Problem description and scope
Chain conveyors are critical components in industrial production, ensuring the transportation of materials in the automotive, food, chemical and energy industries. Failures of chain systems lead to production stoppages and can cause significant economic losses.
This diagnostic guide covers the four main causes of chain conveyor failures:
- Critical failures: Complete chain jamming, chain break
- Significant failures: Intermittent jamming, increased noise level >85 dB
- Minor failures: Power consumption increase >15%, erratic movement
Safety measures
CAUTION! Before starting diagnostics, you must:
- Perform LOTO (Lockout/Tag)
- Disconnect the power supply to the drive
- Relieve pressure in pneumatic tensioning systems
- Use PPE: hard hat, safety glasses, anti-noise headphones
- Beware of stored energy in spring tensioners
- Ensure proper lighting of the work area (minimum 500 lux)
Diagnostic tools are required
| Tool | Specification | Measurement range | Purpose |
|---|---|---|---|
| Vibroanalyzer | SKF CMXA 75 | 0.1-200 mm/s RMS | Bearing and chain vibration measurement |
| Clamps for current | Fluke 376 FC | 0-999.9 A | Engine load control |
| Thermal imager | FLIR E8-XT | -20°C to +550°C | Detection of overheated nodes |
| A ruler for measuring the chain | Steel, 1000 mm | ±0.5 mm accuracy | Measurement of chain elongation |
| Clock type indicator | Mitutoyo 2046S | 0-10 mm, the price of division is 0.01 mm | Measuring sprocket wear |
| Torque wrench | Bahco 7454-2-75 | 15-75 Nm | Control of the tension of bolted connections |
| Endoscope | General Tools DCS1600 | Diameter 5.5 mm | Inspection of hard-to-reach areas |
Initial assessment checklist
| Parameter | What to observe/record | norm | Anxiety |
|---|---|---|---|
| Motor current consumption | Rated current under load | 85-100% of nominal | >110% of nominal |
| Noise level | General noise near the drive | <65 dB | >85 dB |
| Bearing temperature | The temperature of the bearing housings | <70°C | >90°C |
| Vibration | RMS speed on the gearbox housing | <4.5 mm/s | >11.2 mm/s |
| Conveyor speed | Actual transport speed | ±5% of nominal | ±15% of nominal |
| Visual circuit status | Corrosion, deformation, lack of rollers | No damage | Visible defects |
| Recent changes | Repairs, replacements, load changes | Documented | Not documented |
Systematic diagnostic scheme
Step 1: Identification of symptoms
- If the circuit is completely stuck:
- Check the current consumption of the motor (>150% of the nominal)
- If the current is critical → proceed to diagnostics of material accumulation (Step 4)
- If the current is moderately increased → check the circuit tension (Step 2)
- If periodic jamming is observed:
- Measure the vibration at the sprocket engagement frequency
- If the vibration is >7 mm/s at the engagement frequency → diagnosis of sprocket wear (Step 3)
- If vibration <7 mm/s → check chain elongation (Step 2)
- If an increased noise level is observed:
- Localize the source of the noise (drive/tail section/intermediate stations)
- If the drive is noisy → check lubrication (Step 5)
- If the noise is distributed → diagnose the chain and sprockets (Steps 2-3)
Step 2: Diagnosis of chain elongation
- Measure the length of 20 chain links under minimum load
- Calculate the percentage of elongation: ((Actual length - Nominal length) / Nominal length) × 100%
- If the elongation is >2%: The chain needs to be replaced
- If the elongation is 1.5-2%: Increased control, scheduled replacement
- If lengthening <1.5%: Go to sprocket diagnostics
Step 3: Diagnosis of sprocket wear
- Measure the pitch diameter of the sprocket with a watch-type indicator
- Check the profile of the teeth for sharpening or deformation
- If the wear of the diameter is >3% of the nominal: Replacement of the sprocket is mandatory
- If sharpening of the teeth is observed: Replace the chain and sprocket
Step 4: Diagnostics of material accumulation
- Inspect the loading and unloading areas with an endoscope
- Check tension stations for contamination
