»
Materials market need , and a company ’ s commitment to develop innovative solutions that fill the gap between stainless steels and costly nickel alloys . Once the metallurgy is ready for deployment it is important to find the right opportunity . For example , the long-standing relationship between Alleima and the end client , including detailed discussions on the development of the Sanicro ® 35™ and the testing of samples , gave the company the confidence to suggest it as a solution for replacing the heat exchanger tubes . The end client reviewed several metallurgy options and carried out cost-benefit analyses on each one based on the expected lifecycle . After an extensive evaluation of the corrosion and mechanical properties compared to other high-cost nickel alloys under consideration , the refinery selected this alloy for its high performance and cost alternative offering .
Tube material supplier and fabricator collaboration Simultaneously , the company was in ongoing communication with fabricator Brask Inc over the development of the alloy . Brask specializes in the design , manufacture , and repair of shell and tube heat exchangers and pressure vessels . Continuous feedback on the advancement of Sanicro ® 35™ increased awareness and understanding of the grade ’ s progression to the point of its commercialization . It also supported confidence in proving to the end client that fabrication with the material would be straightforward . Heat exchanger bundles for the same end client had been fabricated from hyper-duplex SAF ® 2707 HD in the past . Using Sanicro ® 35™ this time , the fabrication was equally seamless and without issue . The tube material was manufactured in the Czech Republic . However , the lead time was shortened at the request of the end user . To meet the new deadline , the tubes were airfreighted to the U . S ., so that fabrication could begin . In-depth collaboration between the manufacturer and the fabricator early on , including several meetings between the welding experts for alignment on welding procedures , generated confidence on both sides . The early share of information by the stainless producer allowed the fabricator to complete its due diligence and design analysis . Tube samples were supplied in advance so welders could perfect welding details including machine parameters , and gain comfort the weldability of the tube , tubesheet and filler metals selected . Important technical information such as the code case details was also provided , which supports input on filler metal selection , ensuring fabrication went to plan . Using leveraged past experience and test knowledge , welding of the tube to tubesheet joint with no issues was completed . In this case , the tubesheet metallurgy specified was Super Duplex , UNS S32750 . The workability of Sanicro ® 35™ was similar to duplex and hyper-duplex materials used in the past . Each of the bundles consisted of 214 U-tubes and fabrication took three weeks . The bundles were installed in December 2021 and as of this writing are performing without issue . The end client has also recently expressed interest in procuring two more heat exchanger bundles to be made with Sanicro ® 35™ tubes .
Steelmelting at Alleima in Sandviken , Sweden .
To achieve success in completing the first project with a new alloy , the strong partnership between the tube manufacturer and the fabricator was critical . Both teams collaborated and drew from expertise in developing and working with a range of stainless steel and nickel alloys to deliver the solution to the end user .
Advancing materials technology This was the first order for the Sanicro ® 35™ ( UNS N08935 ) super-austenitic grade . It is a high-performance alternative to existing duplex and austenitic stainless steel grades and more expensive nickel alloys . It offers exceptionally high performance , strength , and corrosion resistance at a wide range of temperatures . It is a highly alloyed and chemically balanced PRE 52 superaustenitic grade that offers extreme pitting resistance and outperforms conventional 6Mo alloys . The material ’ s ability to provide a high level of corrosion resistance and strength gives it an excellent price performance ratio compared to alloys with higher nickel content . Its high structural stability provides reassurance that it will maintain its
» End View of U-Tube Bundle
with Sanicro ® 35™ ( UNS N08935 ) Tubes in Fabrication at Brask , Inc . in Pearland , TX .
Heat Exchanger World February 2023 21