Analysis of Causes of Water Ingress in Roll Boxes of High-speed Wire Finishing Mills and Improvement Measures

At present, many high-speed wires adopt famous M 5 generation top cross 45° high-speed non-twisted wire rod rolling mill equipment. Due to the influence of temperature, pressure, friction, etc. during rolling, the high-pressure water from cooling rolls and guiding devices often enters the finishing mill roll box. As a result, the lubricating oil in the thin oil station of the finishing mill is emulsified and deteriorated in advance. If it is not treated in time, it may eventually cause the irreversible deterioration of the lubricating oil and cause the failure of the finishing mill equipment. The water inflow of the finishing mill is extremely harmful to the equipment and lubricating oil, and it is one of the more serious problems faced by steel mills. First of all, after the water enters the finishing mill, it enters the oil tank through the circulation system. If the water enters for a long time and does not deal with it, it will cause the water-oil ratio to increase. It will reduce the service life of the bearing. In the worst case, it will lead to insufficient oil supply of the bearing, poor lubrication and heat dissipation, and eventually eat up the bearing gap due to thermal expansion, resulting in the bearing being scrapped; for oil film bearings, the data shows that the oil entering the lubrication point When the medium water content exceeds 0.1%, the mechanical wear will increase sharply; when it exceeds 0.5%, the lubrication environment will be destroyed, so that an oil film cannot be formed between the shaft and the bearing, the bearing temperature will rise instantly, and the shaft and the bearing will lock up. Phenomenon, a major accident occurred. For gears, if the water content of the lubricating oil is too high, it will not be able to produce an oil film when the gear is meshed, which will increase the temperature of the gear, eat up the gear backlash, and cause the gear to have an annealing effect, which will reduce the strength of the gear. Lead to scrapping of parts such as gears. The occurrence of any of the above situations will have serious consequences, ranging from the scrapping of parts and components, to the scrapping of the entire equipment, and direct economic losses of hundreds of thousands of yuan. Secondly, the water in the roller box of the finishing mill causes water and impurities to enter the oil tank, which emulsifies the lubricating oil and reduces the service life of the lubricating oil; when the impurities in the water pass through the filter, the impurities will block the filter element and reduce the service life of the filter element , Increasing production costs and reducing economic benefits.

Analysis of the reasons for the water ingress into the roller box of the finishing mill

The reasons for the water ingress into the roller box of the finishing mill can be divided into two categories: dynamic seal water ingress and static seal water ingress.

(1) Water enters the movable seal

Water entering the dynamic seal is the most common phenomenon of water entering the roller box of a finishing mill, and it is also the most difficult problem to solve. The main reason is that the waterproof effect of the double lip seal is not good. This point can be divided into the following 4 situations:

1. The quality of the double lip sealing ring itself is not good enough, and there are burrs or curling around the ring. After the unqualified sealing ring is installed, it will be severely deformed after a few days of use and cannot be used, resulting in a large area of water ingress.

2. The slip ring wears out too quickly and cannot be used for a long time. If it is not replaced in time, water will enter.

3. Too small compression on the waterproof side of the double lip seal will also cause water in the roller box.

4. Improper assembly of the double lip seal is also the main cause of water ingress.

5. If the verticality error between the inner circle of the eccentric sleeve and the end face of the stop is too large, this problem will directly cause the uneven compression of the double lip seal ring on the slip ring. During the high-speed rotation of the roller, the double lip seal The ring cannot achieve the sealing effect, and water ingress occurs.

(2) Water ingress of static seals Although water ingress of static seals does not occur often, once it occurs, the amount of water ingress will be very large and cause serious consequences, so we must pay more attention to it. There are three main situations in which water enters the static seal:

1. During the assembly process, if the anaerobic sealant is applied unevenly on the joint surface of the roller box and the cone box, or the sealant is missed or unevenly applied in the bolt holes and pin holes between the two, it will cause the roller box. Water in.

2. Although the sealing plate and the eccentric sleeve are stationary during steel rolling, they move relative to each other when the roll gap is adjusted. Therefore, if the O-ring size between them is not suitable or the wear is serious, it will cause water ingress. In addition, sometimes the pile of steel will deform the sealing plate, resulting in a gap between it and the eccentric sleeve, which will cause water to enter the part.

(3) The solution to the water inflow of the roller box of the finishing mill: Through analysis, we have analyzed the dynamic seal and static seal water inflow problems mentioned above more thoroughly, and now propose a solution to each problem.