- If accumulation >5 mm thick is detected: Immediate cleaning
- Check the effectiveness of the chain cleaning system
Step 5: Diagnosis of lubrication failure
- Check the circuit temperature with a thermal imager (normal <60°C)
- Visually assess the condition of the lubricant
- If temperature >80°C: Critical lubrication failure
- Check the operation of the automatic lubrication system
Matrix of faults and causes
| Symptom | Probable causes (by probability) | Diagnostic test | Expected result upon confirmation |
|---|---|---|---|
| Complete jamming of the chain | 1. Accumulation of material (60%) 2. Bearing failure (25%) 3. Chain deformation (15%) | Visual inspection, current measurement | Current >200% of nominal, visible contamination |
| Periodic eating | 1. Chain elongation (45%) 2. Wear of sprockets (35%) 3. Incorrect tension (20%) | Measuring chain length | Elongation >1.5%, uneven course |
| Increased noise >85 dB | 1. Insufficient lubrication (50%) 2. Wear of chain rollers (30%) 3. Star imbalance (20%) | Thermal imaging control, lubricant analysis | Temperature >80°C, no lubricant film |
| Increase in energy consumption | 1. Increased friction due to pollution (40%) 2. Chain elongation (35%) 3. Bearing wear (25%) | Current trend analysis, vibration diagnostics | Current increase >15%, vibration >7 mm/s |
| Uneven movement | 1. Different stiffness of links (45%) 2. Accumulation of material in stars (35%) 3. Wear of guides (20%) | Step-by-step monitoring of movement | Visually noticeable jerks, different speed of sections |
Analysis of the main causes of failures
Elongation of the chain
Why it happens: Chain elongation occurs due to wear of the pins and bushings due to cyclic loads and insufficient lubrication. The process is accelerated when working in a dusty environment or when the nominal load is exceeded.
How to confirm: Measure the exact length of 20 consecutive links according to the DSTU formula EN 818-7. Use a steel ruler with an accuracy of ±0.5 mm. The permissible elongation for most industrial chains is 1.5-2%.
Consequences of Ignoring: Elongation of more than 3% leads to improper engagement with the sprockets, accelerated wear of the teeth and possible chain skipping or breaking under load.
Sprocket wear
Why it happens: Sprocket wear is caused by the abrasive action of a dirty chain and transported material. Incorrect alignment of the chain accelerates one-sided wear of the teeth.
How to confirm: Measure the pitch diameter of the sprocket at three points according to the method ISO 606. Check the profile of the teeth with a template. A sharpening of the teeth or a decrease in the pitch diameter of more than 3% indicates critical wear.
Consequences of Ignoring: Worn sprockets cause accelerated elongation of the new chain, increased vibration and the possibility of chain jump under peak loads.
Lubrication failure
Why it happens: The failure of the lubrication system can be caused by clogged nozzles, pump failure or the use of poor-quality lubricating material. High temperatures and a dusty environment accelerate the degradation of the lubricant.
How to confirm: Control the circuit temperature with a thermal imager (normal <60°C). Visually assess the presence of a lubricating film on the rollers. Analyze the lubricant for the content of mechanical impurities.
Consequences of ignoring: Insufficient lubrication leads to accelerated wear of all moving elements, seizure of chain joints and possible overheating with thermal damage to the metal.
Accumulation of material
Why it happens: Material accumulates due to inefficiency of the chain cleaning system, stickiness of the transported product, or insufficient self-cleaning chain speed.
How to confirm: Conduct a visual inspection of all available plots. Use an endoscope to inspect closed areas. Accumulation thickness of more than 5 mm is considered critical.
Consequences of ignoring: Material accumulation increases the load on the drive, can cause the chain to seize in the guides and lead to an emergency stop of the conveyor.
