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Silos are increasingly being used to store grain world over as it offers a lot of advantages over bag storage and other means of storage. It is considered as the most economical long term storage for grains. However, it also poses certain dangers which one should be aware of. Many people have suffered injuries in a grain storage complex due to various unsafe conditions. It is dangerous & life threatening and hence one should never enter a grain bin unless it is extremely essential. The leading cause of injuries or deaths in grain silo terminals is suffocation due to grain engulfment and entrapment. There are many unsafe conditions that exist inside grain silo, and one must be aware of all, before planning any entry inside grain silo. Some of these unsafe conditions are described below.
Buildup of Toxic
Gases
In a grain silo there are
two gases that may be present in high concentration. One is Carbon Dioxide, and
another is Nitrogen Dioxide. These gases are called silo gases and buildup
inside silo due to fermentation or infestation of mainly chopped grain inside
silo. Nitrogen dioxide is characterized by a yellow or reddish fog and a bleach-like odor
is more harmful because it causes severe irritation to the nose and throat and
may lead to inflammation of the lungs. Immediately within 2-3 days after the
grain is harvested Nitrogen dioxide gas starts forming and within 2-3 days
after harvesting, buildup to its peak inside silo and thereafter begins to
decrease rapidly in a well ventilated silo. It takes approximately 2 weeks
after the harvest for nitrogen dioxide gas formation to stop completely, but
still entry inside silo is not safe as gas takes time to escape out of silo.
Exposure to high concentration of these gases may cause someone to collapse and
die immediately within minutes of inhalation.
Traces of Phosphine Gas
Fumigation is essential
activity in a grain storage silo complex. Fumigation is carried out with
phosphine gas and hence traces of Phosphine gas may be present inside a grain
silo which is recently been fumigated. Although once the fumigation is over,
the silo is de-sealed and aeration fans are operated to expel residual
phosphine gas out of silo but still some ALP tablet residue may again generate
phosphine gas and hence one must take proper care while entering inside
silo.
Bridged Grain - Collapse of
Grain Mass
Suffocation which is the
leading cause of death in grain storage silos, happens due to grain mass
collapsing on the people due to infestation or excessive moisture.
Infestation happens inside
a silo due to many reasons and this grain infestation that grow inside silo
forms solid masses, crusts, horizontal grain bridges and vertical grain walls
that can collapse. The most common is hard crust formation on the top surfaces
of grain, which stays intact even when you unload the grain from below it. This
crust or bridge is extremely dangerous and collapses under person’s weight and
person gets submerged inside the grain within seconds.
Entering inside the silo
when the gravity flow stops from the silo discharge gates also poses a great
danger as. sometimes while unloading the grain a huge mass of grain or heap
that gets stuck on the wall of silo falls on the people trying to break this
grain mass from the silo wall and may injure or suffocate the people trying to
break the heap.
Flowing Grain – Grain
flowing downwards
One must never ever think
to entering a grain silo when grain is being reclaimed or unloaded from the
silo. Grain that is flowing downwards acts like a sand and anyone who enters inside
silo to break the bridged grain or vertical pile of stored grain will get
completely buried or engulfed in grain in only 7 to 20 secs, if it collapses
unexpectedly. One must also understand that force required to pull out a man
buried in grain mass to the waist is more than 500 kgs hence it is very
difficult to pull out a man engulfed in the grain without trained assistance.
Dust Explosion
Grains have inherent
tendency to generate dust whenever it is conveyed or transported from one place
to another. This dust forms a dust cloud while silo is being filled or being
emptied and whenever this grain dust cloud is in high enough concentration and
get an ignition source it may result into dust explosion as suspended grain
dust is highly combustible. Generally, people enter inside silo when sweep
auger stop working and silo is to be emptied manually. During this silo
emptying process, there are always chances of dust cloud formation and hence
care should be taken not to allow any ignition source inside silo
Grain Silo Entry
requirements
We must take following well
accepted precautions which can minimize grain entry requirements and thus
prevents accidents
However, even after taking
all above precautions there are still some more reasons that makes the silo
entry unavoidable.
Precautionary measures to
Enter Inside Silo
Although one must not enter
Grain Silo but in case grain bin entry is unavoidable, one must follow the
complete silo entry procedure. Entering any grain silo is a process and it
requires planning and preparation. Only the trained people who are fully aware
of all the unsafe conditions that they may encounter inside Silo and are
trained to enter inside the silo should be allowed to enter.
Nobody should be allowed
silo entry without a trained supervisor and Personal Protective Equipment (like
Helmet, Safety Belt, Safety Mask, safety goggle etc.).
Roof exhaust fans must be
operated for at least 15 minutes before allowing people to go inside silo so as
to expel all residual gases. Phosphine gas ppm should be
below 0.3 ppm to allow entry inside silo.
And finally, there should
be a foolproof work permit system to record such silo entries and take
precautionary measures.
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