Of the three types of silos-tower, bag and bunker-stainless steel tower silos are the most widely used. Mainly found on a farm and used in the agricultural industry to store crops or animal feed, known as silage, stainless steel silos range in size and capacity, sometimes containing hundreds of tons of storage.
Silos are typically the largest stainless steel tank on the market, ranging from 10 to 90 feet in diameter and 30 to 275 feel in height. Because stainless steel is easy to clean and has no pores that would absorb or release impurities, these silos are used in the chemical, food processing, mining, pharmaceutical, plastics and water works industries holding substances like milk, crushed limestone powder or corn seed.
Stainless steel is an effective conductor of thermal heat and resists high temperature oxidation which makes it suitable for outdoor use in many different climates. It’s a versatile and common metal that is resistant to corrosion, staining, peeling and cracking. The familiar cylindrical shape of these silos is meant to resist hydraulic pressure, and they always contain at least one manway, or opening, for pressure control.
The process of constructing a stainless steel silo begins with steel, an alloy metal consisting mostly of iron. Chromium is added to the metal; the percentage of chromium determines the grade and corrosion resistance of the final product. Steel and the alloys are melted together in an electric arc furnace and then annealed, a process that alternately heats and cools the steel until hardened.
A thin flexible layer of chromium oxide forms on the outside surface, coating it and in essence sealing it off from abrasive substances. For a silo, the stainless steel is roll-formed. A long strip of stainless steel is fed through a series of rollers that gradually bend the steel into shape.
Since the stainless steel is worked in a cold state, the results are typically lighter and stronger than if the steel had been stretched while hot. After the large curved sheets are cut and prepared, they can be fastened together with bolts or welded, which ensures a seamless watertight construction. If the size allows it, silos are transported on a special delivery truck and then erected by a crane.
Depending on the intended use of the silo, a 45 or 60 degree stainless steel cone can be fitted on the bottom to allow a consistent flow of material. Other nozzles, doors, pipes and fittings are added; some silos require heating, refrigeration or have an agitator installed. The stainless steel silo can sit on the ground or be supported on a stand to allow for easy access to the material inside. The stands vary in size and strength as well as design and can be elevated, legged or skirted.