Failure analysis and maintenance of the lining of the vertical shaft multi rope friction hoist mining shaft pulley wheel

As an important transportation hub connecting underground and ground, multi rope friction hoist is often referred to as throat equipment. Compared to single rope hoists, they have the advantages of high efficiency, high safety, and large applicable wellbore depth, making their applications increasingly widespread. The mining shaft pulley wheel device, as an important load-bearing component of the lifting equipment, is mainly used to protect the wheel flange and lift the steel wire rope with the lining in its groove. How to maintain and maintain it has a significant impact on the service life of the steel wire rope.

1 Multi rope friction lifting system

The working principle of the multi rope friction lifting system is an electric motor driven spindle device, which lifts and lowers the container through the friction between the steel wire rope and the friction pad, achieving the lifting and lowering of materials or personnel. It mainly consists of a friction hoist, mining shaft pulley wheel device, hydraulic braking system, control and transmission system, lifting steel wire rope, balancing steel wire rope, lifting container, mast and corresponding protective devices, as shown in Figure 1.

The mining shaft pulley wheel device is installed on two platforms above and below the mast. Its main function is to adjust the distance between the steel wire ropes on both sides by utilizing the front and rear positions of two sets of mining shaft pulley wheel devices to meet the requirements of lifting the center distance of the container; On the other hand, by adjusting the vertical positions of the two sets of mining shaft pulley wheel devices, a larger angle of the lifting steel wire rope on the friction wheel can be obtained to improve the lifting capacity.

The failure mode of the 2-day wheel gasket

2.1 Structure of the mining shaft pulley wheel device

The mining shaft pulley wheel device mainly consists of a main shaft, a fixed wheel, a movable wheel, a bearing seat, a rolling bearing, a insert, etc., as shown in Figure 2. Among them, there is a fixed wheel in the wheel body, which is connected to the shaft through a key and rotates with the shaft during operation; The rest are movable wheels that are connected to the shaft through bearing shells and can rotate relative to the shaft. The rim groove of the wheel body is equipped with a cushion made of plastic or polyurethane material, which has a small friction coefficient but needs to be wear-resistant and has a specific pressure resistance greater than 2 MPa. The advantage of this type of mining shaft pulley wheel structure is that when the linear speed of the steel wire rope is not completely the same, the traveling wheel and shaft can freely rotate relative to each other, preventing sliding friction between the steel wire rope and the liner, avoiding excessive wear of the liner, and protecting the steel wire rope.

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2.2 Pad friction angle

In order to facilitate the installation of the liner in the groove of the wheel body, it is necessary to cut along the rope groove of the liner at a certain angle, which is called the friction angle. Different materials have different friction angles, as shown in Table 1. When designing the liner, it is necessary to ensure that the cutting angle of the rope groove is not greater than the friction angle.

2.3 Failure forms of mining shaft pulley wheel gasket

(1) Sliding wear. When the steel wire rope and the liner undergo relative displacement, the rough surface of the steel wire rope will pull out grooves on the surface of the liner, resulting in sliding wear of the liner. The longer the relative displacement distance, the more severe the sliding wear. The occurrence of sliding wear is closely related to the friction coefficient of the material. Under the same conditions, the higher the friction coefficient, the shorter the relative sliding distance, and the smaller the sliding wear. Sliding wear leads to a failure rate of up to 90% of the insert.

(2) Pitting corrosion. The grease used in the steel wire rope is easily mixed with hard points such as coal ash, and as the steel wire rope is pressed onto the liner, it will cause pits to form on its surface. If there is relative sliding between the wire rope and the pad, the pit will gradually expand. When the pressure of the grease stored in the pit exceeds the material's bearing capacity, cracks will occur at the edge of the pad pit. Under multiple cycles, cracks continue to expand, pits become larger and deeper, and eventually delamination occurs. The elasticity and toughness of the lining material determine the speed of pitting and peeling. Elasticity

Good materials, when the hard spot pressure is removed, the pits quickly recover, the crack propagation speed is slow, and the pitting and peeling are also slow.

(3) Falling blocks. Pad falling usually occurs at the edge of the rope groove, and there are two main reasons for this: ① material aging. Due to fundamental changes in material properties, the continued use of the insert poses a significant risk and should be replaced immediately The diameter of the rope groove does not match the diameter of the steel wire rope. If the diameter of the steel wire rope is greater than the diameter of the rope groove, when the steel wire rope enters the groove, it first compresses the side of the groove, especially at the sharp corner of the groove, and tightly wraps the steel wire rope. When the steel wire rope leaves the groove, the sharp corner is pulled outward, and the squeezing force disappears. After multiple actions, the material organization fatigue occurs. When the organizational structural force is less than the external applied squeezing force, cracks and propagation occur at the sharp corner, and then fracture; The diameter of the steel wire rope is equivalent to the diameter of the rope groove, but when the depth of the groove is greater than the radius of the steel wire rope, after the steel wire rope enters the groove, the lining undergoes deformation under pressure, and the distance at the opening should be less than the diameter of the steel wire rope. When the steel wire rope leaves the groove, it will have a directional impact on the sharp corners of the groove, and the cyclic action will also cause falling blocks.

3. Maintenance and upkeep of gaskets

3.1 Regular inspection of equipment

Within the first 6 months after the installation and operation of the mining shaft pulley wheel device, the operation status needs to be checked weekly; After 6 months, inspect according to the overhaul cycle. Check the insert mainly to see if there are significant misalignment or falling blocks between the gaskets. If there are falling blocks, analyze the cause. If the gasket falls evenly, it may be due to the failure of the insert material and should be replaced immediately; If uneven block shedding occurs, it may be caused by mechanical factors, and the system operation should be adjusted. Pitting and peeling can cause significant damage to the lining and is one of the main reasons for early failure of the lining. Once it occurs, it not only accelerates the loss of rope groove material, but also causes a sharp decline in material properties at a certain depth at the bottom of the rope groove. This phenomenon should be avoided as much as possible. Once it occurs, excess grease and impurities should be removed as soon as possible between the wire rope and the surface of the pad.

3.2 Liner turning

The long-term operation of the lifting system will result in changes in the force on each steel wire rope. When the adjusting oil cylinder exceeds the adjustable range, the tension difference of the steel wire rope becomes larger and larger, leading to inconsistent movement of the steel wire rope. The sliding wear of the steel wire rope under high force becomes more severe, ultimately resulting in inconsistent bottom diameter of the mining shaft pulley wheel rope groove. At this point, it is necessary to turn the groove of the mining shaft pulley wheel rope, which can extend the service life of the lining and effectively protect the steel wire rope.

3.3 Pad Replacement Conditions

Pads are consumables and must be replaced when worn to a certain extent. Any one of the following three situations must be replaced during use: ① The wear depth is the diameter of the steel wire rope, as shown in Figure 3 (a); ② The remaining thickness of the worn liner is half of the diameter of the steel wire rope, as shown in Figure 3 (b); ③ Wear along the side reaches half the diameter of the steel wire rope, as shown in Figure 3 (c).

Conclusion

The mining shaft pulley wheel insert is an important component of the mining shaft pulley wheel device, which can protect the wheel flange and steel wire rope, and improve the safety of the lifting system operation. Its maintenance and upkeep are particularly important. During regular equipment maintenance, the mining shaft pulley wheel insert should be given priority. In case of failure such as sliding wear, pitting, and falling blocks, timely maintenance and replacement should be carried out to ensure the safe operation of the system.

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