Output instead of carryback

Bulk material places particular high demands on conveyor belt systems. The transported materials are often heavy, pointed or sharp-edged and leave dirt and dust behind. Furthermore, open-air plants are exposed to weather conditions such as temperature fluctuations, humidity and solar radiation. Plant availability however must always be assured; downtimes cause enormous costs. Thus regular maintenance and cleaning is indispensable for smooth operation (Fig. 1).

One of the greatest challenges for operators of conveyor belt systems for bulk materials is the formation of carryback. At the transfer point, part of the conveyed materials does not fall from the belt, but adheres to it until it finally falls off of the return side of the conveyor belt. And it is no small part: according to a study of the Conveyer Equipment Manufacturers’ Association (CEMA), a carryback of 3 t occurs at a conveyor belt system with a width of 1.5 m and a belt speed of 250 m/min – each week. This amounts to annually 150 t of material – and this with just one single conveyor belt system. The financial penalties arising from this material loss are not to be underestimated.

1 Safety and cost factor

However, carryback is a problem even for other reasons. The additional weight of the material that adheres to the belt as well as the increased development of dust and dirt affects the function of the conveyor belt system. Moreover, pointed or sharp-edged materials can cause wear and damages to the system. Higher costs for maintenance and spare parts as well as increased downtimes are the consequences. Furthermore, bulk materials falling down from the return side of the conveyor belt present a considerable safety risk for employees. And last but not least, the remaining material necessitates increased cleaning which, in turn, is again associated with additional costs.

Thus operators of conveyor belt units try to minimize carryback as far as possible. The company Flexco Europe GmbH with its seat in Rosenfeld in Baden-Württemberg and the US-based parent company is specialized in components and accessories for conveyor belt systems. Conveyor belt cleaners are mounted at the materials drop of the conveyor belt where they free the belt from the adhering material (Fig. 2). They consist of a plastic or hard metal blade as well as of a spring tension system which provides optimal contact of blade and conveyor belt (Fig. 3). A system of various cleaners is frequently used: a head cleaner for the removal of coarse material as well as one or more secondary cleaners for fine cleaning. This increases the cleaning effect of the conveyor cleaners which, in many cases, are able to remove more than 90 % of the carryback. In order for the conveyor cleaners to tap the full performance potential, regular maintenance and cleaning is required.

2 Cleaning, inspecting, tensioning

Maintenance of the conveyor belt cleaner should occur according to a defined principle, which, in simple terms, can be summarized as: cleaning, inspecting, tensioning. Thus, cleaning of blade and tension springs should rank first, since both components can only work properly if they are free of material residues. A blocked tension spring may possibly not develop the required force to optimally retain the blade at the conveyor belt. Moreover, a clean conveyor belt cleaner is more easily inspected.

The inspection, i.e. the visual check, is the second maintenance step. It allows the quick and simple recognition of proper functioning of the conveyor belt cleaners. Furthermore, the employee who carries out the visual check can identify damaged parts and replace them. Special focus is on the blade wear: it should be regularly examined and documented how and in which time period the blade wears off and when it should be exchanged. This facilitates the planning of the required maintenance intervals and prevents intricacies, for example by ordering spare parts in time.

The third step is the tension inspection at the spring tension system and the probable correction. If tension is too low, the blade is not tightly attached to the conveyor belt and will remove less carryback. With the tension being too high, however, both blade and belt show more wear, which affects life expectancy of the entire conveyor belt system, since for the smooth operation of the system it is important to regularly check the tension springs, provided they are easily accessible. Therefore, conveyor belt cleaners from Flexco are designed to facilitate quick and easy maintenance work both at the blade and at the tensioning system.

3 Quality pays off

Care and maintenance of a conveyor belt system in general as well as of the conveyor belt cleaners in particular should be comprehensively planned and organized. Apart from the actual service, even other factors play a role, such as the choice of suitable components and spare parts. It is worthwhile paying attention to quality. Due to their high performance, long life span and low maintenance, high-quality parts pay off quickly. In particular the cleaner blade should be durable. The quality of the plastic or metal used is of vital importance. Moreover, the blade material must be adapted to the respective application. Flexco customers can choose between polyurethane, the efficient plastic material which is gentle to the belt, and the powerful and wear-resistant hard metal. In addition, polyurethane cleaners are available in various mixtures, for example, for particular resistance to heat and chemicals (Fig. 4).

Another aspect influencing blade wear is the material path on the conveyor belt, as the materials are hardly ever transported across the entire belt width. Accordingly, a conveyor belt cleaner which is also flush with the unused parts of the conveyor belt is inefficient and rather pointless. A blade however, which corresponds to the material flow width increases the cleaning performance and prevents uneven and unnecessary wear. In the long run, it is worthwhile to invest in an individually adapted solution.

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