Solutions for water ingress at the dynamic seal

1. The solution to the quality problem of the double lip seal itself, whether there is a quality problem in the double lip seal itself, firstly check whether the size between the two lips meets the requirements of the drawing, and secondly, install the double lip seal ring on the sealing plate Later, does the size d between the lips change? If there is a change, it means that there is a problem with the size of the related parts or the problem with the double lip seal itself. Thirdly, install the double lip seal ring on the roller box, and then remove it after the test run to check whether the lips of the double lip seal ring can be restored to the original thickness. This can be used to prove whether it can meet the requirements of use. Once the quality of the seal itself is verified through the above methods, we must start with the purchase channel, replace the manufacturer that provides the seal or require the manufacturer to improve the material and process, strictly control the quality, and ensure that the double lip seals entering the factory are qualified. Product, thus solving the problem of poor quality of the double-lip seal ring itself.

2. The solution for slip ring wear that is too fast, we can solve the problem of slip ring wear that is too fast by changing its material and heat treatment requirements. The surface nitriding is cancelled and the surface is plated with ceramics, which can reduce the generation of nitriding The deformation can also improve the wear resistance of the product to meet the requirements of use.

3. The solution of too small compression on the waterproof side of the double lip seal. There are two types of finishing mill roll boxes, one is 6" roll box, and the other is 8” roll box. Now we take 6” roll box as an example to propose a solution to improve the compression of the waterproof side of the double lip seal.

4. Solution to improper installation of double lip seal: Improper installation of double lip seal can also cause seal failure and cause water to enter the roller box. First, when the double lip seal is installed in the dense plate, the sealing plate must be completely installed in the groove in the double lip seal ring to play a good supporting role. Secondly, tooling must be used during the installation of the double lip seal. It is not allowed to directly install it by hand to prevent uneven force during installation by hand, which may cause deformation of the support ring and cause it to fail to effectively support the double lip seal and cause water ingress. Only by doing the above two points, coupled with the careful operation of the workers, can the double lip seal be installed on the sealing plate intact and without deformation.

5. Solution to the excessive verticality error between the inner circle of the eccentric sleeve and its stop end surface The main quality problem of the eccentric sleeve is that the error of the inner circle and its stop end surface is too large, causing the double lip periphery of the double lip seal ring to be on the slip ring The amount of compression is uneven. During the high-speed rotation of the roller shaft, the double-lip seal ring cannot achieve the sealing effect, and water enters. Through theoretical calculation and actual exploration, we found that if the verticality error between the inner circle of the eccentric sleeve and the end face of its stop is controlled within 0.1, the double lip seal will not be deformed, which is within the scope of our application requirements. Therefore, we must perform inspection before installing the eccentric sleeve on the machine. Only those with a verticality error within 0.1 can be used on the machine. The unqualified ones are picked out for grinding, and the ones that cannot be ground are scrapped directly. The quality of the assembly must be absolutely guaranteed.

The solution to the water ingress at the static seal

The water ingress at the static seal is mainly caused during the assembly process of the roller box cone box, so the most important solution is to assemble carefully and inspect carefully. We can pass the following two aspects Set out to solve.

1. The solution to the water ingress of the joint surface of the cone box roller box: During assembly, "Loctite 515" flat anaerobic sealant should be applied to the joint surface. In the process of closing the box, there will be gaps on the joint surface of the roller box panel and the cone box, which will cause water ingress. In addition, the bolt holes and pin holes connecting the roller box panel and the roller box should also be coated with thread sealant during assembly, and it must be evenly coated. Water entering the roller box in the gap is caused by the lack of waterproof awareness of the assembler or the improper operation of the assembler. Therefore, to fundamentally solve such a problem, it is necessary to strengthen the training of the operators and enhance their waterproofing. Awareness and assembly level to prevent water ingress accidents caused by such reasons.

2. Water ingress solution between the sealing plate and the eccentric sleeve: The O-ring on the eccentric sleeve is used to ensure the seal between the sealing plate and the eccentric sleeve. The improper selection of the O-ring size or serious wear will also cause water ingress. Before assembling, measure the fit clearance between the two, select the appropriate O-ring, generally choose the one that is 0.50～0.80ram larger than the fit clearance. In addition, after using the eccentric sleeve for a period of time, check the wear of the O-ring on it, and replace it in time if it is severely worn. In addition, sometimes the pile of steel will deform the sealing plate, resulting in a gap between it and the eccentric sleeve, which will cause water to enter the part. Therefore, every time there is a pile of steel accident, the place must be inspected to find hidden dangers and solve the problem in time. .

Through our analysis, some reasons and solutions for the water ingress in the roller box of the finishing mill are proposed. In addition to the above-mentioned water ingress, the water ingress of the finishing mill can also be caused by other parts, such as the coupling gland. Water inlet, loosening of the two guide posts on the cone box, water leakage, and water inlet of the plate heat exchanger of the thin oil station of the finishing mill, etc. However, the main reason for the water ingress of the finishing mill in production is still caused by the aspects discussed above. By adopting the above measures, general water ingress problems can be effectively controlled.

We are a Finishing Rolling Mill Area Equipment supplier. If you are interested in our products, please contact us now!