Motorised pulleys for conveying systems
Summary: The many individual operations involved in the processing of coal, ores, rock and gravel, as well as soil, sand, salt, potash and fertilisers, necessitates moving hundreds and thousands of tonnes of dusty, abrasive, corrosive and sometimes wet materials from A to B every day. Motorised pulleys are ever more frequently being used for this purpose, since their design principle makes the conveyors more robust and more durable than if they were equipped with conventional motors. Rulmeca is one of the world’s leading manufacturers of such belt-conveyor drive systems and belt-conveyor pulleys for all types of bulk materials.
Conveyors are classically constructed with motors flange-mounted on the sides. This design principle is simple, and can be implemented using motors from manufacturers that fledgling engineers are already familiar with from their lectures. In many cases, however, these motors feature cast-iron or steel housings with cooling fins that can become clogged when bulk material is being handled, thereby jeopardising the service-life of the motor. If these fins are not kept clean and serviced at regular intervals, the availability of the conveyor will suffer; it will be necessary to replace the motor, and the entire system will be “down” for this time.
The motor is concealed in the tail pulley
Motorised pulleys protected in accordance with IP66/67, on the other hand, provide a compact and entirely enclosed drive unit for belt-conveyor systems. They integrate the motor and gearbox inside the hermetically sealed drive pulley, which is needed at the tail end of the belt conveyor anyway (Fig. 1). This makes them immune to all possible environmental influences, such as dust, water, oil and lubricants, as well as other harmful substances. Thanks to this robust design, they can generally be operated for years on end without any maintenance whatsoever. In addition, components are also actively saved. Due to the gearbox geometry, motorised pulleys also offer greater energy-efficiency than conventional motor/gearbox combinations, signifying that, all in all, there are many reasons for using motorised pulleys. The highest demands are made during the processing of salt, potash and fertilisers where abrasive and corrosive influences are particularly strong.
Protection against corrosion and abrasion
Protected even in case of occasional flooding
Protected even against aggressive chemicals
An important component even without the integrated motor
Quality also optimises shareholder value
Not every conveyor needs such a high quality in the design of the pulleys. The quality of an idler pulley is, nonetheless, ultimately also decisive for relatively simple conveyors, since savings made in the year of investment in the pulley will frequently result in the need to obtain a replacement idler pulley in the following years, whereas a high-quality pulley can be operated for years on end without the need to purchase any replacement. An investment in a higher quality pulley thus pays off in as little as around 1.5 years. Not all suppliers to cement plants in Germany, for instance, have recognised this fact yet, since they concentrate more primarily on short-term shareholder value than on long-term perspectives. To this extent, there is greater need to catch up in Germany than in China, as far as “Made In Germany” quality is concerned, despite the fact that suppliers of such pulleys, including the Aschersleben-based company Rulmeca, are effectively located “on their doorstep”, and, in addition, continually introduce the latest innovations to the market. At the bauma 2019, for example, Rulmeca unveiled a “smart” pulley (Fig. 6) which is intended to make IoT-based monitoring of the temperatures of such idler pulleys possible. It is planned to achieve maturity for series production during the next year or two.
Even more energy-efficient and robust versions available soon
In order to boost the already extremely reliable continuous operation of bulk-materials conveying systems even more reliably, the bearings of the gearbox components have once again been optimised, thereby raising the already high mean time between failure (MTBF) of Rulmeca‘s new TM400 motorised pulleys even further.
The new TM400 generation of motorised pulleys will be available in series production from the fourth quarter of 2019. Users can convert to the new generation without any design effort, with the result that existing plants can also benefit from Rulmeca‘s new motorised pulleys if a motor replacement becomes necessary.
Conclusion
As the described examples have shown, the experience of bulk-material users in cement plants and salt mines, as well as in fertiliser production, are typical: large scale international plants are increasingly putting their faith in motorised pulleys for their conveying systems, since such pulleys are more robust last longer and, in addition, assure a greater level of protection against moisture, abrasion, corrosion and dirt. Some users still have to learn, even today, that high quality is also advisable in the case of conveyor pulleys.