Contact Person : Sharon Wang
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August 21, 2020
Crane wire ropes are commonly used on construction cranes, and are generally braided by many high-strength crane 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 to form a crane wire rope. Some imported crane wire ropes also contain a plastic ferrule, usually in the form of a plastic coating, which is specially treated to cover the rope core. The important crane wire ropes are filled with appropriate lubricants to reduce friction. Domestic crane wire ropes are generally divided into three types: organic (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. The crane wire rope can be divided into a straight winding rope and a cross winding rope according to the mutual direction of the wire winding into a strand and the strand winding into a 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; Crane wire ropes generally take the winding rope as the standard rope. It is stipulated that the rotation direction of the crane wire rope is consistent with the rotation direction of the outer strand helix relative to the longitudinal axis of the crane wire rope, which is divided into left-handed and right-handed. Correspondingly, the direction of rotation of the strands is also specified, that is, the direction of the helix of the outer filaments constituting the strands is the direction of rotation of each share based on the longitudinal axis of the strands.
When the ordinary crane wire rope is used in a single rope, it has the phenomenon of rotating in the opposite direction of the crane wire rope. When used in a pulley block, the crane wire rope will rotate due to the rotation of the crane wire rope, which is commonly known as twisting. Compared with ordinary crane wire ropes, non-rotating crane wire ropes have begun to be widely used. The so-called non-rotating crane wire rope is based on the principle that the torsional moment of the rope and the strands are opposite and equal in magnitude: the imported non-rotating crane wire rope is different. The principle is to make the rope core rotate in the opposite direction to the rope itself.
When the force is applied, the torque generated by the rope core is equal to the torque generated by the outer strands, and the direction is opposite. The strands of the crane 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 densely stranded wire rope can use thicker steel wires. Under the same diameter, the densely 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 the ordinary strand crane wire rope are squeezed more severely between layers, and the surface of the crane wire rope wears faster. The tightly stranded crane wire rope has higher resistance to wear and extrusion.
The correct selection of the crane wire rope directly affects the service life of the rope and causes structural deformation, breakage and accidental failure of the rope. Therefore, the recommended selection principles are as follows:
1. When lifting an unguided heavy object or multiple unguided heavy lifting at a larger height, use a non-rotating crane wire rope;
2. When carrying out a guided heavy lifting once or multiple guided heavy lifting at a small height (such as driving) or using a pair of left- hand and right-hand ropes, ordinary crane wire ropes can be used.
The determination of the direction of the crane wire rope rotation should follow: the drum with the right-handed rope groove is recommended to use the left-handed wire rope; on the contrary, the drum with the left-handed rope groove should use the right-handed wire rope. For single-layer winding non-rotating wire ropes, the above principles must be strictly observed, otherwise it will easily cause permanent deformation of the crane wire rope structure; in the case of multi-layer winding, the rotation direction of the rope is determined by the direction of the drum rope groove, so as to be the next layer Lay the foundation. The friction force and squeezing force of the multi-layer crane wire ropes wound on the drum are relatively large, which is easy to cause the disorder of the rope. Therefore, the crane wire rope with a diameter slightly smaller than the groove pitch and the rope groove diameter should be selected to increase the crane wire rope. The contact area with the drum reduces the friction between adjacent crane wire ropes, thereby increasing the life of the wire rope.
Practice has proved that the diameter of the crane 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 larger the number of outer strands of the crane wire rope, the thinner the single steel wire. This crane wire rope has good flexibility and can well overcome the reverse bending force of the crane wire rope when it enters and exits the drum multiple times. It's easy to wear a rope. 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 crane wire rope. In addition, the minimum diameter and minimum breaking force of the crane wire rope should meet the requirements of the ISO4308 standard during the selection process.