Spillage is fugitive material that falls from the carry side of the conveyor belt, and it is most common around the load zone, but can occur anywhere along the line of the belt.
Spillage often falls on walkways running beside or underneath the conveyor. Spillage can become a drop hazard if spillage falls in lump from a height. Slips, trips and fall risks are increased in areas where there is material spillage on the walkway, which can also create an entanglement risk.
The force with which spillage hits the ground, increases material fracture which increases airborne dust. Depending on the environment, spillage can also contaminate the surrounding area of other materials being conveyed (for example, ship loader facilities where more than one product is being conveyed).
Spillage becomes part of a continuous cycle; misalignment causes spillage, and spillage causes misalignment as the friction on the idler and belt changes, causing the misaligning of the belt.
Fugitive material may bury idlers, conveyor components, or structural supports, requiring costly clean-up labour and replacement parts. Spillage, in particular, leads to material build-up around idlers, which can cause idlers to seize and increase friction on the belt.
Effective control of the spillage can be considered in three stages: loading zone containment, preventing the escape of fugitive material from the carry side of the belt, and controlling the discharge of the material.
Containment at the loading zone can be effectively achieved first by designing the belt to be troughed at the load zone. This works in conjunction with the installation of an effective sealing and skirting system. Other important factors in containing fugitive material include belt support and most importantly, effective and consistent maintenance.
To prevent the escape of fugitive material from the carry side of the belt, the belt should be monitored closely for belt wandering or misalignment, which is a major cause of spillage. Belt wander creates interruptions in production as the belt must be stopped, repaired, and retrained prior to resuming operations. In order for a belt to track in the centre, idlers and pulleys should be aligned, levelled and square to centre line prior to loading the belt. The correct loading of the belt should be distributed in the centre of the belt. In order to install belt tracking or training devices, the belt needs to be monitored in order to identify problem areas that cannot be solved by making adjustments. Once again, the belt should be consistently monitored and maintained for continued prevention of spillage.
Conveyor cleaning at the discharge points removes excess material fines from the conveyor to reduce carryback that falls along the return strand of the conveyor belt, carryback can damage the conveyor structure, increasing the likelihood of spillage.