Maintenance Guides 1 min read

Diagnostics and Troubleshooting Guide: Jamming and Overloading of Chain Conveyors

Technical analysis: Troubleshooting chain conveyor jamming and overload: chain elongation, sprocket wear, lubrication fa

1. Description of the problem and scope of application

This manual is intended for diagnosis and troubleshooting related to jamming and overloading of chain conveyors operated at industrial enterprises of Ukraine. It covers common causes of failure such as chain elongation, sprocket wear, insufficient lubrication and material build-up. Jamming and overloading can lead to unplanned production stoppages, equipment damage and increased maintenance costs. This manual applies to all types of chain conveyors used to transport bulk materials, artificial loads and products in heavy industry.

  • Critical malfunction: Sudden complete jamming of the conveyor, which leads to an immediate stop of the production line. Requires immediate intervention.
  • Serious Malfunction: Frequent stalling or intermittent stalling, causing a significant decrease in performance and load on the drive.
  • Minor fault: Increased noise, vibration or motor current fluctuations, indicating the initial stages of a problem.

2. Precautions

WARNING! Before starting any diagnostic or repair work on the chain conveyor, strict safety precautions must be followed to prevent injury and equipment damage. Failure to follow these rules can lead to serious consequences.

  • LOCKOUT / TAGOUT (LOTO): Always perform the Lockout/Tagout procedure in accordance with the company's internal standards and DSTU requirements EN 1037. Make sure that all sources of energy (electrical, hydraulic, pneumatic) are isolated and blocked. Check the absence of voltage with appropriate devices.
  • STORED ENERGY: Some conveyors may have chain tension systems (spring, hydraulic) or accumulators that store energy. Before starting work, make sure that all stored energy is discharged or locked.
  • PERSONAL PROTECTIVE EQUIPMENT (PPE): Always use appropriate PPE, including safety glasses (DSTU EN 166), safety gloves (DSTU EN 388), safety shoes (DSTU EN ISO 20345) and protective clothing. When working with increased noise - hearing protection equipment (DSTU EN 352).
  • CLAMPING POINTS AND MOVING PARTS: Avoid contact with moving parts of the conveyor. Be aware of pinch points even when the conveyor is off, but has the potential to move due to residual stress.
  • HOT SURFACES: Some components (motor, reducer, bearings) may be hot after the conveyor is in operation. Be careful.

3. Necessary diagnostic tools

The following set of tools is required for effective diagnosis:

Tool Specification / Model Measuring range Purpose
Digital multimeter Accuracy class not lower than 0.5%, TRMS Voltage: up to 1000 V AC/DC; Current: up to 10 A AC/DC; Resistance: up to 40 MΩ Measuring motor current, checking electrical circuits.
Vibration analyzer Frequency range 10 Hz - 10 kHz, measurement of RMS (RMS) vibration speed Vibration speed: 0 - 100 mm/s (RMS) Detection of imbalance, misalignment, bearing defects and component wear.
Thermal imager (infrared camera) Temperature range: -20°C to +350°C, thermal sensitivity 0.05°C Temperature: 0°C to +250°C Detection of overheating of bearings, engines, gearboxes, friction points.
Chain Wear Gauge For the corresponding chain step (ISO 606, DIN 8187/8188) Elongation: up to 3% of the nominal length Direct measurement of chain elongation.
Caliper / Micrometer Range: 0-300 mm (caliper); 0-25 mm (micrometer), accuracy 0.02 mm / 0.001 mm Dimensions: up to 300 mm Measurement of wear of sprocket teeth, shaft diameters.
Tachometer (contact / non-contact) Range: 10 - 20000 rpm Rotational frequency: rev/min Measurement of the actual speed of the conveyor and the motor.
Stroboscope Flash frequency range: 50 - 10000 Hz Frequency: Hz Visual control of the movement of the chain and sprockets under load.

