meanwhile, the next nuclear industry order may be for 10 or 15 tonnes of grade 304 with a cobalt level that is much lower at 0.05%, and with different overall technical requirements. It’s unlikely that this second project will be able to waive their standards to accept the product that is available – instead, it will require a new large production batch of steel. This wide variation of project requirements means that
requests for small quantities are something that steel mills need to evaluate with care. As a result, EPC contractors and fabricators may find it challenging to secure material at a reasonable cost for one-off smaller nuclear projects or refurbishment work. The tighter the specifications covering trace elements,
alloying content and technical demands, the more costly the steel melt. Ultimately the cost of producing a full batch of specialist steel is likely to be borne by the ordering
Above: As a heavily regulated industry, only a few grades of stainless steel are permissible under nuclear codes in critical areas
www.neimagazine.com | September 2023 | 33
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49
