The cost of the conveyor belt is one of the most significant capital expenditure items for many quarry operators, so it’s important to ensure the belt functions to its potential and delivers a satisfactory return on its investment.
However, during either non-operating or motionless periods for maintenance activity, when it is essential that the conveyor remains stationary, long-term risks can occur to the empty conveyor belt that go mostly undetected (see Table 1).
The damage comes from the environment and is caused by exposure to the sun’s ultraviolet rays.
{{image2-a:r-w:200}}UV radiation causes chemical reactions within the rubber, and the decline in the quality of the ozone layer in the upper atmosphere over the past several decades is allowing an increasing level of UV radiation to reach Earth’s surface.
Scientific research has shown exposure to UV radiation increases the acidity of carbon black surfaces and causes reactions within the molecular structure of the rubber. This can have several hidden consequences, such as surface cracking and a decrease in the tensile strength of the rubber. Conveyor belts that do not operate under shelter are especially prone to surface cracking, which can have very serious consequences in terms of the performance of the conveyor belt and its working life. There can also be significant environmental and health and safety consequences, especially when conveying materials with fine particles. These particles penetrate the surface cracks, allowing them to pass through any cleaner system, and discharge as dust as they are shaken out on the return run of the belt.
At first glance fine cracks in the surface rubber may not seem a major problem, but over time the rubber becomes increasingly brittle. Cracks deepen under the repeated stress of passing over the pulleys and drums and, if the conveyor has a relatively short transition distance, longitudinal cracks can also begin to appear. Again, surface cracking may not initially seem a cause of concern, but there are often hidden long-term effects.
{{image3-a:r-w:350}}One is that moisture seeps into the cracks and is able to penetrate the initial layers of the rubber conveyor belt, down to the actual inner structure of the belt. In multi-ply belts the fibres of the weft strands of the plies expand as they absorb the moisture, which in turn causes sections of the inner belt to contract (shorten) as the weft strands pull on the warp strands of the ply. This can often result in tracking problems that are difficult to pinpoint and for which no amount of steering idler adjustment can compensate. Other negative effects include scrapers catching on the cracks and tearing off parts of the cover. This damage is then difficult to repair because re-splicing can become more and more difficult as the adhesion properties of the rubber diminish.
Pre-emptive solutions
There are several important considerations when choosing a productive conveyor belt cover:
- Durability. Advancements in technology mean conveyor belt covers are now manufactured in a variety of optional engineered materials that are suitable to withstand the Australian climate extremes of heat, wind, humidity, rainfall and wind gusts. Materials such as galvanised, pre-lacquered aluminium and polyester fibreglass should be used.
- Lightweight. Ideally the installation of a conveyor belt cover system should require no additional support structure, to make it a better and more cost-effective cover option. Lighter weight belt cover options are simpler to manoeuvre, as well as easing the need for multiple labour resources during future maintenance tasks.
- Easy access. Ongoing access from either side of the conveyor should also be a consideration, so choose a belt cover that incorporates an adequate combination lock/hinge system.
Source: Kinder Australia