Background
An iron ore operation in Minas Gerais, Brazil was experiencing recurring longitudinal belt tears on a 1,200mm wide EP400 conveyor carrying crushed iron ore from the secondary crusher to a screening plant. Over a 14-month period, the belt had been repaired four times for longitudinal tears β each time losing 1β3 meters of belt length at the repair location.
Each repair required a 4-hour conveyor stop and a vulcanized patch. After two patches in the same area, the local belt structure was compromised enough that a full belt replacement was needed.
Failure Analysis
Longitudinal tearing (tears running along the length of the belt rather than across it) almost always has a specific cause β a sharp object or edge in the conveyor system that catches the belt and cuts along it as the belt moves.
A systematic inspection of the conveyor structure was conducted with the belt stopped and inspected section by section. The following were found:
1. A bolt protruding from a return idler bracket. A return idler had been replaced previously and the installer had left a bolt protruding approximately 8mm above the idler frame. When the belt sagged between idlers on the return run, it contacted this bolt periodically. The bolt acted as a cutting tool, producing a longitudinal score that developed into a tear over multiple belt passes.
2. A torn skirt board seal. A section of rubber skirting had torn and the torn piece had folded back, exposing the steel backing plate edge. The steel edge was contacting the belt at the loading zone edge, scoring the cover over an area approximately 15mm wide.
3. Belt edge contact with a conveyor stringer. In one section of the conveyor, the belt was tracking slightly to the right, bringing the right edge into contact with a structural stringer. Belt edge damage and beginning of a longitudinal tear were visible at this location.
Corrective Actions
Immediate: - Remove protruding bolt and replace return idler bracket with correct hardware - Replace torn skirt seal and inspect all skirt seals along conveyor - Adjust tracking to center the belt; install a self-aligning return idler set at the problem section
Systemic: - Establish a monthly inspection protocol covering all return idler brackets, skirt seals, and belt tracking - Install belt sway sensors at the known tracking problem section to provide early warning if belt drifts toward the stringer - Brief maintenance team on longitudinal tear recognition and reporting β early detection prevents a score from becoming a full tear
Outcome
After the corrective actions, no longitudinal tears occurred in the following 18 months of monitoring. The belt installed at the time of the investigation (the fourth repair version) ran through its full service life β approximately 26 months β before planned replacement for cover wear.
The monthly inspection protocol identified two additional protruding fasteners and one partially torn skirt seal during the monitoring period, both corrected before causing belt damage.
Key Points
Longitudinal tears have a cause β find it before replacing the belt. Replacing the belt without identifying and removing the sharp object or edge that caused the tear means the new belt will tear in the same place.
A systematic inspection is faster than repeated repairs. Four conveyor stops for repairs over 14 months totaled approximately 16 hours of downtime, plus the cost of repairs and eventual full belt replacement. The investigation and corrective action took one planned 6-hour inspection stop and solved the problem permanently.
Most longitudinal tear causes are findable by walking the conveyor with the belt stopped. The protruding bolt, torn skirt, and tracking problem were all visible on physical inspection. They had been missed because no systematic inspection routine existed.
Elephant Rubber supplied the replacement EP400 belt and conducted technical consultation for this investigation.