Can The Lifespan of The Movable Jaw Plate Be Extended by Using It Upside Down After Wear?

1、 Problem posing

During the operation of the jaw crusher, the movable jaw plate and the fixed jaw plate together form the crushing chamber, and the material is crushed by compression and bending. In long-term use, the movable jaw plate inevitably experiences wear and tear. For on-site operators and managers, whether it is possible to extend the service life of the jaw plate by using it upside down when it has not completely failed but has already experienced some degree of wear is a practical issue. This article systematically analyzes the distribution law of jaw plate wear, structural design characteristics, feasibility of inverted use, and specific operating methods.

2、 The uneven distribution of jaw plate wear is a prerequisite for inverted use

2.1 Wear is concentrated in the middle and lower parts

A large amount of on-site observation data and wear detection results indicate that the wear of the movable jaw plate shows a significant non-uniform distribution along the height direction. The lower part of the jaw plate, especially in the lower third, has more severe wear, while the upper part has less wear. This wear pattern is universal in different models of jaw crushers and under different material conditions.

2.2 Reasons for uneven wear and tear

The main reasons for the uneven distribution of wear include: the crushing force reaches a high value near the discharge port, and the contact stress in this area is significantly higher than that in the upper part; After multiple compressions in the lower part of the crushing chamber, the material experiences prolonged sliding friction with the jaw plate; The adjustment of the discharge port increases the crushing task undertaken by the lower part.

Due to the concentrated wear in the lower part and lighter wear in the upper part, there is a significant difference in the degree of use of the jaw plate along the height direction. This feature provides the basic condition for inverted use - replacing the underutilized upper part with the lower part to continue functioning, allowing the material of the entire jaw plate to be more fully utilized.

3、 Feasibility basis for inverted use

3.1 Symmetry in Structural Design

Jaw plates are usually made in a symmetrical shape, which is the structural basis for inverted use. Symmetrical design means that the upper and lower ends of the jaw plate are basically consistent in terms of geometric dimensions, tooth profile characteristics, and installation interfaces, and will not interfere with the equipment or have installation difficulties when inverted. The jaw plate of small and medium-sized jaw crushers can be designed in a symmetrical shape, allowing for turning when the lower part is severely worn.

3.2 Coordination of Equipment Maintenance System

In the planned maintenance system of jaw crushers, minor repairs are a relatively frequent type of maintenance. The main job responsibilities of minor repairs include inspecting and repairing adjustment devices, adjusting the clearance between discharge ports, and turning or replacing worn lining plates. The cycle of minor repairs is generally 1-3 months. Inverted operation has a natural fit with this maintenance system and can be arranged for implementation during minor repairs without the need for additional downtime.

3.3 Special Characteristics of Large Jaw Plates

For large jaw crushers, their jaw plates are usually assembled from several pieces. This structural form provides a more flexible way of use - the jaw plates can be exchanged and used with each other. By replacing the lightly worn jaw plates with the heavily worn ones, the wear of each jaw plate can be balanced, further improving the material utilization rate of the entire jaw plate.

4、 Specific operation method for inverted use

4.1 Implementation timing

Inverted use should be arranged when the lower part of the jaw plate is worn to a certain extent, but there is still a lot of margin in the upper part. Specifically, it can be done during minor repairs. Premature inversion can lead to insufficient wear in the upper area before inversion, and the wear rate is still relatively fast after replacing the original upper part with the lower part after inversion, with limited effect on extending the actual lifespan; If inverted too late, it may cause severe wear on the lower part, and the remaining effective tooth height of the jaw plate after inversion is insufficient, making it impossible to continue using.

4.2 Operation steps

The basic operation process for inverted use includes:

Shutdown and cleaning: The equipment is shut down and powered off, the crushing chamber is opened, and residual materials are cleaned.

Dismantling the old jaw plate: Loosen the fixing bolts and remove the worn movable jaw plate.

Inspection status: Check for cracks, local fractures, or other structural damages on the jaw plate. Jaw plates with cracks or fractures are not suitable for inverted use and should be replaced or repaired by welding.

Inverted installation: Rotate the jaw plate up and down, and re fix it to the moving jaw body according to the installation specifications.

