HIGH-PERFORMANCE HOISTING ROPES
Many newer hoists are using high-performance wire ropes for higher strength while using a smaller rope diameter that allows more compact drums and smaller diameter sheaves. So what exactly is a high-performance wire rope.
Steel wire rope, although simple looking from the outside is really a very complex piece of machinery which has the primary function of transmission of tensile forces from the hoisted load to the hoisting machinery. Its primary construction design is to allow repeated changes in the directional pull through a reeving system consisting or sheaves and storage drum. When loaded, every wire rope will develop torque; that is it has the tendency to unlay itself unless both rope ends are secured against rotation and to cause a lower sheave block to rotate and to spin the line parts together.
General-purpose ropes that have historically used in hoisting operations are being increasingly replaced with high-performance wire ropes. This is especially the case in hoists being supplied by European manufacturers such as Demag, Kone, R&M, Stahl and Street Crane. These high-performance ropes typically have higher breaking strength, greater flexibility, better rotation resistance and extended rope life that cannot be met general purpose ropes.
Increased breaking strength is achieved by the compaction process. Standard rope wires are drawn which creates round outer circumference, however, high-performance ropes are compacted and have a flat outer surface. Strand compacted wire ropes have the compaction applied to the individual ropes, while swage compaction is applied to the entire wire rope. Both have their advantage for particular applications.
High-performance wire ropes are usually rotation resistant. Rotation resistance can fall under three different categories. Spin Resistant, Rotation Resistant, and Non-Rotating. In all of these types, the outer layer of strands is twisted opposite of the inner. Rotation resistant and spin resistant type ropes will have one inner layer while non-rotating will have multiple inner strands rotating in a different direction from the outers.
The construction of high-performance wire ropes also improves frictional wear resistance as well as crushing wear. This increased wear will allow a rope to remain in service longer and will reduce the downtime required when changing ropes.
The downside of these ropes is that they require more care when replacing ropes. Compacted, rotational resistant ropes require that the Service Technicians not introduce a twist in the wire rope while spooling the rope into the reeving system of the hoist. If the installation is not performed correctly the hoist block may twist under no load and the rope may fail due to the forces of the twist placed into the rope during installation. This failure may exhibit itself by core protrusion unraveling or bird caging.
Other forms of high-performance rope have been introduced with plastic impregnated cores that resist the damaging effects of punishing dual hoist flipping applications such as die handling.
For more information on wire ropes for hoisting applications contact the experts at your nearest CRANE 1 office.