Wire ropes are commonly used on construction cranes and are generally made of many high-strength steel wires. It firstly consists of single steel wires wound together to form strands, then some of the strands are wound into a rope core, and then outer strands composed of other strands are wound around the rope core into a steel wire rope.
Some imported steel wire ropes also contain a plastic ferrule inside, usually in the form of a plastic coating, which is covered on the rope core through special treatment. Important steel wire ropes are filled with appropriate lubricants to reduce friction. Domestic steel wire ropes are generally divided into organic matter (hemp core and cotton core), asbestos core or metal core according to the rope core material.
There is usually no filler or lubricant inside the rope. According to the mutual direction of the steel wire wound into strands and the strands into the rope, the wire rope can be divided into the winding rope and the winding rope, and according to the twist direction of the strand rope, it is divided into left and right twists in the same direction and left and right alternate twists; imported steel wire rope Generally, the winding rope is used as the standard rope, and the direction of the wire rope is specified to be consistent with the direction of the outer strand helix relative to the longitudinal axis of the wire rope, which is divided into left-handed and right-handed.
Correspondingly, the direction of the strands is also specified, that is, the direction of the helix of the outer filaments constituting the strands is the direction of the strands based on the longitudinal axis of the strands. When the ordinary steel wire rope is used in a single rope, it rotates in the opposite direction of the steel wire rope. When used in a pulley block, the steel wire rope is twisted due to the rotation of the steel wire rope, which is commonly known as twisting.
Compared with ordinary steel wire ropes, non-rotating steel wire ropes have begun to be widely used. The so-called non-rotating steel wire rope is based on the principle that the torsion moment of the rope and the strands are opposite and equal in magnitude: the imported non-rotating steel wire rope is different. The principle is to make the rotation direction of the rope core opposite to the rotation direction of the rope itself.
When force is applied, the torque produced by the rope core is equal in magnitude and opposite to the torque produced by the outer strands. The strands of the steel wire rope can also be made into compact strands by post-treatment methods such as rolling or die extrusion. After treatment, the diameter of the strands will be reduced, and the surface finish will be high. Therefore, the tightly stranded wire rope can use thicker steel wires.
Under the same diameter, the tightly stranded wire rope has a higher filling factor and greatly improves the breaking force. When multi-layer winding is performed on the reel, the outer strands of ordinary strands of steel wire ropes are squeezed more severely between layers, and the surface of the wire rope wears quickly. The tightly stranded steel wire rope has higher abrasion resistance and extrusion resistance.
Whether the wire rope is selected correctly or not will directly affect the service life of the rope and cause structural deformation, breakage and accidental failure of the rope. Therefore, the recommended selection principles are as follows:
1. When lifting an unguided heavy object once or when lifting multiple unguided heavy objects at a larger height, use a non-rotating wire rope;
2. When carrying out a guided heavy lifting or multiple guided heavy lifting at a small height (such as driving) or using a pair of left-hand and right-hand ropes, ordinary steel wire ropes can be used.
The determination of the direction of the wire rope shall follow: the drum with the right-handed groove is recommended to use the left-handed wire rope; on the contrary, the drum with the left-handed groove should use the right-handed wire rope. For single-layer winding non-rotating steel wire ropes, the above principles must be strictly followed, otherwise it will easily cause permanent deformation of the steel wire rope structure; for multi-layer windings, the rotation direction of the rope is determined by the direction of the rope groove of the drum, so as to be used for the next layer. Good foundation.
The friction force between the steel wire ropes of the multi-layer winding drum and the squeezing force are high, which is easy to cause the phenomenon of rope disorder. Therefore, a steel wire rope with a diameter slightly smaller than the rope groove pitch and the rope groove diameter should be selected to increase the wire rope and the drum. The contact area between them reduces the friction between adjacent steel ropes, thereby increasing the life of the steel ropes.
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 eliminates the phenomenon of rope climbing and messy rope. Under the same diameter, the more the number of outer strands of the wire rope, the thinner the single steel wire. This kind of wire rope has good flexibility and can well overcome the reverse bending force of the wire rope when it enters and exits the reel multiple times. easy.
The thicker outer strands have thicker steel wires, which can better resist wear, mechanical damage, corrosion and extrusion. Therefore, only a good combination of the two advantages can be a truly high-performance high-quality steel wire rope. In addition, the minimum diameter and minimum breaking force of the wire rope should meet the requirements of the ISO4308 standard during the selection process.