PROTECTION AGAINST EXPLOSION RISKS WITHIN FEED MILLS
By Kevin Spiess, EMEA Sales Manager for Explosion Protection at BS&B Safety Systems
Animal feed products processed within mills are common fuel for dust explosions due to the nature of their handling and storage. Any time that feed ingredients such as grain or meals are handled or moved, explosive dust can be generated.
EXPLOSION RISKS A fire or explosion results from ignition of combustible material (dust, gas or vapour) when mixed with oxygen in the air. When this takes place inside a grain silo, process or storage enclosure, the rapid rise in pressure could cause a potential violent explosion in milliseconds, placing personnel and property at risk. Dust that has settled on floors or walls can be thrown into the air
by a dust explosion, thus providing fuel for secondary explosions, which can cause more damage than the initial incident. A dust explosion can jump from room to room or from silo to silo. For example, one of the most dangerous areas for grain dust explosions is in the bucket elevator or conveying system linked to a silo. The grain is always in motion, so dust is constantly generated. In addition, sparks or smouldering particles from hammer mill operations may spread from the mill to other more vulnerable equipment.
PROTECTION MEASURES An explosion risk assessment will typically recommend a series of protection measures to be implemented. These range from investment in protection equipment to improvements in housekeeping to eliminate the build-up of deposits of combustible dust which may accumulate on beams in the factory. These may be disturbed by a primary explosion in the process equipment and result in a more severe secondary explosion.
Above: IQR venting system One option is explosion vents or panels which respond to the
rapidly building pressure of a deflagration (an expanding flameball which proceeds below the speed of sound in air) and opens to relieve this pressure. As the developing fireball passes through the open explosion vent, it is intercepted by a quenching module. A stainless steel precision mesh, retained by a frame, performs as a three- dimensional flame arrestor to stop the flame. This quenching module retains the flame and hot gases of a deflagration, as well as absorbing the pressure wave and the burning and unburned dust, as it passes through the explosion vent.
The effects of accidental fires or explosions can be devastating in
terms of lives lost, injuries, damage to property and the environment, and to business continuity.
PAGE 36 JANUARY/FEBRUARY 2014 FEED COMPOUNDER
BESPOKE SYSTEMS A bespoke spark detection and extinguishing system is available for the feed mill industry, designed to detect sparks, glowing embers and hot particles that might become the ignition source for a fire or explosion if allowed to travel on through pneumatic ductwork and conveyors towards other material handling equipment. By preventing sparks, embers and hot particles from reaching dust
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