What is a conveyor belt?
Conveyor belts are used in material handling systems to transport goods or processed materials which can be light or heavy, abrasive, hot or frozen, extremely lumpy and complex powder or granular products of varying shapes and sizes.
Most conveyor belts are composed in two parts:
1) The carcass, through plied woven fabric or steel cord construction, which provide sufficient strength to handle the operating tensions and to support the load.
2) The covers, constructed of different rubber compounds with varying physical properties and chemical resistance to protect the carcass and ensure that the conveyor belt delivers an economical life span.
What is the Conveyor Belt Structure, Fabric Ply and Material?
In order to maintain the proper function of your conveyor system, it is important to understand the components that will facilitate the conveying of various product formations and their challenges without compromising the systems effectiveness and durability.
These systems can be 1000’s of metres long. One of the most vulnerable components is the conveyor belt, as it is exposed to extreme materials that are initially dropped onto it from various heights, speeds and directions. These materials then shift while being conveyed causing further abrasion or even cuts and tears in some of the most harshest environments in the world.
In order to counteract these disagreeable conveying conditions, the belt composition is multilayered. ASC belts are comprised of 3 layer characteristics:
- A resilient top ‘fit for purpose’ cover layer
- A layered fibrous, flexible tensile strength layer
- A ‘fit for purpose’ bottom cover layer
The carcass as shown in the above ContiTech fabric belting illustration should be designed with the ability to stretch and contract under pressure. Naturally high tensile strength elasticity and the ability to resist impact are essential carcass features. The carcass can be varying types such as woven with a warp and weft and with a blend of materials such as polyester, nylon, steel wire or in some cases cotton among others. For Contitech Melbourne, Victoria and surrounding states feel free to call us for advise andcompetative pricing.
The warp and weft for fabric conveyor belting have differing characteristics to assist with the belt’s resilience. The warp is made up of longitudinal cords which are fundamental for tension, impact resistance and elasticity. The weft serves as an integral set of transverse fibres, which resist cuts and tears but are also exceptionally flexible and allow troughing.
The belt decisive strength is measured in kilonewtons per metre which should be displayed with the number of plies in the carcass. For example a 4ply belt with a polyester warp and a nylon weft has a tensile strength of 1000kN/m. This measure is also known as a 4 ply EP1000 = a 4 ply PN250 where the strength of the actual individual plies are displayed.
Textile (Fabrics) for Belting:
Woven polyester, nylon plain and crows foot weave (CFW) are popular to ensure high tensile strength/weight ratio, required ﬂexibility as well as low elongation and high mechanical impact resistance.
Polyester offers great fatigue and abrasion resistance and is a more stable option than cotton or nylon, now utilised in 75% of belt manufacturing. With excellent mildew resistance, low water retention and great dimensional stability, polyester is now a popular choice for belt construction.
Nylon was an ideal replacement for cotton and was the first polyarnide synthetic fibre to be utilised in belting construction. The main draw-back of nylon is that it has a compulsion to absorb water to up to 10% of its own weight, thus making it unsuitable to be solely used in wet conditions as the dimension of the belt will alter. However it has a number of positive attributes:
- brilliant fatigue, impact and mildew resistance
- good resistance to abrasion
- good resistance to impact fatigue and strength.
Cotton was once the preferred option for belting, representing 80% of the market. It is now used as a very small percentage of belt construction as it is vulnerable to mildew infestation and has very poor durability when subjected to damp or wet conditions. In order to counter these shortcomings, synthetic fibres have replaced cotton as the preferred material. There are still cotton-based belts available, as cotton transmission belting from 2 ply ~ 6 ply ratings.
Crows Foot Weave is specifically woven to ensure that if the conveyor belt is ripped it will travel across the belt to minimise damage to the conveyor. This design ensures that the threads succumb to lighter warp which accommodates the heavier weft threads to attain preeminent levels of rubber penetration to strengthen the belt. This is often described as a 2×2 broken twill fabric weave with each warp thread interweaving with 2 weft threads to ensure greater belt durability.
Kevlar is made up of extremely strong fibres but tends to require a larger investment. Its incredibly robust aramid fibres are even tougher than steel! These fibres have immense thermal stability, durability against wear as well as impact and are non-flammable. They are so strong that the construction of the fabric only requires a single ply warp and weft to sustain the elongation for a straight warp belt and for belts below 1600 PIW. For higher tensions of 4500 PIW, the belt will require a multitude of plies.
