The specification of the conveyor belt, or the type to be used depends on various factors; speed, width,
length of travel, inclines, components of its carriage etc.
The belt is made up of:
Fig:Self unloader discharging stone cargo
The belt carcase:
is the tensile structure of the belt between the top and bottom covers.
These are of various types: woven fabric – multi-ply, reduced-ply, PVC impregnated solid
weave, steel-chord cable etc. The functions of the belt carcase are to:
Fabric conveyor belt:
- Provide strength.
- Withstand tension.
- Provide lateral stability (cross rigidity).
- Ensure alignment on the track.
- Absorb the impact of cargo loading.
- Offer resistance to tear.
- Have ability to hold mechanical fasteners.
- Provide strength to spliced areas.
The carcase fabric is made of lengthwise yarns called ‘warp’ and
crosswire yarns called ‘wefts’. The ‘warp’ yarns are tension bearing, while the ‘weft’ yarns
provide cross rigidity and impact tolerance. The warp and weft yarns are interwoven in many
patterns: plain weave, straight warp weave, etc. with fillers and binders.
Usually has three or more plies (layers) of interwoven fabric which are
bonded together by elastic-polymer compounds. The number of plies (layers) determines the
belts load ability and tensile strength. These types of fabric belts are of an older design, and
have been phased out.
Uses weaves of high-strength synthetic fibres, nylon and polyester,
which are formed into special fabric designs forming solid weaves of higher dimension,
reducing the number of plies required. It incorporates thin layers of rubber between plies, or in
the special weave design of its fabric.
Solid weave belts:
are formed from a single ply layer of fabric yarns, woven into a special
design creating one solid weave, which is impregnated and covered with PVC. This type of belt
requires relatively thinner covers and is more abrasion resistant.
Steel-cord conveyor belts:
are belts whose carcase is made of a single layer, of numerous
parallel steel cables, embedded in rubber bonding. These steel cables forming the carcase are
the belt’s tensile members. The belt construction is of three types:
That which uses cables and rubber.
- That which is reinforced by transverse synthetic fabric cords and has one or more plies
- That which utilises transverse reinforcement including steel chords, or steel wires interwoven.
This type of belting is used where operating tensions are high, extension of the belt is
unacceptable, and the belt take-up has a limited travel area.
The life of the belt depends on:
Proper training to prevent wear of edges.
- Avoiding contact with heat, oil or chemicals.
- Proper maintenance of its carrying components, with replacement of broken rollers, idlers etc.
- Avoiding objects other than cargo falling onto the belt, as these will tear or gouge the belt.
- Avoiding spillages, as these will fall between the belt and its carrying components, and cause
damage. Carrying out inspections, edge repair and cold repair regularly.
- Adequate cover, and wetting of the belt when carrying out hot-work in its vicinity.
The elasticity and elongation of the belts:
- Elastic stretch occurs during acceleration or deceleration.
Structural stretch is the elongation of the carcase when warp fabric stretches under load, and
part of this stretch remains unrecoverable, resulting in an increase in the overall length of the
belt. It is therefore necessary that good practices such as maintaining the correct operating
tension, and gradual start-up without sudden shock loads, are carried out to increase the belt
The technical information supplied by the manufacturer must be referred to for the characteristics of
the belts in use, and also to make a choice when ordering the belts. The following information is
Cargo holds bulk flow gate, basket gate & non - consolidated feeder
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- Rated tension.
- Ply separation length.
- Load and troughing parameters.
- Type of splice.
- Gauge of covers.
- Pulley radii.
- Cleaning recommendations.
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