Marion 8200 Dragline - Hoist and Drag Drums

Problem: To raise and lower the 68 yard bucket on this dragline, cables are used with large winches known as the hoist and drag drums.

The drums are bolted together in segments from the inside with 3" studs and nuts. OEM specifications required the old style fasteners to be tightened to 12,315 ft-lb of torque on grade 5 materials to produce 246,260 lbs of clamping force. This application experienced many broken studs over the years and prompted the mine to try replacing the bolts with grade 8 materials. This would have required a higher torque of 19,000 ft-lb which the mine was not able to produce with their existing equipment. It also did not address the short clamping length and coarse thread situation. The new materials did not make any significant difference.

Solution: The mine changed to Superbolt tensioners (MT-300-8/w) and new 4140HT studs with 8 tpi threads. The high preload of 428,400 lbs was achieved with only 233 ft-lb of torque required. The added flex from the Superbolt tensioners more than doubled the elasticity of the bolted connection. Tightening the nuts was an easy task inside the drums where space is limited.

Two halves of the large split gear which turns these drums are both bolted together and fastened to the drum itself using our product.