ARAMID IN CONVEYOR BELTS EXTENDED LIFETIME, ENERGY SAVINGS AND ENVIRONMENTAL EFFECTS

In recent years, aramid fabric as reinforcement in conveyor belts has gradually found its position among the traditional textile and steel cord reinforcement materials. The main arguments for this trend are enhanced lifetime and energy savings. Aramid has already been in use for more than three decades in some niche applications such as phosphate mines and steel production plants because of its corrosion and heatresistant properties. The background of aramid as reinforcement material is briefly described here. Practical examples are reported, demonstrating increased lifetime, which consequently reduces maintenance and maximises output. In mining operations, the transportation of minerals and overburden accounts for a significant share of energy consumption and CO2 emissions. Aramid in conveyor belts reduces the weight of the belt and lowers the system rolling resistance. This leads to energy savings and lower CO2 emissions. With the Customer Benefit Model, an eco-efficiency tool, quantitative proof is provided that saving the environment and financially sound business practices can go hand-in-hand. The potential energy saving by using aramid in the carcass and as an additive in cover compounds is an input parameter for the Customer Benefit Model. An energy saving calculation tool, based on DIN 22101, has been developed and will be explained in this paper. The model uses a combination of Jonker’s and Lodewijks’ theories.

BACKGROUND The properties of aramid will only be briefly described here, since these have already been covered previously at Beltcon by Arts and Lodewijks. For the sake of completeness, the relevant details are summarised. Poly-paraphenylene terephthalamide, also known as aramid from 'aromatic amide', is a very strong and lightweight synthetic fibre. It has a high modulus, is thermally stable, and highly impact and chemically resistant. It can be used in conveyor belts in two different ways: 1. as aramid-reinforcement fabric in the carcass 2. as a chemically treated aramid-based additive to the bottom cover compound in order to lower rolling resistance.

For the carcass, the so-called straight warp fabric construction is most commonly applied. A schematic view of the fabric embedded in rubber is shown in Figure 1. It consists of aramid cord in the warp direction, polyamide 6.6 in the weft direction, held together by a polyamide binder yarn in the warp. Similar to the commonly used textile fabric (EP), the aramid fabric is treated with a Resorcinol-Formaldehyde-Latex (RFL) dip formulation to obtain sufficient adhesion between the fabric and skim compound.

The key advantage of using an aramid-based fabric over a steel cord carcass is its lightness, as shown in Figure 2. Aramid fibres have a density of just 1.44 g/cm3 and are thereby five times stronger than steel on a weight-to-weight basis.

Compared to the textile materials, polyamide 6.6 and polyester, the high tenacity and heat resistance of aramid are the most important parameters to consider, since they allow the use of a single fabric layer reaching high strength classes up to at least 3 150 N/mm.