As tons of material per hour are quickly dropped with great force through receiving chutes onto a receiving conveyor, fugitive cargo often piles up around the frame, and dust migrates throughout the area collecting on idlers, pulleys and floors and affecting air quality.
Workers have to continually clean up the material before it encapsulates the belt, potentially exposing them to a hazardous work area around a moving conveyor, where even incidental contact can result in serious injury. Considering that most conveyor injuries occur though routine maintenance or clean up, controlling fugitive material is becoming one of the primary elements in a well organised effort to reduce hazards and prevent injuries.
Reduced profit margins
“Conveyor operators need only take a broad look at the expense that fugitive material has on a system to realise the full cost that accompanies inefficient
transfer point designs,” says Jerad Heitzler, Product Specialist at Martin Engineering. “Problems such as improper belt support, badly sealed chutes, damaged idlers and uneven cargo distribution can all result in spillage and belt mistracking. They also contribute to increased costs for lost material, premature equipment failure, maintenance and cleanup, as well as the potential for injury and compliance issues. These factors raise the cost of operation and reduce profit margins.”
Containment is the key to avoiding spillage and dust, and there are a number of components designed for this purpose. Although shaped transfer chutes and rock boxes direct the material flow to mitigate the concussion of material on the belt, most high-volume operations need one or more impact cradles to absorb the force of the cargo stream. Heavy duty impact cradles can be equipped with rubber or urethane impact bars with a top layer of slick UHMW plastic to minimise belt friction.
“Within the settling zones which are located after the impact cradle in the conveyor chute box, slider cradles can then create a troughed belt to centre the cargo and reduce disruption quickly, aiding in dust settlement,” says Jerad. A smooth belt path should have no gaps, minimising disruption and
promoting containment, allowing dust and fines to settle into the cargo stream prior to leaving the containment area.
“With a constant stream of material crashing on the impact point of the receiving belt, the transfer point can be extremely turbulent, and this turbulence must be contained. By slowing the airflow in the skirted area, suspended dust is allowed to settle onto the cargo path,” adds Jerad.
By closing gaps and keeping a tight seal on the belt, apron seals can also be attached to the chute walls to prevent fugitive dust and fines from escaping. “A crucial requirement in any transfer point designed for reduced spillage and high efficiency is an effective skirting and wear liner sealing system at the edge of the belt,” explains Jarod. Modern designs feature external skirtings, which establish the tight belt seal needed to eliminate fugitive dust and fines.
“Managers concerned with the overall safety and cost of operation need to review potential hazards, the impact of rising labour costs for cleanup and maintenance, combined with the expense of potential fines or forced downtime, to determine specifically how they can affect the bottom line,” concludes Jarod.