The choice of wire rope under working conditions

Source:Solar|Date: 2020-08-03| Hits

Steel wire rope as a structural part has its use restrictions. Knowing the working conditions of the wire rope can be appropriate when selecting the rope. The wire rope cannot work under the following conditions:

1) The working environment temperature is too high or too low. Excessively high temperature will cause the steel wire rope fiber core and plastic coated material to soften, the destruction of the fiber rope core will cause damage to the steel wire rope structure, and the softening of the plastic coated material will greatly reduce its wear resistance and destroy its original function. At the same time, the high temperature causes the premature loss of lubricating oil inside the wire rope and accelerates the wear of the wire rope. Too low temperature will cause the steel wire rope structure to become brittle, reduce the performance of metal materials, and may cause the steel wire rope to suddenly break and cause safety accidents. Steel core wire rope has higher high temperature resistance than other wire ropes.

2) Although the steel wire rope has good impact resistance, certain abrasion resistance, extrusion resistance and certain flexibility, it is necessary for the working environment to be very harsh (such as strong impact and severe abrasion). Use with caution. By increasing the diameter of the wire rope, selecting a higher strength wire rope, and improving the protection measures of the wire rope, the life and safety factor of the wire rope can be effectively extended.
The selection of wire rope is something that users must care about. Reasonable selection can avoid unnecessary losses and reduce investment.

1) Strength
  The tensile force value of the wire rope when it is broken is called the breaking force of the wire rope. The total breaking force of steel wire refers to the sum of the breaking force of all steel wires in the wire rope. In writing, the wire rope strength generally refers to the nominal strength. The user selects the wire rope of corresponding strength according to his needs, and the strength of the wire rope selected by the user must be greater than the minimum breaking force of the rope.

2) Fatigue resistance
The fatigue resistance includes the fatigue resistance of the steel wire. A steel wire rope must have good fatigue resistance, and the steel wire must have good fatigue resistance. The steel wire through proper heat treatment has better performance than the original. The fatigue resistance of a steel wire rope also depends on the structural design of the steel wire rope. For steel wire ropes of the same diameter and structure, a rope with more steel wires has better fatigue resistance than a rope with less steel wires.

3) Abrasion resistance
In use, the steel wire rope has sliding and rolling friction with the sheave and the drum. When the steel wire rope is bent and twisted, the speed of the different layers is inconsistent, thereby forming the friction inside the steel wire rope. The wear resistance of the steel wire rope mainly depends on the structural design and technology of the steel wire rope. For steel wire ropes of the same diameter and structure, the thicker wire rope has better wear resistance than the thinner wire rope.

4) Crushing resistance
Impact is an external force that may damage the cross-section of the wire rope, either strands or steel wires. Impact resistance refers to the resistance of the wire rope or strand or steel wire to external effects. When the wire rope is deformed due to impact, the steel wire inside the wire rope will be difficult to move and slide normally, resulting in a decrease in the overall performance of the wire rope. Generally speaking, steel core wire rope has better impact resistance than fiber core wire rope. The cross-twisted wire rope has better impact resistance than the same direction. 6-strand wire rope has stronger impact resistance than 8-strand wire rope. Shaped strand wire rope has better impact resistance than round strand wire rope. The multi-strand steel wire rope can effectively resist impact due to the existence of multiple strands and has good impact resistance.

5) Resistance to metal loss and deformation
Metal loss refers to the abraded metal of the outer wire of the wire rope in actual operation. Metal deformation refers to the shape of the outer wire of the wire rope. Resistance to metal loss is actually abrasion resistance. The general metal deformation is called "hammering", and the exposed side seems to be hit by a hammer. See Figure 5. "Hamming" usually occurs on the drum, and sometimes also occurs on the sheave when the rope is in close contact with each other on the drum. "Hammering" causes metal failure, and wire failure during operation.

6) Stability
Stability usually refers to the use and working performance of the wire rope. It is not a quantitative but qualitative view of things. The steel wire rope we produce always makes it more stable. The pre-deformed wire rope is more stable than the non-pre-deformed wire rope. The alternating twist is more stable than the same direction twist. A strand made of 7 wires is more stable than a strand made of many wires. There is no specific measurement method for stability.

7) Bend ability
       Flexibility refers to the ease with which the wire rope is bent into an arc. The primary factor affecting bending performance is the diameter of the wire rope. The second is the structure of rope and strand, technical composition and rope core structure. A thin steel wire rope must have better bending performance than a thick steel wire rope, and a steel wire rope with a fiber core has better bending performance than a steel wire rope with other cores.

8) Residual stress Reserve strength
       Residual stress is the residual stress caused by various deformations during the formation of the wire rope. Residual stress is the main reason for the fatigue failure of the steel wire rope. These stresses enlarge the tiny cracks in the steel wire during repeated deformation, making the cracks bigger and bigger, and finally breaking the steel wire, which in turn causes the wire rope to fail. The residual stress in the rope can be removed by mechanical or heat treatment. Deformation after the final stage of twisting and pre-deformation before twisting can effectively reduce the stress in the wire rope.