Abstract: Mechanical seal design, installation and maintenance of vertical rolling mill bearing are important links to ensure normal operation of rolling mill and prolong bearing life. The design principle, installation steps and maintenance methods of bearing mechanical seal for vertical roll mill are introduced in detail. Through reasonable design and correct installation and maintenance, the problems of lubricating oil leakage, impurity entry and seal failure are effectively prevented, and the working efficiency and reliability of the vertical roller mill are improved.

Key words: vertical rolling mill; Bearing mechanical seal; Installation and maintenance

0 Introduction

Vertical rolling mill is one of the important equipment in the metal processing industry, and the design, installation and maintenance of the bearing mechanical seal has an important impact on the normal operation of the rolling mill and the life of the bearing [1]. The purpose of this paper is to provide relevant knowledge of bearing mechanical seal design, installation and maintenance of vertical roll mill, help related personnel to understand the working principle of seal, better grasp the correct installation steps and effective maintenance methods, so as to ensure the normal operation of the mill and the reliability of the bearing.

1 Technical requirements for bearing mechanical seal installation of vertical roll mill

1.1 Requirements for shaft curvature

The curvature of an axis is the degree of curvature of an axis in the direction of its length. In mechanical sealing devices, the bending degree of the shaft should generally be controlled within 0.05mm [2]. Ensure the straightness of the shaft, that is, the axis of the shaft should be kept straight to avoid the problem of seal failure or unstable operation caused by the bending of the shaft. The bending degree of the shaft exceeds the specified range, which will lead to uneven force on the seal, thus affecting the sealing effect.

1.2 Gland Requirements

The gland is an important part of the mechanical seal device, which is used to fix and press the seal. The concentricity tolerance between the gland and the corresponding seal with the stop of the shaft center line is generally 0.05mm. The center line of the gland and the seal should be concentric to ensure the normal operation of the seal. At the same time, the actual verticality *** tolerance of the plane touching the gland and the gasket to the center line should be controlled at 0.03~0.05mm[3]. Ensure that the contact surface of the gasket and the shaft can be kept parallel to achieve an effective sealing effect. If the concentricity of the gland and the seal or the perpendicularity of the contact plane between the gland and the gasket exceed the specified range, the seal will not be tight or uniform, thus affecting the sealing effect.

1.3 Requirements for shaft coupler

The shaft coupling is used to connect the shaft and the transmission device, and plays the role of transmitting power. Alignment error of the shaft coupling refers to the position deviation of the shaft. For the gear coupling, the alignment error should be controlled between 0.08 and 0.10mm. For elastic couplings, the alignment error is generally controlled at 0.05~0.06mm. Ensure that the shaft coupler can correctly connect and transmit power to avoid vibration and noise problems caused by excessive alignment error. If the alignment error of the shaft coupling exceeds the specified range, it will cause the uneven force of the shaft coupling, which will affect the transmission effect and the stability of the equipment.

1.4 Rotor oscillation requirements

Rotor oscillation refers to the oscillating or shaking phenomenon of the rotor during operation. In the mechanical seal device, the oscillation quantity near the corresponding shaft sleeve at the moving ring seal ring should be controlled within 0.06mm [4]. Ensure that the vibration of the rotor during operation is controlled within a reasonable range to avoid seal failure or bearing damage caused by excessive vibration and pendulum. Excessive rotor oscillation will lead to the uneven force of the seal, thus affecting the sealing effect and the stability of the equipment.

1.5 Requirements for axial channeling

Axial movement refers to the displacement of the shaft along the axial direction during operation. The actual axial channeling momentum should be controlled within ±0.5mm. Ensure that the axial displacement of the shaft during operation does not exceed a certain range to avoid friction and wear between the shaft and the seal. If the axial channeling momentum exceeds the specified range, it will lead to uneven force on the seal, thus affecting the sealing effect and the normal operation of the equipment.

2 Vertical rolling mill bearing mechanical seal design

The labyrinth seal cover uses a multi-channel sealing structure (see Figure 1) to effectively prevent the leakage of liquids or gases and prevent dust and impurities from entering the bearing interior. In addition, in order to further improve the sealing effect, 1 O-shaped sealing ring is added to the contact surface of the sealing cover on both sides and the inner hole of the bearing seat [5]. The O-ring has good sealing performance and can effectively prevent the leakage of liquid or gas.

FIG. 1 Design of bearing mechanical seal

Lip seal is a common form of shaft seal, through the lip structure and close contact with the shaft surface, and achieve the sealing effect. The material of the positioning sleeve is 42CrMo, and the surface is heat treated to improve the hardness and wear resistance of the positioning sleeve, thereby increasing the reliability and life of the seal. A groove is designed on the surface of the positioning sleeve near the roll side. The function of this groove is to collect the lubricating oil leaking from the bearing and guide it to the sealing cover to avoid the leakage of lubricating oil, so as to maintain the lubrication effect of the bearing. The grooves need to be designed to match the structure of the seal cover to ensure the smooth flow of lubricating oil into the labyrinth seal cover, while preventing dust and impurities from entering the bearing interior.

3 Vertical roll mill bearing mechanical seal installation and maintenance strategy

3.1 Installation steps of bearing mechanical seal

1) Before installation, it is necessary to check whether the size and processing accuracy of each component meet the design requirements. If there is a deviation or unqualified situation, it is necessary to correct or replace it in time to ensure that the mechanical seal can operate normally after installation.

