Rebuilding a defunct bucket wheel excavator into a higher-performance machine
At an inland port in Superior, Wisconsin, one of BNSF Railway’s three bucket wheel excavators, used to load taconite (low-grade iron ore) on ships, had been out of service for many years because parts were no longer available for the 50-year-old machine. Anticipating an increase in ore supply in less than a year that would far surpass the loading capacity of its two functioning bucket wheels, BNSF wanted the third machine not just up and running fast but improved and rebuilt to a higher standard for better performance and reduced downtime.
IMPACT TO OPERATIONS
- Lost loading capacity – 1 hour of downtime = 3,500-4,000 tons of lost throughput.
- Downtime in cold weather – the original engine design left the lube system, programmable logic controller (PLC) and motor control center (MCC) exposed to winter temperatures as low as -40°F (-40°C).
- Downtime for structural repairs – high-stress joints in the original design along with lower-grade steel than what’s available today meant the machine required more frequent structural repairs.
- Downtime from overworking the machine – the original control system lacked automated limiters, meaning operators could damage the machine by exceeding its working capacity.
Starting with a machine tear-down and relocation to our ISO-certified manufacturing facilities in Gillette, L&H improved the bucket wheel excavator design, upgraded the electrical system and rebuilt all major assemblies to better-than-new condition.
Redesigning key structures, upgrading materials used, and improving the control systems
The few existing design prints weren’t usable as a starting point for the overhaul, so the L&H team used laser trackers and FARO arms to measure and model the machine, followed by finite element analysis (FEA) to understand the dynamic loads.
L&H engineers reviewed the entire machine design, finding multiple opportunities to eliminate failure points and improve it:
- Using higher-grade steel and modern materials
- Changing weldment fit-ups and eliminating high-stress joints
- Building an enclosed, pressurized engine house for the lube system, PLCs and MCC room
- Installing a completely new electrical package
- Increasing machine capacity and installing PLCs to regulate that capacity
Following design improvements, L&H custom-manufactured and rebuilt every major assembly on the machine—the ladder boom, mast, gantry, discharge booms, side frames and carbody.
“My experience working with the entire L&H team was fantastic. This included everyone from the owners to the engineers, the coordinators, and the welders and machinists on the floor. It was obvious there was a total commitment by all involved at L&H to complete the project on time and on budget with the highest level of quality possible.”
—Jeff Schurman – Shop Superintendent – Equipment, BNSF Railway
An Honestly Better machine: stronger, higher-capacity, more reliable
Working in 26,000 man-hours in just 12 months—with no safety incidents in the shop or field—L&H completely modernized, upgraded and rebuilt the bucket wheel loader, producing a customized, higher-performance, greater-capacity machine that is 80% new and exceeds OEM specifications on multiple fronts.
Once L&H delivered and commissioned the machine in January 2015, BNSF began moving stockpiles and putting the machine through its paces in preparation for the impending increase in its taconite supply. L&H and BNSF are now discussing complete modernization of the port operation’s other two bucket wheel excavators, with the possibility of building a completely new and improved machine from the ground up, with design improvements beyond what could be achieve within the parameters of this first project.