Baking & Snack - June 2015 - 106

INGREDIENT HANDLING

ent, the greater the fire and/or explosion risk."
There are several variables to determine an ingredient's
combustible dust potential. "Certain ingredients rank higher
on the risk scale using the minimum ignition energy (MIE),"
Mr. Pecha said. He noted such measurements as the speed of
the pressure rise (Kst), as well as the maximum pressure of a
dust explosion (Pmax), can assist bakers and equipment manufacturers to determine the proper level of protection needed
for the equipment.
The higher the Kst value, the greater the speed at which
a dust deflagration can build, according to Mr. Stricker.
Granulated sugar may be rated the lowest level on the ST Class
system chart, which the US Chemical Board uses to rank explosion risks, but others like starches may have a ST2, or moderate, rating while materials such as aluminum powder get the
highest risk or ST3 rating.
In addition to relying on the ST Class chart for determining
a dust's deflagration index, technicians can select from a variety of test kits to determine a dust's explosive potential.
Bakers and millers, however, should exercise caution in using published Kst values, according to Lisa Arato, sales engineer, Zeppelin Systems USA, Odessa, FL. They simply don't
tell the whole story regarding the raw material parameters and
characteristics that bakers are actually dealing within inside
their plants.
"This value should be based on the actual particle size, moisture content and chemical properties of the ingredient after it
has gone through the process," Ms. Arato explained. "You can
look up a Kst value for any ingredient or find it on the Internet.
However, that doesn't necessarily mean that it's the ingredient
that you're using as they come from different sources and may
tend to degrade and get smaller after going through the conveying lines. You're not going to be able to have that exact Kst
value that you need unless you run through a test that determines what you are going to see out in the field, which is difficult to replicate.
"You can take granulated sugar and test it, and it won't ignite," she continued. "But then you can take that granulated
sugar and run it through a conveying system, and the particle
size becomes a lot smaller. In a high-concentration dust cloud,
it will ignite easily. Those are two very different conditions."
Specialty ingredients such as those used in gluten-free products - especially if they are mishandled - can pose a higher
risk than flour.
"If you manage things correctly, they're not a problem.
They're not dangerous, but you need to take care in handling
some ingredients, especially gluten-free ingredients like corn
starch, rice starch or rice flour - all of which can be a potential
issue if not handled correctly," Mr. Hunter said. "If you design a
system for flour and change it over to rice starch and you don't
do a risk assessment to see if there are any changes that you
need to do, then that potentially could introduce some risk."
According to OSHA, particles smaller than 420 microns are

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