Tightening and anti loosening: Tighten the bolts symmetrically and step by step, and install spring anti loosening devices as needed to prevent the bolts from loosening during operation.

Parallelism check: Ensure that the movable jaw plate and the fixed jaw plate maintain appropriate parallelism, and that the tooth profile is in a basic meshing state (with the tooth peak aligned with the tooth groove).

4.3 Coordination with other repair methods

Inverted use can be coordinated with weld repair. For jaw plates that have already worn out and failed, the method of welding can be used to restore the tooth profile. Welding repair can be carried out before or after inverted use to further extend the overall service life of the jaw plate.

5、 The Effects and Limitations of Inverted Use

5.1 Actual effect

Inverted use can make the wear of the jaw plate along the height direction more uniform, avoiding the situation where the lower part is severely worn while the upper part still maintains a lot of tooth height and is forced to be replaced. By reversing the operation, the total service life of the jaw plate can be extended to a certain extent. This method does not require complex processes and specialized equipment, and can be completed in routine minor repairs, with the advantages of low cost and easy implementation.

For large jaw crushers, the mutual exchange between each jaw plate can also make the wear distribution more uniform, avoiding premature scrapping of the entire jaw plate due to rapid local wear.

5.2 Issues to be noted

Inverted use is not suitable for all situations, and caution should be exercised in the following situations:

When there are cracks in the jaw plate, it is not advisable to invert it: if cracks have already appeared in the jaw plate, the crack area may transfer to a location with greater stress after inversion, accelerating the risk of fracture. This type of jaw plate should be repaired by welding or directly replaced.

Change in bite angle of the upper part after inversion: If the bottom of the jaw plate is severely worn, there is a risk of excessive bite angle in the upper part of the crushing chamber after inversion, which may lead to a decrease in clamping force on the material. Therefore, after inverted use, it is necessary to check whether the biting conditions of the crushing chamber have changed, and adjust the equipment parameters if necessary.

Uneven wear leads to changes in tooth profile fit: After the jaw plate wears, the tooth profile changes, and the tooth profile fit with the fixed jaw plate after inversion may not be as ideal as when newly installed. After installation, the alignment of the tooth peaks and grooves should be checked to ensure that they are in a basic meshing state.

The number of inversions is limited: a jaw plate can usually be inverted once, and in some cases, it can be inverted twice, but the remaining effective tooth height decreases after each inversion. After being inverted to a certain extent, the jaw plate still needs to be replaced or repaired by welding.

5.3 Comparison with other methods of extending lifespan

Inverted use is one of the methods to extend the lifespan of jaw plates, and it is more effective when used in conjunction with the following measures:

Reasonable selection of jaw plate material: The jaw plate should be made of materials with high hardness to resist compression micro cutting failure, and materials with sufficient toughness to resist fatigue failure caused by chiseling impact.

Tightening and anti loosening: Install springs on the fixing bolts to improve the anti loosening and vibration reduction ability of the jaw plate fixing bolts.

Material adaptability adjustment: Conduct random inspections on each batch of materials, and promptly adjust the main parameters of the crusher to match the incoming materials when significant fluctuations in material properties are found.

Installation quality control: When installing new jaw plates, pay attention to fastening and ensure smooth contact between the jaw plates and the surface of the machine body. A layer of plastic material such as lead plate, plywood, or cement mortar can be placed between the two surfaces.

6、 Conclusion

After the wear of the movable jaw plate, its lifespan can be extended by using it upside down. The feasibility of this method is based on two basic facts: firstly, the wear of the jaw plate is concentrated in the middle and lower parts, while the wear of the upper part is relatively light; The second is that the jaw plate is usually designed in a symmetrical shape, with the structural conditions for inverted installation. Inverting the worn lower jaw plate during minor repairs to allow the underutilized upper part to continue to function is an effective means of improving the utilization rate of jaw plate materials. For large jaw crushers, the jaw plates can also be interchanged for use.

However, inverted use is not suitable for all situations, and factors such as crack conditions, tooth fit, and bite angle changes in the jaw plate need to be considered. Combining inverted use with reasonable material selection, standardized installation and fastening, timely material adaptability adjustment, and necessary weld repair can more effectively extend the service life of the jaw plate, reduce spare parts consumption and operating costs.