4. Initial assessment checklist

Before starting a detailed diagnosis, it is necessary to collect information about the current state and history of the conveyor:

Checkpoint Observation description / Data recording Purpose
General symptoms Describe exactly what happened: sudden jamming, gradual slowing down, unusual noises, vibrations, smell of burning, smoke. Record the time and circumstances. Determine the nature of the malfunction.
Working conditions What material was transported? What was the ambient temperature? Was the conveyor at full capacity? Identify the factors that could have contributed to the malfunction.
Event Log / Alarm History Check the conveyor control panel or the A/C system for error codes, motor overload warnings, overheating, etc. Record the sequence of events. Get failure history and identify previous signals.
Visual overview Inspect the conveyor along its entire length: the presence of accumulated material, damage to the chain (broken links, rollers), sprockets (broken teeth, significant wear), guides, tension stations. Identify obvious mechanical damage or foreign objects.
Lubrication level Check the oil level in the gearbox and the centralized lubrication system (if applicable). Check for grease on the chain. Assess the condition of the lubrication system.
Last Service When was the last maintenance performed (lubrication, tension adjustment, wear check)? Has work been done that could affect the conveyor? Link the fault with service cycles.
Appearance of the material Have the properties of the transported material changed (moisture, particle size, abrasiveness)? Determine the effect of the material on the conveyor.

5. Systematic diagnostics (Block diagram of solutions)

Diagnosis of jamming and overloading of the chain conveyor should be carried out sequentially:

  1. SYMPTOM: Conveyor suddenly stopped or does not start with motor current exceeding.
    1. Check 1: Presence of foreign objects and material accumulation.
      • Actions: After activating LOTO, carefully inspect the conveyor path, loading/unloading area, tensioning and driving stations.
      • IF significant accumulation of material or foreign object is detected:
        1. Probable cause: Blockage due to material or foreign object.
        2. Actions: Remove the obstacle. Check the operation of the conveyor.
      • IF there are no obvious obstructions: Go to 1.b.
    2. Check 2: Motor voltage and current, protection status.
      • Actions: Caution live! Measure the motor voltage and current in all phases with a multimeter (clamps). Check the operation of thermal relays, automatic switches.
      • IF the current is significantly higher than rated (greater than 120% of rated) when trying to start:
        1. Probable cause: Conveyor mechanical jamming or motor/gearbox failure.
        2. Actions: Go to 1.c.
      • IF the current is normal, but the motor does not rotate:
        1. Probable cause: Malfunction of the motor (phase break, interturn short circuit), clutch or gearbox.
        2. Actions: Activating LOTO. Disconnect the motor from the gearbox. Try starting the engine without load. Check the resistance of the motor windings. If the engine runs, check the gearbox and clutch.
    3. Check 3: Check chain tension.
      • Actions: Activate LOTO. Visually assess the chain slack on the idler arm. Measure the sag according to the manufacturer's recommendations (usually 1-2% of the distance between the centers of the sprockets).
      • IF chain sags too much (more than 2%):
        1. Probable cause: Chain lengthening.
        2. Actions: Go to section 7.1.
      • IF the tension is excessive (the chain is stretched like a string):
        1. Probable cause: Incorrect adjustment or jamming of the tension station.
        2. Actions: Go to section 7.4.
    4. Check 4: Assess sprocket wear.
      • Actions: Activate LOTO. Inspect drive and tension sprocket teeth for wear (hook wear, sharpening, uneven profile).
      • IF significant sprocket wear is found:
        1. Probable cause: Sprocket wear.
        2. Actions: Go to section 7.2.
    5. Check 5: Lubrication Status.
      • Actions: Activate LOTO. Check for lubrication on chain links. Assess the quality of the lubricant (contamination, discoloration).
      • IF the chain is dry, rusty, or the oil is dirty:
        1. Probable cause: Insufficient lubrication or use of the wrong oil.
        2. Actions: Go to section 7.3.
  2. SYMPTOM: Increased noise, vibration, jerks during conveyor operation.
    1. Check 1: Visual inspection of chain movement.
      • Actions: Caution! Moving parts! Watch the movement of the chain along its entire length, especially in the areas of sprockets, turns and tension stations. Use a strobe for slow motion.
      • IF there is uneven movement, "floating" of the chain on the teeth of the sprockets or frequent jerks:
        1. Probable cause: Chain elongation and/or wear of the sprockets.
        2. Actions: Go to 2.b.
    2. Check 2: Vibration measurement.
      • Actions: Using a vibration analyzer, measure the vibration on the bearings of the engine, gearbox, drive and tension shafts.
      • IF the vibration exceeds the allowable limits (for example, more than 4.5 mm/s of the SCZ for class ISO 10816-3):
        1. Probable cause: Bearing wear, misalignment, chain elongation, sprocket wear.
        2. Actions: Analyze the vibration spectrum to accurately identify the source. Go to sections 7.1, 7.2.
    3. Check 3: Temperature control.
      • Actions: Using a thermal imager, measure the temperature of the engine housing, gearbox, bearings, as well as the chain and sprocket sections.
      • IF bearing temperature exceeds +70°C, or gearbox > +90°C, or significant local overheating (>20°C relative to adjacent areas):
        1. Probable cause: Insufficient lubrication, excessive friction, overloading, wear of bearings/teeth.
        2. Actions: Go to sections 7.3, 7.4.

