Industrial Chain Failures: A Visual Guide to Wear Patterns Part 2
- Rotated or displaced pins
How to identify them
Riveted pin ends normally have a consistent orientation.
A pin may have rotated when you find:
- Displaced riveting marks.
- Unusual gaps between plates.
- Red debris around the joint.
- A nearby stiff link.
- Excessive side movement.
- Irregular noise.
Common causes
Typical causes include:
- Insufficient lubrication.
- Contamination inside the joint.
- Seized articulation.
- Excessive chain tension.
- Overload.
- High pressure between the pin and bush.
When the joint cannot articulate, torque may transfer to the press fit between the pin and the outer plate. The pin can then lose its original position.
Corrective action
Replace the chain. A rotated pin indicates that a structural joint has lost its correct fit.
Next, inspect lubrication, tension, cleanliness and chain capacity.
- Pitting corrosion
How to identify it
Pitting corrosion creates small cavities in the metal surface.
Although the damage may look minor, some pits penetrate deeply. They can reduce the effective cross-section of plates and pins.
Pay particular attention to pits located:
- Around plate holes.
- On the pins.
- Beneath deposits.
- Close to a crack.
- Where liquid can collect.
Common causes
Pitting may result from:
- Moisture.
- Condensation.
- Frequent washdowns.
- Chemicals.
- Salt.
- Unsuitable lubricant.
- Incorrect material selection.
Corrective action
Replace the chain when the pits are deep or close to highly stressed areas.
Review the chain material and surface protection. The application may require:
- Stainless steel.
- Surface treatment.
- A corrosion-resistant coating.
- A self-lubricating chain.
- Better protection against liquid ingress.
- Stiff chain links
How to identify them
A stiff link does not straighten after leaving the sprocket.
As a result, the chain may retain a kinked shape. It can also generate noise, vibration and impact.
Common causes
Stiff links often result from:
- Poor lubrication.
- Lubricant applied in the wrong area.
- Dirt inside the joint.
- Corrosion.
- Bent plates.
- Misalignment.
- Side pressure.
- A twisted chain.
What to check
With the machine isolated, articulate accessible links by hand.
Check whether the stiffness:
- Appears in one location.
- Repeats at regular intervals.
- Coincides with contamination.
- Develops after washdown.
- Is associated with corrosion.
Corrective action
If the problem is at an early stage, suitable cleaning and lubrication directed into the joint may restore movement.
Replace the chain when the link remains stiff, is deformed or shows corrosion.
- Uneven wear and elongation
How to identify them
Uneven wear may cause:
- Alternating tight and loose sections.
- Changing tension during one revolution.
- Different elongation between sections.
- Irregular movement.
- Unequal wear between parallel chains.
- Periodic vibration.
Common causes
In a single-chain drive, the cause may be:
- Uneven lubrication.
- Stiff links.
- An eccentric sprocket.
- A bent shaft.
- Pulsating loads.
- Localised contamination.
In parallel-chain systems, additional causes include:
- Different chain lengths.
- Unequal tension.
- Asymmetrical loading.
- Different lubrication conditions.
- Unmatched chains.
Corrective action
Measure elongation in several sections. A single overall measurement may hide a severely worn area.
For parallel drives, use matched chains and replace the complete set. Replacing one chain alone can increase load imbalance.
How to diagnose a roller chain failure
A reliable diagnosis should follow a consistent process.
- Record the initial condition
Before cleaning or dismantling:
- Take photographs from both sides.
- Mark the damaged position.
- Record operating hours.
- Note recent maintenance.
- Check for jams or overload events.
- Inspect the complete drive
Do not inspect the chain alone. Check:
- Sprockets.
- Shafts.
- Bearings.
- Guides.
- Tensioners.
- Lubrication system.
- Guards.
- Supporting structure.
- Torque-limiting devices.
- Take measurements
Measure or verify:
- Chain elongation.
- Tension.
- Alignment.
- Link movement.
- Tooth profile.
- Load distribution.
- Operating temperature.
- Identify the root cause
Before installing a replacement chain, ask:
- Is the chain capacity sufficient?
- Does lubricant reach the pin and bush?
- Are the sprockets aligned?
- Is the tension correct?
- Is there contamination or corrosion?
- Are shock loads, jams or overloads occurring?
- Verify the repair
Inspect the drive again during its first operating hours.
Recheck tension, alignment, noise and temperature.
When should the machine be stopped?
Stop the machine when you find:
- Cracked plates.
- Displaced pins.
- Broken rollers.
- Deep corrosion pits.
- Seized links.
- Permanent deformation.
- Chain jumping.
- Significant loss of plate thickness.
- A risk of component detachment.
Continuing to operate may turn a local defect into a complete chain failure.
Frequently asked questions about industrial chain failures
Why does an industrial chain wear out?
Common causes include poor lubrication, misalignment, contamination, incorrect tension, overload and worn sprockets.
How can I identify chain misalignment?
Typical signs include side wear, contact marks on one side of the sprocket, noise and lateral chain movement.
Should sprockets be replaced with the chain?
Replace sprockets when the teeth are sharp, deformed or hooked. A worn sprocket can significantly reduce the life of a new chain.
Can a cracked chain plate be repaired?
No. A cracked plate has lost structural strength. The chain should be removed and replaced.
Why do chain links become stiff?
Stiffness usually results from contamination, corrosion, insufficient lubrication, deformation or side pressure.
What causes chain tension to change during one revolution?
Possible causes include uneven wear, a stiff link, an eccentric sprocket, a bent shaft or localised elongation.
Wear reveals the symptom, not always the root cause
Wear patterns provide valuable information. However, they should never be assessed in isolation.
Side wear points towards an alignment problem. Hooked sprocket teeth suggest poor engagement or chain elongation. Stiff links often indicate lubrication, contamination or corrosion problems.
The correct approach is to inspect the complete drive and eliminate the root cause before fitting a new chain.
Iris Chains manufactures transmission and conveyor chains for different loads, speeds, temperatures and environmental conditions.
Correct failure analysis helps determine the most suitable material, treatment, geometry and lubrication system. As a result, unplanned downtime can be reduced and service life can be extended.
