Silo
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Silos are strucures for storing bulk materials. Most commonly silos are used in agriculture to hold grain or fermented feed known as silage.
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Types of silos
Three types of silos are in widespread use today:
- Tower silos
- Bunker silos
- Bag silos
Tower silos
Tower silos are cylindrical structures, typically 12-24' (4-8m) in diameter and 30-80' (10-25m) 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 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.
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 6-8' (2-3m) 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
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.
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.