Practical Guide to Conveyor Belt Maintenance: Track Adjustment, Weld Inspection, Belt Tension and Roller Replacement

1. Scope and Purpose

This practical guide describes the essential maintenance procedures for industrial conveyor systems. The primary goal is to ensure operational reliability, extend component life and maintain production efficiency. Specific attention is paid to the correct track adjustment of the belt, thorough inspection of belt welds, accurate measurement and correction of belt tension, and the systematic replacement of worn rollers. Performing these tasks correctly is crucial for preventing unplanned downtime and ensuring personnel safety. These procedures apply to various conveyor systems common in the Benelux manufacturing sector, including rubber, PVC and PU belts, and include both flat and trough configurations.

Preventive maintenance, as described herein, significantly reduces the risk of malfunctions. It is recommended that these inspections and maintenance tasks are performed as part of a structured preventive maintenance program or when visual indications suggest a deviation from normal operating parameters.

2. Safety measures

The safety of staff is our top priority at all times. Ignoring the safety precautions described below could result in serious injury or death.

• LOCKOUT/TAGOUT (LOTO): Before starting any work on the conveyor belt, it is mandatory to disconnect the machine from the power supply and secure it in accordance with the NEN-EN-ISO 14118 standard (Safety of machines - Prevention of unexpected start-up). Ensure complete isolation of all energy sources (electrical, hydraulic, pneumatic, mechanical) and locking with a personal lock and tag. Always test for no voltage with suitable measuring equipment.
• PERSONAL PROTECTIVE EQUIPMENT (PPE): Wear required PPE at all times, including:
  • Safety glasses (according to EN 166) for protection against flying particles.
  • Safety gloves (according to EN 388) to protect against sharp edges and crushing.
  • Safety shoes (according to EN ISO 20345) with steel toe and sole.
  • Hearing protection (according to EN 352) in noisy environments.
  • High-visibility clothing when working in an environment with moving traffic.
• DANGER ZONE: Stay out of the danger zone of rotating and moving machine parts. Keep a safe distance from the belt, drums and rollers when the belt is in operation.
• ELECTRICAL SAFETY: Turn off main switches and check for no voltage before inspecting or replacing electrical components. Follow the NEN 3140 standards for low-voltage installations.
• TRAPPING : Be alert to the risk of crushing between the belt and the rollers, drums, baffles or construction. Never use hands or tools to remove materials while the belt is running.
• FALLING OBJECTS: Ensure that all loose tools, parts or materials are secured to prevent falls, especially when working at height.
• CHEMICALS: When using cleaners, lubricants or repair materials, always consult the safety data sheets (SDSs) and use recommended PPE.
• SPACE: Provide sufficient working space around the conveyor belt. Place the necessary barricades and warning signs.

Always carry out a risk analysis before starting work and discuss it with the team.

3. Required Tools and Materials

A complete set of specific tools and suitable materials is essential for the safe and efficient execution of maintenance tasks. Before starting work, check the availability and good condition of all necessary equipment.

4. Pre-Maintenance Inspection Checklist

Perform this visual and functional inspection before starting detailed maintenance procedures. This helps identify priorities and the scope of work required.

5. Step-by-Step Procedure

5.1 Preparation and Safety

1. Gather all necessary tools and materials (see Section 3) and ensure they are in good condition.
2. LOCKOUT/TAGOUT (LOTO) PROCEDURE PERFORM:
   • Switch off the conveyor using the local control switch.
   • Identify and locate all energy sources of the conveyor system (main switch, motor protection, pneumatic valves, hydraulic pumps).
   • Turn off all energy sources and secure them in the 'off' position.
   • Place personal padlocks and Do Not Operate tags on all isolated energy sources.
   • Check the de-energization of electrical components with a calibrated multimeter (e.g. 400V AC and DC measurement), directly on the motor terminals.
   • Release any stored energy (e.g. hydraulic pressure, tire tension by securing counterweights).
   • If necessary, place physical blocks to prevent unintended movement.
3. Secure the work area with warning tape and place "Work in Progress" signs.

5.2 Track adjustment Conveyor belt (Tracking Adjustment)

This procedure is intended to correctly center the conveyor belt on the frame and prevent running against the side walls. This extends the life of the tire and construction.

