Problems encountered with troughed belt conveyors have the potential to injure employees, shut down the production line, and incur substantial costs in repairs and production losses.
Choosing a reputable conveyor manufacturer and having a system designed around the unique needs of the specific handling application goes a long way in maintaining efficiency and prolonging equipment life, but even the best conveyors can still encounter issues through normal wear and tear or unforeseen production changes.
The ability to quickly troubleshoot an under-performing or stalled conveyor is crucial in minimizing downtime and preventing further damage and loss, but when a problem occurs, it can be hard to know where to start troubleshooting.
Fortunately, the rubber belt itself is often a reliable indicator, hinting at the underlying problem through wear pattern, running problems, and more. Use the guide below to quickly assess and resolve common conveyor problems often exhibited in the belt.
Note: This is not a comprehensive list and does not substitute for the expertise of a professional. Always consult your original equipment manufacturer 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.
Troubleshooting: Be Alert & Safe
During conveyor inspection, be alert for any abnormalities such as strange odors, leaks, sounds, or visual wear. Other potential indications of a problem include excess material spillage, process bottlenecks, a change in product quality, or other sign of underperformance. When troubleshooting, always follow all necessary safety measures.
Operators and maintenance personnel should be trained on the system so they are able to safely troubleshoot any issues that arise.
Problems With How the Belt Runs
Problem: Belt “runs off” one side of head or tail pulley.
Potential Cause: When a conveyor belt runs off one side of the terminal pulley, this is most often an indication that something is not right with the pulley itself. Typically, this type of belt behavior results when the pulley is either not square with the axis of the belt, or when the pulley shaft is not level transversely. Material buildup, as well as worn or missing lagging can also cause this behavior.
Fix: To resolve this issue, confirm that the pulley shaft is level horizontally. Use several idlers (carrier or return) prior to the pulleys to train the belt. Improve cleaning procedures if buildup is an issue and replace worn or missing lagging if necessary.
Problem: Belt runs to one side at a particular point on the frame.
There are many possible reasons why a belt runs toward a particular point on the frame. Among them:
Potential Cause: Idlers prior to the point of trouble may not be square with the frame.
Fix: Minimally advance the end of several idlers on the run-out side.
Potential Cause: The conveyor frame may be either out of alignment, or is not transversely level.
Fix: Use a string to check alignment along the length of the conveyor. Use a level to check alignment across the width of the frame. Adjust alignment as needed.
Potential Cause: There could be material buildup on idlers and return rollers, or idlers may be damaged or frozen.
Fix: Improve maintenance practices and/or install a cleaning device such as a belt cleaner.
Potential Cause: The terminal pulley may be out of alignment.
Fix: Check and adjust both terminals.
Potential Cause: Spilled material may be forcing the belt to move to one side.
Fix: Find and correct the cause of spillage.
Problem: The entire conveyor belt, or a long segment of it, runs to one side (Mistracking)
Here again, there are many factors that may cause an entire conveyor belt (or long section) to run to one side:
Potential Cause: The structure may be out of alignment, or not level transversely.
Fix: Check and correct.
Potential Cause: It’s possible the belt is not cut and spliced squarely. Similarly, the belt could be bowed as a result of poor storage conditions.
Fix: In the case of new belt conveyors, operate under the full load tension for the “break-in” period. If condition persists, a new, higher-quality belt may be required. For bowed conveyor belts, a complete replacement is necessary.
Potential Cause: Material is being loaded on the belt conveyor off center.
Fix: Correct the cause at loading point.
Potential Cause: Belt is tensioned improperly.
Fix: Adjust the pulleys as needed.
Problem: Belt is running erratically
Potential Cause: The belt may be too stiff to train. Alternatively, improper belt tension could also be causing the belt to run improperly.
Fix: Check quality manufacturer of belt for proper specifications on conveyor. Check belt tension and adjust pulleys as needed.
Potential Cause: Twisting of frame on portables and stackers.
Fix: Brace loading hoppers so load and loading stresses do not allow frame to twist out of line. Adjust belt tension.
Problems With Belt Wear
Problem: Excessive stretching
When a belt is exhibiting extensive stretching, there are two primary causes:
1.Belt tension is too high.
