In many industries, the integrity of the materials or products being conveyed is of utmost importance. This is especially true in the food processing industry, where materials are particularly fragile, and breakage can lead to many negative consequences.
However, even though preserving material integrity is crucial during the conveying process, no less than 29% of industrial facilities state that material breakage is one of the top three conveying challenges they face on a daily basis.
Material breakage
Material breakage is defined as the separation of material particles into two or more pieces under the action of stress. Any place where the product or raw material is sliding against a conveyor surface (be it a tube, flat surface, or any other) can cause material abrasion and possibly material breakage.
Breakage generally leads to a decrease in product value. In the food industry, even the smallest amount of breakage can lead to lost product, sanitation issues, and decreased efficiency.
Avoiding breakage is important
- When the material is easily degraded, such as in the case of friable materials, fragile materials, or materials otherwise prone to damage.
- When the consistency of blends or mixes must be preserved. This is vital for snack foods, breakfast cereals, tea blends, and other products that require an even combination of ingredients.
- When product dusting is a concern, some materials create more dust than others when they are broken. It can lead to respiratory issues for workers, equipment malfunctions, and other dust hazards, including dust explosions.
In short, breakage costs money – whether it’s wasted product, downtime for repairs, or poor quality products that need to be reworked or scrapped.
The ultimate goal of every production facility, especially if they’re dealing with specialty materials or blends/mixes, should be to find ways to reduce or eliminate material breakage altogether.
Why Does Material Break?
The main reason why material breaks during conveying is due to impact. Other potential causes of breakage may be excessive vibration, high temperatures, chemical erosion, electrostatic discharge and moisture damage. The two most common types of impact are free-fall impact and collision impact.
Free-fall impact
When fragile material is dropped, thrown, or otherwise falls from a high point, it’s likely to break. Free-fall impact commonly occurs when a material is transferred between different conveyors when fed into the conveyor or discharged from it. This type of breakage is commonly seen in bucket elevator systems and other gravity-based conveyance systems. As the material is lifted and then released into the chute or trough, it drops and collides with the surface below, which can cause it to break.
Collision impact
Collision impact happens when two pieces of conveyed material collide – for example, two particles hit each other in mid-flight. It also occurs when a particle collides with a stationary element, such as a conveyor wall, a belt, a pipe, or other conveyor components. This type of breakage is commonly seen in screw conveyors and pneumatic conveying systems. The particles travel at high speeds as they move through the system (especially in pneumatic conveyors), and when they collide with an object, it can cause them to break.
Conveying lines
Since the main reason for material breakage during conveying is due to impact, we offer some general advice for preventing material breakage in conveying lines:
- Using vibratory feeders instead of rotary airlocks or a screw feeder
Vibratory feeders help minimize the amount of breakage at the inlet without using the rotary shaft of a screw feeder or blades from a rotary airlock.
- Smooth speed change
When the speed of the conveyor changes, it can cause a sudden impact that can break the material. Try to gradually make any speed changes (accelerations or decelerations) to avoid this.
- Using gentle curves
Curved sections in your conveyor can cause the material to slow down and make more contact with the surface below, which increases the chances of it breaking. Avoid using sharp curves, or use a low-friction material for the surface to help reduce the amount of contact.
- Monitoring temperature and humidity
Make sure that the environmental conditions in your facility are within the recommended ranges to help minimize material degradation.
Tube Conveyors
A perhaps obvious but often overlooked solution to reducing or eliminating material breakage is a gentle conveying system. It will use low-speed, high-volume movement to slowly push the material along the conveying line without too many contact points – meaning no impact and no breakage.
This is where tubular conveyors come in. A tube conveyor is an enclosed system with a tubular loop to move material through a facility. The material is fed into the first tube, and as it moves through the tube, it is gradually and seamlessly transferred to the next one. This process continues until the material reaches the end of the conveyor.
The material is moved thanks to circular solid discs evenly spaced along a cable that runs the length of the tube. These enclosed discs gently push the material along. The discs are connected to a gearbox, which is connected to a motor. The speed of the motor determines the speed of the discs and, therefore, the speed of the material.
Because there are no abrupt changes in direction or speed, and because the discs are constantly moving the material along, there is virtually no chance for it to break. Tube conveyors can be designed to operate at low speeds, which means that the material has less chance of being exposed to excessive vibration or high temperatures. And because of the material the conveyor is constructed from (stainless steel), there is also no risk of chemical erosion or electrostatic discharge.
Closed system
Due to the enclosed nature of the tubular conveyor, environmental conditions (temperature and humidity) can be more easily controlled, which is another way of minimizing material degradation.
