About two years ago, BNSF Railway approached L&H with a project that included the entire overhaul of an antique bucket wheel used in Minnesota to move taconite onto conveyor belts that move the material onto barges. Manufactured in the 1960’s, the machine needed a full workup of engineering, rebuilding and manufacturing in order to function at its full capacity again.
Scope of Work
After inspecting the machine before tear down, it was determined that the bucket wheel was un-repairable. The ship-loading facility was previously using all three bucket wheels they had on site, and with one being down a quick turn around time was crucial. L&H was confident that they could provide BNSF with a machine that was 80% new, using little of the remaining structure within a year.
Throughout our company history our team has taken great pride in discovering machine pit-falls and creating an improved product. When L&H took this project on, our goal was to give the customer a better machine.
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. Engineering reviewed the entire machine design, finding multiple opportunities to eliminate failure points and improve it.
One of the major enhancements to the L&H bucket wheel was the use of higher-grade steel and modern materials. Changes were made to the weldment fit-ups, which eliminated high-stress joints. The major structures were also newly designed and engineered to decrease the frequency of structural repairs. Another major design change was made to the rear revolving frame and engine house of the bucket wheel. Previously, all of the components of the engine house were exposed to the extreme elements where temperatures may reach -40°F. With the L&H upgrade, the brains of the machine are now housed within a pressurized and heated room.
A completely new electrical package is on this bucket wheel and PLCs were installed to regulate the increased capacity that L&H upgrades included. Following all of these 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.
Once L&H delivered and commissioned the bucket wheel 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 achieved within the parameters of this first project.Bucket Wheel Excavator Case Study