Storage silo
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Storage silos are structures for storing bulk materials. Most commonly silos are used in agriculture to hold grain or fermented feed known as silage.
Types of silos
Three types of silos are in widespread use today:
- Tower silos
- Bunker silos
- Bag silos
Tower silos
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Tower silos are cylindrical structures, typically 12 to 24 ft (4 to 8 m) in diameter and 30 to 80 ft (10 to 25 m) in height. They can be made of many materials. Wood staves, concrete staves, cast concrete, and steel panels have all been used, and have varying cost, durability, and airtightness tradeoffs. Tower silos containing silage are usually unloaded from the top of the pile, originally by hand using a pitchfork, and most often today using mechanical unloaders. Bottom unloaders have been used at times, but have problems with difficulty of repair, and will not work when the silage sticks to the walls of the structure and will not fall down.
An advantage of tower silos is that the silage tends to pack well due to its own weight, except in the top few feet. The tower silo was invented by Franklin Hiram King.
In Australia, many country towns in grain-growing areas have concrete tower silos to collect grain from the surrounding towns and store it ready for transport by train or road to an export port.
Bunker silos
Bunker silos are trenches, usually with concrete walls, that are filled and packed with tractors and loaders. The filled trench is covered with a plastic tarp to make it airtight. These silos are usually unloaded with a tractor and loader. They are inexpensive and especially well suited to very large operations.
Bag silos
-->Bag silos are heavyweight plastic bags, usually around 6 to 8 ft (2 to 2½ m) in diameter, and of variable length as required for the amount of material to be stored. They are packed using a machine made for the purpose, and sealed on both ends. They are unloaded using a tractor and loader or skid-steer loader. The bag is discarded in sections as it is torn off. Bag silos require little capital investment. They can be used as a temporary measure when growth or harvest conditions require more space, though some farms use them every year.
Also, a name given to any large cylindrical structure with impervious walls, e.g. missile silo.
Safety and
Silos are hazardous, and people die every year in the process of filling and maintaining them. The machinery used is dangerous, and with tower silos workers can fall from the silo's ladder or work platform.
There have also been many cases of silos exploding. If the air inside becomes laden with finely granulated particles, such as grain dust, a spark can trigger an explosion powerful enough to blow a concrete silo apart.
There are two main problems which will necessitate cleaning. Bridging occurs when the material consolidates at the base of the silo. Rat holing occurs when the material starts to adhere to the side of the silo. This will reduce the operating capacity of a silo as well as leading to cross-contamination of newer material with older material. There are a number of ways to clean a silo and many of these carry their own risks. However since the early 1990s acoustic cleaners have become available. These are non-invasive, have a minimum risk profile and can offer a very cost-effective way to keep a silo clean.
See also
An unusual and famous tower silo is the Henninger Turm in Frankfurt am Main, Germany, which has an observation tower on its top.
References
- Beedle, Peggy Lee. [4. "Silos: an agricultural success story"], University of Wisconsin-Extension: 2001, G3660-4.
External links
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