Silo and Bin Failures
by Joseph Marinelli
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Most of our articles to-date pertain to testing and
ensuring reliable bulk solids flow. Silos, bins, hoppers, bunkers, vessels, etc. can
experience catastrophic failure if not designed and maintained properly.
There are many reasons why silos fail, usually due to loads applied
to silo walls that are not capable of resisting them. Failures can consist of complete
collapse of the structure, denting in a metal cylinder or cracking in a concrete wall.
Several areas of concern when dealing with silo structural
considerations are: First is the design of the structure requires knowledge of the
material's flow properties. Determining the type of flow pattern that will develop aids in
the prediction of wall pressures while the material is stationary or flowing.
Non-uniform loads, caused by eccentric material withdrawal must be
considered. If you design a silo, you must have a full appreciation of the loads that can
be applied to the walls of the structure by the bulk solid flowing within. Some of these
flow related loading conditions include:
- bending of circular walls caused by eccentric withdrawal
- nonsymmetrical pressure distributions caused by protrusions or even
inserts
- self induced vibrations
During the silo construction, there are two ways problems can arise:
- uneven foundation settlement
- faulty construction caused by inferior materials or the lack of
enough rebar
A bulk material for which the silo was not designed may impose loads
completely different from which the silo was originally designed. Your silo may be
designed to handle material that has a bulk density of 50 lb./cu. ft. If all of a sudden
you put much heavier material in the silo, the imposed loads will be greater that those
for which the silo was designed.
If a side discharge or side port is put in a silo designed to
discharge from the center, eccentric loads will develop due to the preferential flow
channel that develops. The wall pressures developed by a preferential flow channel are
less than those of the rest of the silo. The subsequent eccentric loads can cause dents to
occur in the region of the preferential flow channel.
When designed and maintained properly, your silo will remain
problem-free for many years. However, material changes, shoddy workmanship and neglect can
lead to structural failures.
Help others by posting your comments, suggestions and
experiences with bulk solids feeding or any other materials handling concerns you may have
on our On-Line Help Forum. For
past Ask Joe ! Articles, visit the Ask Joe! Archived Articles.
Guest articles for the Ask Joe! Column are always welcome,
for more information please contact Joe Marinelli directly at his email address:
joe@solidshandlingtech.com.
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