Many types of conveyor belts are used today in a variety of industries. You can find lightweight belts in the food industry, package handling, agriculture, airport baggage handling, automotive, warehousing, and a number of other areas. Heavyweight belts are found in industries such as aggregate, grain, wood products, metals, minerals, ores, and power plants.
Conveyor belts are typically produced in slabs 60 or 72 inches wide and in lengths from 500 and 1000 feet. Distributors usually purchase these slabs and slit them to width, and sell smaller belts to satisfy their customer’s requirements.
Most conveyor belts are a combination of tension bearing warp yarns, lateral fill or weft yarns, and rubber or plastic components. This consists of a carcass that includes textile or metallic tension bearing elements that are impregnated with rubber or plastic material, and also have rubber or plastic covers on both sides.
Components of Conveyor Belts
The purpose of textiles in conveyor belts is to provide both strength for tensioning and strength for handling the load. Textiles add rigidity and improve mechanical fastener retention to the belt as well.
The textiles used in conveyor belts are generally synthetic, with polyester and nylon being the most common. However, natural fibers such as cotton and wool can also be used. Each fiber has its own set of characteristics which may make it more suitable for a particular application.
Almost all textile carcass structures are woven in one of several types of configurations, including, but not limited to, plain weave, satin weave and twill weave. Some belts are made with non-interwoven parallel cords, and some solid-woven cotton belts are manufactured and used without any elastomeric impregnate.
The Elastomers or Compounds (Rubber or Plastic)
The rubber or plastic components in the carcass serve to impregnate and bind together the textile structures. Most conveyor belt textile structures are treated with an adhesion promoting chemical material before the elastomer compound is applied to them. The types of rubber used may be natural and/or synthetic. Plastic usually means thermoplastic and refer to PVC or urethane. Thermoset urethanes are also used.
The compounds used in conveyor belts serve to protect the textile against wear and abrasion in the conveyor system. Compounds also provide adhesion to layers of textiles and prevent the textiles from wearing against each other as the belt flexes around the conveyor system.
Conveyor belt covers add a cushion to reduce product impact, provide a sacrificial wear surface and protect the carcass from the abusive materials being conveyed. Covers may not be included on belts where a low coefficient of friction is needed. A variety of rubber compounds are available, designed for specific service conditions and materials to be conveyed. These include wear resistance, elevated temperatures, oil resistance and fire resistance. Some rubber compounds made specifically for resistance to oils, for example NBR (Nitrile Butadiene Rubber) come in varying degrees of oil resistance. Common compounds found in conveyor belting include natural rubber, SBR, Buna-N, Neoprene and Butyl.
The Carcass Construction
The belt carcass maintains tension and supplies structural strength, resistance to stretch, flex fatigue and breakdown due to high speed flexing, as well as shouldering all the work in supporting and pulling the load. The carcass consists of multiple plies of rubber impregnated fabric, bonded together with friction and skim coats. Metallic tension components used in conveyor belts usually are individual parallel steel cables. There are however, woven steel cord structures that are used to a very limited degree. Additionally, some low tension conveyor belts consist simply of a sheet of a strong, high modulus, wear resistant plastic.
Fabricated belting consists of a wide variety of value-added profiles and/or operations to manufactured flat belting. Fabricating belt can improve the conveyor’s ability to perform functions it would otherwise be unable to do.
Simple fabrications may require nothing more than techniques to vulcanize splices, install mechanical lacing, or punch holes for anchoring attachments. More complicated fabrication uses heating processes to melt or fuse profiles like thermoplastic guides, cleats, and sidewalls onto belting. Rubber profiles are also vulcanized, either by heat and pressure, or by chemical bonding. Such profiles may be more elaborate and include herringbone chevron styles, transverse cleats, v-guide tracking configurations, curbed flanged edges, or angular profiles to prevent material roll-back from steep angles.
Special fabricated belting with complex designs include high angle steep incline conveying and profiles blending technology from both vulcanizing and bonding of two or more surfaces together.
Corrugated sidewall belting, with or without cleats, are popular fabrications of growing importance and wide-spread use. Together with molded belting operating at extreme speeds, high heat, and tensions, fabricating experts make belts available which can handle very complicated tasks.
Fabricated belting is found in food and industrial markets. They may be used in either light or heavy duty applications and may be made from common materials or exotic rubber-like compounds or thermoplastics.