Hoppers

When the electrodes are rapped, the dust falls into hoppers and is stored temporarily before it is disposed in a landfill or reused in the process. Dust should be removed as soon as possible to avoid packing, which would make removal very difficult. Hoppers are usually designed with a 50 to 70° (60° is common) slope to allow dust to flow freely from the top of the hopper to the bottom discharge opening. Some manufacturers add devices to the hopper to promote easy and quick discharge. These devices include strike plates, poke holes, vibrators, and rappers. Strike plates are simply pieces of flat steel that are bolted or welded to the center of the hopper wall. If dust becomes stuck in the hopper, rapping the strike plate several times with a mallet will free this material. Hopper designs also usually include access doors, or ports. Access ports allow easier access for cleaning, inspection, and maintenance of the hopper (Figure). Hopper vibrators are occasionally used to help remove dust from the hopper walls. Hopper vibrators are electrically operated devices that cause the side walls of the hopper to vibrate, thereby removing the dust from the hopper walls. These devices must be carefully designed and chosen so that they do not cause dust to be firmly packed against the hopper walls, and thereby plug the hopper. Before installing vibrators to reduce hopper plugging, make sure they have been successfully used in other, similar industrial applications.