BMT WBM has deployed an innovative DuraCluster modification and repair scheme, which dramatically improves the fatigue performance of cluster joints on existing tubular dragline boom designs. Once implemented, this modification significantly reduces maintenance and inspection workloads and dramatically reduces the problem of long-term fatigue cracking associated with the existing cluster design.

On a recent job for Westmoreland Coal Co., BMT was able to offer both reduced downtime and outage costs. Once installed, it also reduces the risks to operators and maintenance teams in having to lower the boom and carry out complicated weld repairs with limited access.

The long dragline booms comprise a number of tubular chords with interconnecting lacings welded to the chords at cluster joints. Stresses are concentrated at the cluster joint weldments and over time, fatigue cracking becomes endemic. BMT’s methodology prevents the need to cut and replace windows in lacings by removing the problematic design detail and improving load paths. Furthermore, DuraCluster can dramatically extend the fatigue life of dragline booms by reducing the stress concentrations.

“A boom replacement can cost in the region of $20 million and would require a three-month machine outage,” said Charles Constancon, director of Canadian services for BMT WBM. “With this modification and repair, the cluster design can be upgraded in around one week per cluster, depending on the extent of chord repair required, while multiple clusters can be modified simultaneously. With equivalent repair costs reduced to approximately $2 million, this is an extremely attractive incentive for mining companies. While DuraCluster provides a step change in life to cracking for tubular boom construction, it is equally applicable to tubular masts.”