Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/708006
AGGREGATES MANAGER / July 2016 33 action on the surface of the pulley. Wing pulleys are typically used in tail pulley applications to reduce the build up of material between the belt and pulley. Trapped materials fall through the paddle-like formations of the pulley. Lagged winged pulleys are used in ap- plications with abrasive material present on the return side of the belt. It is natu- ral, under these conditions, for the wing tips to wear prematurely. The rubber lagging will add life to the pulley. Shafting is commonly considered to be a part of the pulley assembly since the strength and rigidity of the assem- bly depends on both of these compo- nents. When choosing shaft diameter, it is important to consider both the shaft diameter required for strength and shaft diameter required for defl ection. Depending on the pulley assembly, either strength or defl ection may be the deciding factor of shaft diameter. Belt cleaners Carryback is the fugitive material that sticks to the belt after the belt passes over the head pulley and, subsequent- ly, creates fugitive material piles along the underside of the conveyor. Fugitive material is a costly problem, considering that many maintenance hours are spent cleaning fugitive material piles. In order to correct carryback, a belt cleaner is used. This is usually a form of wiper or scraper device mounted near the discharge (head) pulley. A common type of belt cleaner is the pre-cleaner. This is often referred to as the primary cleaner and functions by scraping off most of the carryback leaving only a thin layer of fi nes on the belt. The pre-cleaner is mounted on the face of the head pulley just below the discharge trajectory. This allows the material scraped from the belt to fall with the discharge materials. Multiple cleaner systems are the preferred method for eliminating carry- back. The multiple systems consist of a pre-cleaner and one or more secondary cleaners. In addition to the improvement in belt cleaning, multiple belt clean- er systems increase the time interval between scheduled maintenance times. Belt cleaners should be positioned as close to the head end as possible. Secondary cleaners are designed to remove the thin layer of fi nes left by the pre-cleaner. It's best to place the sec- ondary cleaner in contact with the belt while it is still against the head pulley. This enables the cleaner to scrape against a fi rm surface. There are several types of belt cleaners available to eliminate carry back. The brush type can be driven by the pulley motion or motorized. This type is effective on dry materials, as the bristles of the brush sweep the belt clean. The disadvantage to brush type cleaners is the potential for build up on the brush's bristles. Pneumatic type belt cleaners send a stream of air across the face of the pul- ley to blow off the carryback materials. They are best utilized when moving dry materials. The disadvantages of the pneumatic cleaners are the expense of the continual air stream, and the cre- ation of airborne dust, as the carryback is not deposited in the discharge pile. There are two styles of wash-type cleaners that use water to clean the belt. The fi rst is a system that sprays a misting of water on the belt in order to make the scraping process easier. The second type uses a high-pressure wash to completely remove carryback. Problems occur with these types of cleaning systems with the removal of the sludge that is created. However, in some cases, the water-material mixture can be returned to the material load. These sys- tems also have the potential for trouble under cold operating conditions. Return belt cleaner systems, also known as v-plows, are used to prevent large objects and tramp iron on top of the return belt from damaging conveyor components. A low-pressure mechanical scraping is used to remove the material from the belt. Maintenance is an important part of the life span of any piece of equip- ment. The harsh operating conditions experienced by aggregate conveyor systems not only increase the need for proper maintenance, but also create a need for design considerations that facilitate proper maintenance. In many cases, proper design considerations may reduce the cost and time involved with conveyor maintenance. AM The ideal transfer point is designed to load the belt in the center and at a uniform rate. Article courtesy of Superior Industries.