Types of Belt Cover Cracking
Belt cover cracking can occur in several distinct patterns, each indicating a different root cause. Identifying the crack pattern is the first step to finding the correct solution.
Surface Crazing (Network of Fine Cracks)
A network of fine surface cracks resembling a dried riverbed is almost always caused by ozone attack. Ozone in the atmosphere attacks unsaturated rubber compounds (SBR, NR) at the surface, breaking the polymer chains. This type of cracking is cosmetic in early stages but eventually allows moisture ingress that accelerates carcass degradation.
Prevention: Use EPDM or CR (neoprene) compounds which have better ozone resistance for outdoor storage or outdoor conveyors. Apply antioxidant/anti-ozone wax to stored belts.
Transverse Cracking (Cracks Across Belt Width)
Cracks running perpendicular to belt travel are typically caused by flexing fatigue at the pulley. The rubber compound bends repeatedly around the pulley, and if the compound has hardened with age (or is too hard from incorrect specification), it cracks at the point of maximum bending stress.
Prevention: Ensure minimum pulley diameter is correct for the belt. Check belt tension β?over-tension increases bending stress. Replace aged belts showing transverse cracking before carcass damage occurs.
Longitudinal Splitting (Cracks Along Belt Length)
Cracks running parallel to belt travel are often caused by oil or chemical contamination that swells and softens the rubber unevenly, creating stress concentrations. They can also result from impact damage at loading points.
Edge Cracking
Cracks at the belt edges indicate belt mistracking causing the edge to contact structural steel, or inadequate edge rubber coverage protecting the carcass.
Storage and Ageing Cracking
π‘ Belt Storage Rules
Conveyor belts should be stored: in a cool, dark environment (below 25Β°C); away from electric motors and welding equipment (ozone sources); rolled on the original drum β?never flat; with a minimum of 3 months stock rotation. Belts stored incorrectly for more than 2 years may show surface crazing before installation.
Diagnosing the Cause
| Crack Pattern | Most Likely Cause | Action |
|---|---|---|
| Fine surface network | Ozone / UV ageing | Check storage conditions; replace if deep |
| Transverse, at pulleys | Flexing fatigue / over-tension | Check pulley diameter; verify tension |
| Longitudinal along centre | Impact damage or oil | Check loading zone; test for oil contamination |
| Edge cracking | Belt mistracking | Fix tracking; install edge guards |
| Around splice area only | Splice stress concentration | Re-splice with correct method |
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