Wood shredding for biomass – the ‘performance vs safety’ debate

Kuchl, 22.03.2016

In the modern resource sector, biomass producers are constantly pressured to work ever-smarter, to the point that the ‘performance vs safety’ battle can become hard to manage. Christoph Lahnsteiner, product manager at waste shredding specialist UNTHA, considers the role that technology manufacturers play – is it possible to improve safety, by design, without compromising the bottom line?

There are many reasons machinery manufacturers innovate. Continued research, development and engineering enables them to maintain their competitive edge and capitalise on new opportunities. But that innovation would mean nothing if it didn’t address the imminent and upcoming challenges customers face.  For example, when processing waste wood for biomass, operators understandably focus on performance-centric criteria such as shredder capacity, throughputs and cost efficiencies. Fortunately, the spotlight is growing on energy consumption too – after all, there seems little point creating a renewable energy feedstock if the production process itself is a drain on valuable resources.

Shredder manufacturers naturally focus their efforts on developing solutions that will continuously excel in these areas. But could it be argued that, with so much knowledge at their fingertips, they should be innovating for even greater benefit? Safety has not always been a prime concern within wood shredding. But increasingly stringent waste policing, the number of devastating plant fires that dominate the global headlines, and the general uplift in sector standards, mean safety has stepped to the fore. Now, more so than ever, manufacturers therefore have an inherent responsibility to design shredders with safety in mind.

As the age old saying goes, prevention is better than cure. So, of course sprinkling systems should be installed throughout wood shredding facilities and rigorous cleaning regimes should be followed daily. But careful design considerations within the shredders themselves will help to overcome the risk of fire or explosion from the outset.

Wood shredding has a natural propensity to produce high levels of dust. However, shredders can now be engineered to have a slower rotor speed, without compromising throughputs. As a result, they generate less dust and the potential for a spark is also reduced.  Studies have also shown that high-speed wood shredders can produce up to 25% fines, whereas with slower speed equivalents this figure will drop to as little as 5%. Choosing the right shredder can therefore protect the safety of a plant whilst yielding up to 20% more material per tonne and reducing the disposal costs associated with non-biomass specification outputs.

For added shredder protection in this potentially volatile environment, anti-explosive Atex-specification motors and electronics can be installed. Carefully positioned UV, infrared and spark detectors on a shredder’s inlet hopper and discharge conveyor, can also sense when a fire is likely to begin. And, in the event of alarm activation, extinguishing nozzles, positioned in the same place as the sensors and thus pointing directly at the fire risk, can automatically spray water onto the targeted area to suppress the outbreak.

Such considerations will not only please operators within the biomass industry – they’re likely to appease insurance providers too. If the shredder is mobile, and it is possible to move this high value capital asset outdoors, the insurance benefits are multiplied.

It is important to realise however, that fire safety is not the only consideration to make when shredding wood for biomass – ergonomic design is also crucial. Shredders should be purposefully built with maintenance simplicity and operator safety in mind. That’s why features such as clever foreign object protection mechanisms are now commonplace. If a shredder automatically stops and the problematic material can be extracted with ease, this minimises the risks associated with an operator entering the machine to retrieve the object. Pioneering computer diagnostics that automatically detect a potential maintenance issue also reduce the need for a human to investigate the situation. These less intrusive operational methods are incredibly beneficial when it comes to employee wellbeing.

When service and maintenance activity is required, ‘next generation’ wood shredding technology prioritises operators working in an upright position, without the need to hunch or over-stretch. The number of lumbar complaints will fall, employees will be more content and productive in their work, and the business costs associated with unfit or absent employees will be overcome.  This adds significant strength to an organisation’s corporate social responsibility status – something a forward-thinking company will strive for.

Even the shredder’s drive concept can improve safety and wellbeing. An electric drive, for example, will reduce noise and exhaust gas emissions, ensuring a more comfortable working environment. And in the absence of a diesel engine, there will not be any areas of high temperatures where a fire could ignite.

The list of safety considerations just goes on and on, and, ultimately, these factors should be paramount within any waste plant. However, when it’s possible to improve safety standards without there being a detrimental impact on site performance, the argument to build such a robust and secure facility, is stronger still.

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