Types Of Conveyor Belt Carcasses

Conveyor belting comprises two essential components: the inside carcass and the outer covers. The carcass serves as the belt's core structural element, tasked with supporting the load of cargo conveyed on the conveyor. Its primary function is to transmit the tension required to lift and move the loaded belt, while also absorbing the impact energy generated as material is loaded onto the belt. If the carcass fails to manage this initial impact energy, regardless of the belt-support system used, premature belt failure can occur. The carcass must be adequate to allow proper splicing techniques and strong enough to handle the forces that occur in starting, moving, and stopping the loaded belt. The carcass also provides the stability necessary for proper support between idlers and for maintaining alignment.

Most carcasses consist of one or more plies of woven fabric, although heavy-duty belting may integrate parallel steel cables to replace some or all of the fabric layers. Carcass fabrics typically feature yarns woven in specific patterns: warp yarns, running lengthwise parallel to the conveyor and bearing tension; and weft yarns, positioned transversely to enhance impact resistance, mechanical fastening, load support, and overall fabric stability.

Historically, conveyor belts utilized cotton yarns for textile reinforcement, often incorporating a breaker fabric between the cover and the carcass to improve cover adhesion and resistance to wear.

During the 1960s and 1970s, there was a shift in carcass reinforcement materials, with modern conveyor belts predominantly utilizing synthetic fabrics such as nylon, polyester, or their blends. These materials offer superior strength, adhesion, resistance to wear and abuse, fastener holding capacity, and extended flex life compared to traditional natural fabrics. In some specialized applications, fabrics incorporating aramid fibers are employed, providing exceptional strength, minimal elongation, and heat resistance. However, breaker fabrics are seldom used with these synthetic fabrics due to limited additional benefits.  

Types of Carcasses:

1. Multiple-ply belting

   Multiple-ply belting is usually made up of two or more plies, or layers, of woven cotton, rayon, or a combination of these fabrics, bonded together by an elastomer compound. Belt-strength and load support characteristics vary according to the number of plies and the fabric used. The multiple-ply conveyor belt was the most widely used belt through the mid 1960s, but today it has been supplanted by reduced-ply belting.

2. Reduced-ply belting

   Reduced-ply belts consist of carcasses with either fewer plies than comparable multiple-ply belts or special weaves. In most cases, the reduced-ply belt depends on the use of higher-strength synthetic textile fibers concentrated in a carcass of fewer plies to provide higher unit strength than in a comparable multiple ply belt. The technical data available from belt manufacturers generally indicate that reduced-ply belting can be used for the full range of applications specified for multiple-ply belting.

3. Steel-cable belting

   Steel-cable conveyor belts are made with a single layer of parallel steel cables completely embedded in the rubber as the tension element. The carcass of steel-cable belting is available in two types of construction. The all-gum construction uses only the steel cables and rubber; the fabric-reinforced construction has one or more plies of fabric above and/or below the cables but separated from the cables by the cable rubber. Both types have appropriate top and bottom covers. Steel-cable belting is produced using a broad range of cable diameters and spacing, depending primarily on the desired belt strength. Steel-cable belting is often used in applications requiring operating tensions beyond the range of fabric belts. Another application is on conveyors where, due to limitations in the distance the take-up system can travel, the belting cannot be allowed to stretch significantly.

4. Solid-woven belting

   This type of belting consists of a single ply of solid-woven fabric, usually impregnated and covered with PVC with relatively thin top and bottom covers. The surface of PVC belts is often rough on purpose to aid in conveying on inclines, but the rough surface makes belt cleaning more difficult. The abrasion resistance of PVC is lower than rubber, so some solid-woven belts are made with a combination of PVC core and rubber covers.