The carcass is the most important part of a conveyor belt, as it has to absorb the tensile stresses imposed on the belt to convey the material and to comply with all mechanical and thermal requirements. The purpose of the rubber covers is to protect the carcass. The quality of the covers depends on the application of the conveyor belt. The carcass consists of a number of plies of reinforcement, which are separated by rubber layers.
There is a range of basic materials suitable for belt reinforcement. Over a period of time the most suitable all-round combination has proven to be Polyester (E) yarns in the warp (longitudinal) and Nylon (P) yarns in the weft (transverse) directions. Belting textiles using this construction have been designated as EP fabrics.
EP fabrics are especially suitable for absorption of high tension and impacts. They are highly chemical resistant, impervious to moisture and have low elongation at high working stress. The fabrics are classified according to their longitudinal tensile strength. Fabric strengths of 63 N/mm up to and including 630 N/mm are available.
The top cover (upper side of the belt) provides protection for the carcass. Selection of cover quality, thickness and profile depend on the material to be conveyed and the working conditions.
The surface of the top cover can be smooth or profiled in accordance with the material conveyed and the conveyor’s angle of incline.
The thickness of the top cover depends on the kind of materials carried and the service conditions (type of load, incline angle, fall height, etc.). The thickness ratio between top and bottom cover should be 3:1 at a maximum.
The bottom cover protects the inner part of the carcass. Its thickness is about 30 - 50% of the top cover thickness. For use on slides, the bottom cover consists of low friction fabric.
Conveyor belts can be supplied with moulded (rubber) edges as well as with cut (sealed) edges. Full synthetic carcasses do not require moulded edges except for chemical resistance.
The table gives a guide to the minimum cover gauge, which should be used for various applications.