Silos - Silo Design, Silo Size & Variations

Silos and storage vessels or bins can come in a wide variety of sizes and materials the type that springs most readily to mind in most people is the tower silo. This is simply a vertically arranged pipe into which material is placed and which will empty under the force of gravity when an aperture or apertures at the bottom are opened.

While the system described above would work for storage of a liquid, bulk materials have some unique properties due to their sharing characteristics. Of both liquids and solids these characteristics are what makes working with bulk solids so interesting. Unfortunately interesting rarely goes hand in hand with easy.

In real world situations where bulk materials are stored, side wall friction, internal friction, resonance and vibration, wind loading, space and height constraints, abrasion and of course cost all require careful consideration in silo design.

These constraints and the different ways that designers overcome them can lead to a very wide variety of shapes and sizes of silos. The most common material for building silos are concrete and steel although polymer silos and even brick built silos exist in considerable numbers.

Silos can range in size according to use from a couple of kilos to several thousand tonnes and consequently from a few millimetres in height to several tens of meters. Read about the world's tallest silo, the Henninger Turm in Germany which is 120 metres high.

Silo designing requires a set of skills and often a wide range of experience. While tools such as Jenike design basis or Johanson Indiciser are available the true skill lies in understanding the sometimes counter intuitive basic principles and knowing the exceptions where these tools can not be relied upon.

In such a highly tuned design it is not surprising that small changes in the material stored within the silos, the condition of the interior walls and even fabrication methods can have disastrous effects on flow of the materials. A material compacted under its own weight can for instance show considerable increases in its unconfined shear strength which can lead to ratholing or piping with a very small change to the silos geometry arching or bridgeing.

And material stored in silos can range from the basic necessities of life such as grains and food stuffs, raw materials such as aggregates and ores to very expensive manufactured items such as chemical compounds and medicines.

The ability to store and use (when needed) food and goods allows specialisation of labour which results in greater productivity, skilled workers and better quality products and so contributes in no small way to our modern society.

A silo can therefore be seen as a towering symbol of modernity and of people's ability to work together to a common aim. Most of the time, however, to most people silos will remain merely thought of as "the one with the hopper that bridges and we have to hammer on!" Its does us no harm to occasionally look back at how far people have come together whether that be from standing on the shoulders of giants or from getting a good view from the top of a silo.