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Cliffs Natural Resources: NSM-Rotary Car Dumper Replacement

In the spring of 2010, Lakehead Constructors was contracted to replace the tandem rotary car dumper for North Shore Mining in Silver Bay MN. There were considerable structural, logistical, and schedule limitations. The dumper was to be replaced inside an existing dumper structure that contained multiple roof structure levels, main electrical feeds, and major dust collection apparatus and would require considerable structural demolition.

Having a limited shutdown schedule for replacement, the new dumper barrels had to be pre-assembled (to a certain point) at a worksite outside of the existing dumper building. Logistically, the worksite consisted of an approximate 60′ wide by 120′ long area with operating railroad tracks immediately adjacent to both sides of the pre-assembly site. These same time constraints and existing building configurations mentioned above forced us to come up with a unique method of installation, we would go through the wall rather than the typical method of coming through the roof.

The rotary dumper was 61′-1″ long by 26’6″ in diameter, and it weighed 259,200 lbs. The pre-assembled dumper was transferred to modified railcars on a specially designed temporary transfer truss via a traveling hydraulic lift system. Once the dumper/truss was properly secured to the railcars a locomotive engine was used to push dumper into the dumper building. The next logistical issue to deal with was pushing the system across a temporary rail trestle that was erected in the dumper vault, remove the temporary trestle from underneath the dumper/truss, relocate the traveling hydraulic lift system into the dumper building, lift the truss/dumper off the railcars to remove the upright portion of the truss/railcar interface and lower (with about 2″ of clearance) the truss/dumper onto the new trunnions in the dumper vault. After the dumper rails made contact with the trunnions, the temporary truss was detached from the dumper barrels, and then lowered onto the railcars so it could be removed from the dumper and building.

Pre-assembly of the new tandem rotary dump, including the temporary truss, was accomplished in two months. Demolition of the existing dumper, re-locating the new dumper from its pre-assembly site, setting, and final assembly and adjustment of the rotary dump was accomplished in 19 days. This project was accomplished on time and without any lost time accidents.