While belt conveyors provide a reliable, efficient bulk handling solution, they can experience occasional problems. And when issues arise, they can wreak havoc on a production line. Below are some of the most commonly seen issues when working with belt conveyors, including what causes these problems and how to prevent them.
Note: This is not a comprehensive list and does not substitute for the expertise of a professional. Always consult your original equipment manufacturer or manual to ensure all necessary safety, maintenance, and troubleshooting guidelines are followed. Maintenance and storage procedures should always be carried out by a trained professional. FEECO does not make any representations or warranties (implied or otherwise) regarding the accuracy and completeness of this guide and shall in no event be liable for any loss of profit or any commercial damage, including but not limited to special, incidental, consequential, or other damage.
Carryback is the material that remains on the belt after discharge and is perhaps the most common struggle among conveyor pulley. Typically all conveyors experience carryback to some extent, but given its potential for serious consequences, keeping it to a minimum is essential.
WHY CARRYBACK IS AN ISSUE
Carryback creates a messy and potentially hazardous work environment, as it gets into the undercarriage and surrounding area of the conveyor. This can cause outages and increase the time devoted to cleaning and maintenance.
Not only does carryback create a mess, but material allowed to build up on rollers, idlers, and pulleys degrades these components, causing excessive wear. Further, a buildup of carryback can also cause belt tracking issues, potentially wearing and damaging the belt.
WHAT CAUSES CARRYBACK
Carryback is largely a result of the conveyed material’s characteristics and propensity for sticking. In general, a material with a higher moisture content is more likely to stick to the belt. Similarly, carryback can be more of a problem in humid environments where hygroscopic materials pull moisture from the air, increasing the likelihood of sticking.
Sticking can also occur when condensation is produced as a result of extreme temperature differences between the material and the belt.
HOW TO PREVENT CARRYBACK
The best way to prevent carryback is to utilize one or more belt cleaners. Belt cleaners can be installed at both the head and tail pulley and serve to ride against the conveyor belt, dislodging any material that may be adhered to the belt. These devices substantially reduce buildup on the belt, and depending on the level of carryback, several options may be appropriate. Common options include a self-cleaning tail pulley, return side belt plow (v-plow), and dual belt cleaners.
Routine cleaning should also be prioritized as part of a conveyor head pulley maintenance program in order to minimize any remaining buildup on components.
CONVEYOR BELT MISTRACKING
Tracking, or training, refers to the way in which the belt rides on the rollers. Conveyor belts should always track centrally. Mistracking occurs when the conveyor rubber belt rides unevenly on rollers, favoring one side over the other.
Like carryback, mistracking can cause several issues in a conveyor system. This includes uneven belt wear, belt damage resulting from catching or rubbing on surrounding infrastructure, material spillage, warped belting or belts that are not square, and more.
Mistracking is also recognized as a safety violation by the US Department of Labor’s Mine Safety and Health Administration (MSHA). When a belt is not tracking properly, areas that are normally safe can become pinch points, presenting a hazard to workers. Mistracking can also cause material to fall off of the conveyor, falling on to workers and equipment, or creating piles that present a safety risk.
WHAT CAUSES MISTRACKING
Since conveyor bend pulley are carefully balanced, any number of factors may be the source of mistracking, making it difficult to identify the origin of the problem. Potential causes of mistracking include improper idler spacing, seized or worn rollers, a misaligned frame, material buildup on any part of the conveyor, excessive belt tensioning, and a worn or damaged belt, to name a few.
HOW TO PREVENT MISTRACKING
The range of possible mistracking causes make a blanket solution to prevention impossible. There are, however, measures that can help to reduce the potential for this issue to occur.
Conveyors can fall out of perfect alignment through normal wear and tear. As a result, routinely inspecting alignment of the conveyor structure and its many components helps to prevent mistracking. Off-center loading can also create an alignment issue, so ensure that chutes are positioned centrally over loading areas.
Since mistracking can be caused by material buildup, it’s also important to keep the belt conveyor, idlers, and pulleys clean. This will reduce wear on components, which could also cause mistracking.
