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Research on the service life of crane wire rope

Research on the service life of crane wire rope

Wire ropes play a very important role in crane work, but many wire ropes are scrapped before their service life is reached, which invisibly increases business costs and reduces efficiency. The research work on crane wire ropes should be strengthened, the factors affecting the life of the steel ropes should be analyzed, how to choose the wire ropes and how to use them correctly, and the inspection and maintenance of the wire ropes need to be analyzed. Safe and normal operation has a positive effect.

1. Analysis of important factors affecting the life of crane wire rope
Crane wire ropes are often subjected to the interaction of various stresses such as tensile stress, contact stress, shear bending stress, etc. during operation, and eventually fail. The main failure pattern in the working process of steel rope is fatigue broken wire. In view of the failure of the steel heel, the factors affecting the service life of the crane wire rope were discussed from the two aspects of wire rope gauge and load wheel diameter.
First, lay length. When manufacturing steel wire rope, choose suitable parameters such as diameter, number, control distance and digging direction according to its design type, because the rationality of parameter selection will directly affect the service life of steel wire. When the steel wire rope is under load, if the contact stress between the strands and the steel wire inside the strand is too large, a stress concentration effect will occur, which will cause the wire rope to fatigue and break, and ultimately lead to a shortened service life of the steel heel. In addition, the digging distance of the steel wire rope and the tension formed during the digging process will increase the fatigue of the steel rope, and it is very easy to cause the appearance of wire rope.
Second, the pulley diameter. Under normal circumstances, crane wire ropes and pulleys must be used together. In the entire operating system, the main role of wheel cleaning is to provide corresponding guidance and support for the wire ropes, which can form labor-saving wheel sets and speed-increasing wheel sets. After the steel rope is burned through the Greek wheel, the inside of the rope will be affected by the bending stress of the steel wire, causing the overall bending fatigue of the steel wire. During the working process of the crane, the wire rope and the wheel will have contact and mutual movement, and the friction between the two will increase when they are in contact, which will cause the fatigue and wear of the wire rope. Experimental studies have shown that the diameter of the Greek wheel directly affects the bending stress and the degree of fatigue damage of the steel rope during the use of the steel rope and the micro wheel.

2.How to improve the service life of crane wire rope
2.1 Correct selection of wire rope
When selecting wire ropes, many users have similar misunderstandings: the higher the strength of the wire rope itself, the better. In fact, this view is wrong, although the stronger steel rope can carry a larger load and has a certain degree of resistance. Extrusion ability, but its toughness will inevitably decrease by then. Fracture is more likely to occur during bending and twisting operations. Therefore, the choice of wire rope is not the stronger the better, but the choice according to the actual work situation. The following factors should be considered when choosing steel wire.
First, when cranes operate in highly corrosive environments, they must first choose galvanized steel ropes. Experimental research shows that the service life of zinc-fed steel rope in a highly corrosive environment is three times that of ordinary steel wire rope.
Second, when the main form of damage to the crane is inductive damage, it is necessary to preferentially choose the connecting wire rope with relatively thick outer steel wire on the crane.
Third, for cranes whose main form of damage is bending fatigue, a wire-contact wire rope should be selected.
Fourth, when the crane is operating in a high temperature and open flame environment, it is necessary to choose a steel wire rope with a metal core or an asbestos core.

2.2 Normative management of crane use
In general, crane wire ropes are mainly affected by tensile stress, bending stress, extrusion stress and acceleration/deceleration dynamic stress. Tensile stress, dynamic stress and extrusion stress are all related to lifting load. If the lifting load is small, the stress on it is small and the service life of the steel wire is long. However, in the actual operation process, many cranes are overloaded, and there are many irregular operations, so that the dynamic stress and impact they bear increases and ultimately reduces the service life of the steel wire. In this regard, it is necessary to improve the understanding of the standardization of crane use management.
First, clarify the operating procedures of the crane and operate in strict accordance with the requirements. It is forbidden to overload cranes and "driving cars".
Second, install crane weight limiter and moment limiter in accordance with relevant regulations. Ensure that the crane operates within the specified range.
Third, improve the standardization of the use of wire rope end fixing devices. For example, when using a U-shaped card, ensure that the U-shaped bend of the rope clamp is pressed against the wire rope. Because the U-shaped bend of the wire rope is easily crushed and broken and the wire is broken, if it is installed and used in reverse, the service life of the wire rope will be reduced.
Fourth, pay attention to the selection of models when replacing parts such as wire rope reels and thumbwheels. There is a close relationship between the service life of the wire rope and the bending radius of the wire rope. When the diameter of the rope pulley and the coil is reduced, the mesh wire rope will deform. The bending stress it bears will also increase, and the corresponding wire rope wear will increase. The service life is reduced. Therefore, when replacing such piano parts, pay special attention to the choice of diameter.

