As will be seen below, troughed belt conveyors are only one of the types of belt conveyors available in the market today however, the troughed belt conveyor takes numerous forms and is used in many different applications with tremendous success.
It is important to draw a distinction between bulk handling of materials and unit handling. The former refers to the transportation of particulate product(s) on a continuous basis for example, the conveying of lumpy ore from a mine to a processing plant or for transporting coal from a stockyard to a bunker above a crusher.
'Unit handling' on the other hand is generally described as discontinuous as this involves the transportation of for example, packed boxes, filled bags of cement and so forth.
Troughed belt conveyors as described in this Handbook refers to conveyors which are used to convey product in bulk.
A brief introduction to troughed belt conveyors and factors which affect the selection and design of conveyors is provided below.
Functional Description (refer to figure below)
A troughed belt conveyor comprises an endless, rubberized flat belt (a) suspended between pulleys at either end and supported along its length by a number of rotating idler rollers (b). The belt is driven via one of the pulleys (usually the head pulley (c)) and the tension in the belt is maintained by using a sliding pulley (d) which is tied to a gravity take-up unit (e).
The material (f) is loaded onto the conveyor at the tail-end via a chute (g) and is transported along the carrying-side (h) to the head-end where it discharges into a discharge chute (i) which guides the product onto the downstream equipment.
Impact idlers (j) are located at the loading point to support the belt where the load impacts onto the belt as it is dropped down the loading chute.
Once the material has been discharged from the carrying belt, the return belt (k) is guided back to the tail pulley on return idlers (l).
The impact, carrying and return idlers are spaced at different intervals. On the carrying-side, the mass of the belt plus the load conveyed is greater than the mass to be supported on the return-side and thus, for the tension in the conveyor belt (by the take-up and induced by the drive unit), the idler spacing is selected accordingly. This 'sag' in the belt between the carrying and return idler sets must therefore be designed on the basis of the heaviest load that the conveyor is to transport.
Snub pulleys (m) are sometimes incorporated into the design of a conveyor in order to increase the angle of wrap (n) of the belt on the drive pulley. The greater wrap angle on the pulley allows more power to be introduced into the belt as is passes around the drive pulley without slip occurring. In this way, fewer drives are needed on longer conveyors or conveyors with high conveying loads.
Anatomy of a Troughed Belt Conveyor
There are many possible variations in the design of a troughed belt conveyor depending on the purpose and duty for which the conveyor is being designed. Similarly the choice of individual components, features and accessories found on a conveyor should be selected on the basis of the functions which have to be performed by the conveyor.
At this point in the Beginners Guide the learner is introduced to the different components and basic arrangement and features which are found on the majority of troughed belt conveyors throughout the world.
In this section a graphic image of a typical troughed belt conveyor is provided together with detailed images and photographs of specific components. The learner should also study the nomenclature and terms used by engineers and designers when describing troughed belt conveyors.
Types of Belt Conveyors
The term 'troughed' belt conveyor originates from the form of the carrying belt within the supporting idler sets and differentiates this conveyor from alternative bulk handling belt conveyor types which include 'Pipe', 'Sicon', 'Sandwich', 'Pocket or Sidewall', 'Cablebelt', 'Square', 'U-con' conveyors, etc.
Examples of these different types of conveyors can be seen below.
The type of conveyor to be used in any particular application depends on a number of factors including the conveying route, properties of the material to be transported, environmental considerations etc. These are dealt with in more detail in the section "Conveyor Selection Criteria" of this Handbook.
Applications for Troughed Belt Conveyors
Troughed belt conveyors are used extensively throughout the bulk materials handling industry and examples of applications where this type of conveyor is commonly used are listed below (click thumbnail for images) :-
Short plant conveyors - horizontal, inclined or declined.
Long overland conveyors - straight or curved.
Boom conveyors - stacker-mounted, slewable.
Elevated conveyors in gantries.
Inclined mine shaft conveyors.