(April 15, 2011)

Belt drives are key to numerous manufacturing applications but, like most production-critical components, they are increasingly under the spotlight with regard to the need to improve efficiency and total cost of ownership.

The choice is typically between v-belts and synchronous belts, although alternatives to v-belts which claim to be ‘maintenance-free’ are becoming more and more widely available. However, like all components, belts will only perform well if they are correctly specified, installed and commissioned. The focus should always be on reducing total cost of ownership, which means that maintenance costs must be considered alongside initial purchase costs.

The first key decision is to choose the correct belt for the application. While v-belts are widely used and generally reliable, synchronous belt drives are more energy-efficient and therefore offer a cost-effective method of improving overall system efficiency in many applications – particularly as energy costs continue to rise.

However, it is perhaps in the area of maintenance where synchronous belts offer the most pronounced benefits. While v-belts need to be run in for 24 hours, retensioned, and then be checked typically every 2000 hours – with the associated downtime costs - to deliver optimum performance, synchronous belts require minimal maintenance and retensioning, with downtime significantly reduced as a result.

The latest synchronous, high-performance, Poly Chain carbon belts from Gates have also been developed to offer far greater power-carrying capacity than was previously achievable along with exceptional flex fatigue resistance, enabling them to bend more easily around pulleys. These products offer a typical 5 per cent energy efficiency advantage over v-belt drives. It is worth noting that in ‘stop-start’ applications an inverter drive or soft start will also be needed.

Where synchronous belts are not an option, Optibelt offers a range of ‘maintenance-free’ v-belts which offer significant advantages over traditional v-belts. Red Power belts boast a range of unique features including high-strength polyester cords, meaning minimal permanent stretch; transversely orientated fibre-filled rubber, supporting tension cords so they do not sag into the groove; and a highly abrasion-resistant outer jacket which helps reduce tension loss due to wear. They can generally be used as a direct replacement for standard belts with no need for pulley changes, and can be expected to significantly outlast conventional v-belts, transmitting up to 40 per cent more power, and maintaining up to 96 per cent efficiency without retensioning.

Cost saving using synchronous belts

To estimate the potential energy savings achievable through changing standard v-belts to Poly Chain carbon synchronous belts requires calculation of the motor efficiency based on its kW, the cost of energy, and the hours per year that the system will be operational. For a system based around a 30kW motor running at 1500rpm for 8736 hours per year at an energy cost of £0.06 per kWh, fitting a high-performance Poly Chain carbon belt drive will deliver an annual energy saving of around £940, and a saving of more than seven tonnes of CO2.

The savings are even more marked when larger motors are involved. One company in the water sector which replaced the v-belts with Poly Chain carbon belts on a 75kW four-pole aeration blower reduced its energy usage by more than £2,000 per annum, or around 6.7 per cent, equating to nearly 16 tonnes of CO2.

Installation and commissioning

Once specified, ensuring the correct belt installation tension is absolutely critical to achieving optimum performance. Under-tensioning can result in excess slippage when using v-belts or, in the case of synchronous belts, damage to belt teeth. At the other end of the scale, over-tensioning can cause belt overload, resulting in cord failure, and also severe damage to motor bearings and shafts. Indeed, incorrect tension of any kind is likely to reduce overall belt life and for this reason a tension meter should always be used when fitting new belt drives.

Correct alignment is also integral to delivering optimum performance. Misalignment is likely to cause belt tracking problems and premature failure. A variety of products are available to assist the alignment process, with laser alignment devices being one of the most cost-effective ways of solving this problem.

Once properly installed and commissioned, routine maintenance to synchronous belts should be minimal with products enjoying an extended life and delivering significant performance and efficiency benefits across the board.

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