Problem description and scope
This diagnostic guide is designed to identify and eliminate jams and overloads in chain conveyor systems. Problems are classified according to criticality: critical (complete stoppage of production), major (reduction in productivity >20%), minor (local work disruptions).
The guide covers diagnosing the four main causes of failure: chain elongation due to wear, sprocket wear, lubrication system failure, and material build-up on working surfaces. It is used for chain conveyors with a chain pitch of 12-80 mm, load up to 50 kN/m according to DSTU EN 818-7.
Safety measures
WARNING: Be sure to perform the LOTO (Lockout/Tag) procedure before starting diagnostics. Chain conveyors contain stored mechanical energy.
Mandatory personal protective equipment: helmet, safety glasses, work gloves with cut protection (EN 388, level 3), special shoes with metal toes.
Dangerous conditions during diagnostics: a stretched chain under load, sharp edges of worn sprockets, the presence of abrasive dust, slippery surfaces from leaking lubricants.
Diagnostic tools are required
| Tool | Specification/Model | Measurement range | Purpose |
|---|---|---|---|
| Digital multimeter | Fluke 117 or equivalent | 0-600V AC/DC, 0-10A | Measuring motor current, checking sensors |
| Vibration analyzer | SKF CMAS 100-SL | 10-1000 Hz, 0.1-200 mm/s RMS | Diagnosis of bearings and inaccuracies |
| Thermal imager | FLIR E60bx | -20°C to +120°C | Detection of overheating of bearings and gearboxes |
| Vernier caliper | Mitutoyo 500 series | 0-200 mm, accuracy ±0.02 mm | Measurement of chain and sprocket wear |
| Time type indicator | GOST 577-68 | 0-10 mm, the price of division is 0.01 mm | Control of the beat of stars |
| Thickness gauge | Set 0.05-1.0 mm | According to DSTU ISO 3325 | Checking gaps in the chain |
Initial assessment of the condition - a checklist
| A parameter to observe | What to write down | Normal values |
|---|---|---|
| Motor current under load | Current/nominal, A | 85-105% of nominal |
| Conveyor speed | Actual/estimated, m/min | ±5% of the estimate |
| Bearing temperature | °C, thermal imager or contact thermometer | <40°C above ambient |
| Noise level | dB(A) at a distance of 1 m | <85 dB(A) according to DSTU ISO 11688 |
| Recent changes in the system | Date/description of modifications | Maintenance records |
| History of emergency signals | Error codes, frequency of occurrence | SCADA event log |
Systematic diagnostic scheme
- Primary assessment of symptoms:
- If the conveyor stopped with an overload alarm → go to point 2
- If the conveyor is working, but with an increased current (>110% of the nominal) → go to item 3
- If there is excessive noise or vibration → go to item 4
- If slipping or non-rhythmic movement is observed → go to point 5
- Full stop analysis:
- Measure the locked rotor current (LRA)
- If LRA >500% of nominal → mechanical blocking (item 6)
- If LRA 200-500% of nominal → excessive load (item 7)
- Analysis of increased current:
- Measure chain elongation according to the DSTU method EN 818-2
- If the elongation is >1.5% of the initial length → replace the chain
- If the elongation is <1.5% → check the wear of the sprockets (item 8)
- Analysis of noise and vibration:
- Measure vibration on the supports of the drive sprocket
- If the vibration speed >4.5 mm/s RMS → sprocket or chain inaccuracy
- If the bearing temperature is >80°C → lubrication failure
- Slip analysis:
- Visually assess the accumulation of material on the sprockets
- Check the tension of the chain → the deflection should not exceed 2% of the length of the run
- Mechanical locking:
- Visual inspection for foreign objects
- Checking free movement manually after disconnecting the drive
- Overload:
- Checking the weight of the transported material
- Evaluation of resistance in support rollers
- Sprocket wear:
- Measure the thickness of the sprocket tooth with a caliper
- Check the tooth profile with a saber in accordance with DIN 8187
Failure and reason matrix
| Symptom | Probable causes (by probability) | Diagnostic test | Expected result upon confirmation |
|---|---|---|---|
| Full stop with overload | 1. Accumulation of material (60%) 2. Bearing jamming (25%) 3. Chain deformation (15%) | Visual inspection, temperature measurement | Visible accumulations, local overheating >100°C |
| Increased motor current | 1. Chain extension (50%) 2. Wear of sprockets (30%) 3. Lubrication failure (20%) | Elongation measurement, tooth profile control | Elongation >1.5%, tooth wear >20% |
| Excessive noise >85 dB(A) | 1. Wear of sprockets (45%) 2. Chain defect (35%) 3. Shaft inaccuracies (20%) | Vibration analysis, beat measurement | Vibration speed >4.5 mm/s, beating >0.2 mm |
| Irrhythmic movement | 1. Chain extension (55%) 2. Accumulation of material (30%) 3. Wear of guides (15%) | Movement monitoring, gap measurement | Variable speed ±10%, increased gaps |
| Local overheating | 1. Lubrication failure (70%) 2. Overload (20%) 3. Inaccuracies (10%) | Thermal imaging examination, analysis of lubricant | Temperature >80°C, lubricant degradation |
Root cause analysis for each failure type
Chain extension
Elongation of the chain occurs due to the wear of the hinge joints under the influence of cyclic loads. The critical parameter is an increase in the chain pitch by more than 1.5% of the nominal value according to DSTU EN 818-2.
