What are the inspection and maintenance methods of elevator wire rope? [answered]

Abstract: elevator, as a symbol of human material civilization, is widely used in shopping malls, hotels, office buildings and houses. It has become an indispensable means of transportation for people's production and life and an indispensable carrier for the rapid development of economy and society. As a special equipment of electromechanical integration, elevator has inherent risk attributes. Its inspection and detection not only meets the requirements of the safety law of the people's Republic of China on special equipment, but also verifies the work quality of installation, transformation, repair, maintenance, use management and other links. As an important component to ensure the safe operation of elevator, steel wire rope bears great responsibility. This paper expounds the importance of elevator wire rope detection, and mainly explores the monitoring and maintenance methods of elevator wire rope.

Importance elevator is a kind of common large-scale equipment, which is widely used in high-rise buildings, such as shopping malls, hospitals, residences and office buildings. Maintaining elevator safety is an important work, because once there is a problem, it is likely to be a major safety problem, resulting in property loss and even casualties. Steel wire rope is the most critical suspension device in all parts of the elevator, Almost all the quality of the elevator car needs to be borne by the steel wire rope. At the same time, the steel wire rope is also the key component to make the car move up and down, and its friction with the elevator sheave is the driving force for the overall lifting of the elevator. Therefore, it is no exaggeration to say that the quality assurance of the steel wire rope is the key link to ensure the safe and smooth operation of the elevator car, so we must pay special attention to it. At present, the quality of steel wire rope can be basically guaranteed. As long as it is used under normal conditions, there are few steel wire rope breaks. Generally, the safety problems of elevator steel wire rope include corrosion and fracture of elevator steel wire rope in the air, smaller diameter of elevator steel wire rope, inadequate maintenance of elevator, etc. Therefore, the safety of elevator steel wire rope must be paid attention to, and safety inspection and maintenance shall be carried out regularly to prevent safety accidents.

1、 Common problems of elevator wire rope safety

（1） Corrosion and fracture of elevator steel wire rope during the actual operation of the elevator, the steel wire rope has always been exposed to the air. When the iron in the steel wire reacts with oxygen and moisture in the air, the steel wire rope will be corroded to varying degrees, resulting in the reduction of the strength of the steel wire rope of elevator crane and greatly reducing the service life of the steel wire rope. The corrosion of the steel wire rope must be checked regularly, Repair and replace in time to reduce the possibility of elevator failure and try to avoid safety accidents.

Elevator steel wire rope is composed of many kinds of steel wires. The performance and safety of all these individual steel wires affect the overall safety of the steel wire rope. However, during the operation of the elevator, the wear, corrosion and deformation of the steel wire are inevitable. Therefore, attention must be paid to the inspection and repair of elevator equipment to ensure the safety of the elevator during its service life.

（2） The diameter of elevator wire rope becomes smaller

As an elevator traction equipment, the elevator steel wire rope is subjected to various tensile forces in the working process. When the elevator is overweight and exceeds the maximum tensile force that the steel wire rope can bear, the yield strength of the steel wire rope is reached, and the deformation of the steel wire rope will not be recovered. Therefore, the diameter of the steel wire rope will decrease with the increase of service life, which will eventually lead to cracks or even fractures of the steel wire rope, resulting in elevator safety accidents.

（3） Insufficient attention to elevator wire rope

Elevators are frequently used, and the elevator wire rope is easily worn, corroded and aged. Inadequate maintenance of elevators is the main cause of elevator failures and safety accidents. The survey shows that elevator accidents ranked second in the national ranking of special equipment safety accidents in 2019, with 33 accidents, accounting for 25.83% of the accidents, resulting in 29 deaths, accounting for 24.37% of the deaths of special equipment accidents. According to the analysis, the main causes of accidents are:, First, improper use and management, in which illegal operation is the main reason, which is reflected in the illegal operation, improper operation or even unlicensed operation, lack of maintenance and poor management of operators; second, the quality and safety defects in the process of equipment manufacturing, maintenance, installation, disassembly and operation; Among the elevator accidents, 9 accidents were violations and improper operation, 1 accident was undocumented operation, 4 safety component failures and equipment defects, 2 improper rescue and 8 inadequate maintenance and safety management. These elevator safety accidents seriously threaten our life safety. Enterprises should pay more attention to elevator safety, strengthen the inspection of elevator hoisting machinery wire rope in the later stage, and pay attention to maintenance.