1. Short Trial Run and Observation:
   • After releasing the LOTO (temporarily and for this purpose only), start the conveyor belt briefly and observe the belt's run. Note the direction and degree of deviation.
   • Turn the belt off again and perform the LOTO procedure again before continuing with the adjustment.
2. Identify Adjustment Points:
   • The adjustment is usually made at the tension or return drum, or via special steering rollers. Locate the adjustment bolts on the sides of the frame that affect the angle of the drum or roller.
3. Adjustment procedure:
   • If the belt deviates to one side (e.g. to the right), the drum/roller on the opposite side (left) should be moved slightly forward, or the side where the belt runs (right) slightly backward.
   • Use a wrench to loosen the adjustment bolts. Adjust the adjustment bolt in small increments of up to a quarter turn (90°).
   • Turn the adjustment bolt on the "lagging" side of the drum/roller (where the belt runs toward) slightly in (backwards), or turn the adjustment bolt on the "leading" side (where the belt runs away from) slightly out (forward). This forces the band to move to the "leading" side.
   • Avoid overcorrection. Too large adjustments can cause the tire to slip in the other direction and lead to instability and further damage.
4. Check and Repeat:
   • Repeat steps 1 and 3. Restart the tape (briefly) and observe the loop. Repeat the adjustment until the belt runs centrally. An acceptable lateral deviation is generally less than 5 mm on either side of the tire relative to the structure.
   • Also check that the rollers continue to rotate freely after adjustment.
5. Tightening:
   • Once the tire is tracking correctly, tighten the adjusting bolts securely with the torque wrench. Consult the machine specifications for the correct torque, usually 80-120 Nm for M12 bolts and 150-250 Nm for M16 bolts. This prevents unintentional shifts during operation.

5.3 Welding inspection Conveyor belt

The integrity of the belt weld determines the lifespan and reliability of the entire conveyor belt.

1. Locating Welds:
   • Rotate the belt manually or by jog control (after temporarily overriding LOTO) to locate all welds. Mark each weld for systematic inspection.
2. Visual Inspection of Vulcanized Welds:
   • Check vulcanized (bonded) welds for signs of delamination, blistering, cracking, topcoat detachment, or abnormal hardness. Pay extra attention to the edges and transitions of the weld.
   • Acceptance criteria: The weld must be visually seamless. No visible cracks or bubbles larger than 2 mm. The flexibility should not differ significantly from the rest of the tire.
   • Small hairline cracks seem harmless, but can quickly become larger under load. Document and monitor this critically.
3. Visual Inspection of Mechanical Welds:
   • Check mechanical (riveted or screwed) welds for loose fasteners, corrosion, protrusions, or wear of the metal elements. The ends of the weld must not touch the belt structure.
   • Acceptance criteria: All fastening elements must be securely fastened. No visible corrosion affecting structural integrity. No protruding parts that could snag materials or damage scrapers.
   • A loose mechanical weld area can irreparably damage the belt and is a safety risk. Address immediately.
4. Repair or Replacement:
   • If significant damage compromises tire integrity, repair or replacement of the splice should be considered. Refer to the tire or repair material manufacturer's instructions.

5.4 Tire Pressure Measurement and Adjustment

Proper belt tension is vital to prevent drive drum slippage and minimize excessive stress on bearings and the belt.

1. Safety:
   • Perform LOTO before performing inspections on the tensioning system.
2. Preparation:
   • Make sure the tire is empty and stationary.
3. Measurement of Tire Pressure:
   • Use a suitable tire pressure gauge. Follow the meter manufacturer's specific instructions.
   • Place the gauge on a flat and freely accessible part of the belt, preferably in the return section where the belt is unloaded.
   • Measure the belt tension at at least three different points along the belt (for example, near the drive drum, in the center of the return section, and near the return drum). Write down the values.
   • Compare the measured values ​​with the specifications provided by the conveyor belt manufacturer. Typical values ​​are between 2.0 N/mm and 3.5 N/mm bandwidth.
4. Tire Tension Adjustment:
   • If the measured tension is out of tolerance (usually ±10% of specification), it must be adjusted.
   • For screw tensioners: turn the adjusting screws evenly in or out to increase or decrease the tension. Make sure the drum axis remains parallel to the main axis. Measure again after each significant adjustment.
   • For counterweight tensioners: add or remove weight. Check the free movement of the weight system.
   • For hydraulic tensioners: adjust the pressure in the hydraulic system according to the manufacturer's instructions.
   • Insufficient belt pressure leads to belt slippage on the drive drum, causing wear and loss of capacity. Excessive belt tension overloads the bearings and the belt itself, resulting in premature wear and failure.
5. Check and Tighten:
   • Repeat the measurement after the tension has been adjusted.
   • Tighten all tensioning system locknuts and pins securely to the recommended torque (e.g. 100 Nm for tensioning screws).

