The selection of the conveyor belt must also ensure that the full load of material for which the conveyor has been designed can be supported on the belt, as the belt spans between two idler sets. The following table is a guide to the minimum number of plies considered necessary for a correct load support, based on a belt sag between idlers being limited to a maximum of 2% of idler span.

Troughability of fabric belt

In addition to the selection of a belt based on the minimum number of plies, the stiffness of a fabric belt across its width is affected by the number of plies in the belt i.e. more plies result in a stiffer belt. If the belt is too stiff, it will not stay correctly in the troughed idler sets (see example below) in an empty condition. This often results in misalignment of the belt relative to the conveyor structure. The following table indicates the maximum number of plies, which a fabric belt should have, to ensure the correct troughability and belt alignment.

PULLEY LAGGING

There are primarily three categories of lagging, which are used on pulleys and they are described below: Rubber lagging is applied to pulley shells in order to improve the friction between the pulley and the belt. Conveyor drive pulleys are often supplied with diamond grooved lagging. Ceramic lagging or lining of a pulley is used in instances where the pulley operates in extremely aggressive conditions. An example of such conditions are the pulleys on a bucket elevator, where the pulleys operate within the enclosed elevator housing and material cannot be prevented from becoming trapped between pulley shell and belt.

GENERAL THEORETICAL DESIGN GUIDELINES

All belt conveyors shall be designed according to the applicable guidelines (DIN, CEMA,ANSI).From experience, see some initial characteristics of bulk material, density, physical conditions etc.

BELT SPEED

A number of factors should be considered when determining the correct conveyor belt speed. They include the material particle size, the inclination of the belt at the loading point, degradation of the material during loading and discharge, belt tensions and power consumption.