Is too much pressure being placed on machinery that safety could be compromised?

Written by: Marcus Brew | Published:
Managing director of UNTHA UK Marcus Brew

While the majority of recycling, waste management or alternative fuel production facilities have an evident environmental agenda, it would be naïve to suggest that such plants exist purely for altruistic reasons.

Of course the ‘green’ benefits associated with these operations are vital to the UK’s resource security and progress towards a more sustainable economy. But unless the businesses are community-backed, they exist to make a profit too.

This is nothing to be ashamed of – profit is not a dirty word and if organisations can responsibly harness the wealth in waste, then this is something to be praised. In fact, their actions may even inspire other organisations to think smarter about their own approach to resource management.

In the face of often turbulent market conditions, with fluctuating recyclate commodity values and changeable demand for energy-from-waste (EfW) fuels, for example, one of the easiest ways to safeguard profit levels is to minimise the shredding costs per tonne.

But the term easy is used very loosely here, because this cost-control objective is often far from straightforward to achieve.

For some operators, this performance-driven mindset homes in on the need for speed. After all, it is logical that the more material a shredder can handle, the higher the throughputs and the greater the revenue-generating potential of the technology.

But, however simple the ‘capacity = profit’ mantra sounds in principle, it is actually far from being this clear-cut. Concentrate too much on speed, and the inherent risks of the facility could soon escalate as a consequence.

The target speed for a wood shredder, for example, should be no higher than 60rpm. Above this and the machine will generate a significant level of dust, which not only makes for a dirty shredding process, but also poses a significant fire hazard.

Balance a slower rotor speed with high torque, however, and the technology can maintain throughputs of 40 tonnes per hour, while generating less dust and thus reducing the risk of a spark. Not only this – the true capacity of the shredder will be optimised too.

Sticking with the wood shredding example, the biomass market demands a fuel manufactured to a defined specification, for utmost energy value.

Operators should therefore strive to maximise the proportion of ‘on-specification’ feedstock that they can manufacture if they are to optimise their revenues, not to mention customer satisfaction. Dust-like, non-specification material (fines) will therefore not suffice. In fact, it represents nothing but a cost.

Studies have shown that high-speed wood shredders can produce up to 25% of fines, whereas with slower-speed equivalents this figure will drop to as little as 5%. As a result, choosing the right machine can yield up to 20% more saleable product, reduce the disposal costs associated with non-biomass material and protect the fire safety of the plant.

It is also important to note that this throughput vs safety debate is not exclusive to the world of wood shredding. The processing of confidential paper presents similar risks if a high-speed machine is used, for example.

And it cannot be forgotten that high-speed applications also typically result in high wear. This is both costly and disruptive from a maintenance perspective, and the greater downtime a plant experiences, the more the throughputs will be affected anyway.

So, is the industry demanding too much from shredding technology? Often, from a price perspective, yes. But in general, no. Technology is advancing apace, so why not search for a machine that can tick all the boxes? Heightened safety can be engineered, by design, thanks to the ongoing level of innovation within the market. And improved safety mechanisms needn’t be to the detriment of performance, or the bottom line.

Marcus Brew, managing director of UNTHA UK


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