Step-by-step troubleshooting procedures
Replacing the extended chain
- Preparation: Disconnect the drive, reduce the chain tension to minimum
- Dismantling: Remove the connecting link with a special tool
- Installing the new chain: Install the new chain, making sure the locks are oriented correctly
- Tension Adjustment: Set the tension according to the manufacturer's recommendations (usually 1-3% of the chain length)
- Check: Check the chain for a full turn, check the smoothness of the stroke
- Tightening torque of the bolts of the tensioning device: 45-65 Nm according to DSTU EN 13411-1
Replacement of worn sprockets
- Dismantling: Remove the chain, unscrew the fastening bolts of the sprocket (moment: 120-180 Nm)
- Shaft inspection: Assess the condition of the keyways and shaft surface
- Installing a new sprocket: Install a new sprocket, check the alignment with a laser leveler (accuracy ±0.5 mm)
- Balancing: If necessary, balance the sprocket (permissible imbalance <6.3 g×mm/kg)
- Control measurements: Check the runout of the sprocket <0.3 mm
Restoration of the lubrication system
- Cleaning the system: Flush the pipelines and nozzles with solvent
- Filter replacement: Install new filter elements (fineness of filtration 25 μm)
- Refueling with fresh lubricant: Use a lubricant of the appropriate viscosity ISO VG 220 according to DSTU 4839
- Feed settings: Set the feed rate to 1-3 g/m chain per hour
- Testing: Carry out a test run, check the even distribution of the lubricant
Cleaning from accumulations of material
- Mechanical cleaning: Remove build-up with a hand tool, avoid damaging the chain
- Washing: If necessary, wash the chain with a jet of water under a pressure of up to 50 bar
- Adjusting the scrapers: Adjust the clearance between the scrapers and the chain to 2-5mm
- Drainage check: Ensure free flow of fluids from the conveyor housing
- Prevention: Install additional brushes or air knives if necessary
Prevention measures
| The main reason | Prevention strategy | Control method | Recommended interval |
|---|---|---|---|
| Elongation of the chain | Regular tension check, high-quality lubrication | Measurement of the length of the control segment | Monthly |
| Sprocket wear | Alignment control, timely replacement of chains | Measurement of pitch diameter and tooth profile | Every 3 months |
| Lubrication failure | Scheduled maintenance of the lubrication system, oil quality control | Analysis of lubricant samples, temperature control | Weekly |
| Accumulation of material | Adjusting the cleaning system, speed control | Visual inspection, measurement of accumulation thickness | Every day |
| Overload | Weight control and material distribution | Drive current monitoring | Continuously |
Spare parts and components
| Description of the part | Specification | When to replace | Category UNITEC |
|---|---|---|---|
| Industrial roller chain | ISO 606, step 15.875-50.8 mm | At elongation >2% | Chains and sprockets |
| Sprockets with hardened teeth | Steel 40X, HRC 40-50 | With wear >3% of the pitch diameter | Chains and sprockets |
| Connecting links | According to the type of chain | Every time the chain is replaced | Attachment and connection |
| Screw tensioning devices | Stroke 100-500 mm, load up to 50 kN | When the threads are worn | Mechanical components |
| Roller bearings | SKF series 22200, accuracy class C3 | With vibration >11.2 mm/s | Bearings |
| The lubrication system is automatic | Productivity 0.1-2 l/min | When the pump fails | Lubrication systems |
| Polymer cleaning scrapers | Polyurethane, hardness 90 Shore A | At wear >50% | Sealing and cleaning |
| Chain guides | Steel with polymer coating | When forming grooves >2 mm deep | Guide elements |
To select the appropriate spare parts and receive technical advice, visit the UNITEC-D catalog: https://www.unitecd.com/e-catalog/
Reference materials
- DSTU EN 818-7:2018 - Short-circuited chains for lifting and transporting machines. Security. Part 7: Class T Fine Precision Chains
- ISO 606:2015 - Short Circuit Precision Roller Chains and Sprockets
- DSTU 4839:2007 - Industrial oils. Classification and designation
- EN 1070:1998+A1:2008 - Safety of machinery. Belt conveyors for bulk materials
- ISO 14694:2003 - Industrial chains. Test methods and acceptance criteria
- Maintenance manual for UNITEC-D chain conveyors
- Labor safety standards for the maintenance of conveyor equipment NPAOP 0.00-8.03-93