6. Matrix "Failure-Cause"

Symptom Probable causes (in descending order of probability) Diagnostic test Expected result (if the cause is confirmed)
Conveyor suddenly jams, does not start 1. Foreign object / Significant accumulation of material
2. Jamming of the tension station
3. Chain breakage or sprocket tooth damage
4. Jamming of the shaft bearing		 Visual inspection; Manual scrolling (after LOTO); Overview of the tensioning station The presence of a foreign object; The tensioning station does not move; Visible break/damage; The bearing does not rotate.
Engine overload, frequent stops, protection tripping 1. Excessive elongation of the chain
2. Significant wear of the sprockets (especially the drive sprocket)
3. Insufficient lubrication of chain/bearings
4. Excessive accumulation of material along the tract
5. Incorrect adjustment of the chain tension (excessive tension)		 Measurement of chain elongation; Review of stars; Inspection of the lubrication system; Visual inspection of the tract; Measuring chain slack. Elongation > 3%; Hook-like wear of teeth; Dry or rusty hinges; The material blocks movement; Slack < 1% or very tight.
Increased noise, grinding, chain jerks 1. Extension of the chain
2. Wear of sprockets
3. Insufficient lubrication
4. Misalignment of shafts / Shifting of supports
5. Contamination or wear of the guides		 Measurement of chain elongation; Review of stars; Lubrication check; Measurement of misalignment of shafts (indicator); Visual inspection of the guides. Chain extension; Hook-shaped wear; Lack of lubrication; Misalignment > 0.1 mm; Visible wear of the guides.
Local overheating (bearings, chain, gearbox) 1. Insufficient lubrication
2. Bearing wear
3. Excessive chain tension
4. Conveyor overload
5. Malfunction of the gearbox		 Thermal imager; Lubrication check; Tension measurement; Motor current measurement; Inspection of the gearbox (lubricant level/quality). Bearing temperature > 70°C; The bearing "makes noise"; Excessive tension; Motor current > nominal; Contaminated lubricant in the gearbox.

7. Analysis of the root causes of malfunctions

7.1. Chain extension

Explanation: Chain elongation is a natural process that occurs due to wear of the surfaces of the hinge joints (fingers and bushings). Under the influence of load and cyclic movement, the metal of the hinges gradually wears, increasing the pitch of the chain. This leads to the fact that the chain begins to run unevenly on the teeth of the sprocket, causing shocks, vibration and increased friction. According to DSTU EN ISO 606, the maximum permissible elongation of the chain before replacement is 3% of the initial length.

How to confirm: LOTO activation. Use a chain elongation meter or manual method: measure the length of 10-20 chain steps (depends on total chain length) without tension and compare it to the nominal length (N * chain steps). Calculate the percentage elongation. Check several sections of the circuit.

Damage, if not eliminated: Uneven load on the teeth of the sprockets leads to their accelerated wear, especially hook-shaped. Vibration and noise increase, the load on the bearings and gearbox increases. It is possible for the chain to "jump out" of the sprocket or break it, which will lead to an emergency stop and significant damage to the conveyor and drive mechanism.

7.2. Sprocket wear

Explanation: Sprocket tooth wear is the result of constant contact and friction with the chain. Sprockets are subject to abrasive wear (especially when material hits), fatigue wear, and sliding wear, especially when the chain is extended. A hook-shaped profile of the teeth, sharpening or thinning of the teeth indicate significant wear, which worsens the engagement with the chain.

How to confirm: LOTO activation. Visual inspection of sprocket teeth. Pay attention to the hook-shaped profile, the sharpening of the tops of the teeth, the thinning of the base of the tooth. Use a caliper to measure tooth thickness and compare to new sprockets or manufacturer's wear tolerances.

Damage if not repaired: Worn sprockets do not provide proper engagement with the chain, resulting in "slippage", shock loads and increased vibration. This accelerates the wear of the chain and bearings, and can cause the chain or sprocket to break, leading to a serious accident and downtime.

