Diagnostics and Troubleshooting Guide: Conveyor Belt Convergence

1. Description of the problem and scope of application

Conveyor belt overlap is a critical fault that results in significant operational problems, including belt edge damage, material spillage, conveyor structural damage, and unplanned shutdowns. This manual is intended to systematically diagnose and eliminate the causes of belt overlap on various types of belt conveyors used in Ukrainian industrial production, including stationary, mobile and inclined conveyors.

Classification of severity:

• Critical: The belt constantly overlaps when touching the conveyor frame, resulting in rapid belt damage, component destruction, or a high risk of fire. Immediate stop of the conveyor is mandatory.
• Severe: The tape periodically overlaps or has a marked tendency to overlap, causing moderate shedding of material and gradual damage to the edges of the tape. Requires immediate intervention.
• Minor: Slight, sporadic tape overlap without significant shedding or damage. It can be a warning sign of more serious problems. Requires monitoring and scheduled diagnostics.

2. Precautions

SAFETY WARNING: Before performing any diagnostic or repair work on the belt conveyor, be sure to follow the lockout and tagout (LOTO) procedures in accordance with NPAOP 0.00-1.76-18 (Occupational safety rules during the operation of load-lifting cranes, lifting devices and the corresponding equipment) and internal standards of the enterprise. Make sure all power sources (electrical, hydraulic, pneumatic) are disconnected and locked out. Note the accumulated energy in the conveyor tensioning devices (counterweights, hydraulic/pneumatic tensioners). Use appropriate personal protective equipment (PPE): safety glasses, helmet, protective gloves, safety shoes. Avoid moving parts of the conveyor while it is in operation, except when required by a diagnostic procedure that does not require physical contact. Comply with DSTU EN ISO 12100:2016 standards (Machine safety. General design principles. Risk assessment and risk reduction).

3. Necessary diagnostic tools

4. Initial evaluation checklist

5. Systematic diagnostic algorithm

This algorithm will help systematically identify the root cause of tape overlap.

1. Determine the overlap area:
   • If the belt overlaps at the loading area:
     1. Check the centering of the material loading:
        • If the material is fed asymmetrically → Go to the section "Uneven material loading"
        • If the material is fed symmetrically → Continue
     2. Check the condition of the lining of the loading chute and aprons:
        • If the lining is worn/missing, the aprons are displaced → Go to the section "Wearing of linings/aprons"
        • If lining and aprons are OK → Continue
     3. Check the roller supports of the loading area:
        • If the rollers are dirty/jammed/missing/incorrect angle → Go to the section "Malfunctions of the roller supports"
        • If the rollers are normal → Continue
   • If the belt coincides on the drive or tension pulley:
     1. Check the alignment of the pulleys and the perpendicularity of the axis of the pulleys to the axis of the conveyor:
        • If the pulleys are not aligned/perpendicular → Go to the section "Violation of the axis of the pulleys"
        • If the alignment and perpendicularity are normal → Continue
     2. Check the condition of the lining of the pulleys:
        • If the lining is worn/damaged/missing/material build-up → Go to the section "Wear of the lining of the pulleys"
        • If lining is normal → Continue
     3. Check the condition of the pulley bearings (vibration, temperature):
        • If the bearings overheat/vibrate → Go to the section "Pulley bearing malfunctions"
        • If the bearings are normal → Continue
   • If the tape matches in the middle area (upper/lower branch):
     1. Check the uniformity of the tape tension across the width:
        • If the tension is uneven → Go to the section "Uneven tape tension"
        • If the tension is even → Continue
     2. Check the condition of the roller supports in this area:
        • If the rollers are dirty/jammed/missing/incorrect angle → Go to the section "Roller support malfunctions"
        • If the rollers are normal → Continue
     3. Check the uniformity of the thickness and stiffness of the tape, the condition of the joint:
        • If the tape has deformations, edge damage, poor joint → Go to the section "Defects of the tape or joint"
        • If the tape is normal → Continue
     4. Check the horizontality and straightness of the conveyor frame:
        • If the frame is deformed/not horizontal → Go to the section "Deformation of the conveyor frame"
        • If the frame is normal → Continue
2. General checks:
   1. Check the overall belt tension:
      • If the tension is insufficient or excessive → Go to the section "Incorrect overall belt tension"
      • If the tension is normal → Continue
   2. Check the operation of the centering rollers/roller stations:
      • If the centering rollers are jammed/not working → Go to the section "Centering roller malfunction"
      • If the centering rollers are normal → Maybe a complex problem, go through all the previous points again.