Confirmation of the diagnosis: Measure the length of 20 chain links in an unloaded state. Elongation is calculated according to the formula: Δ = (L_fact - L_nom) / L_nom × 100%.
Consequences in the absence of intervention: Progressive wear of sprockets, increase in dynamic loads, possible accidental chain breakage with risk of injury.
Sprocket wear
The wear of the sprockets manifests itself in a change in the profile of the tooth and a decrease in its thickness. Critical wear is achieved when the tooth thickness is reduced by 20% or when the profile angle changes by more than 5° according to DIN 8187.
Confirmation of the diagnosis: Measure the thickness of the tooth at the height of the pitch circle diameter. Check the profile of the tooth with a special ruler. Assess the uniformity of wear around the perimeter of the sprocket.
Consequences in the absence of intervention: Accelerated wear of the chain, increased noise, possible jump of the chain from the sprocket.
Lubrication system failure
Failure to lubricate leads to dry friction in chain links and bearings. Diagnosed by an increase in temperature above 80°C and a change in the color of the lubricant.
Confirmation of the diagnosis: Thermal imaging examination of critical points. Lubricant sampling for analysis of viscosity and content of wear products. Checking the operation of the lubrication supply system.
Consequences in the absence of intervention: Jamming of bearings, accelerated wear of the chain and sprockets, possible fire hazard from overheating.
Accumulation of material
Accumulation of transported material on the working surfaces increases resistance to movement and can lead to blocking. Especially critical for sticky or abrasive materials.
Confirmation of the diagnosis: Visual inspection of sprockets, guides and tensioning stations. Measurement of the thickness of accumulations. Evaluation of the efficiency of the cleaning system.
Consequences in the absence of intervention: Progressive increase in resistance, overloading of the drive, a complete stop of the system is possible.
Step-by-step elimination procedures
Elimination of chain elongation
- Stop the conveyor and perform the LOTO procedure
- Loosen the tension station to the minimum tension
- Remove the connecting link of the chain with a special tool
- Remove the extended chain from the conveyor
- Install a new chain with similar characteristics according to DIN 8187
- Adjust the tension: chain deflection 2±0.5% of the length of the run
- Check idling for 15 minutes
- Recheck the tension after 4 hours of operation
Replacement of worn sprockets
- Perform LOTO and remove the chain from the drive sprocket
- Disconnect the drive shaft from the gearbox
- Dismantle the worn sprocket using a puller
- Clean the mounting surfaces of the shaft from dirt
- Install a new sprocket with shaft runout control ≤0.1 mm
- Tighten the fasteners with a torque according to the technical documentation
- Restore the connection with the gearbox with alignment control
- Install the chain and adjust the tension
Restoration of the lubrication system
- Stop the supply of lubricant and drain the system
- Flush oil lines with solvent according to EN 12300
- Replace filters and seals in the supply system
- Fill the system with fresh lubricant of the recommended type
- Adjust the supply of lubricant: 2-5 ml/m of chain per hour
- Check the even distribution of the lubricant along the length of the chain
- Monitor the temperature of the bearings during the first shift
Cleaning from accumulations of material
- Stop the conveyor and wait until it is completely emptied
- Mechanically remove build-up from sprockets and guides
- Clean position sensors and control systems
- Check the operation of scrapers and brushes of the cleaning system
- Adjust the pressure in the compressed air blowing system
- Test the efficiency of cleaning at idle speed
- Відновити нормальну експлуатацію з підвищеним контролем
Preventive measures
| The root cause | Prevention strategy | Monitoring method | Recommended interval |
|---|---|---|---|
| Chain extension | Correct lubrication, load control | Measuring the elongation of 20 links | Every month |
| Sprocket wear | Use of hard alloy coatings | Control of the tooth profile with a ruler | Every 3 months |
| Lubrication failure | Automatic lubrication supply system | Lubricant consumption and quality control | Every week |
| Accumulation of material | Effective cleaning system | Visual control of cleanliness | Every day |
| Overload | Material weight control system | Motor current monitoring | Continuously |
Spare parts and components
| Description of the part | Specification | When to replace | Category UNITEC |
|---|---|---|---|
| Drive chain | DIN 8187, step 19.05-50.8 mm | Elongation >1.5% | Power transmission → Chains |
| Drive sprocket | Steel 40X, HRC 45-50 | Tooth wear >20% | Power transmission → Sprockets |
| Support bearing | Series 6200-6300, accuracy class P6 | Temperature >80°C | Bearings → Ball bearings |
| Chain lubricant | ISO VG 220, temperature -20/+120°C | Color/viscosity change | Lubricants → Industrial |
| Cleaning scraper | Polyurethane 85 Shore A | Depreciation >50% | Conveyor equipment → Cleaning |
| Tension device | Screw or hydraulic | Lack of regulation | Conveyor equipment → Tension stations |
To select the appropriate spare parts and receive technical advice, visit our electronic catalog UNITEC-D. Our engineers will help determine the optimal solutions for your equipment.
Link
- DSTU EN 818-2:2018 Short-link chains for lifting loads. Part 2. Medium tolerance chains for chain blocks and lifting devices
- DIN 8187:1996 Roller chains, sprockets and chain-related products
- DSTU ISO 11688-1:2019 Acoustics. Recommended Code of Practice for the Design of Low Noise Machinery and Equipment
- EN 12300:2020 Lubricants. Classification of industrial lubricants
- DSTU ISO 3325:2018 Probes for measuring thickness. Technical conditions
- UNITEC Conveyor Systems Maintenance Guide (www.unitecd.com/maintenance-guides/conveyor-systems)