Slight off-tracking issues can be remedied by “knocking idlers,” a practice in which idlers are skewed a small amount to correct an off-tracking belt.
Belt slippage typically occurs around the drive/head pulley and happens when the belt and pulley do not have enough grip to adequately turn the belt around the pulley.
WHY BELT SLIPPING IS AN ISSUE
Belt slipping reduces productivity and efficiency, causing process upsets, or preventing the proper amount of material from being conveyed. It can also cause belt wear and damage, and put added stress on the motor, resulting in premature failure.
WHAT CAUSES SLIPPAGE
There are several reasons why a belt experiences slipping. This includes:
Low temperatures (cold temperatures can reduce the amount of grip between the pulley and belt)
Improperly installed pulley lagging
Buildup on pulley
Inadequate belt tension
Worn head pulley
Smooth pulley surface
Load that is too heavy for conveyor
HOW TO PREVENT SLIPPAGE
There are several ways to prevent slippage. Maintaining an adequate belt tension is critical to preventing slippage. It’s important to note, however, that while over-tensioning the belt may seem like an easy fix, this should be avoided, as it can stretch and damage the belt, as well as put added stress on the motor.
When there is not enough grip between the pulley and the belt, consider installing lagging. Lagging is a material added to the surface of the pulley for increased traction.
Alternatively, a snub pulley may be installed. A snub pulley is simply an idler installed at a point which increases the arc between the belt and pulley to improve friction between the two.
Material spilling off of the conveyor is also a commonly encountered problem. While spillage can occur at any point along the conveyor path, not surprisingly, it is most common at load and transfer points.
WHY SPILLAGE IS AN ISSUE
As with other issues, material spilling off of the conveyor belt reduces productivity and efficiency, encourages product/material loss, and increases wear on equipment. Further, as mentioned, spillage can be a significant safety hazard, falling on employees and increasing the likelihood of employees slipping or falling.
WHAT CAUSES SPILLAGE
In general, it is not uncommon to see some level of material spillage. Excessive fugitive material, however, likely indicates an underlying issue. Typical causes of excess spillage include belt misalignment, belt damage or wear, high-impact loading, and chute misalignment.
HOW TO PREVENT SPILLAGE
Spillage in general is managed by a well-designed conveyor system. The use of skirtboards and dust pick-off points are useful in reducing the potential for material spillage.
Ensuring that chutes are clear and located centrally above the loading zone will also help to prevent spillage. Additionally, impact beds for heavy loading prevent the belt from sagging, which can also release fugitive material.
Keeping conveyors aligned and in proper working order will also help to prevent excess fugitive material from escaping, as any deviation from proper operation has the potential to spill material.
PREVENTION IS KEY
Any one of the aforementioned issues has the potential to cause serious problems: premature equipment failure, unexpected downtime, employee injuries, and more. Even if problems do not reach a high level of severity, however, they still represent unnecessary hazards and losses in productivity and efficiency. For these reasons, a preventative approach to conveyor problems is always the best policy.
Regularly inspect the steel cord conveyor belt to look for signs of trouble: excessive material spillage, abnormal sounds, visual indicators, or other abnormalities. Always ensure that the equipment, as well as the surrounding area, are kept clean. Replace conveyor components that begin to show signs of wear.
By taking these measures, the potential for unexpected downtime and lengthy repairs is greatly reduced.
Troughed belt conveyors offer reliable handling in nearly any setting, but they can occasionally exhibit issues, particularly if not kept clean and maintained; carryback, mistracking, slippage, and spillage are some of the most commonly encountered issues when working with belt conveyors. While each issue presents significant risk and potential for damage, these issues are largely prevented by keeping a close eye on conveyor operation and performance, and promptly addressing any issues that arise.
FEECO manufactures custom belt conveyors and conveyor systems for use in nearly every industry, with expertise around hundreds of materials. Our Customer Service Team offers a full range of services for conveyors, from replacement parts, to repairs, and even inspections and conveyor audits. For more information on our belt conveyors or conveyor parts and service support, contact us today!
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