A functional illustration of the REMBE Q-Box flameless vent. IMAGE: REMBE
REMBE Q-Box flameless explosion protection installed on covered conveyors. PHOTO: REMBE
Flameless Explosion Protection for Combustible Wood Dust When passive explosion venting is needed inside a pellet mill or in areas where conventional venting is unsafe, REMBE has a reliable solution. BY JERAMY SLAUNWHITE
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Slaunwhite
ood dust is not only a nuisance to industrial facilities but can also be deadly. Combustible wood dust can cause explosions in equipment and building compartments under specific conditions. The five elements of a dust explosion are: fuel, oxygen, ignition source, suspension of the fuel in a dust cloud and containment. Removal of one item eliminates the chance of a combustible dust explosion. Eliminating fuel, oxygen or the ignition source prevents combustion from occurring. Removing suspension reduces the rate of combustion and possibly
fuel ignition. If containment is not present, a flash fire or deflagration can still occur but pressure will not accumulate. It is the accumulation of pressure in a confined volume that can lead to catastrophic failure or an explosion. Among the various methods to protect against a dust explosion, deflagration relief venting is the simplest and most common. Deflagration venting consists of a designed weak point in the protected enclosure, typically a door or panel, which quickly opens at a predefined pressure. This allows the internal pressure and active deflagration generated by rapid combustion of dust to exit the vessel before accumulating and exceeding the enclosure failure strength. Deflagration vents are sized and selected by knowledgeable application specialists according to a standard such as NFPA 68 (Standard on Explosion Protection by Deflagration Venting). Deflagration venting is a reliable, passive method of explosion protection for exterior vessels located in unoccupied areas. Extreme care and caution must be considered with respect to the orientation of deflagration vents as the effects of successful explosion protection include rapid discharge of pressure and fireball from the vents up to as much as 60 meters. An open deflagration inside a facility not only poses a risk associated with fire and pressure discharge but also the potential of a secondary explosion on the building itself from residual dust layers.
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22 PELLET MILL MAGAZINE | ISSUE 3 2020
