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Dec-2016

Advanced high alloy stainless steels

The real solution to guard equipment against environmental stresses like corrosion is use of advanced high alloy stainless steels.

Magnus Brodin
Sandvik Materials Technology
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Article Summary
Against the pressures faced by operators to maximise both efficiency and cost-effectiveness in refineries, corrosion poses a real threat. In fact, problems of corrosion are hugely damaging for the industry as a whole and have accounted for approximately 6% of its GDP annually by causing disruptions and downtime through unscheduled maintenance and equipment failures.

As a developer and manufacturer of advanced stainless steels and special alloys for the most demanding environments, Sandvik Materials Techology has seen first-hand the important role of enhanced and more durable materials have helped our customers optimise their refinery operations. We advise that the real solution to guard equipment against environmental stresses like corrosion is use of advanced high alloy stainless steels.

Heat exchangers are a good example, as they are widely relied upon as an energy source in refineries and must operate continuously in harsh environments while under enormous stress. The effectiveness, or otherwise, of the material chosen for the heat exchangers will have a substantial knock-on effect upon processes across the entire plant. At the same time, it has become increasingly apparently that conventional materials such as carbon steels can no longer satisfy these performance demands.

This is why new material developments are among the evolving technologies that will prove so crucial to the industry’s future. The capabilities of materials such as stainless steels must also continually improve as the global oil refinery market increases in size driven by factors like rising energy demand and new, increasingly corrosive sources of crude oil.

For these reasons, while duplex stainless steels have become well established for use in heat exchangers over the decades, it has been necessary for Sandvik to evolve its materials offering with hyper-duplex (HD) stainless steels. These grades, like Sandvik SAF 2707 HD material, are designed to offer better resistance to pitting and crevice corrosion and higher mechanical strength than all duplex, and super-duplex, stainless steels available on the market.

Nevertheless, more advanced materials can present new issues for operators. If we look at the Asia-Pacific (APAC) region, for instance, the past year has seen oil prices rise after the fall to an extent. But it remains to be seen whether prices grow to a level that permits operators to invest seriously in their production. The question is: can operators afford these better materials?

The APAC markets have been restricted by falling oil prices and a resulting loss of market confidence in recent times. Yet, through dealings with our own customers in the region, Sandvik recognises that there is much to look forward to for companies that are equipped to withstand the current climate.

For the customer, being ‘equipped’ entails searching for better materials which can offer superior overall performance and help to maximize plant operational time, while also proving cost-effective. So, while a more advanced high alloy material may entail a higher initial investment, we always advise customers of the longer-term benefits that counterbalance the price.

Heat exchangers again provide a good example. Such was the case for one operator that, having installed Sandvik SAF 2707 HD as its heat exchanger tube, was able to reduce its number of plant shutdowns from eight to just one over an eight-year period. The result has enabled large cost savings for the refinery and greatly reduced the necessity for equipment replacements.

Then there are new design opportunities. Advanced high alloy stainless steels can permit the use of thinner tube walls, thus reducing the volume of material required and lowering weight and costs. In Sandvik’s experience, existing heat exchangers have been retubed with hyper-duplex stainless steel tube even when the process has been undertaken several times before. The same heat exchanger design can also be used and the fabrication procedure unaltered due to the material’s improved cold-working properties.

Advantages of using advanced high alloy stainless steels are felt across the refinery and it is through these benefits that Sandvik remains closely committed to bringing a real difference to industries in APAC. Our hyper-duplex grades have surpassed all expectations against conventional titanium grades in the region, and we continue to work closely with various refineries and multinational companies to help them achieve greater productivity and reduce overall costs, despite fluctuating oil prices.

Whether they are located in the APAC or elsewhere, operations must always make any investment decision with one eye on the industry’s future. But it is worth taking note: even when unfavourable market conditions restrict companies’ abilities to invest in infrastructure, the long-term operational advantages of better quality materials should not be overlooked.
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