The concept of the rope property of “flexibility” for improvement in rope life is not new to industry. However, in surface mining, most wire rope companies have offered only one choice of rope geometry for any given rope size.
The Excavator Family of Bethlehem Mining Ropes are offered in two geometries which result in rope properties which are either (A) more flexible, or (B) more abrasion-resistant.
The flexibile Type A is specifically designed for hoist ropes and drag ropes with reverse bends in the rope path. These ropes generally are produced in diameters 1-3/4” through 4-3/4” and contain 49 to 77 wires per strand. This geometry is used in conjunction with the more ductile metallurgy of Excavator grade.
The abrasion resistant Type B is specifically designed for drag ropes with straight fairleads. The relatively large outer wires can accomidate much more surface wear. Rope diameters 1-3/4” through 4-3/4” are produced. These ropes contain 26 through 57 wires pe strand. The Type B geometry achieves optimum performance when used in conjunction with the more abrasion-resistant metallurgy of Excavator-AR grade.
Many wire rope users have observed that heavily loaded ropes fail internally due to the failure of the IWRC. Such conditions illustrate that heavy IWRC stresses exist, which promote fewer fatigue cycles and create short rope life. Bethlehem designed Maxi-core to improve rope life under these conditions.
Maxi-core utilizes an IWRC design which features eight strands around a strand center. Maxi-core’s IWRC provides longer life and therefore increases the overall service life of the rope. Because of its specialized IWRC. Maxi-core is resilient and able to accommodate shock loads better than conventional IWRC designs. Maxi-core also adds 33% more core support to the outer strands thereby reducing internal stresses and promoting longer rope life.
As with all Bethlehem Excavator Family Ropes, Bethlehem does not publish Maxi-core rope strengths. Bethlehem relies on specific rope improvements and specialized features to provide rope designs which give proven superior field service.
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