Belts: Driving forward efficiency
30 April 2014
By understanding the different ways in which belts are constructed to satisfy a range of performance requirements and applications, engineers can install components that will maximise efficiency and significantly cut maintenance costs, says Phil Burge, country communication manager for SKF
What do we find when we take a look inside a modern drive belt? Nothing special, you may think, but you’d be wrong. With drives expected to work reliably day upon day (and in some applications around the clock), the best manufacturers are investing their belts with some impressive technological innovations. These developments are based on performance feedback from all belt drives, from those in less demanding environments, to those that perform in especially challenging stop-start applications, as well as those working in extreme temperatures and/or contaminated environments.
Historically, the over-familiarity of belt-driven equipment – fans, pumps, blowers, conveyors – has frequently led to poor system design, incorrect installation and insufficient or inefficient maintenance, resulting in motor driven systems that operate at a level far below their optimum efficiency. However, the pressure to minimise energy consumption has changed attitudes, and encouraged the designers and engineers of today’s belts and drive chains to devise ever-more robust components that optimise power transmission. Exceptionally robust wedge belts are now available that have been tested under the most challenging conditions and, with excellent results having been achieved in applications such as mining, a series of special features have been incorporated into power transmission components.
To achieve these advancements, the beneficial properties of several different materials have been carefully considered, selected and successfully applied, in tandem with enhanced component design. As a result, failures caused by such common issues such as incorrect fitting, tensioning and pulley alignment can be significantly minimised.
A look at recent developments in the construction of the V belt, or wedge belt, illustrates how improvements in the materials and component design employed in the construction of belts can overcome common causes of failure and inefficiency. For example, the problems of elongation and incorrect tensioning have been addressed by belts with exceptionally strong polyester-coated internal tension members. Similarly, pulley groove wear has been reduced by the addition of abrasion-resistant cover fabric, which helps protect belts from friction heat if they slip out of position. Pulley groove wear occurs when a slipped V belt heats, hardens and wears the pulley groove into a U shape; a replacement V belt cannot transmit power effectively because there is now little contact between the V-shaped belt and the U-shaped pulley, and this leads to premature replacements of both components.
However, there are now belts available that can resist the elongation and friction heat that results in pulley groove wear. SKF Xtra Power wedge belts, for example, feature a multi-layer construction, with a tough polyester tension cord being embedded between layers of polychloroprene over a rubber base, and encapsulated in a long-life fabric coating. This advanced construction enables the belt to accommodate heavy tension loads with minimal elongation, resulting in the delivery of up to 40% more power than some traditional standard wrapped belts, with an energy efficiency capability of up to 97% and increased operating life.
When Belgian zinc recycler Rezinal discovered that belts needed to drive the fans in the plant were being replaced approximately every two months, we specified SKF Xtra Power Belts, which offered a lifespan more than 10 times that of the previous component to deliver two years’ service. The upgrade cut both environmental waste and plant costs, while Rezinal enjoyed the additional benefits of increased performance, reliability, safety and efficiency.
So, while drive belts are, and will remain, a familiar feature across the engineering industry, it is important to remember that there are some powerful innovations taking place beneath their deceptively simple surface. Like many other components in today’s engineering environment, drive belts have benefited from a range of improvements and the engineer who takes note of these changes and specifies the most appropriate components can reap the rewards of enhanced energy efficiency, reduced downtime and significant cost savings.