Wire rope used in construction cranes is very common, generally by a lot of high strength steel wire wound. It first consists of a single steel wire wound together to form strands, and then some strands are wound into a rope core, and then an outer strand composed of other strands is wound into a wire rope around the rope core. Some imported wire ropes also contain a plastic plug inside, usually in the form of a plastic coating specially treated to cover the core of the rope, important wire ropes are filled with appropriate lubricants to reduce friction.
Domestic wire rope according to the rope core material is generally divided into organic matter (hemp core and cotton core), asbestos core or metal core three, the rope is usually no filler or lubricant.
Wire rope according to the wire wound strand and strand wound rope mutual direction can be divided into smooth winding rope and cross winding rope, and according to the strand twist is divided into left, right and left, right intertwist; Imported steel wire rope generally cross winding rope as the standard rope, the specified direction of the steel wire rope and relative to the longitudinal axis as the benchmark of the outer helix of the same direction, divided into left and right rotation. Correspondingly, it also provides the rotation direction of the share, that is, the longitudinal axis of the share as the benchmark, the direction of the helix of the outer wire of the share is the rotation direction of each share. When ordinary wire rope is used in a single root, there is the phenomenon of wire rope rotating in the opposite direction. When used in the pulley block, it will cause hoisting wire rope twisting because of wire rope rotation, commonly known as wringing. Compared with ordinary wire rope, non-rotating wire rope has been widely used at present. So-called non-rotating wire rope is based on the principle, namely the rope strands of torque in the opposite direction and equal: imports of non-rotating wire rope is different, its principle is to make the rope of the screw to rotate to the opposite, with rope itself when loading, the rope core with foreign shares equal torque, torque in the opposite direction.
The strand of the wire rope can also become a tight strand by rolling or die extrusion after treatment, the diameter of the strand will be reduced after treatment, and the surface finish is very high. Therefore, the tight-strand wire rope can be used with thicker steel wire. Under the same diameter, the tight-strand wire rope has a higher filling coefficient and the breaking tension is greatly improved. When multi-layer winding is carried out on the drum, the outer strand of the ordinary steel wire rope is extruded more seriously between layers and the surface of the steel wire rope is worn faster. The tight-strand wire rope has higher wear resistance and extrusion resistance. Whether the wire rope is chosen correctly or not directly affects the service life of the rope and causes structural deformation, fracture and accidental failure of the rope.
Therefore, the recommended selection principles are as follows:
1) When a non-guiding heavy lifting or multiple non-guiding heavy lifting is carried out at a large height, the non-rotating steel wire rope is selected;
2) When a guided heavy lifting or multiple guided heavy lifting at a smaller height (such as driving) or left and right rotation rope in pairs, ordinary steel wire rope can be used. The determination of wire rope rotation should follow: left-handed wire rope is recommended for the drum of the right-handed rope groove; conversely, right-handed wire rope should be used for the drum of the left-handed rope groove. For single-layer winding non-rotating wire rope, the above principles must be strictly observed, otherwise it is easy to cause permanent deformation of wire rope structure; In the case of multi-layer winding, the winding direction of the rope is determined by the direction of the drum rope groove, in order to lay the foundation for the next layer. Multilayer winding drum wire rope mutual friction and extrusion pressure are large, easy to produce rope phenomenon, so the diameter of wire rope is slightly smaller than the rope groove pitch and rope groove diameter, to increase the contact area between wire rope and drum, reduce the friction between adjacent wire rope, so as to improve the life of wire rope.
Practice has proved that the diameter of the wire rope is 1% smaller than the pitch of the rope groove, which helps to arrange the rope tightly and effectively eliminate the phenomenon of rope climbing and rope disorder. In the same diameter, the more the number of wire rope outer strand diameter is thinner, the thinner the single wire rope, the good flexibility of this wire rope, can be very good to overcome the wire rope in and out of the drum by the reverse bending force, rope is also easy to wear. The thicker outer strand, with thicker wire, is more resistant to wear, mechanical damage, corrosion and extrusion. Therefore, only the two advantages of a good combination, is the real high-performance high quality wire rope. In addition, wire rope in the selection process should also pay attention to its minimum diameter and minimum breaking force should comply with the provisions of IsO4308 standard.
