In recent years, with the gradual increase of large-scale modern mines, the use of equipment is also increasing. For safe production, how to use and maintain it correctly is particularly important. Here, analyzing the failure form and cause of friction lining has certain guiding significance for the use and maintenance of friction lining.

There are many types ofkoepe hoist drum inserts. Among them, GDM326 friction liningsare widely used. They can be used as multi-rope friction linings for cold rolling mills and friction linings for rail cars, as well as monkey car linings, rope linings, wheel linings, and tube linings. Pads, winch pads, lifter friction pads, winch pads, etc.

1. Performance parameters of koepe hoist drum inserts

1.1. The friction coefficient is the most important parameter of the koepe hoist drum inserts, and its size determines the lifting capacity of the hoist and the safe and stable operation. Different materials, different friction pairs, and the media between them are different. The reflected friction coefficient is also different. The friction coefficient on coal mine hoisting is formed by the dual friction pair formed by the steel wire rope and the liner under the condition of grease as the medium. Therefore, the friction coefficient of the hoist is also composed of the liner, the steel wire and the grease. Determined by the joint role of the

1.2. Hardness

Hardness reflects the ability of the material to resist deformation. The hardness of non-metallic materials is much lower than that of steel. However, when the wire rope is in contact with the gasket, the deformation can absorb the kinetic energy generated by the vibration, jitter and torsion of the wire rope, and reduce the vibration of the equipment. At the same time, the deformation of the gasket can increase the contact area between the gasket and the wire rope and increase the friction. The triangular strand and the oval strand wire rope developed in recent years are designed to increase the contact area between the wire rope and the pad.

1.3. Compressive strength The working state of the friction liner determines that the liner should have a certain compressive strength. The design specification points out that the maximum working pressure of the liner under the normal working state of the hoist is below 3MPa. Taking into account special circumstances, Such as emergency braking, the working pressure of the pad is doubled.

1.4. Anti-aging rubber and plastic materials have a fatal weakness, that is, aging. Once the material is aging, the mechanical properties will drop sharply. If it is not replaced in time, there will be major accidents. For example, polyurethane aging occurs after two years of normal storage. Research and use show that the friction pad made of GDM326 material, whether it is long-term use or long-term storage, the performance index of the pad hardly changes, and the anti-aging performance is good.

1.5. Environmental environment such as temperature, water, snow, ice, dust, etc., because it changes the state of the medium between the pad and the friction pair, it has a great influence on the friction coefficient of the pad.

2、 Failure mode of friction pad

2.1 Wear and tear are divided into sliding wear, adhesive wear and non-uniform wear.

(1) Sliding wear The wire rope and the liner are relatively displaced, and the rough surface of the wire rope will pull out the groove on the liner surface, that is, the liner will produce sliding wear. The longer the relative displacement distance, the more serious 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.

(2) Adhesive wear In the work of the hoist, the wire rope and the liner frequently contact. Under the action of alternating pressure, the surface of the high-strength steel wire rope will adhere to the tiny liner material, that is, the liner will produce adhesive wear. Adhesive wear is related to the bonding force between material molecules. If inorganic substances are added to the material, the continuity of the material will be destroyed, the intermolecular bonding force will be reduced, and adhesive wear will increase. If the selection of the friction pad material satisfies the normal operation of the hoist, sliding wear and adhesive wear are normal losses.

(3) Non-uniform wear and inconsistent wear of the rope groove: During the use of the gasket, the working state of each rope groove should be the same, and the wear of the rope groove should be the same. If there is a difference between the wear of a rope groove and the other, a certain wire rope can be judged When the working conditions of the machine have changed, the wire rope should be adjusted at this time, and the rope groove should also be adjusted. Rope groove wear deviation: The entire rope groove is elliptical, and the reason is that a certain section of the wire rope is abnormal. The abnormality of the wire rope should be eliminated and the rope groove should be adjusted.

2.2、 Pitting spalling

The equipment operates normally, and the pressure of the liner is below 3 MPa, which is far less than the compressive strength of the liner and will not damage the liner. There is a grease medium between the steel wire rope and the liner, and the medium is mixed with other hard points such as coal ash. These hard points will be embedded in the liner under suitable conditions and form pits on the surface of the liner. It will expand under multiple actions, and then the grease will enter the pits. At this time, the grease in the pits will generate a lot of pressure. When the pressure is stronger than the material's bearing capacity, cracks will occur in the weak parts of the material, that is, the edges of the pits. After multiple actions, the crack expands, and finally peeling occurs, that is, the pit becomes larger and deeper, and finally becomes a piece. At the same time, the next cycle starts, and the cycle speed is accelerated and the time is shortened. The elasticity and toughness of the material determine the speed of pitting and spalling. For materials with good elasticity, when the particles are pressed into the external force and removed, the pits will recover quickly, that is to say, when the pits are formed, the number of times the particles act; good toughness Material, the crack growth rate is slow. Therefore, similar materials have high hardness, poor fatigue resistance and poor use effect.

Pitting spalling damages the gasket greatly, which is the main reason for the early failure of the gasket. Once it occurs, it will not only accelerate the loss of the rope groove material, but also cause the material performance at a certain depth at the bottom of the rope groove to drop sharply. This phenomenon should be tried as much as possible avoid. Once it happens, remove excess grease and impurities between the wire rope and the surface of the pad as soon as possible.

2.3、 Drop block

The liner breakage usually occurs at the edge of the rope groove. There are two main reasons. One reason is that the material is aging, and the other is that the material receives a large alternating stress.

In the first case, since the material properties have undergone fundamental changes, the continued use of the gasket is in great danger and should be replaced immediately.

In the second case, the alternating stress is caused by the mismatch between the rope groove diameter and the wire rope diameter. When the diameter of the wire rope is greater than the diameter of the rope groove, when the wire rope enters the rope groove, the side of the rope groove is first squeezed, especially the sharp corners of the rope groove receive the greatest squeezing force, and the wire rope is tightly wrapped, and the wire rope leaves the rope groove at the sharp corners. When receiving the outward pulling force, the squeezing force disappears. After multiple actions, the material structure will be fatigued. When the structural force of the structure is less than the externally applied squeezing force, cracks will occur at the sharp corners and expand, and then break. The diameter of the wire rope is equivalent to the diameter of the rope groove. When the depth of the rope groove is greater than the diameter of the wire rope, after the wire rope enters the rope groove, the liner deforms under the action of the pressure. The distance between the openings should be less than the diameter of the wire rope. A certain impact force is generated on the sharp corners of the rope groove, and the cyclic effect will also cause block loss.

If the balance of the equipment is not well adjusted, the wire rope will shake and vibrate when the hoist is running. The kinetic energy generated by jitter and vibration, acting on the gasket for a long time, will also cause the weak edge of the gasket groove to fall off. However, the block loss in this case changes with the shaking degree of the wire rope. The size of the block loss in each groove is different, and it may also be a block in a circle of the rope groove.

Once the lumps of the liner fall off, first determine what caused it. If all the liners fall off evenly, the material should be analyzed first; if uneven lumps occur, mechanical reasons should be dominant. The lumps caused by the mechanical action of the steel wire rope usually do not affect the overall quality of the gasket and can be used continuously; if the lumps are caused by aging, they must be replaced immediately.

3. Conclusion

Through the research on koepe hoist drum inserts , it has certain guiding significance for the maintenance and use of koepe hoist drum inserts. At the same time, it provides a strong guarantee for the improvement of technical performance and safe operation of large and medium-sized mines.