Martin Engineering’s High Speed Roller Cradle is designed to protect other conveyor
components from impact damage at crucial conveyor system loading points.

The mine-for-leach process uses bacteria to extract copper from ore and solvent extraction/electrowinning (SX/EW) to recov-er copper from the resulting leach liquor. The crushed copper ore is delivered to a single leach pad by a series of overland and portable conveyors. At a transfer point handling minus ¾-in. (minus 19-mm) agglomerated copper ore with a 20% moisture content, a 72-in. (1,828-mm) belt perpendicularly feeds a 60-in. (1,524-mm) belt from a straight 12-ft (3.65-m) drop.

The customer was using standard OEM impact idlers in the load zone; however, with the heavy loading conditions, mainte-nance personnel were forced to change an average of four to five rollers and one to two complete frames per month due to compo-nent failures. “The standard idlers simply could not withstand the heavy load and lengthy drop, costing downtime for repairs as well as the expense of replacement components,” said Martin Engineering Service Technician Doug Brown.

To address the problem, the maintenance supervisor met with Martin Engineering and asked for suggestions. Brown recom-mended the company’s newly introduced High Speed Impact Cradles and installed the units shortly after. “After seven weeks of operation, approximately 2.9 million mt of material have been conveyed across the load zone, and there have been zero compo-nent failures,” he said.

The new cradles use Martin Engineering’s Trac-mount technol-ogy to slide in and out easily for maintenance. The modular com-ponents are light enough to be removed by hand, without using a crane or other equipment to handle them.

“We wanted something that was slide-in, slide-out,” said Martin Engineering Global Product Manager Chris Schmelzer. “These new cradles were designed using Finite Element Analysis, so we could confirm that they’d be strong enough, without having to overbuild them. We can make it as strong as it needs to be, without adding excess weight, so workers can remove and replace components without using heavy lifting equipment.”

An innovative load zone design uses an elastomer bar suspen-sion system that absorbs and distributes the material load being transferred, reducing the stress on the idlers’ rolling components and support structure. One patent-pending design innovation is the use of connecting brackets near the top of the idler frame to hold the three rollers together. These connector brackets are designed to allow multiple modular cradles to be tied together, so that the idlers throughout the entire load zone work together as a system.