Some glass fibre compositions are ideal for very high temperature situations of up to 730ºC. After this temperature, they will however begin to transform from their existing state. Generally, glass fibre is ideally suited to working at temperatures of up to 537ºC. This figure does not define a temperature at which they will begin to burn but more where flexibility and elongation are compromised, and large diameter pulleys will be necessary to preserve the belt integrity.
The Most Desirable Ply Composition
Synthetic ply configurations are the most favourable composition for most industrial textile types outside of heavy mining. Combinations of polyester (E) warp threads should be placed in a longitudinal direction and the transverse should be comprised wefts of polyamide (P). The industry refers to this synthetic construction as EP.
At All State Conveyors, we carry a wide range of Polyester/Nylon (EP) conveyor belts, which have been proven to provide a high level of product performance and are equipped with numerous rubber cover compounds and fillers to suit your conveying task.
Steel Cord Belting
ASC can supply steel cord or wire meshed reinforced conveyor belts as shown in the below ContiTech illustration. There are some advantages associated with these belts, for example they are particularly useful for high tension situations where the belt needs to transverse long distances and carry very heavy loads typically associated with mining. The steel wire formation has limited elongation and they have a very good ability to flex and retain its shape.
However, the main disadvantage is the weight of the belt and the amount of energy taken to mechanically dive the system and would typically used in heavy mining.
Conveyor Belt Covers
The Conveyor Cover is an integral component of your conveyor belt system. It safeguards the belt from wear by absorbing actions of abrasion, impact and temperature, all of which are designed to increase the longevity and working performance of your belt.
Cover Grade Qualities, Surfaces and Thicknesses
If the carcass is not protected by the cover it would be subjected to the following possibilities: abrasion, gouging, cutting, corrosion or chemical attacks from natural and synthetic solvents penetrating the carcass or even initiating a fire by electrical discharge or extreme heat.
There are a number of multi-ply covers with differing rubber compound compositions designed to protect the belt from the various hazards listed above, particularly at the point of loading. These covers are identified by their ability to resist certain hazards and would be stamped into the belt during the OEM belt manufacturing process.
There are a number of ways in which a cover is able to be finished to give the belt certain properties as follows:
- Flat and smooth so that it is easy to clean
- To boost carry traction and inclined capacity with cleating profiles
- Coloured compounds to meet specific industries such as food or pharmaceutical
- Chemical or heat resistance
The Cover Quality Does Not Always Mean A Thicker Cover
The primary purpose of the cover is its ability to resist wear and abrasion and is not necessarily governed by the cover thickness. In some cases, it is necessary to have a thicker cover especially when rock fall is being loaded against the direction of the belts running direction but this is not always the case. The top cover should not typically exceed a3~1 ratio in thickness comparison to the thinner pulley cover, which is not directly affected by the loading of rock aggregate or similar product formations, but the bottom cover must be in some way wear resistant as to travels over the support rollers and drive drum configurations.
Cover Rubber Compounds Characteristics
Covers are formulated with differing natural and formulated compounds to assist various industrial and manufacturing applications. Natural rubber, butadiene and styrenebutadiene are primary polymers used to manufacture various types and grades of industrial belting.
Covers are fabricated to meet the desired application, always with a primary polymer and a broad ranging mixture of modifiers and fillers, which develop the foundation for the conveyor belt cover characteristics.
All State Conveyors offer high quality textile conveyor belts with numerous ‘fit for purpose’ covers made from a variety of rubber compounds combined with various fillers to provide differing protection scenarios such as: heat, fire and electrical resistance: abrasion, cut, and gouging or oil and solvent resistant which are able to suit your conveying needs.
What is the OEM Belt Marking Protocol?
How Long Should a Belt Last?
A belt will last depending on a number of factors. These variables could mean the difference between it economically lasting for only a short period of time or for many years. If the original choice of belt is correctly made, the risk of belt damage will be minimised. However, if variables such as the materials being transported and the operational environment has changed, this can affect the belt durability. Therefore, it is very important to choose a belt cover composition, carcass and tensile strength appropriate for your situation.
All State Conveyors experienced belt specialists are able to help you to choose the right belt for your application and situational needs, and show you how to extend the life of your belt through proper maintenance and design improvements.
Are You Ready to Choose the Conveyor Belt That Suits Your Conveyor Task?
We are happy to assist with all of your conveyor tech questions. You can find and read further details of our stocked comprehensive range of Rubber Textile Conveyor Belts, click here or click below.