Duplex tanks

Expansions in the duplex market?

John Butterfield - 2 July 2015

According to recent research carried out for the Stainless Steel World magazine, duplex stainless steels still have only a tiny share of the market for stainless steels. However, customers are increasingly drawn to it because of its favourable strength-to-weight ratio, which allow materials savings of up to 50% compared with austenitics. Its use is also likely to increase because of the material’s strength and corrosion resistance prospects.

About the author

Mr John Butterfield
John Butterfield is Editorial Manager at KCI Publishing. A new field of interest for him is additive manufacturing.

Upside opportunities

With a world market share of around 1%, duplex stainless steels are still underrated. Their market share is higher in Europe (3.9%) than in the America or Asia, but the European economy is especially stagnant at the moment. This means that the main upside opportunities are in the Americas and especially Asia, where the share is only 0.3%.

Euro/Africa, 233,000 t, 3.4%
Americas, 20,000 t, 0.9%
Asia, 62,000, 0.3%
Total, 316,000, 1%
(Source: ISSF Crude Steel Survey 2012)

In the Middle East, too, the opportunities presented by both desalination and the oil & gas industry suggest that opportunities for duplex abound. This is why Special Piping Materials opened a new warehouse in the Middle East which specialized exclusively in duplex and super duplex grades - the first company in the region to carry these grades in stock (1).

Many end users are beginning to appreciate that for the same strength, duplex can save material use up to 50% compared with other types of stainless steel. This is an essential advantage at every stage, from welding and fabrication to transport and installation. The advantages in terms of space saving, reduced fuel consumption during transportation and ease of manoeuvring are telling advantages for duplex stainless steels. This is especially true of lean grades.

More duplex in tanks

Duplex use appears to be on the increase in the construction of certain types of tanks (food, diary, alcohol). Gert Gijssens, of the Belgian firm of Kametal, recently reported that more customers are getting to know about duplex and are changing to duplex from other stainless grades. The main attraction is weight saving, but corrosion resistance is important as well. His company recently delivered some duplex tanks to Belarus.

Duplex is especially interesting for tank construction in the food & drink and diary business, because of the twin demands of weight reduction and corrosion resistance. Even in a mildly corrosive application such as drinking water tanks, duplex grades such as the lean grades 2304 and LDX 2101 have been specified. One company that has made a specialty out of water storage tanks is PVI Industries. PVI recently installed four tanks 3,000-gallon tanks in an apartment/office building complex in British Columbia, Canada. Each of the tanks will be connected to a plate-and-frame heat exchanger to generate domestic hot water. The tanks are made of a Outokumpu’s LDX 2101 lean duplex grade (which PVI has trademarked as AcquaPLEX®). It can withstand temperatures up to 200F, though the recommended maximum temperature is 140F. The water heaters are welded using advanced techniques such as synergic pulse welding machines and six-axis robotic welding. An in-house pickling and passivation process is employed to ensure that the material is restored to its fully passive condition after welding has created a heat-affected zone. This makes the material far more resistant to materials that are susceptible to chloride stress cracking, such as 316L.

Another water heating tank made from duplex stainless steel is offered by Lacaze Energies. The water of the solar DHW Coil Cylinder is heated from solar energy or some other source. It has one or two coils made from 316L and has electrical pins made of Incoloy. Duplex is used in several new products that heat water from domestically produced solar energy, including Kingspan’s Tribune HE, Heatraesadia’s Megaflo and Grant’s DuoWave Solat.

To read more about the duplex stainless steel market see the full article.

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