Many factors can cause the tension to be too high, and as such, there are many potential ways to resolve the issue:
- Increase the belt speed, while maintaining the same capacity.
- Reduce the tonnage while maintaining the same speed.
- Install drive pulley lagging.
- Use less weight on gravity take-up, or less tension on screw take-up.
- Check for worn idlers or spilled material.
- Check tonnage capacity and belt tension against belt specs.
- Check tensions at skirts
2.Belt construction is too light.
To confirm that belt construction is too light, check the tonnage capacity and belt tension against the belt specifications. The fix in this case is to replace the belt with one of adequate specifications.
Problem: The belt is exhibiting severe wear on the pulley side.
Potential Cause: Idlers may be sticking, or the impact or load zones may be worn. Overloading could also be occurring.
Fix: Replace bad rolls. Improve maintenance practices. Reduce loading if necessary.
Potential Cause: Material is being allowed to spill onto the return belt.
Fix: There are many potential ways to resolve spillage of material on the belt. This includes:
- Use of a sealed hopper
- Install a self-cleaning tail pulley
- Return belt covers
- Prevent sloppy loading with deep trough idlers
- Add a return plow prior to the tail pulley
Potential Cause: The head pulley fasteners could be protruding.
Fix: Replace worn lagging.
Potential Cause: Slippage may be occurring on the drive pulley.
Fix: Use rubber lagging on the drive pulley. Use grooved or herringbone type. If needed, install a snub pulley to increase drive pulley contact.
Problem: There are short breaks in the carcass.
Potential Cause: Similar to the previous issue, breaks in the carcass could indicate a loading impact from sharp lumps.
Fix: Reduce the loading impact and employ impact idlers or bed.
Potential Cause: The chosen belt is not a good fit for the application.
Fix: Replace the belt with one more suited to the application.
Potential Cause: It’s also possible that material is getting between the belt and the pulley.
Fix: If this is the case, improve maintenance practices to reduce fugitive material between belt and pulley.
Problem: Breaks are occurring at the belt edge.
Potential Cause: Belt edges may be “folding up” on structure at or near pulleys.
Fix: Retrain belt properly.
Potential Cause: Material is jamming under the hopper or skirt boards.
Fix: Adjust for proper clearance and relief.
Potential Cause: The final idler is too close to the head pulley or too high.
Fix: Adjust final idler location or height.
Potential Cause: A sharp, convex curve is present in the system.
Fix: Adjust to a more gradual curve.
Problem: Belt edge is exhibiting wear
Potential Cause: When a belt exhibits wear at the edge, it is often a sign of misalignment, which can allow the belt to run out of line and rub against a structure.
Fix: Follow OEM recommendations for correcting belt alignment. Retrain as needed.
Problem: Belt is exhibiting transverse breaks near fasteners
Potential Cause: Fastener plates are too long for the pulley size. (For mechanical splice only)
Fix: Use correct lacing and/or use larger pulleys.
Problem: Excessive “cupping”
Cupping occurs when the edges of the belt curl up. Cupping is expected as a part of normal wear and tear over time, but excessive cupping could be an indication that something is wrong. There are many reasons why a belt may exhibit excessive cupping:
Potential Cause: The belt may be over-tensioned.
Fix: Reduce take-up tension or counterweight on gravity take-up. Check for drag from stuck idlers. Reduce loading rate or increase belt speed to reduce tension. Make certain that the belt is adequate for the tension requirements.
Potential Cause: Deep trough idlers and a low elasticity in belt fabric are causing high tension.
Fix: Use adjustable transition idlers at terminals for longer transitions between deep trough and pulleys. Use belting with moderate stretch. Ensure proper transition distances.
Potential Cause: Belt has been stretched or is worn out.
Fix: Replace belt.
Potential Cause: The top cover is too heavy for the thin-ply belt.
Fix: Consult a quality belt manufacturer.
Problem: Belt is hardening and/or cracking
The hardening and/or cracking of a rubber conveyor belt is a result of exposure to heat. To resolve the issue, use a Neoprene hot material belt. Use oil for lubrication.
