Metal Loss and Deformation

Metal loss refers to the actual wearing away of metal from the outer wires of a rope. Metal deformation is the changing of the shape of a rope's outer wires. Both frequently occur at the same time, although one usually predominates.

In general, resistance to metal loss by abrasion (also called "abrasion resistance") refers to a rope's ability to withstand metal being worn away along its exterior. This is due to the rope having sliding contact with another hard object. The resulting loss of steel reduces the wire rope's strength and can accelerate the occurrence of broken wires.

 In most cases, metal loss has three main causes:

• An improper rope fleet angle. As the rope enters or leaves a sheave, it contacts the sheave flange, causing wear to both the rope and sheave.
• Grooves that are too small in a sheave. The rope slides between the flanges as it seats in the groove, causing rope wear.
• Pulling drag rope through the "roll" of rock at the edge of the pit can also result in rope surface wear.

 

Metal deformation (also called "peening") is the flattening of the wire's external surface caused by slapping against a hard object such as a rock, sheave or a roller. The steel is not worn away, but pushed to the side. This deformation shortens the rope's fatigue life because the distorted shape of the wires impairs the normal sliding and adjusting when the rope operates. It also frequently results in the formation of martensite.