Reducing Crane Wheel Failures at the Midwest Plant of U.S. Steel

摘要

United States Steel Corporation's Midwest Division plant is a 1960's Sheet and Tin Finishing Facility, located on the southern shore of Lake Michigan, 40 miles from Chicago. The plant is well designed and has been continuously upgraded over the years. It has a highly productive workforce, sturdy production equipment, and efficient material flow that turn out quality products. There are 47 total EOT cranes in the Division. The majority were built to Association of Iron and Steel Engineer's, AISE, Technical Report No. 6, "Specification for Electrical Overhead Cranes for Steel Mill Service". The crane builders were Morgan, Reading, Alliance, Northern, P&H, and Zenar. The crane capacities range from 10- ton to 75- ton. The majority of the cranes are double hoist of 50/15-ton capacities. The cranes' bridges are usually eight-wheeled cranes, nearly evenly split between either double A-5 drives or double A-4 drives. (See Figures 1 and 2) The majority of the bridge wheels are double-flanged, flat-treaded and usually 24" or 27" diameters. The crane wheel surface hardness is 57 - 63 Rc. All wheel assemblies have spherical roller bearings. Bridge speeds are in the 400-450 fpm range. 250 VDC series motors power the vast majority of the bridges; however, there are a few 440 VAC applications. The runway bridge rail system is predominately a floating rail expansion bay system held by standard type H1 single welded clips and holders on a steel underlayment base. The bridge rails are #175 crane rail 39'-0" lengths with bolted splice bar joints. The majority of the rail spans are 120'-0" or 130'-0"; however, there is a runway of 1745 feet in length that facilitates the use of synthetic rubber nosed rail clips mounted on a synthetic rubber pad with flash-butt welded rail connections. This particular report will refer specifically to the A-5 drive with the 230 VDC series motor on the runways with the flash butt as well as the splice bar rail applications.