5.5 Roller Replacement

Timely replacement of worn or defective rollers is essential for proper belt running and the prevention of belt damage.

1. Safety and Preparation:
   • Perform LOTO.
   • Identify the roller(s) to be replaced using the pre-inspection checklist (Section 4) and clearly mark it.
   • If necessary, remove the top layer of materials and clean the immediate area around the roller.
2. Removing Old Roller:
   • Support the conveyor belt at the level of the roller(s) to be replaced using safety blocks or a roller jack to lightly lift the belt and release pressure from the roller.
   • Remove any security covers or brackets that hold the roller in place.
   • Loosen and remove the roller locking pins or bolts.
   • Carefully remove the defective roller from the assembly. If necessary, use a rubber mallet to loosen stuck axles.
3. Roller Suspension Inspection:
   • Clean the roller suspension and inspect it for wear, corrosion, or structural damage. Repair or replace if necessary.
4. Installing New Roller:
   • Make sure the new roller matches the specifications of the roller to be replaced (diameter, length, axle size, bearing type).
   • Place the new roller in the suspension. Ensure correct alignment so that the roller axis is perpendicular to the belt track. This is crucial for straight belt running.
   • Secure the roller with the locking pins or bolts. Tighten the bolts with the torque wrench. Typical tightening torques for roller fastenings are 60-100 Nm for M10 bolts and 80-150 Nm for M12 bolts, depending on construction and bolt quality (according to EN ISO 898-1).
   • After tightening, check whether the roller can rotate freely.
   • If required, lubricate the bearings of the new roller with the recommended lubricant (ISO VG 220, NLGI 2).
   • Improper alignment of a new roller can cause immediate belt drift, edge damage, or excessive wear of the belt and other rollers. Always check the alignment carefully.
5. Finalization:
   • Remove the support blocks or jack.
   • Replace all security covers.

6. Post-Maintenance Verification Checklist

Perform these tests after completion of maintenance work to confirm correct operation of the conveyor system.

7. Troubleshooting manual

This table provides an overview of common symptoms, possible causes and corrective actions for conveyor systems.

8. Recommended Maintenance Schedule

A structured maintenance schedule helps maximize conveyor life and minimize operational risks. The frequency may vary depending on operating hours, load and environmental conditions.

9. Reference Spare Parts

For an efficient maintenance program, it is crucial to have the right spare parts in stock. Below you will find an overview of common components that can be replaced during conveyor belt maintenance.

For a complete overview of spare parts and detailed specifications, visit the UNITEC-D e-catalog: https://www.unitecd.com/e-catalog/

10. References

• NEN-EN-ISO 14118: Safety of machines - Prevention of unexpected start-up.
• NEN-EN-ISO 14122 (series): Safety of machines - Permanent means of access to machines.
• NEN 3140: Operation of electrical installations - Low voltage.
• EN 166: Personal Eye Protection – Specifications.
• EN 388: Protective gloves against mechanical risks.
• EN ISO 20345: Personal protective equipment – ​​Safety shoes.
• EN 352 (series): Hearing protectors.
• ISO 6789: Measuring tools – Torque wrenches and torque screwdrivers – Requirements and test methods.
• ISO VG 220: Industrial gear oil (standard for lubricant viscosity).
• NLGI 2: Consistency class of fat.
• CE Machine Directive 2006/42/EC: For the safety of machines.
• ATEX Directive 2014/34/EU: Concerning equipment and protective systems intended for use in potentially explosive atmospheres (if applicable to your installation).
• Original Equipment Manufacturer (OEM) manuals and specifications.