Food Protection Trends - July/August 2021 - 441

INDUSTRY PRODUCTS
Food Processing: Selecting a Conveyor to Minimize
Dust Explosion Risk from Cablevey Conveyor
In food processing, powder or bulk solid products can
combust, including grains, flour, and sugar. A key factor in
determining dust explosion risk is the product's sensitivity
to static electricity discharge in specific concentrations
and fuel-to-air ratios, as well as its sensitivity to ignition in
ambient air or processing conditions.
Static electricity can ignite a combustible dust cloud inside
a food processing conveyor system if the minimum ignition
energy of the dust is very low. Powder and dust conveyed at
high velocity speeds through metal pipe or ducting can build
up an electrostatic charge in the dust and potentially ignite.
Because static charge can accumulate at different points in
the system, the equipment should be fully grounded to earth
so it does not discharge into the line.
In food processing conveyor systems, dust explosion
hazard is greater at connection points such as inlets,
outlets, and ducts, where powdered product is transferred
into bins, hoppers, and containers, potentially causing a
dust cloud to form.
Conventional open mechanical conveying systems,
which utilize many moving parts, can become an ignition
source. Bearings and out-of-alignment belt conveyors can
be problem areas if they cause sparks or generate heat
from friction.
Although some conveyor systems, such as pneumatic
powered equipment, are enclosed, using high-velocity air
can also potentially create a " dust cloud " inside the tube, as
well as outside on its exit, although dust collectors and filter
receivers can reduce this effect.
One solution is selecting a conveyor, such as a tubular
drag conveyor, that conveys powdered material more slowly
and gently. Tubular drag conveyors are enclosed systems
that utilize a coated, flexible stainless-steel drag cable pulled
through on a loop.
Because tubular cable conveyors do not suspend
transported powders within high-velocity airstreams like
pneumatic conveyors, this imparts " less energy " into the
conveyance, which reduces the risk of a dust explosion.
Unlike other conveyor systems, tubular cable conveyors
operate on low horsepower with less heat and friction,
using energy-efficient, variable-speed motors of less than 5
HP each.
Cablevey Conveyors
+1 800.247.3344
Oskaloosa, IA
www.cablevey.com
With tubular cable conveyors, solid circular discs (flights)
are attached to a cable, which pushes the product at low
speed through the tube without the use of air, reducing the
potential for dust cloud formation and preserving product
integrity. The systems can convey up to 2000 cubic feet per
hour (56m3/hr.) of powders, granules, etc. with numerous
layouts using multiple inlets and outlets.
Without high-speed contact or scraping, the lower speed,
lower energy motors of tubular drag conveyors also reduce
sparking risk. Also, the slower velocity reduces any friction
and heat generated to well below an ignition point, limiting
it about 10 to 20°F above ambient temperature.
July/August Food Protection Trends 441
http://www.cablevey.com
Food Protection Trends - July/August 2021

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