Maintenance and scrapping of steel wire rope

Steel wire rope is widely used in various lifting and transportation equipment. Its quality not only has a direct impact on equipment safety and production, but also related to personal safety.

1. Use of steel wire rope

Practice has proved that the working conditions of steel wire rope have a great impact on its service life. Its working characteristics are: generally, it moves around a variety of pulleys and bears a lot of tension (traction) and friction between ropes. When working, it is often in a state of bending and deformation. The steel wire rope used in the open air is eroded by wind, sun, rain, cold and heat all year round, and the damage is very serious. Corrosion can reduce the strand diameter of steel wire rope, greatly reduce its destructive tensile force and impact resistance, and seriously affect its service life. Even some steel wire ropes with excellent structure can not show their superior performance due to serious corrosion.

Wear, corrosion and fatigue wire breakage generally work together, and the factors that work are different due to different purposes and environments. In order to prevent the failure of steel wire rope and avoid major accidents, appropriate maintenance and detection methods must be adopted to ensure the normal use of steel wire rope.

2 main causes of wire rope failure

Because the steel wire rope is often in the working environment of wear, friction, humidity and corrosion, it bears repeated bending and deformation, as well as large load and long-term disrepair. During the high-speed operation of the steel wire rope, the components in contact with the roller, idler (wheel) and other components produce severe friction. If the component surface is damaged or the steel wire rope itself is poorly lubricated, great friction will be generated; When a section of steel rope is squeezed or stuck, it will also produce great friction, resulting in the formation of a martensite layer on the surface. The martensite phase itself is a brittle phase with poor fatigue resistance. In the use of steel wire rope, fatigue first produces cracks in the martensite layer, which will continue to spread and extend, and finally lead to wire breakage. Sometimes, the surface of steel wire rope is "blue" and "paste" at the use site, which are caused by the increase of surface temperature due to severe friction.

3 maintenance and inspection of steel wire rope

3.1 operation

The speed of steel wire rope shall be stable during operation, and overload operation shall not be allowed to avoid impact load.

3.2 maintenance

The steel wire rope has been coated with enough grease during manufacturing, but after operation, the grease will gradually decrease, and the surface of the steel wire rope will be stained with harmful substances, which will lead to the wear of the steel wire rope and pulley and the rust of the steel wire rope. Therefore, it should be cleaned and refueled regularly.

3.3 inspection records

The use of steel wire rope must be checked regularly and recorded. In addition to the above cleaning and refueling, the regular inspection shall also check the wear degree, wire breakage, corrosion degree of steel wire and the wear of vulnerable parts such as pulley groove, lifting ring and hook. In particular, the external and internal wire breaks of the steel wire rope at the consolidation of the steel wire end, through the pulley block and drum.

4 scrapping of steel wire rope in use

The scrapping of in-service steel wire rope is based on daily inspection and regular mechanical and technological performance inspection. The scrapping and renewal of in-service steel wire rope should be judged from the following aspects:

4.1 change of wire rope diameter. For the diameter reduction calculated based on the nominal diameter of the steel wire rope, if the lifting steel wire rope or braking steel wire rope reaches 10%, the steel wire rope must be replaced.

4.2 the steel wire rope is worn. If the thickness of the outer steel wire is worn by 50%, it must be replaced.

4.3 broken wire of steel wire rope. Based on the ratio of the cross-sectional area of broken wire in one lay distance to the total cross-sectional area of steel wire rope, it must be replaced if it reaches 10%.

4.4 the steel wire rope is rusted. When the steel wire in the steel wire rope is blackened, rusted and pitted pits, it shall not be used as lifting personnel. The steel wire rope is seriously rusted, and the pitted pits form grooves. When the outer steel wire is loose, regardless of whether the diameter of the steel wire rope is changed or how many broken wires are, the strength and toughness of the steel wire rope are greatly lost and must be scrapped immediately.

4.5 regular inspection data. Generally, only two items of steel wire breaking force and bending are tested. When the ratio of the cross-sectional area of the unqualified steel wire to the total cross-sectional area of the steel wire reaches 25%, and the safety factor calculated by the qualified steel wire breaking force is lower than the safety factor specified for the corresponding purpose, the steel wire rope must be replaced.

4.6 accidents. When the steel wire rope is subjected to accidental tank jamming, sudden stop, extrusion damage and severe external force during operation, resulting in serious deformation of the steel wire rope, the number and diameter of broken wires do not meet the above requirements, and the length is extended by 0.5% due to strong force and tension, the steel wire rope in the stressed section must be replaced or renewed.

4.7 during the use of steel wire rope, if abnormal conditions such as the sudden increase of the number of broken wires, the sudden acceleration of elongation and the sudden strengthening and thinning of steel wire rope are found, the rope must be replaced immediately.

The scrapping regulations of steel wire rope are summarized through a large number of scientific calculations and lessons learned. They are safety regulations that users must abide by.

5 Conclusion

The management, inspection, maintenance and scrapping of steel wire rope are closely related to safety production and personal and property safety. In order to further improve the reliability and service life of steel wire rope, it is necessary to twist steel wire rope with uniform quality, stable performance and advanced structure, as well as correct use and maintenance. It is an essential and important link for users to master the knowledge of inspection, maintenance and scrapping of in-service steel wire rope