Fixing mistracking belts and belt cleaning can lead to successful conveying.
By Kevin Fales
There is nothing more frustrating than watching your operation go from working at peak productivity to a complete stop because of an issue with your belt conveyor. The odds of this happening are low if you keep up to date with proactive, preventative maintenance. This is especially true with conveyor belts. Performing regularly scheduled assessments should alert you to a problem with your belts and the components they interact with.
During those belt assessments, it is common to come across some mistracking since even the slightest movement or change in the conveyor can throw the belt off track. Mistracking can result in several productivity-stalling problems, including downtime and cost from total belt replacement; safety hazards that could result in fines and the possibility of workplace injuries; and lost materials due to spillage from the mistracked belt.
If caught early and fixed, a mistracking belt does little damage to the conveyor or the belt. However, if missed or left unfixed, other types of damage can occur.
Identifying and fixing mistracking is an involved process that includes finding the cause of the mistracking, surveying the problems that have occurred based on the mistracking, and determining what device to use to solve the problem. But it’s important to start with the basics.
What Causes Mistracking?
When searching for the cause of mistracking, special attention should be paid to splices, the conveyor structure, and any material build up on or, damage to, the idlers and pulleys. Load zones are often good places to recognize belt mistracking. When material is not being leaded centrally, the belt may pull left or right until the material sits on the center of the idlers.
Perhaps the most common cause of mistracking is material build up. When sticky materials adhere to idlers and pulleys, high spots build up on the rollers, causing the belt to wander. Material build-up can cause the idlers to seize, creating drag on the belt that can also put it out of alignment.
This buildup can also change the tension of the belt, which can result in shorter life of the belting and other components, like cleaners. Belt cleaners are an effective way to keep idlers and pulleys free of carryback material. Installing an effective cleaning system will go a long way toward keeping belt mistracking and other common system problems caused by carryback in check.
If that doesn’t work and the problem isn’t structural, you may need to look into a belt tracker. Before finding a device that can help solve your problem, you must first identify what type of mistracking you are experiencing. If your belt is constantly mistracking and moving back and forth, you are experiencing wander. A belt that runs to one side constantly is simply mistracking. The device you choose depends on which type of mistracking is occurring, along with the belt tension and belt speed, thickness, width, and whether the belt reverses.
A proper belt positioner is the simple, reliable solution for problem belts that consistently mistrack to one side of the conveyor. A belt positioner works on the return side belt using simple angled rollers mounted in a fixed position to quickly and continuously funnel the belt into the correct path. This is a quick, simple solution for belt tracking problems caused by conveyor misalignment mishaps, ground shifts, or on temporary systems.
Belt positioners are not meant to work with top-side belt mistracking, however, or for belts that mistrack from side to side. Ideal for use on belts with medium-to-high running tensions, a belt positioner is not appropriate for use on belts with low running tensions.
For top side or return side belts that wander from side to side, it is best to choose an active belt tracking device that adjusts based on the movement of the belt. An active belt tracking device that affects both friction and the belt tension will most effectively track the belt. Many of these belt tracking devices will also have guide rollers that help actuate the movement of the belt tracking device. If that is the case, it’s important to note that often these devices will not work on reversing belts.
Reversing belts typically need a different style of belt tracking device designed to work in both directions. Before putting a belt tracking device on your belt, clarify that it will work on reversing belts if the application warrants, otherwise, it may do more harm than good.
Finally, while not often mentioned, it is also important to consider what materials are used to make the rollers on your belt trainer. For example, urethane lagged rollers will last longer than rubber rollers. Also, some trainers use standard, onsite rollers that can be used for replacement at any time, making maintenance quick and easy.
Monitoring Your Entire System
Inspecting and performing maintenance on all of your conveyor system components should be part of an overall maintenance plan. You can save yourself time and money with scheduled work stoppages for maintenance and by replacing equipment before they cause damage to other components in your system. The amount of effort you put into proactive maintenance will decrease the amount of unexpected downtime, help keep your workers safe, and help your operation run more efficiently.
Belt Cleaning 101
Carryback is the product that makes its way past the drop off point and runs back along the underside of the conveyor bel. The amount of carryback on the belt can depend on a number of factors including the type of product, whether it be iron ore, coal or aggregate; the way the belt is oriented; or even the climate or environment surrounding the application. No matter what the cause, the goal is always consistent: to recover the carryback product before it creates hazards and results in a loss of productivity.
When carryback leaves the belt, it has to go somewhere; that somewhere is typically the ground, creating mountains of product. This isn’t only a significant on-site hazard, but it creates a clean-up job that can lead to unscheduled downtime for the site.
Carryback on a conveyor is inevitable no matter what the product, however avoiding this is typically no problem if you’ve got the right equipment installed. With some sites losing close to a ton of product every day just because of carryback, recovering the lost product seems like the obvious solution to an increase in productivity and revenue. However, picking the right equipment to solve the issue of carryback isn’t always as straight forward as a “one product fits all” type of purchase. Below we’ve outlined the best methods for combatting carryback.
Selecting a Belt Cleaner
Picking equipment to combat carryback can vary depending on the application. While some options are more financially viable, they may not achieve the desired result in heavy-duty settings. Belt cleaning tools include precleaners, secondary cleaners, spray bars, and wash boxes. Each of these work effectively for different purposes; however on their own they don’t always eliminate carryback as a whole and can leave a gap in your defense.
Precleaners and Secondary Belt Cleaners
Precleaners (also called belt scrapers) with tungsten carbide tips or polyurethane blades are designed to scrape material off the conveyer belt, and are usually positioned on the head pulley. Precleaners are designed to scrape off up to 60%-70% of material, typically removing the larger pieces.
