What are the causes of wire rope fracture?

Steel wire rope is widely used in mines, but it often causes safety accidents due to improper maintenance and management. At present, most vertical shaft hoisting equipment use steel wire rope as a fixed container and power transmission medium. Once the hoisting wire rope breaks, it will bring a series of malignant accidents such as skip falling to the bottom. In order to prevent accidents, the intact state of the wire rope is of great significance for the safe operation of the main hoisting equipment. This paper will focus on the analysis of the causes of wire rope damage, and put forward the corresponding preventive measures.

1. Causes of fracture of hoisting wire rope

The hoisting steel wire rope used in the mine is generally twisted into strands by a certain fine steel wire rope, and then several strands of steel wire are woven into ropes. In order to slow down the aging of the steel wire rope and reduce the friction resistance, a rope core made of fiber is generally set in the steel wire rope, and the rope core is fully soaked with special anti-corrosion oil.

Strand breakage

The main causes of strand fracture include fatigue fracture, excessive wear, serious corrosion and excessive tensile stress.

Fatigue fracture is mainly due to the fact that the steel wire rope needs to bear tensile stress for many times in the process of lifting heavy objects, which makes the steel wire rope very easy to fracture.

The corrosion is serious, because the vast majority of vertical shafts will be affected by water pouring, and the corrosivity of mine water is strong, which leads to the corrosion of steel wire rope in the process of use.

If the tensile stress is too large, the steel wire rope will be carefully selected according to its actual use before the design of the lifting equipment, so the possibility of tensile fracture in the process of normal use is small. However, if the operation is improper, the container will be over rolled and stuck, resulting in the instantaneous increase of the tensile stress value of the steel wire rope and fracture.

1.2 rope diameter reduction

The reduction of wire rope diameter is mainly caused by wear. In addition, under the action of mine water, the wire rope will also be rusted, resulting in the reduction of the effective diameter of the wire rope. In case of lifting over winding and other accidents, some strands of the wire rope will be broken under the action of large impact force, resulting in the reduction of the effective diameter.

Generally, the steel wire rope will experience a large deformation stage in the early stage of installation. Generally, the deformation of the steel wire rope will gradually converge after the lifting container is used for 15 days, and the deformation rate will show a gradual increasing trend in the later stage of use. This deformation is generally called the normal elongation of the steel wire rope. However, in the process of use, if the deformation of the steel wire rope increases gradually for three consecutive days and there is no convergence trend, it indicates that the steel wire rope has been damaged. In the process of using the lifting container, if there is an accident such as over winding, it will lead to the sudden elongation of the steel wire rope. It is generally believed that if the elongation exceeds 5% of the total factory of the steel wire rope, it is very likely that the steel wire rope has broken.

2 measures to prevent damage of hoisting wire rope

2.1 select the matching steel wire rope according to the purpose of the lifting equipment

For the multi rope friction hoisting equipment, the steel wire rope with the same twist shall be generally selected, and the triangular strand form shall be selected for the section shape. At the same time, in order to ensure that the steel wire rope has good stress characteristics, the proportion of the left twist part and the re twist part shall account for 50% respectively. At the same time, in order to reduce the corrosion of the mine water in the shaft to the steel wire rope, the selected steel wire rope shall generally be galvanized.

2.2 enhance the matching of lifting drum and steel wire rope to avoid excessive wear

During the selection of lifting container, the diameter of the drum shall be reasonably determined, so as to ensure that the steel wire rope can have a reasonable radius of curvature after bypassing the drum and avoid large bending stress of the steel wire rope during operation. Ensure that the diameter of the steel wire rope matches the width of the rope groove. If the width of the rope groove is too small, the extrusion force on the steel wire rope will increase, and the excessive friction between the steel wire rope and the groove wall will make the steel wire rope break from the outside to the inside. If the width of the rope groove is large, the contact area between the steel wire rope and the rope groove will increase. During the operation of the steel wire rope, it will swing left and right in the rope groove, which will increase the wear rate of the steel wire rope.

2.3 keep the steel wire rope in good lubrication condition and reduce the risk of corrosion and aging

In the process of daily use, it is necessary to ensure that the steel wire rope is in a good lubrication state, and the lubricating oil used should have good temperature adaptability to ensure that it still shows good workability under high temperature, will not be easily lost, and will not harden due to low temperature. The viscosity of the lubricant should be able to make the steel wire rope not peel off from the steel wire rope body after bearing a certain vibration load and the erosion of mine water.

2.4 strengthen the daily maintenance of steel wire rope. Full time personnel must be assigned to carefully and carefully check the wire breakage of steel wire rope every day. In order to ensure its effect, the speed of lifting equipment should be controlled within 0.3m/s. If it is found that the broken wire area has reached 5% of the total cross-sectional area of the steel wire rope during the inspection, it shall be replaced in time. For the skip cage and other equipment dedicated to lifting materials, the requirement can be appropriately increased, but it shall not exceed 10% of the total cross-sectional area of the steel wire rope.

When the lifting equipment is stuck suddenly, the equipment operation shall be stopped immediately, because the steel wire rope is easy to break under the action of large impact load. If the elongation of the steel wire rope exceeds 0.5%, it must be replaced.

When the lifting materials and personnel share a set of equipment, the steel wire rope must be tested for hiding the rope head every 180 days. If it does not meet the relevant requirements, it is strictly prohibited to operate with defects and replace it immediately. During the use of steel wire rope, the occurrence of "rope biting" shall be avoided to the greatest extent. The adjacent section between the lower rope and the upper rope shall be especially used as the key area of inspection. In order to ensure the balance of stress between different rope sections, the amount of rope staggering shall be maintained at one quarter of a circle every quarter.

3 conclusion

1) The main causes of strand breakage, rope diameter reduction and elongation deformation are the three main causes of hoisting wire rope damage.

2) In order to reduce the risk of damage of hoisting wire rope, we should focus on the following aspects: select the matching wire rope according to the purpose of hoisting equipment; Enhance the matching of lifting drum and steel wire rope to avoid excessive wear; Keep the steel wire rope in good lubrication condition; Strengthen the daily maintenance of steel wire rope