7.3. Insufficient lubrication

Explanation: Lubricant plays a critical role in reducing friction and wear in chain link joints and bearings. Insufficient or poor-quality lubrication leads to direct contact of metal surfaces, which causes a significant increase in friction, intensive wear and overheating. High temperature reduces the viscosity of the lubricant, impairing its protective properties.

How to confirm: Activation of LOTO. Visual inspection of the chain (especially the hinges) - it should be covered with a thin film of grease. Check the level and condition of the grease in the centralized lubrication system, if any. Measure the temperature of the chain and bearings with a thermal imager during operation (if safe and possible).

Damage if not corrected: Increased friction and overheating lead to rapid chain elongation, bearing failure, loss of conveyor efficiency and significant increase in energy consumption. The end result is conveyor jamming, component failure, and unscheduled repairs.

7.4. Accumulation of material and jamming of the tensioning station

Explanation: Excessive accumulation of transported material (loose materials, dust, small fractions) on the conveyor frame, under the chain, on the guides or in the area of ​​the tensioning station can create additional resistance to the movement of the chain. This increases the load on the drive and can lead to jamming. The tension station can jam due to material build-up or corrosion, preventing the chain from compensating for its elongation.

How to confirm: LOTO activation. Thorough visual inspection of the entire conveyor path, especially under the chain, in the places of turns, tensioning and drive stations. Check the mobility of the tension station, try to manually move it. Check for corrosion or mechanical interference.

Damage if not removed: Material build-up causes engine overload, increased chain and sprocket wear, and can cause complete seizing. Jamming of the tension station does not allow maintaining the correct tension of the chain, which leads to its excessive sag or, conversely, to excessive tension and destruction.

8. Step-by-step troubleshooting procedures

8.1. Elimination of chain elongation

  1. Diagnosis: Measure the elongation of the chain. If the elongation exceeds 3%, the chain needs to be replaced. If the elongation is less than 3% and there is a margin of travel of the tensioning station, the adjustment can be performed.
  2. Tension adjustment (for elongation up to 3%):
    1. LOTO activation.
    2. Loosen the fastening of the tensioning station.
    3. Use the adjusting bolts or the hydraulic system to move the idler sprocket until the optimum sag is achieved. Typical sag: 1-2% of the distance between the centers of the sprockets on the idle branch. Control the sag in the center of the span.
    4. Tighten the tensioning station fasteners to the torque recommended by the manufacturer (for example, 150-200 Nm for M20 bolts).
    5. Verification: Remove LOTO. Carry out a test run of the conveyor without load, then under load. Check the smoothness of the chain movement, the absence of jerks, vibration and excessive noise. Monitor the motor current.
  3. Chain replacement (for lengthening more than 3%):
    1. Activating LOTO.
    2. Dismantle the old chain. It may be necessary to cut it or separate it with a special tool.
    3. Install a new chain. Make sure the direction of chain travel is in accordance with the manufacturer's recommendations.
    4. Adjust the tension of the new chain as described above.
    5. Verification: Remove LOTO. Do a test run, controlling the parameters. Make sure all connections are secure.

8.2. Replacement of worn sprockets

  1. Diagnosis: Inspect the sprocket teeth for hook-like wear, sharpening.
  2. Replacement:
    1. Activation of LOTO.
    2. Dismantle the drive (or tension) sprocket. Pullers and special tools may be required.
    3. Install a new sprocket. Make sure it is oriented correctly and sits on the shaft without play. Fasten it according to the instructions (for example, with a torque of 300 Nm for a wedge connection).
    4. Critical: If a sprocket is replaced, it is always recommended that the chain be replaced as well, as a worn sprocket and an old extended chain will not work effectively together and will accelerate the wear of the new component.
    5. Verification: Remove LOTO. Carry out a test run, controlling the smoothness of the movement, the absence of noise and vibration.

8.3. Restoration and optimization of lubrication

  1. Diagnosis: Visual inspection of the chain, checking the level and quality of the lubricant in the gearbox and lubrication system.
  2. Procedure:
    1. Activating LOTO.
    2. Thoroughly clean the chain from old dirty grease, dust and abrasive particles. Use appropriate cleaners.
    3. Use the chain lube recommended by the manufacturer (eg mineral lube with adhesive additives ISO VG 220-460 or high temperature synthetic lube). Apply grease to the inside of the chain so that it gets into the joints.
    4. Check and top up the oil level in the gearbox to the mark. If the lubricant is dirty, replace it completely.
    5. Check the operation of the centralized lubrication system: pressure (typical 5-10 bar), availability of grease at all points, setting of grease supply intervals.
    6. Verification: Remove LOTO. Start the pipeline. Visually check for sufficient lubrication. With the help of a thermal imager, monitor the temperature of the chain, bearings, gearbox - it should stabilize at a normal level.