2) Before installation, it is necessary to apply an appropriate amount of mechanical lubricating oil to the surface of the roll to reduce friction and wear. In addition, it is also necessary to scrub the parts and remove the dust and impurities on the surface to ensure that the installed parts are clean and dust-free.

3) Install parts in the correct order and position according to drawings and assembly requirements. During the installation process, pay attention to the positioning and alignment of the parts to ensure that the matching size and clearance between the parts meet the requirements.

4) According to the design requirements and the specific situation of the equipment, determine the installation sequence of the mechanical seal. Usually, the labyrinth seal cover and O-ring are installed first, and then the positioning sleeve and lip seal are installed. During the installation process, pay attention to the correct installation position and direction to ensure that the fit between the seal and the bearing is tight, and there is no loosening or skew.

5) After installation, it is necessary to conduct a comprehensive inspection and testing of the entire mechanical seal device. Check for loosening, deformation or other abnormal conditions to ensure the normal operation of the auxiliary device. At the same time, it is also necessary to test the sealing performance to verify the effect and reliability of the mechanical seal.

3.2 Daily maintenance of bearing mechanical seal

1) Before each drive, the installation of the mechanical seal should be carefully checked. Ensure that all components are installed in the correct order and position, and that the seal caps, O-rings, positioning sleeves and lip seals are in the correct position. In addition, it is also necessary to check whether the sealing cover and positioning sleeve are tight to avoid loosening or falling off.

2) Before driving, gently turn the roll with your fingers to check the operation of the bearing. If the bearing rotates smoothly, there is no blocking resistance, no abnormal friction sound and vibration, it indicates that the lubrication and sealing of the bearing are working normally. If abnormal conditions are found, such as blocking, frictional sound or vibration, it is a sign of bearing seal failure or insufficient lubrication, and it needs to be repaired or replaced in time.

3) It is very important to check the lubrication of bearings regularly. Observe whether the lubricating oil of the bearing is enough, whether there is oil leakage or excessive oil stains. At the same time, it is necessary to carefully listen to whether there are abnormal sounds when the bearing is running, such as noise, scratching or abnormal noise. These abnormal sounds are the performance of bearing seal failure or insufficient lubrication, and timely measures need to be taken to repair or replace.

3.3 Mechanical seal failure treatment of machine bearing

1) If there are overheating and smoking problems during the actual rotation of the bearing mechanical seal of the vertical roll mill, this is caused by seal failure or insufficient lubrication. First of all, we need to stop the operation of the machine and ensure safety. Then, check the installation of the mechanical seal and confirm that the seal cover, O-ring, locating sleeve and lip seal are in the correct position. If it is found to be loose, off or damaged, it needs to be repaired or replaced in time. At the same time, check the condition of the lubricating oil to ensure that the lubricating oil is sufficient and that there is no oil leakage or excessive oil stains. If insufficient lubrication is found, the appropriate amount of lubricating oil needs to be added in time. If the above inspection and repair measures do not solve the overheating and smoke problems, you need to consider replacing the mechanical seal or conducting more in-depth troubleshooting.

2) If a small amount of water is still found to enter the bearing box after completing the installation of the bearing mechanical seal, it is caused by seal failure or improper installation. First of all, we need to stop the operation of the machine and ensure safety. Then, check the installation of the mechanical seal and confirm that the seal cover, O-ring, locating sleeve and lip seal are in the correct position. If it is found to be loose, off or damaged, it needs to be repaired or replaced in time. At the same time, check whether the sealing cover and positioning sleeve are tight to avoid loosening or falling off. If the above inspection and repair measures do not solve the water entry problem, you need to consider replacing the mechanical seal or conducting more in-depth troubleshooting. In addition, it is also necessary to check the sealing performance of the bearing box to ensure that the sealing ring of the bearing box is intact and to avoid water entering from the side of the bearing box.

4 Conclusion

In practical applications, attention should be paid to the selection of seals and the accuracy of the installation position, regular maintenance, timely replacement of worn seals, to ensure the integrity and effectiveness of the seal. At the same time, strengthen the monitoring and troubleshooting of the rolling mill running state, deal with the abnormal situation in time to ensure the safe and stable operation of the rolling mill. Through reasonable design and correct installation and maintenance, the working efficiency of vertical roller mill can be improved, the bearing life can be extended, and the development of metal processing industry can be contributed.

【 Reference 】

[1] Cao Xiaoming, Luo Kaifang. Research on Installation and Maintenance of Bearing Mechanical Seal for Rolling Mill [J]. Architectural Engineering Technology and Design, 2017 (17) : 4 340-4 342.

[2] CAO Wenqiang. Analysis and Practice of burning Bearing Fault in Shiheng Special Steel bar Line Mill [J]. Shandong Metallurgy, 2023,45 (3) : 70-71.

[3] Zhang Wenqi, Yang Shufan, Lu Jinsong. Structure Improvement of Circulating Lubrication and Cooling System of Support Roll Bearing in Rolling Mill [J]. Journal of Wuhan Polytechnic Institute of Technology, 2021,33 (1) : 18-20.

[4] Jian Yancheng, Jia Weilong, Wang Shunli, et al. Fault Diagnosis and Analysis of bearing Cage of 14# Gear box of Pre-Finishing Mill in a Steel Mill [J]. China Equipment Engineering, 2021 (14) : 267-269.

[5] LIU Liangyi, Xie Yi. Installation and Maintenance of oil Film Bearing for 3 500 mm medium thickness plate rolling Mill [J]. Modern Metallurgy, 2022 (6) : 48-50.