2、 Inspection technology of elevator wire rope

Scrapping conditions and inspection methods

There is no time limit for scrapping the elevator traction wire rope. However, there is a scrapping standard. Tsgt7001-2009 stipulates that the traction compensation wire rope shall be scrapped in one of the following cases:

① Cage distortion, rope core extrusion, kink, partial flattening and bending: ② broken wires are scattered in the whole steel wire rope, and the number of broken wires in a single strand in any pitch is greater than 4: or the broken wires are concentrated in a certain part or strand of the steel wire rope, and the total number of broken wires in a pitch is greater than 12 (for steel wire rope with 6 strands) or greater than 16 (for steel wire rope with 8 strands):

③ The diameter of the worn steel wire rope is less than 90% of the nominal diameter of the steel wire rope.

Inspection method:

（1） Visual and manual methods

Visual inspection and manual inspection are the most basic methods to detect the wear, corrosion and diameter of elevator steel wire rope and the fracture of surface steel wire structure. They can make a preliminary judgment on the wear condition of elevator steel wire rope. Firstly, check the traction force of the steel wire rope. The experiment shows that the influence of dynamic tension on the service life of the steel wire rope is far greater than that of static tension. Moreover, the uneven stress of the steel wire rope of each elevator hoisting machine also seriously affects the service life of the steel wire rope and the safety of the elevator. Therefore, when carrying out the elevator safety maintenance inspection, carefully check and adjust whether the stress of the elevator steel wire rope is uniform, Ensure that the tension difference of each steel wire rope is 5%

To avoid serious wear between individual steel wire rope and rope groove due to strong gravity.

Secondly, the fracture of the steel wire rope should be checked. The appearance of the broken wire of the steel wire rope caused by different reasons is different. Experienced elevator maintenance personnel can judge it by visual inspection and manual inspection. The broken wire caused by wear is generated in the outer layer of the steel wire rope of the elevator crane, and the fracture is flat, which is formed by the continuous friction between the steel wire rope and the wheel groove during the operation of the elevator, In order to reduce the damage of this kind of friction to the steel wire rope, we need to take precautions. During the installation of the elevator, we should select the rope groove type suitable for the steel wire rope. During the installation process, we should calibrate it so that the center of the rope groove coincides with the center of the steel wire rope, so as to avoid the situation that only one side of the steel wire rope rubs with the rope groove: the fracture of the broken wire caused by corrosion is uneven and irregular sharp, The surface of the steel wire rope will produce dense concave convex points due to oxidation reaction. When these pits cover the steel wire rope and are visible to the naked eye, it is necessary to consider replacing the steel wire rope and stop the loss in time; The broken wire caused by overload, that is, the broken wire caused by the overload tension of the elevator steel wire rope. This kind of fracture is similar to the cup mouth. It can be visually detected that the appearance of the steel wire rope will be seriously deformed, the steel wire rope core will even be exposed, the lubricating oil of the rope core will flow out, and the steel wire rope will be rolled and accumulated. In this case, it is necessary to replace the new steel wire rope in time.

It is worth noting that at present, the visual inspection method and manual inspection method used by elevator maintenance personnel tend to use experience for maintenance and inspection. In foreign countries, all elevators are tested with professional equipment. Obviously, using equipment to detect the problems of elevators is more accurate and scientific. In addition to the horizontal comparison, let's take a vertical look. The so-called vertical comparison refers to the comparison between the new generation and the old generation of elevator maintenance staff. The new generation of elevator maintenance staff uses less experience and is more willing to use the established knowledge and public theorems in books, while the old generation of elevator maintenance staff can flexibly respond to the problems of elevators with their years of experience. It can be said that when using visual method and manual method, the working mode of the older generation of elevator staff is more suitable to use these two methods, while the maintenance staff of the new generation of elevator workers may need to change their flexibility in maintenance rather than rely on the knowledge learned in textbooks.

