Better Belts Yield Big Benefits In Incline Conveying.
By Michael Schroeder
Due to their very nature, aggregates operations often require conveying on an incline, typically on intricate conveyor systems with multiple belted conveyors running at once and at different heights and speeds.
While many may think a conveyor belt is simply just a piece of rubber and fabric, that rubber and fabric is full of technology to keep the product moving through the system correctly. This technology, in fact, is a critical part of an incline conveying system – yet it is still often an afterthought.
Taking a strategic approach to selecting the right conveyor belt can have substantial impacts to output, cost, efficiency and operational uptime. In this article, we take a closer look at the key considerations.
Not all rubber belting is created equal – For starters, rubber conveyor belting has come a long way over the years, and with new technology built into the rubber compounds, along with customer engineered fabrics, it’s important to understand and utilize these advantages.
For example, in some applications utilizing a lighter more flexible conveyor belt while maintaining high-abuse resistance can lead to improved energy savings and less wear on auxiliary components like rollers and bearings. The right belting technology can increase abrasion resistance to the conveyor belt surface, extend the belt life, lessen the total cost of ownership, enhance performance, and limit down time on the conveying system.
The right cleats on a conveyor belt can make or break an operation – To prevent material spill back when conveying bulk materials on an incline, cleats are added to the conveyor belt to help capture the material from the loading zone to the discharge. The cleats work to keep the material and system running smoothly. Depending on the angle, speed and material being moved it requires the right cleat style and pattern to optimize the conveying operation.
Cleat height is one of the primary characteristics to consider when determining what is needed for a conveying operation. The taller the cleat, the higher incline can be achieved while still reducing material spill back.
Larger cleats hold rocks and concrete better and help maintain forward momentum. In addition, a higher cleat profile and steeper incline provides value by allowing operators to reduce the length requirements of the belt and size of the conveyor system in its entirety. A cleated belt presents the opportunity to shrink the footprint of the equipment, because it can convey at upwards of 40 degrees and create higher efficiencies in your operation.
A cleat’s profile also needs to have adequate radius and chamfer features to prevent cleats from cracking and tearing from the belt carcass. Most cleat profiles will be drafted from the base to the top of the profile to help release it from the molds post-vulcanization. Fabricated cleated belts made via skiving and gluing have a higher tendency to delaminate and fail compared to more durable, single-step vulcanized manufacturing. Cleat ends, in most cases, are angled to prevent stress build-up around rollers and pulleys that can also lead to cleat failure, reduced capacity, and downtime.
Different cleat heights and belting patterns can drastically change the way the system operates. Take for example, Continental’s Direct X cleat pattern, which is designed to directionally improve product flow control. The pocket-style cleat pattern captures conveyed material immediately upon loading, reducing the amount of product movement on the belt cover, which limits cover wear.
The nested pattern promotes a smooth, quiet transition on the return rollers, reducing noise and vibration on the job, and the cleats are integrally molded onto the base belt, meaning no cleat separation or delamination will occur. All of this lends itself to longer belt life, reduced cost of belt repair and replacement, and the overall more efficient movement of aggregate material on the site.
Cleat angles are critical – The angle of the cleat in relation to the drive and tail pulleys is also a key to conveying success. Too little angle (parallel to the roller) can cause cleat chatter because of the lack of continuous contact between the rollers and cleat profile, resulting in excessive vibration, noise, and eventually, cleat failure. If the cleat angle to the rollers is too large (perpendicular to the roller), cleat cracking can ensue, followed by cleat tear and separation from the belt carcass.
Furthermore, cleat height in conjunction with angle will determine the minimum pulley diameter the belt requires to operate. Taller cleats with large angles to the rollers will experience higher bending stress and are at greater risk of cracking and tearing.
Considerations before buying a belt – Because the belt impacts an operation’s overall performance, it is important to understand belt fundamentals. Consider these tips to select the best belt for the job:
1. Establish the performance requirements. If you want to increase belt life and lower total cost of ownership, your OEM or belt provider can help you determine the best belt construction specifications based on your performance requirements. The cleats will be irrelevant if you don’t start with a proper base and belt construction. Identifying the optimal combination of fabric, rubber, construction, cleats and lacing can deliver big benefits. The best approach to identify the ideal conveying solution is to discuss your overall conveying requirements with your conveying system provider. The right belt construction can provide energy savings, increase roller and bearing life, and decrease maintenance costs.
2. Determine the ideal cleat profile (size and shape). The size of the material being conveyed should determine the cleat height, shape and angle. Matching the profile to what materials you are moving and at what angles will help inform which solution is best. There are numerous cleat options available from a wide range of belting suppliers. Some belt manufacturers can also engineer a custom cleat profile to help reach peak operational performance for specific needs.
3. Determine your cleat design. The cleat design that will work best for you is largely based on the arrangement of your conveyor system. In the aggregates industry, the ideal belt design varies based on the angle of the incline. Depending on the material size and aggressiveness, it may require a custom cleat design to ensure proper material conveyance, limited material spill back and durability of the cleats leading to longer belt life and less down time.
4. Determine cleat frequency. There is a science behind how frequently cleats should be positioned on a belt to provide the best output. Belting suppliers can help identify the sweet spot between the type of product being conveyed, the speed the conveyor is moving, and how often to repeat the cleat pattern. For example, the Direct X cleat pattern is designed to carry the material across the width of the pattern and provide constant contact with the return rollers for a smooth operation. Make sure you understand why the recommended frequency is the best option for your operation.
5. Understand how the cleats are adhered to the belt. How cleats are adhered to the belt construction can substantially impact belt life, which is why belt construction is so important. A belt fabricator modifies premade belting using secondary processes and tools, like glue chemicals and metal bolts, to add cleats. Continental, for example, uses an innovative proprietary process that combines the raw (uncured) belt carcass and rubber cleat extrusions through extreme heat and pressure to vulcanize the belt, which provides the strongest cleat adherence achievable.
Although conveyor belts are often an afterthought, the ideal belt will have the right technology built into the rubber to yield the best results for your operation. By considering variables such as cleat height, profile, pattern and frequency, aggregates operators can often rock lower equipment downtime, decreased costs. and increased efficiency and profitability.
Michael Schroeder is the head of product management for conveying solutions, ContiTech, USA at Continental. Schroeder has more than two decades of experience in rubber belting engineering and conveying.