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Joy Global has also introduced the Design Failure Mode and Effects Analysis (DFMEA) process. This process looks at possible failure mode, and weighs the severity and the probability of occurrence. These factors are combined to define an index for each component or subassembly of the equipment. This approach is extremely beneficial in the prioritization of design efforts and resources. Joy Global structures have gained an enviable reputation in the mining industry and this is due to exacting design, the use of high strength steels, automated welding that increases weld integrity and the elimination of stress prone transverse welds.

 

Joy Global has also developed a scientific relationship between test and underground life expectancy. Joy Global now works with its customers to provide them with a better insight into this relationship to establish a life plan for the equipment.

 

The hydraulic legs or jacks, used to set the canopy to the roof, generally are double telescopic to provide maximum open-to-closed height ratio. Joy hydraulic legs are extruded allowing large diameter ports in the forging for faster fluid flow and faster cycles. The elimination of vulnerable welded stack pipes also increases reliability. The extruded design also benefits the leg geometry by allowing the leg to be positioned closer to vertical in a given seam height. The more near vertical the leg stands, the better its load is applied to the mine roof. The Joy Global design of canopy and base structures includes four large quality steel castings for areas of load input at the end of the legs. FEA design has eliminated stress risers and produced greater life expectancy.

 

Joy Global has invested several years of research and testing on bearing materials and has developed a robust scientific method for the analysis of bearing loads. Simplistic classical methods are no longer appropriate. The improvement in bearing materials complements the much superior seal material and seal design to provide extended life expectancy of modern Joy hydraulic legs legs. Other features include a variety of base lift arrangements to free the base from soft floor conditions, and a reverse mounted advancing ram and relay bars to over come difficult applications.