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​Lean duplex makes a breakthrough in flour silos

6月 03, 2013    

​Spain is witnessing the construction of pioneering silos for human wheat flour: the silo builders not only go for stainless steel but opt for Outokumpu’s duplex LDX 2101® as the grade.
Wheat largely feeds the world: it is the most important human food grain by global production. Almost as important as wheat to humans is the storage silo for wheat flour in the route to market from mill to consumer.
To date, silos for wheat flour meant for human consumption have been built out of paint-coated carbon steel. However, when silo fabricator Metal Alimentaria, S.L. of Barcelona began to design a new wheat flour silo in early 2005 to be built in Ávila, Spain, the builders became convinced of the superior qualities of stainless steel for the application: not only would stainless guarantee uncompromised sanitary standards – a must in the foodstuffs industry – it is practically maintenance free and avoids the electrical insulation that coating produces – a problem in flour silos where electrostatic induction should be avoided. Metal Alimentaria decided to implement a pioneering concept, using stainless steel for the silo walls.
The grade initially selected was austenitic EN 1.4301 (ASTM 304). Material thicknesses of 6…9 mm were required. However, such thicknesses in 1.4301 proved extremely challenging for fabrication because of the required level of corrugation in the silo wall panels.
​Outokumpu’s Spanish sales team introduced a solution: using Outokumpu’s proprietary Duplex grade LDX2101, which features close to twice the mechanical strength compared to 1.4301, material thickness could be reduced to 4…5 mm, making fabrication possible. The resulting weight saving compared to the original design was significant, estimated between 125 and 150 metric tons. Metal Alimentaria proceeded to build the silo with 180 tons of LDX2101, as well as with 80 tons of 1.4301 for other sections where thinner material was specified and where 1.4301 was still the more economical choice at the time.
Another stainless steel silo for wheat flour went into planning in September 2006, this one in Barcelona and fabricated by Desarrollo Agroindustrial del Silo, S.L. of Barcelona. By that time, soaring nickel prices had made LDX2101 competitive in price to 1.4301 thanks to its low nickel content. After discussions with Outokumpu’s Spanish sales team, Desarrollo Agroindustrial del Silo was convinced of the merits of LDX2101 and decided for an all-LDX2101 structure, for reasons of the high quality of the product, a very significant material saving, exceeding 200 tons, and a lower price even in the thinnest sections compared to 1.4301. Outokumpu will be supplying 500 tons of LDX2101 sheet in the thickness range of 4…5 mm for the project during 2007.