Sunday, April 9, 2017

Hazardous Area Heater Control Systems for Coal Hoppers and Conveyors

Explosion proof control system
Explosion proof control system.
A major hazard in coal burning utilities is the transfer and storage of coal due to the presence of highly combustible coal dust. Mitigating the risks of combustible dusts eliminate the potential for dust explosions. It is critically important that any coal handling or coal storage facility have access to experienced application engineers who understand the specific requirements when handling coal and managing coal dust.

Electric heat is very often used to prevent coal freeze-ups in hoppers and conveyors. The most common electric heaters used are are exterior mounted panel heaters with carefully calculated watt densities to keep sheath temperatures low. A less preferred solution is the use of tubular heating elements that may have higher sheath temperatures. Tubular heaters are usually clamped or stud-welded to the exterior of the coal hopper or conveyor chute.  In either case, a control system must be employed to maintain operating temperatures and to safely limit temperatures below dust ignition temperatures.  Since the presence of coal dust in the atmosphere is considered normal, the use of explosion proof housings, conduit, and wiring practices is required for these control systems.

Explosion proof control system
Internal view.
Hotfoil, a New Jersey manufacturer of electric hopper and coal handling heating systems,  designs, engineers, and fabricates custom control systems specifically for these applications. 

With decades of experience in hopper, conveyor, and tank heating systems they provide their customers with a single-source, turn-key, electrical heating and control system solutions provider. All products are 100% quality tested prior to leaving the facility, and an added plus is that they provide on-site start-up assistance.