Wire Rope Composition
Wire rope breakage during the hoisting of top silo unloaders occurs with alarming frequency. At worst, such mishaps h***e resulted in severe injury and death. Even where no one is injured, costly damage to equipment and time lost during a critical harvest period make the ‘dropping’ of an unloader a very expensive incident!
In some cases, wire rope failure is the result of undersized rope and/or incorrect rigging ha***are being used at the time of installation. More often, breakage occurs due to misuse and/or inadequate maintenance.
Wire Rope Composition
A wire rope is composed of a number of wire strands formed helically around a central axis. The axial member is known as the core, and may be made of various materials, such as fibre or steel.
Wire rope is aptly described as a precision machine. In operation, its strands change position with respect to each other. Individual wires within each strand preform in a similar manner. The relati***hip between these parts is carefully engineered to permit the rope to function ***oothly in operation.
As with other precision equipment, internal lubrication must be provided during fabrication. This combats frictional forces (which oppose movement of parts) and prevents corrosion.
Operating factors which affect a rope in service are tension, wear, bending, crushing and corrosion. Neglect and misuse will substantially reduce a wire rope’s useful life.
Choosing the Right Rope
Wire rope is ***ailable in a variety of grades and configurati***. To the layman, the critical factors in selecting a rope are breaking strength and diameter.
An adequate factor of safety is crucial in wire rope use. For silo unloader hoist rope, the recommended safety factor is 5:1. In other wo***, if a silo unloader weighs one ton, the wire rope used must h***e a minimum ultimate breaking strength of five t***.
Rope diameter is important for compatibility with rigging ha***are. In particular, the wire rope must seat properly in the she***es (pulleys) to ensure *** of movement without undue wear to rope or she***e.