World Grain - November 2023 - 42

GRAIN OPERATIONS
Continuous housekeeping and sanitation
(regular cleaning of the elevator), and
regularly scheduled bearing service
should be top priorities at all grain
elevators and at flour and feed mills.
tion duct; static electricity; a cigarette lighter or lit
cigarette; a cutting torch or welding; metal sparks
from a grinder; metal to metal sparks; a dropped tool;
lightning, etc.
All the elements for a grain dust explosion are present in a
grain handling facility. Oxygen and confined spaces are most
difficult to control. This leaves eliminating ignition sources
and controlling dust through material handling techniques and
housecleaning as the important variables in eliminating dust
explosions.
Additionally, low relative humidity weather conditions are
thought to be a major factor in explosions
where static electricity may have been the
ignition source and where the grain dust was
very dry.
Minimum explosive concentration
The minimum explosive concentration
(MEC) for grain dust, grain flour, or ground
feed ingredients varies according to the particle
size (smaller particles are more powerful)
and energy (caloric) nature of the product. Extracted
flour from wheat, oats, and corn may have different explosive
energy than wheat, corn, sorghum, milo, and oat dust. Corn
starch is considered one of the more volatile and powerful
grain products, but all grain dust and flour should be considered
as very dangerous.
A Texas A&M University dust control scientist suggests
that the MEC range is about 50 to 150 grams per cubic meter,
depending on the type of dust and the size of particles.
This equates to the same MEC level used by the National
Grain and Feed Association (NGFA). The NGFA states that
Guidelines to minimize grain dust explosion conditions
Listed below are grain dust control
and prevention procedures. All elevators
and mills should be doing
item number one, housekeeping
and sanitation, for elevator safety
and worker health, as well as for integrated
pest management (IPM)
purposes. It is the most important
safety practice in any elevator or
mill.
* Maintain a rigorous housekeeping
and sanitation program
inside the grain elevator
structure. Keep grain dust
cleaned up in all working areas
of the elevator.
bearings, and on belt conveyor
drive and idler bearings.
* Install belt rub sensors inside
bucket elevator leg casings to
detect belt misalignment to
prevent friction heating.
* Maintain a periodic (weekly
or bi-weekly) bearing temperature
monitoring program.
Document periodic bearing
temperature
readings
and
* Implement a weekly or biweekly
(or as specified by the
manufacturer) bearing lubrication
program, based on the
bearing manufacturer's specifications.
*
Use a food-grade mineral oil
spray system on grain during
transfer and loadout.
* Install bearing temperature
monitors on leg boot, head,
and knee pulley shafts, on
horizontal drag head and boot
42
compare with previous readings.
A substantial bearing
temperature increase (10°F to
20°F or more in a week or two)
may indicate bearing failure
and the need to replace the
bearing.
* Replace steel cups with plastic
cups in elevator legs.
* Use anti-static belting material
in legs and horizontal belt conveyors.
*
Install quick-opening cleanout
doors on leg boot side panels
for grain and dust cleanout.
* Install dust aspiration systems
at grain transfer points or ventilation
systems in tunnels and
galleries with open conveyors,
and truck dump pits where
dust accumulation is a problem.
*
Install dust aspiration or suction
ventilation systems on
inside enclosed legs and conveyors
to keep suspended
dust below MEC levels.
* Clean out dust collectors and
change filter bags at intervals
recommended by the manufacturer.
*
Clean out dust cyclone collector
holding bins at scheduled
intervals.
* Install dump pit baffles on truck
dump pits to provide a major
reduction in airborne dust during
dumping operation.
* Incorporate explosion relief
panels and devices in elevator
design.
* Install explosion proof electrical
outlets and equipment in
sensitive areas.
* Train employees on the dangers
and prevention of dust
explosions.
November 2023 / World Grain / World-Grain.com
http://www.World-Grain.com
World Grain - November 2023

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