6. Matrix "Symptom - Cause - Diagnostic test"

7. Root cause analysis of malfunctions

Violation of alignment of pulleys

Explanation: Pulleys, especially the drive and tension pulleys, play a key role in maintaining the linear movement of the belt. Violation of their alignment or perpendicularity to the axis of the conveyor causes an oblique displacement of the belt. This can be axial displacement (pulleys not parallel) or angular (pulleys not perpendicular to the belt). Frequent reasons are installation errors, deformation of support structures, loosening of fasteners, wear of bearings.

How to confirm: Use a laser alignment meter. The permissible deviation from the parallelism of the pulley axes should not exceed 0.5 mm per 1 meter of the pulley length. Measure the diagonals of the conveyor frame from the center of the pulleys - they should be equal. Check the horizontality of the pulleys with a level.

Damage if not corrected: Prolonged overlap leads to rapid wear of belt edges, damage to pulley linings, premature failure of pulley bearings due to uneven loading, damage to conveyor frame.

Uneven material loading

Explanation: If the bulk material is fed onto the belt asymmetrically (off to one side), this creates an uneven load distribution and causes the belt's center of gravity to shift, causing it to run toward the higher load. This is often seen at loading points due to improper adjustment of loading chute, discharge plows or deflectors.

How to confirm: Visual inspection of the loading point during operation. The material must be evenly distributed along the central axis of the tape. Check the condition and position of the guide aprons and their clearance to the belt, which should be 5-10 mm.

Damage if not eliminated: Spilling of material, contamination of the conveyor area, rapid wear of belt edges, damage to roller supports due to sticking of material.

Tape or joint defects

Explanation: The conveyor belt itself may be the source of the problem. Damage to the edges, delamination, uneven thickness, or most often - a poor quality or damaged joint. A joint that is not flat, perpendicular to the belt axis, or has uneven stiffness across the width will act as a constant force causing the belt to overlap.

How to confirm: Thorough visual inspection of the tape along its entire length, paying special attention to the edges and all joints. Check the evenness of the joint using a ruler or level. Measure the width of the tape in several places.

Damage if not repaired: Complete destruction of the belt at the defect/joint, resulting in long-term conveyor downtime and significant replacement costs.

Malfunctions of roller bearings

Explanation: Roller supports (carrying and supporting) must rotate freely and be perpendicular to the axis of motion of the belt. If the roller jams, it becomes a stationary point of friction, causing the tape to overlap. Skewed rollers or roller supports also actively affect the direction of movement of the belt. Contamination of the rollers or their incorrect installation can also be the cause.

How to confirm: Visual inspection of all rollers during conveyor operation (from a safe distance). If the roller does not rotate, this is a malfunction. Use an ultrasonic detector to detect roller bearing noise or a thermal imager to detect overheating (roller bearing temperature > 80°C - emergency value, > 60°C - attention). Check the installation angle of the rollers (for grooved roller supports). The permissible skew of the roller support is no more than 2 mm per 1 meter.

Damage if not repaired: Belt wear, increased energy consumption, roller bearing destruction, roller axis damage, possible ignition from overheating.

Incorrect tape tension

Explanation: Belt tension is critical for its stable movement. Insufficient tension causes the belt to slip on the drive pulley and cause it to oscillate, which can cause overlap. Excessive tension, on the other hand, causes excessive stress on the pulley and roller bearings, accelerates belt wear and can cause it to break. Uneven tension across the width of the tape will also cause overlap.

How to confirm: Use a strain gauge to measure belt tension according to the conveyor or belt manufacturer's recommendations. Typically, the working tension is 2-4 N/mm of tape width, or 1.5-2.5% of the breaking strength. Check the operation of the tensioner.

Damage if not repaired: Belt slippage, increased drive pulley wear, rapid belt wear, bearing failure, belt rupture.

