Symptom Appearance Probable cause Correction
Worn contour    Abnormal wear rubbing on guides Replace roller chain when 5% worn. Check roller chain alignment or increase clearance
Pin galling   Inadequate lubrication Reduce load or roller chain drive speed. Provide proper roller chain lubrication
Tight joints Dirt or foreign substance packed in joints or corrosion or rust or bent pins Clean & re-lubricate roller chain.   Replace roller chain.   Replace roller chain
Hooked sprocket
teeth
  Excessive roller chain wear Replace roller chain and roller chain sprocket 
Abnormal protrusion or turned pins    Excessive internal friction caused by high loading and inadequate lubrication Replace roller chain, improve lubrication and eliminate overload conditions
Cracked plates (fatigue)   
Crack from aperture towards edge of linkplate at 90º to line of pull. Note there is no linkplate distortion.
Loading beyond chain's dynamic capacity (above fatigue endurance limit) Replace chain with roller chain of larger dynamic capacity or eliminate high load condition or dynamic (impulse) overloading

 

Symptom Appearance Probable cause Correction
Fractured plates (tension mode)
Note material distortion
High overload   Replace roller chain and correct cause of overload
Arc like cracked plates (stress corrosion)   Severe rusting or exposure to acidic or caustic medium, plus static pressure at press fit (between pin and pin linkplate).  No cyclic stress is necessary for this phenomenon to occur. Replace roller chain and protect from hostile environment.
Enlarged holes   High overload Replace roller chain and correct cause of overload
Corrosion pitting   Exposure to corrosive environment   Replace roller chain and protect from hostile environment. 
Broken, cracked or deformed rollers     Speed too high
Sprockets too small
Replace roller chain and reduce speed Replace roller chain and use larger roller chain sprockets
Broken pins   Extreme overload Replace roller chain. Eliminate cause of overload or redesign roller chain drive
Rusted chain   Exposed to moisture  
Water in lubricant 
Inadequate lubrication
Replace roller chain and protect from moisture Change roller chain lubricant Replace roller chain and improve roller chain lubrication