Problems With Cover Compound Wear
Problem: Cover is exhibiting swells or spots
Potential Cause: Spilled oil or grease are or have been on the belt.
Fix: Locate the source of the spill/leak and improve housekeeping practices.
Potential Cause: The troughing idlers may be over-lubricated.
Fix: Again, improve maintenance practices.
Potential Cause: There may be oil in the material.
Fix: Remove the source of oil if possible. If this is not an option, replace belt with the proper oil-resistant covers for the application.
Problem: The cover is getting cut or slashed.
Potential Cause: When the cover is exhibiting cutting or slashing, this could be a result of sharp material impact.
Fix: If this is the case, impact idlers, load tables, or cradles can be added. Some narrower belts or those with lighter loads may require a softer drop zone (no horizontal idler) at the load area. The chute design could also be modified to allow for better delivery of the material to the belt. A slope could also be added to the chute to allow material to slide onto the belt more gently.
Potential Cause: Tramp iron or other material could also be causing the cutting/slashing.
Fix: Use a metal detector or overhead magnet above the head pulley.
Problem: The top cover is exhibiting wear such as grooving, gouging, longitudinal ripping, or stripping
Again, one of any number of factors may be at play, causing wear on the top cover:
Potential Cause: Hopper or skirt board rubber is too stiff where pressed.
Fix: Use pliable skirt board rubber (not old belt) and adjust properly, adjust skirt seals of minimum clearances, and/or install slides in place of outer troughing rolls.
Potential Cause: There may be a gap between idlers at the loading point, allowing material to grind between the belt and flashing.
Fix: Space idlers more closely at the loading point and adjust to proper clearance.
Potential Cause: Skirt board metal is too close to the belt.
Fix: Adjust to proper clearance.
Potential Cause: The width between skirts is too narrow.
Fix: Widen spacing and taper the opening in the direction of belt travel.
Potential Cause: Belt deflects at the loading point allowing material to jam between the seals and belt.
Fix: Use loading hopper with slides for belt edges, or shift the idler or chute so that loading impact is just ahead of the idler.
Potential Cause: Material is jamming against belts at the head pulley in full bin or plugged chute.
Fix: Add plug chute switches, or observe more careful operation.
If top cover wear is excessive, there could be another reason for the issue, such as:
Potential Cause: Return rolls may have a build up of material, causing them to stick.
Fix: If rolls are stuck, they will require repair or replacement. For dirty return rolls, install rubber disc returns. Ensure belt cleaners are functioning properly. Retention/replace belt scrapers where necessary.
Potential Cause: The belt may be dragging through spilled material.
Fix: Improve cleaning and housekeeping procedures.
Potential Cause: Loading conditions are poor (ex., side loading).
Fix: Improve chutes and hoppers.
Potential Cause: The cover may be of a low tensile rating.
Fix: When replaced, use a higher quality, and possibly heavier cover.
Potential Cause: There may be excessive sag between idlers caused by shifts in the load. Belt tension may be too loose.
Fix: Adjust pulleys to retention belt.
Be Proactive about Conveyor Issues
Any observed abnormalities in a conveyor system should be addressed immediately in order to avoid excess damage or failure. When the source of the problem is unclear, consult the OEM or other qualified service expert.
Routinely inspect the conveyor to catch problems before they have a chance to escalate. Having the OEM or other service technician conduct regularly scheduled conveyor inspections will also help to catch any potential problems early. The frequency of recommended inspections varies per operation, ranging from a couple times per year, to monthly in especially demanding cases.
Conclusion
The bulk material handling equipment in any operation is critical to maintaining process uptime and efficiency. Troubles with conveyors often manifest as a problem with the belt, but it can be hard to pinpoint the cause and know how to resolve it. Catching problems early is essential in avoiding unnecessary downtime and lost production. Consult a reputable service provider such as FEECO International to expedite issue identification and resolution.
FEECO has been engineering custom bulk material handling equipment and systems since 1951. Our customer service engineers are highly skilled in assessing process and handling systems, as well as implementing and/or retrofitting any adjustments or repairs needed. For more information on our conveyor services, contact us today!