8. Step-by-step troubleshooting procedures

SAFETY ALERT: Always perform LOTO before any physical intervention on the conveyor.

8.1. Alignment of pulleys

1. Perform the LOTO procedure.
2. Clean the surfaces of pulleys and bearing assemblies from dirt.
3. Install the laser alignment meter on the pulleys (drive and tensioner, or other problematic ones).
4. Measure current values ​​of axial and angular deviation.
5. Adjust the position of the pulley support bearings using special adjusting bolts or shims until the deviation values ​​are within ±0.25 mm per 1 meter.
6. Check the fixation of the fastening bolts. Tightening torque according to tables ISO 898-1 (Mechanical properties of fasteners).
7. Remove the LOTO and perform a test run of the conveyor with no load, observing the belt movement.

8.2. Material loading adjustment

1. Perform the LOTO procedure.
2. Check the position of the loading bucket, unloading plows and deflectors.
3. Adjust the position of these elements to ensure a symmetrical and central flow of material onto the belt.
4. Check the clearances of the aprons of the conveyor: they should be 5-10 mm above the belt to prevent spillage, but not to create excessive friction.
5. Remove the LOTO and perform a test run with the minimum load, gradually increasing it while watching the tape move.

8.3. Belt or joint repair/replacement

1. Perform the LOTO procedure.
2. If the tape has minor edge damage or local delamination, repair using cold vulcanizing adhesive or special repair materials according to the manufacturer's instructions (UNITES-D: Tape Repair Kits).
3. If the joint of the tape is damaged or uneven, it is necessary to perform its complete processing (vulcanization) or mechanical connection in accordance with the technology. Make sure the new joint is flat, perpendicular to the axis of the tape and has the same thickness across the entire width.
4. In case of significant damage or degradation of the tape, complete replacement of the tape.
5. Remove LOTO and test run the conveyor.

8.4. Maintenance/replacement of roller bearings

1. Perform the LOTO procedure.
2. Identify any jammed, damaged or missing rollers.
3. Replace defective rollers with new ones that meet OEM specifications.
4. Check that all rollers rotate freely.
5. Make sure that all roller supports are installed perpendicular to the axis of the conveyor. If necessary, adjust their angle of inclination using a level and tape measure. Permissible skew ≤ 1 mm per 1 meter of roller support length.
6. Clean the rollers and roller supports from the adhering material.
7. Remove LOTO and test run.

8.5. Tape tension adjustment

1. Perform the LOTO procedure.
2. Loosen the tensioner to the minimum level.
3. Gradually increase the tension using the values ​​recommended by the conveyor manufacturer. Measure the tension of the tape with a strain gauge. Aim for optimum tension to avoid slippage on the drive pulley without overstressing the system.
4. SAFETY WARNING: When working with tension devices, be careful with spring and counterweight systems as they have significant stored energy.
5. After the initial adjustment, remove the LOTO and start the conveyor. If necessary, fine-tune the tension during operation (if possible and safe), avoiding direct contact with the moving belt.

9. Precautions

10. Spare parts and components

To order spare parts and components, refer to our e-catalog UNITEC-D.

11. Links

• NPAOP 0.00-1.76-18. Rules of labor protection during operation of cranes, lifting devices and corresponding equipment.
• DSTU EN ISO 12100:2016. Machine safety. General design principles. Risk assessment and risk mitigation.
• DSTU 3051-95. Conveyors. Terms and definitions.
• DSTU 2439:2018. Conveyor belts made of rubber fabric. General technical conditions.
• ISO 5048:2020. Continuous mechanical handling equipment – ​​Belt conveyors with carrying idlers – Calculation of operating power and tensile forces.
• ISO 898-1:2013. Mechanical properties of fasteners made of carbon steel and alloy steel – Part 1: Bolts, screws and studs with specified property classes – Coarse thread and fine pitch thread.
• ISO 10816-3:2009. Mechanical vibration – Evaluation of machine vibration by measurements on non-rotating parts – Part 3: Industrial machines with nominal power above 15 kW and nominal speeds between 120 r/min and 15,000 r/min when measured in situ.
• Conveyor Equipment Manufacturers (OEM) Operation and Maintenance Manuals.