3. Regularly check and maintain the wire rope
The steel wire rope is made by multiple digging on the basis of multiple cold drawing of high-quality high-carbon steel wire. It has a spiral structure with a complicated space, and its bendability is much higher than that of steel wires made of steel rods with the same tensile strength. The coefficient of elasticity is one third of that of steel, and it has strong impact absorption characteristics. At the same time, the material characteristics of the wire rope itself also determine the particularity of its defects. The longer it is used, the more serious the damage to the rope will be. After being worn and rusted, the force-bearing area of the wire rope will decrease or even change color. At that time, the fatigue, surface hardening and corrosion of the wire rope will cause its internal performance to decrease, and any defect will cause the entire wire rope to be scrapped.

3.1 Inspection of spare parts of wire rope
In fact, the corresponding performance of the wire rope will gradually decline after being put into use, so the various parts of the wire rope must be checked during use. Generally speaking, it is relatively difficult to conduct a comprehensive and detailed inspection of the steel wire. However, in actual operation, parts that are easily damaged must be regularly inspected by special personnel to avoid serious consequences during later operations.
First, after the wire rope is added, carefully check the cleaning wheels, rope grooves and drums that enter and leave. These are the parts that are prone to defects during operation.
Second, strictly carry out the inspection of the fixed place of the wire rope head. Because the wire rope around the fixed place of the rope head is often squeezed, it is prone to rust and broken wires.

3.2 Inspection of the whole wire rope
A comprehensive and overall inspection of the wire rope is required.
First, the inspection results of the wear of the wire rope can directly reflect the contact between the wire rope and the matching wheel groove, and then can also use this to understand the load capacity of the wire rope in actual operation. Common inspection methods include measuring the diameter of the wire rope, Use flaw detectors for testing, etc.
Second, check the wire breakage of the steel wire. The wire rope after being put into use cannot avoid wire breakage. Especially with the increase of the quasi-use time, the number of broken wires is more frequent. In actual operation, it is difficult to stop using the wire immediately after the wire is broken. In this case, the continuous load-bearing capacity and service life of the wire rope can be tested by checking the number of broken wires in a cut distance and the time between two broken wires; The steel rope can be inspected visually and with thumbs. Before the thumbs are operated, the medium oil must be poured on the surface of the wire rope and used as a grease to clean the entire steel wire. Then, hold the cotton yarn to wrap the wire rope slowly. Move fast. If the yarn is broken, it means that there is a broken wire. If conditions permit, the wire-stirring flaw detector can be used for accurate detection.
Third, the internal inspection of the wire rope is much more difficult than the external inspection. During the inspection, the appropriate pliers can be used to clamp the wire rope at a distance of 100~200mm to rotate in the opposite direction. At this time, the wire rope strands will bulge under the influence of external force. When the rope strands are raised, carefully observe the internal lubrication, corrosion and new wire of the steel rope. Pay attention to the operation to prevent excessive displacement of the rope strands and permanent color change of the steel wire. Appropriate force should be used after the inspection is completed. Rope me back to the original position.

3.3 Maintenance and maintenance of wire rope
It shows that the maintenance of the wire rope needs to be strengthened in the work, so as to extend the service life of the wire part of the jack.
First of all, ensuring the safe use of wire ropes and extending their service life depend to a large extent on the quality of maintenance and maintenance work.
Secondly, the steel rope must be run at least twice a month during use. Before the start of the lubricating work, the impurities on the steel rope should be cleaned with medium oil, and then the steel rope should be dipped in 80℃ high-humidity lubricant to ensure that the lubricating oil fully penetrates into the fiber rope core.
Finally, during lifting operations, it is necessary to ensure the straightness of the wire rope to prevent knots and looseness, and to avoid excessive friction between the wire rope and the hard surface of the tin, especially to avoid two or more steel wires. The ropes overlap again.

4. Conclusion
The above is mainly to analyze the factors that affect the life of the crane wire rope, and put forward measures on how to improve the life of the wire rope. It mainly proposes three aspects of inspection and maintenance, and the inspection of the components of the steel rope to ensure that the components are qualified. ; Check the whole wire rope to ensure that there is no wear; maintain and maintain the wire rope to ensure its service life. In addition to the inspection and maintenance of these three aspects, the steel wire should be selected correctly and the steel rope should be used correctly to ensure that the steel wire used is produced by a regular manufacturer and is of qualified quality. While ensuring the quality of steel, it also ensures the safety of personnel.

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