Wire rope maintenance is a vital part of crane safety, performance and longevity. Hundreds of components work together to lift and suspend huge amounts of weight, so keeping this thin band of strength in proper condition is essential. American Cranes & Transport (ACT) Magazine recently published a summary of what steps should be taken to keep wire rope operating smoothly.
Sheaves need to be able to move freely and without wobbling. This prevents vibration which can cause fatigue to the wire rope. Additionally, the groove should be one percent larger than the maximum rope diameter including its allowable tolerance. Sheaves that are worn or too small can cause forced twist deformation, while tolerances that are too large can cause damage from lack of support. Rollers should also be inspected regularly to be sure they’re free of corrugation and wear, and that the bearings operate smoothly.
Bending a wire rope causes individual strands to rub against each other, and that rope running through a sheave is subject to wear. A wire rope that is not properly lubricated will cause friction and a drastic shortening of its lifespan. In general, ropes should have a thin coat of maintenance lubricant applied every six to 12 months. Its properties must be compatible with the original lubricant and designed specifically for wire rope. It must be able to penetrate and evenly coat all the strands of wire as opposed to just remaining on the outermost surface.
Wire rope should be sufficiently tensioned on the drum during installation, and a good amount of tension is five to ten percent of the working load limit. This causes the wire to tighten and resist crushing from the incoming loaded rope. Applying tension is not just a one-time event as unused wire slowly loosens and should have tension reapplied during crane maintenance.
Another suggestion to extend the rope’s lifetime involves cutting a length equal to 1-1/4 drum wraps from the drum end, which will reposition the wear points. This should be done three or more times during the rope’s lifespan, and before these sections show more wear than the rest of the rope.
These points just scratch the surface of maintaining the safety and integrity of a crane’s wire rope. Read the entire article at American Cranes & Transport’s website by clicking here. Images above courtesy of ACT.