Draglines have long booms comprising 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.

“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 proposed modification, the cluster design can be upgraded and repair costs reduced to approximately $2 million — an extremely attractive incentive for mining companies.”

The construction comprises a Reimann plate that provides an interface between the main chord and tubular lacings at a cluster joint. Such a design allows the lacings from the chord to be cut away, thereby providing easy access to remove damaged or previously repaired material. The exposed chord can then be inspected and fully repaired before installing the plate.

“This modification and repair approach could not only significantly extend the lives of existing tubular boom and mast structures, it could also provide excellent access for weld repairs to take place, therefore minimizing the safety risks for operators,” Constancon said.