Page 50 - HUB-4 Magazine Issue 77
P. 50

  Quarrying
Identifying and addressing conveyor idler issues
 On any belt conveyor system that moves bulk materials, the belt must run straight and true to maximize its life, minimize fugitive material and safety hazards, and achieve high system efficiency. There can be many consequences of a mistracking belt, but all result in higher costs and increased maintenance. Even a slight belt misalignment can lead to a variety of issues, from small annoyances to full-blown catastrophes.
The most obvious effects include spillage and dust that require personnel to do cleanup, which is unproductive work that introduces risks from activities in close proximity to the moving conveyor. Spillage from non-centered cargo often gets into idlers and pulleys, reducing bearing life and causing them to seize, leading to friction damage on the belt and potentially starting a fire.
A misaligned belt can also come in contact with the stringer, causing fraying, shredding or splice damage. Great lengths of valuable belting can be destroyed with surprising speed, and even the support structure itself can be damaged. A
compromised bracket or support can cause a catastrophic idler failure, which could damage other components of the system and require extensive downtime to repair. Further, there is potential for injury from a damaged belt or loose idler not to mention the increased exposure to injury from too frequent a need to clean.
“I’ve been working around conveyors for 20 years, and I’ve seen thousands of belts,” observed Martin Engineering Process Engineer Dan Marshall. “I’ve seen just about every problem that can be caused by a mistracking belt, but one thing I’ve never seen is a belt that runs true right out of the box. All conveyors, no matter how well designed and built, have some belt wander.”
A wide variety of circumstances can lead to mistracking, and operators have tried many things to correct the alignment. Some have elected to place an obstacle such as a block of wood in the belt path, so it won’t travel too
far out of line. This occasionally improves the situation, but more often it’s just temporary and the belt will eventually slice through the obstacle.
Many operators have realized that pivoting an idler is a quicker and more effective way to steer a belt. This common approach is called “knocking an idler,” striking it with a hammer to move it slightly and realign the belt.
Equipment manufacturers have also designed components to help align a belt, and these solutions can be successful in specific applications. They include specially-shaped rollers, angled idlers and devices that apply pressure to the belt edge to push it back in line.
“While these mechanisms can improve a belt that’s consistently off-center in one direction, they do not react to dynamic belt movement, meaning that they don’t correct intermittent belt wander,” Marshall continued. “To combat such changing conditions, engineers designed the tracking idler. Unlike the edge correction approach, the device senses belt movement in either direction, and pivots the idler slightly to steer the belt back into position. It doesn’t apply a great
“Knocking” an idler with a mallet to change its position
 | p50 |
www.hub-4.com Nov/December 22 - Issue 77
    



















































































   48   49   50   51   52