1. Problem Description and Scope
This guide is intended for maintenance technicians, reliability engineers, and maintenance managers experiencing jams or overloading incidents on chain conveyor systems. These problems manifest themselves as an unexpected shutdown of the equipment, excessive current consumption of the motor, abnormal noises (squeaking, clicking) or visible degradation of the chain and associated components. These failures, if not addressed, can lead to critical production shutdowns, irreversible damage to equipment and risks to personnel safety. This document addresses major causes such as chain elongation, sprocket wear, lubrication failure and material buildup, specifically for applications in the aerospace and energy industries, where reliability is essential.
Equipment affected: All types of chain conveyors (roller, cleat, scraper, elevator) used for the transport of unit or bulk loads.
Severity classification:
- Critical: Total shutdown of the production line, immediate safety risk.
- Major: Significant reduction in capacity, progressive damage to equipment, potential safety risk.
- Minor: Intermittent abnormal noises, slight increase in power consumption, warning signs of wear.
2. Safety Precautions
CAUTION: Before any intervention on the conveyor, it is CRITICAL to apply the Lockout/Tagout procedure (Lockout/Tagout, LOTO) in accordance with standard NF C 18-510 or the company's internal directives to prevent any untimely start-up. Stored energy (mechanical, electrical, hydraulic, pneumatic) must be dissipated. Wearing Personal Protective Equipment (PPE) is mandatory: protective gloves EN 388, safety glasses EN 166, safety shoes EN ISO 20345, and protective helmet EN 397.
RISK OF MOVING PARTS: Never work on a live or moving conveyor. Chains, sprockets and scrapers can cause crushing, shearing and tearing.
RISK OF BURN: Motors, gearboxes and bearings can reach high temperatures (above 60°C). Use an infrared thermometer to check the temperature before contact.
HANDLING LUBRICANTS: Use appropriate gloves and avoid prolonged contact with the skin. Consult product safety data sheets (MSDS).
3. Required Diagnostic Tools
| Tool | Specification/Model | Typical Measuring Range | Objective |
|---|---|---|---|
| CAT III digital multimeter | True RMS, min. 1000V AC/DC, 10A AC/DC | Voltage (V), Current (A), Resistance (Ω) | Motor current measurement (overload diagnosis), circuit continuity. |
| Vibration analyzer | Triaxial accelerometer, resolution 0.1 mm/s | 0 - 50 mm/s (RMS) | Detection of bearing wear, misalignment, pinion tooth defects. |
| Infrared thermal camera | Resolution ≥ 160x120 pixels, sensitivity ≤ 0.05 °C | -20°C to +650°C | Identification of hot spots (failing lubrication, excessive friction, engine overheating). |
| Digital caliper | Accuracy 0.02 mm, range 0-300 mm | Linear dimensions | Measurement of chain elongation (chain pitch), sprocket wear (tooth width, bore depth). |
| Chain elongation gauge | Specific to chain pitch | % elongation | Direct measurement of chain wear by elongation. |
| Chain tension meter | Mechanical or electronic | Force in N or kgf | Checking the correct chain tension. |
| Industrial endoscope | Diameter ≤ 8 mm, flexible length, LED lighting | Visual inspection | Inspection of inaccessible areas (accumulation of materials, condition of bearings). |
| Strobe | Frequency range 30-30000 FPM | Rotation speed/frequency | Observation of the movements of the chain and sprockets at apparent slow speed. |
4. Initial Assessment Checklist
| Control Element | Observation / Information to Record | Acceptable Value / Note |
|---|---|---|
| Operating conditions | Load transported (mass, volume), conveyor speed, operating cycle. | Within equipment design limits. |
| Alarm/fault history | Drive error codes, PLC, supervisory systems (SCADA). | Note possible frequencies and correlations. |
| Recent changes | Maintenance carried out, replacement of parts, adjustments of parameters, change of product conveyed. | Any modification can be a potential cause. |
| Motor electrical consumption | Reading on integrated ammeter or measurement with multimeter. | Lower than the nominal current (In) or the defined alarm threshold (e.g., < 80% In at nominal regime). |
| General visual inspection | Presence of foreign bodies, debris, accumulation of materials, visible deformations (chain, support), condition of the crankcase. | Absence of any obstructive or damaged element. |
| Abnormal noises and vibrations | Type of noise (clicking, grinding, rubbing), approximate location. | Smooth, quiet operation. |
| Lubrication status | Presence of lubricant on the chain, color, apparent viscosity. | Visible, clean and uniform lubricant film. |
5. Systematic Diagnostic Flowchart
This path must be followed sequentially to isolate the root cause of the jam or overload.
- Start of Diagnosis
- Initial symptom: Conveyor stoppage or motor overload.
- Action: Proceed to lockout (LOTO) of the equipment.
- Action: Complete the Initial Assessment Checklist (Section 4).
- Initial symptom: Conveyor stoppage or motor overload.
- Checking for Mechanical Obstruction and Material Buildup
- Question: Is there an obvious visual obstruction (foreign body, product buildup) along the chain path or at the sprockets?
- If YES:
- Action: Remove the obstruction.
- Action: Check the integrity of the chain and sprockets after removal.
- Action: Resolution: Restart and observe. If the problem persists, go to step 3.
- If NO: Go to step 3.
- If YES:
- Question: Is there an obvious visual obstruction (foreign body, product buildup) along the chain path or at the sprockets?
- Chain Wear Diagnosis (Elongation)
- Action: Measure the elongation of the chain using an elongation gauge or a caliper over a section of at least 10 steps (ref. EN ISO 606).
- Measurement: Nominal elongation = Measured length / (Nominal pitch x Number of steps).
- Alarm Threshold:Elongation > 1.5% of the nominal pitch (for power transmission chains). Elongation > 2% for conveyor chains.
- Question: Does the measured elongation exceed the acceptable threshold?
- If YES (Excessive elongation):
- Probable cause: Wear of the chain joint.
- Action: Confirm by visual inspection (excessive clearances).
- Resolution: Chain replacement (Section 8.1). Proceed to step 6 for preventive measures.
- If NO: Go to step 4.
- If YES (Excessive elongation):
- Action: Measure the elongation of the chain using an elongation gauge or a caliper over a section of at least 10 steps (ref. EN ISO 606).
- Gear Wear Diagnosis
- Action: Visually inspect the gears (motor and transmission) for signs of wear in