However, when the material is sticky, there is a humid climate, or there is simply not enough room precleaners need more help to clean the belt. In these circumstances, many will chose to employ a secondary or even a tertiary cleaner.
However, we can imagine you want to clean off more than 70% of your carryback.
Secondary belt cleaners are belt cleaners that are built to scrape materials left on the belt beyond the head pulley. Secondary cleaners are located just beyond where the belt leaves the head pulley, and anywhere else where necessary down the beltline. Secondary cleaners are especially good at removing fines and can, in some settings, increase cleaning efficiency to more than 90%. However, if you’re working with extremely sticky material or in abrasive or corrosive climates, you may need a heavier-duty solution.
Typically used alongside secondary cleaners, spray bars (also referred to as spray poles) offer another source of protection in combatting stubborn carryback. Adding water to the equation helps either break down or collect remaining carryback in a form that is easily cleaned from the belt.
Water can have drawbacks including: uncontrolled material movement, spillage, and material degradation. Issues like this can result in downtime and clean-up cost, equipmentdamage, and corrosion of the conveyor structure and components. However, a well thought out water management program can typically outweigh these negatives.
Plans that incorporate a recycled water system and controlled runoff will negate these issues. Along with water management systems, investing in a spray bar that has a maximum inlet pressure of 145 psi will give you the perfect balance between having enough water to clean your belt, and avoiding nasty issues like material degradation. Allowing your site to incorporate a water-based cleaning system is often integral to the productivity of a cleaner when a standard cleaning system just won’t do.
The Ultimate Cleaning System
In some settings, a precleaner, secondary cleaner, or spray bar just don’t cut it when trying to remove carryback. Incorporating a wash box into your conveyor allows you to virtually eliminate carryback, even in the toughest applications.
A wash box is a fully enclosed system which incorporates both belt cleaners and spray bars. The spray bars flush material off the bottom pan out the drain portal, fully containing the waste wash water. This means you get a clean belt and waste water-management system in one.
Make the Move
Ready to make the move towards clean belt by taking the steps outlined above, or are you still not sure where to start? Request a free assessment today and one of our Flexco experts will evaluate your entire belt conveyor system and help you find the right solutions for your challenges.
Kevin Fales is a product manager for Flexco.
VULCANISATION VS. MECHANICAL FASTENING: TRUE OR FALSE?
Most belt conveyor operators know that when it comes to the critical issue of belt splicing, there are two primary options to consider – vulcanised splicing through heat or chemicals and mechanical fastening with metal hinges or plates, according to Aaron Rosso, senior product manager, Flexco.
What they may not know are all of the factors that influence the decision and ultimately determine the success of the splice. To help operators better understand the conditions that impact the decision, Flexco compiled a “True or False” quiz on vulcanisation vs. mechanical fastening. Test your knowledge and conceptions of this critical process below:
- You can’t repair higher tension belts with mechanical fasteners.
False. With the use of synthetic carcass belts and improved fastener designs, mechanical fasteners are compatible with high-tension belts, with ratings of up to 2,000 PIW.
- Mechanical fasteners can prevent the sift through of carried materials.
True. While vulcanised belts are ideal for the prevention of material sift-through, mechanical fastening may actually be preferable in many instances. If the splice is done properly, sifting should not be a problem. Solid plate splices can be sift-proof, and if filler tape is used with a bolt solid plate fastener, sifting is eliminated.
- Mechanical fasteners are noisy, incompatible with belt cleaners and scrapers, and generally damage the belt.
False. Conveyor belt damage, noise, and damage to the cleaner can all be avoided when mechanical splices are properly installed, maintained, and countersunk by skiving the belt.
- Some belts are not well-suited to vulcanisation.
True. There are a number of conveyor belt conditions that can interfere with the ability to vulcanise. Older and/or worn fabric belts have weaker belt layers that will become brittle as heat is applied during vulcanization. Older rubber belts also present challenges as the bondable properties of rubber will deteriorate over time. Finally, some operations may not have sufficient belt length to vulcanise as the process will require some take-up to successfully complete.
- My belt can be vulcasized anytime or anywhere.
False. One of the primary challenges with vulcanisation is the need for specific conditions to produce a proper splice. Vulcanisation requires clean, dry, and relatively warm conditions to succeed. Multiple factors – including chemical residue, excessive moisture, and extreme temperatures – can interfere with the curing of the adhesives and cause nicks and/or bubbles. This will result in a weakened splice. Additionally, vulcanising can be very difficult in areas that aren’t easily accessible, further limiting the conditions conducive to the process.
- Vulcanisation will require notable downtime.
True. In fact, vulcanisation requires an operation to shut down the belt for a substantial amount of time – much longer than a mechanical splice would. The chemicals used in the process require several hours to cure, ensuring a minimum of eight hours of down time. Perhaps more significantly, vulcanisation requires a trained professional that will likely have limited availability, determining when the work can ultimately be scheduled.
- Vulcanisation won’t compromise my belt strength.
False. Even when done or completed properly, vulcanising weakens the conveyor belt, removing an entire ply of strength. The effect is even more severe on improperly conducted vulcanisations. A mechanically fastened splice, however, does not compromise the belt’s integrity when installed correctly.
- Vulcanised splice inspection can be difficult.
True. It is nearly impossible for the naked eye to detect the early signs of adhesion breakdown in a vulcanised splice. Often, operators aren’t even aware that they are experiencing a problem until a vulcanised splice fails – a catastrophic event that requires the immediate shutdown of the line.
Conveyor belt and belt-splice damage will always be a fact of life in most material-handling applications. While every splicing process has its limitations, belt conveyor operators can make more efficient decisions by better knowing all of the factors to consider when deciding between a vulcanised splice and the use of mechanical fastening.