Wire Rope Inspection
All wire ropes in service eventually wear out. It’s important for an experienced inspector to regularly perform detailed and thorough examinations to ensure they meet accepted safety standards.
In addition, visual inspections should be completed each shift or working day to identify signs of damaged steel cables. If you have questions about the condition of your wire ropes, experts at Wilkof Industrial are always available to help and can be contacted by phone or email.
Critical inspection areas for wire ropes fall within several broad categories:
- Distortion is a deformation in strand structure. Depending on severity, these conditions usually require replacement of the wire rope. Formation of a loop that has been tightened, creates an irreparable kink. A permanent bend in the steel cable is known as a dogleg. Shock loading, also called birdcaging, because the condition resembles a birdcage, is caused by sudden release of tension and the rebound from the overload, or from the wire rope being pulled through tight sheaves or wound on a drum that’s too small. A protruding core is obvious when the rope core becomes visible through its outer strands. Scrubbing is caused by steel cable rubbing against itself or another object, causing wear and displacement of wire strands along one side of the rope. A wire rope subjected to pounding by strikes or itself will eventually show signs of peening, as if the steel cable had been hammered.
- Diameter Reduction is caused by a variety of factors, and is a sign of steel cable degradation. Abrasion of outer wires gradually occurs with continued use over drums and sheaves; the wire rope should be replaced when one-third of the outer wire diameter is worn away. Visible exterior broken wires should be closely monitored – the American National Standards Institute has produced a guide for the acceptable number of broken wires, depending on type of rope and its use. All steel cables experience rope stretch. It’s a normal phenomenon that begins with a break-in period, followed by a long period of minimal stretch. However, when stretch rate begins to rapidly increase, the steel cable has reached the end of its useful life.
- Heat Damage can be present after a fire or high temperatures. It’s marked by discoloration; fiber core ropes are particularly susceptible and typically the wire rope should be replaced. Similarly, steel cable that has created an electric arc should be replaced. This occurs when the steel cable is in contact with a live power line or was used as a “ground” in an electric welding circuit. Signs of degradation are fused, discolored and/or annealed wires.
- Corrosion is often a silent and unnoticed problem that can spread throughout the steel cable. It typically occurs due to insufficient lubrication. Slight rusting can usually be corrected with lubrication. However, severe rusting can lead to fatigue failures. A clear wire rope lube can be applied to prevent corrosion. Or, a galvanized wire rope may be required in particularly corrosive environments.
- Breaks, cracks or bends can occur on wire rope end fittings. The cause of the problem should be corrected and replacement usually is necessary. Wires that break with square ends and show little surface wear are signs of a fatigue fracture, and can occur in the crown or valley of the steel cable. In almost all cases, these failures are related to bending stresses or vibration. A more flexible steel cable or increased sheave or drum diameter can sometimes correct the problem. Special attention should also be paid to areas with localized conditions where unnoticed abrasions and breaks can occur. These are “hidden” sections, such as drum crossovers and flange points, where the wire rope is not typically visible.
If you have questions about the condition of your wire ropes, experts at Wilkof Industrial are always available to help, contact us today.