8.4. Elimination of material accumulation and jamming of the tensioning station

  1. Diagnosis: Visual inspection, attempt to manually move the tensioning station.
  2. Procedure:
    1. Activating LOTO.
    2. Thoroughly clean the entire path of the conveyor from the accumulated material, especially under the chain, on the guides, in the area of the sprockets and tension stations. Use shovels, brushes, vacuum cleaners.
    3. If the tension station is jammed:
      • Clean it of material and corrosion.
      • Lubricate the guide elements and threaded connections.
      • Try to develop it using light impact tools and penetrating lubricant.
      • Replace damaged elements of the tensioning station (for example, worn screws, bushings).
    4. Verification: Remove LOTO. Do a test run. Make sure that the tensioning station moves freely (if it is automatic) and that there is no accumulation of material.

9. Precautions

The root cause Prevention strategy Monitoring method Recommended interval
Chain extension Regular tension adjustment. Use of quality chains. Optimal lubrication. Measurement of chain elongation; visual control of sagging. Monthly (or every 200 hours of work).
Sprocket wear Timely replacement of the extended chain. The use of sprockets made of high-quality steel. Visual inspection of sprocket teeth; profile measurement. Once a quarter (or every 500 hours of operation).
Insufficient lubrication Development and adherence to the lubrication schedule. Use of recommended lubricants. Visual control of the presence of lubricant; inspection of the centralized lubrication system; temperature control with a thermal imager. Weekly (visual); Monthly (system); Quarterly (temperature).
Accumulation of material Regular cleaning of the conveyor. Installation of scrapers and cleaners. Optimization of loading/unloading nodes. Visual inspection of the conveyor tract; control of scrapers. Alternately / Weekly.

10. Spare parts and components

Description of the part Specification / Standard When to replace Category UNITEC
Drive chain Roller chain, DSTU EN ISO 606 (DIN 8187/8188), pitch [mm], number of rows [one/two], steel grade [for example, 40Mn]. With elongation > 3%, visible damage (cracks, broken links). Drive chains
Drive sprocket Material [e.g. C45], Number of Teeth [Z], Pitch [mm], Fit Diameter [mm], Type [Single Sided/Double Sided]. With hook-like wear of teeth, aggravation, significant thinning. Always when replacing the chain. Drive sprockets
Tension sprocket Similarly, the drive, material, number of teeth, pitch. With significant wear of teeth, deformation. The sprockets are tensioned
Shaft bearings (drive/tension) Type [eg 22216K], Size [DxW, mm], Accuracy Class [P0/P6], Manufacturer. With significant noise, vibration, overheating, backlash. Rolling bearings
Lubricant for chains Type [eg mineral/synthetic], viscosity [ISO VG 220-460], adhesive properties. According to the lubrication schedule, in case of contamination. Lubricating materials
Lubricant for gearboxes Type [eg GL-5], viscosity [ISO VG 320/460]. According to the schedule, in case of pollution, lowering of the level. Lubricating materials
Tension device Model, type (screw/spring/hydraulic), size. In case of mechanical damage, jamming, impossibility of adjustment. Conveyor components

You can find all the necessary spare parts and accessories for the repair and maintenance of chain conveyors in the electronic catalog of UNITEC-D.

11. Links

  • DSTU EN ISO 606:2018 (EN ISO 606:2015, IDT) Drive roller chains. Technical characteristics.
  • DSTU EN ISO 10816-3:2004 Vibration. Evaluation of machine vibration based on measurement results on stationary parts. Industrial machines with a nominal power of more than 15 kW and a nominal speed from 120 rpm to 15,000 rpm.
  • DSTU EN 1037:2018 (EN 1037:1995 + A1:2008, IDT) Machine safety. Prevention of unexpected start.
  • Operation and maintenance manual for a specific type of chain conveyor (OEM documentation).
  • UNITEC-D internal standards for safety and maintenance of conveyor equipment.

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