When you have a wide, heavy rubber belt, the motor power required to move it and the increased mechanical strain on the system can lead to rising costs, both in energy use and maintenance requirements. Here Marcin Grzeszek, Manager Industry Segment Recycling at conveyor belt manufacturer Habasit, discusses the key considerations when selecting a belt material for a recycling facility to help keep costs down and maximize efficiency.
We all assume that recycling is always a beneficial process for the environment. After all, how can taking our used, discarded products and converting them into something new possibly be a bad thing? Well, global recycling facilities are struggling with this very problem as the rising costs and energy consumption associated with running recycling lines are beginning to mean the process is no longer worthwhile. However, what many in the recycling industry do not realize is that many of their problems can be overcome by ensuring that they are using the right belt material for the job.
The traditional belt of choice
Traditionally, rubber belts have been the first choice for use in recycling applications and are still widely used despite new materials becoming more readily available. Rubber belts have several key advantages, such as high mechanical strength, cut resistance, and high abrasion resistance. These are particularly valuable for separating mixed waste, especially when materials like brick, concrete, glass, and steel are involved.
However, rubber belts have a couple of major disadvantages, including that they are slow to run and extremely energy intensive compared to other options. This is mainly caused by the high thickness and weight of rubber belts compared to alternative materials. For example, typical running speeds for a 3 m wide rubber belt are between 1 m/s and 1.5 m/s, whereas other materials can achieve speeds between 4 m/s and 6 m/s.
Furthermore, because of their weight, larger pulleys are needed to drive rubber belts compared to similar sized belts made from lightweight materials. To make matters worse, the added tension on the pulleys increases the energy required to drive the belt and causes more wear and tear on the system, increasing ongoing maintenance costs. So, with all the challenges associated with the recycling industry’s traditional go-to belt material, what are the alternatives?
Alternatives to rubber belts
Lightweight materials, such as Polyvinyl Chloride (PVC), are becoming increasingly more popular for applications like eddy current separators or general conveyors. PVC products are much lighter than conventional rubber belts and doesn’t require heavy construction of conveyor. They also consume less energy in operation. The lower energy required to operate the system and lighter conveyor build lowers a facility’s ongoing operational costs and reduces its carbon footprint, something that is becoming a growing priority for many businesses.
While not as durable as rubber belts, PVC belts are well suited to transport materials like plastic and paper where there is less mechanical strain put on the belt than when transporting materials like brick and concrete. However, PVC does not work well if exposed to sunlight and very low temperatures, below -10oC.
Another alternative to rubber and PVC belts is Thermoplastic Polyurethane (TPU). Generally, TPU belts have the highest upfront costs out of the three materials, but a lower total cost of ownership.
TPU belts are lightweight, roughly half the weight of similar sized rubber belts, facilitating faster, wider recycling lines. This results in TPU belts having lower ongoing energy and maintenance costs compared to rubber belts while having an increased throughput. Furthermore, TPU belts are extremely durable and have high abrasion and cut resistance, meaning they are well suited to work with most materials without operators needing to worry about damaging the belt.
However, TPU belts are not without their downsides. TPU is not as resistant to extremely hot water as PVC. This means that TPU belts are not well suited for applications involving a hot wash, such as the trommel separation of PET plastics where they are used to remove excess debris or labeling.
With every type of belt material comes its own list of pros and cons, it is easy to see why the industry might get confused. By consulting with a knowledgeable conveyor partner, such as Habasit, the recycling industry can rest assured that it is always using the most suitable material for the application.
