The humble horizontal baler might not be the most exciting but of kit, but it plays an essential role in compacting recyclables to facilitate economic handling, storage and transportation.
What is less recognised is the importance of the conveyor, both to feed the baling operation and other production line processes. Like the baling press, the conveyor is ubiquitous across the sector but is frequently taken for granted, with little consideration as to whether it is effective or efficient at what is designed to do.
Given the wide range of conveyor types, making the right decision can be challenging. A proper assessment of the site should cover the type and range of materials to be processed, the weight and volume that is expected to be handled, and the available working space and electrical supply.
Conveyors that are overfilled and spilling material or underfilled are typical. Inefficiencies will affect the overall effectiveness of the operation, so poor design and inappropriate conveyor choice are often the reason. But belt speed, overloading issues, poor synchronisation with other machinery and maintenance issues play their part too.
As the baler will not deliver uniform, well-compacted and consistent bales of material unless the feed conveyor is up to the job, it also means the business will not achieve maximum payload weights for the bales produced.
A smooth and consistent flow of material optimises baler loading and minimises the number of compression strokes and therefore power and time required to achieve bale density and weight. Productivity depends in part on the effectiveness of this relationship. So how can you achieve it?
Of course the conveyor needs to be robust enough for the environment and the weight of the materials to be handled. Reliability is crucial too: the last thing you want is constant shutdowns because this inevitably brings other processes to a halt. Planning for your conveyor is crucial.
Understanding material volumes and throughput is important and there is a huge range of options: slider-bed, steel slat, rubber or steel belt, chain driven, inclined, swan neck, fully en-closed, in-floor or on-floor designs.
Generally, a chain conveyor will be used where larger volumes are being handled. A slider-bed is more appropriate for lighter materials and smaller volumes and will generally cost less.
Products such as refuse-derived fuel, which can be much denser in volume than card and plastics, require higher specification parts for chains, belts, motors and gearboxes. The corrosive nature of the material can also mean higher wear and maintenance considerations.
Achieving a continuous and even flow of material will also depend on factors such as belt width, motor sizes (powerful enough to handle the weight of the material to be conveyed) and control systems.
The temptation to fit a low-cost standard option might provide initial savings, but it is unlikely to deliver the expected performance and is more likely to result in frustration and downtime. Bespoke solutions designed and tuned for a specific environment are guaranteed in the long run to be more cost-effective and safer to use.
With the right design, a conveyor feeds material at the optimal rate for a given process, and at a volume and speed that matches other machines or processes. Control systems and telemetry should link each piece of machinery so that they work smoothly and harmoniously as one.
So it is important the supplier is equally competent with both the mechanical and software aspects of the chosen solution.
In-floor addition improves loading to baler
St Helier Municipal Services on Jersey has operated a Middleton ME80 baler with an on-floor slider-bed conveyor since 2014.
An inclined section carries material from floor level up to another horizontal section that delivers material into the baler hopper. This has worked well with fault-free, cost-effective production.
But with all recycling being shipped off-island for reprocessing and volumes on the increase, it was recognised that an upgrade to the conveyor would be beneficial.
An in-floor section has been added, which extends the slider-bed conveyor with a pit section to improve loading. An original design of the facility which anticipated upgrades meant this was a straightforward operation, and the new section could be fitted with minimal disruption.
The in-floor section simplifies and speeds up loading while reducing the level of manual handling, allowing material to be simply tipped or pushed on to the conveyor deck.
Ease of access for scheduled cleaning and maintenance are important design considerations to limit service interruption.
Mark Smith is engineering director at Middleton Engineering