（2） Tool measurement

Under normal operation, macroscopically check the state of the steel wire rope. If any doubt is found, use the steel wire rope flaw detector to detect the full length or sectional sampling measurement: measure and judge the change of the diameter of the steel wire rope. During the measurement, use two points at least 1m away from each other, and measure twice in the direction perpendicular to each other. The average value of four measurements is the measured diameter of the steel wire rope. Measuring the diameter of the steel wire rope can timely find out whether the steel wire rope is often overloaded, Whether the stress of each steel wire rope is uniform.

In order to ensure the safety of the elevator and find the hidden dangers of wear, corrosion and fracture of the steel wire rope of the elevator hoisting machinery in time during the elevator maintenance, the research on the detection method and technology of the elevator steel wire rope has always been the key research project concerned by various countries. At present, the widely used detection method and technology is the electromagnetic detection technology. For the detection of the fracture and corrosion of the steel wire rope, the magnetic flux leakage detection method is adopted, Using a special probe to magnetize the wire rope locally, when the wire rope has the problems of wire breakage and corrosion, some characteristic parameters of the magnetic field will change, and the change value of the parameters is the key factor to judge the defects of the wire rope. This electromagnetic detection technology has higher accuracy in checking the damage of steel wire rope than the visual method and manual method, and the information obtained is more detailed. It can also make qualitative and quantitative analysis on the corrosion and fracture of steel wire rope, and even get the detailed quantity and cross-section information of broken wire, which is helpful for technicians to have a comprehensive and accurate understanding of the condition of elevator steel wire rope.

However, the electromagnetic detection technology is still not perfect, and there are many problems and deficiencies. For example, during electromagnetic detection, the output signal is easy to be affected by external environmental factors, resulting in a great reduction in the accuracy of the detection results. Once the inspectors are careless and fail to pay attention to the external environmental conditions, they are prone to information distortion, and wrong information is easy to lead to wrong judgment, which is very unfavorable to elevator safety: secondly, electromagnetic detection technology requires more equipment, high quality and difficult to carry, In real life, when testing the elevator wire rope, it is inconvenient for the testing technicians to carry and use, and the testing operation is not easy: there is also the electromagnetic testing technology, which can not detect the small damage problem of the elevator wire rope. Moreover, because it is testing a long section of wire rope, if the detected damage degree of the wire rope is less than the detection length, the small damage problem is more difficult to find, These undetected minor damage and fatigue of the steel wire rope will bury hidden dangers for the safety of the elevator.

3、 Maintenance of elevator wire rope

（1） Lubricate the steel wire rope regularly

When the elevator is working, when the steel wire rope is bent under the action of tension, the relative position moves between the small steel wires, resulting in large friction. Therefore, in order to ensure the safety of the elevator and prolong the service life of the elevator steel wire rope, the steel wire rope should be lubricated regularly, that is, the elevator steel wire rope has undergone a special lubrication process during production, so as to ensure that all steel wire surfaces are covered with lubricating oil, However, due to the impact of wear and dust caused by long-term use, the original lubricating oil will be lost, and the lubricating oil has a good protective effect on the steel wire rope, which can isolate the air and avoid the oxidation reaction and corrosion of the steel wire rope. Therefore, regular lubrication is essential. When lubricating the steel wire rope, pay attention to the amount of lubricating oil and ensure that it is uniform and not excessive, otherwise the steel wire rope will slip in the rope groove and the traction force will be small, Cause elevator safety accidents.

（2） Clean the steel wire rope regularly

The surface of the steel wire rope shall be cleaned every six months, because the lubricating oil is easy to combine with some dust to produce dirt attached to the surface of the steel wire rope. These dirt not only accelerate the wear of the steel wire rope, but also hinder the infiltration of new lubricating oil. If these dirt are cleaned irregularly, the steel wire rope will be more likely to break during mutual extrusion due to the larger diameter of these attachments, And it is not conducive to the inspection of electromagnetic detector. It is better not to use some liquid cleaners to clean the steel wire rope, because these cleaners are generally degreasing type, which will destroy the grease inside the steel wire rope. Brush, cotton yarn and compression of air should be used. After cleaning, some lubrication work should be carried out on the steel wire rope, which is considered to be completed. The wear of non lubricated steel wire rope is more serious, which will greatly reduce the service life of the elevator.