Abstract: To address the problem of abnormal online burnout of the rolling mill bearings due to poor lubrication, the oil-gas separator was optimized. The oil-gas pipe was changed from a high-pressure metal hose to a high-pressure transparent hose. A three-way pipe was developed to ensure emergency oil supply for the rolling mill, which improved the equipment operation rate and hourly output, achieving good results.

Key words: Short-stress-line rolling mill; Bearing; Lubrication system; Improvement

0 Introduction

The lubrication method for the bearings of the short-stress-line rolling mill is oil-gas lubrication. The thin oil from the oil station passes through a primary oil distributor, a secondary oil distributor on the base of the rolling mill, a tertiary oil distributor on the rolling mill, and then is transmitted through a metal hose to the bearing box of the rolling mill. Finally, under the action of high-pressure air, a layer of oil protection film is formed on the rolling elements of the bearing, achieving lubrication for the bearings. Since this lubrication is fully sealed, it is necessary to frequently plug and dismantle the quick-change head for on-site inspection of whether there is oil-gas and whether the oil circuit is unobstructed. This is both time-consuming and labor-intensive, and also increases the additional loss of spare parts. The transmission side space is narrow, which is prone to safety accidents. In addition, the initial tertiary distributor was an oil-gas distributor, where oil and high-pressure air were mixed in this distributor. With the extension of usage time, this distributor constantly experienced blockages and damage to the oil inlet plugs. Due to its full sealing, it is impossible to check online whether the distributor is damaged. Many times, accidents such as the burning of the rolling mill bearings due to lack of oil-gas lubrication occurred because of the failure of the distributor.

1. Technological Improvement

The content is aimed at the aforementioned phenomenon. To maximize control or ensure the online oil and gas lubrication effect of the rolling mill bearings, extend the service life of the bearings, and reduce bearing damage caused by water ingress or lack of oil, the goal is to achieve energy conservation, cost reduction, and improvement of equipment operation rate and hourly output. The Preparation Workshop of the Vanadium Steel Rolling No.1 Plant has formulated a detailed technical plan based on the actual production situation at the site after careful research.

1.1 Optimization of the Oil and Gas Distributor

The crude oil and gas distributor is of the power piston type. During use, it is greatly affected by external factors (oil pressure, clearance, temperature, etc.) and its own quality. There are frequent online operation stoppages, especially more frequent and obvious in winter when the temperature is low, which seriously affects the normal lubrication of the rolling mill bearings. To solve this problem, after detailed research, it was decided to change the distributor to a wind-powered direct-through type. The oil and gas are mixed before the filter and then enter the distributor; the distributor, based on its own unique structure, evenly distributes the oil and gas to each lubrication point in the bearing box of the rolling mill. Since there is no power piston, the oil and gas can pass through the distributor smoothly even under low pressure or low temperature conditions.

1.2 Improvement of the Oil and Gas Pipe

The oil and gas pipe between the three-level distributor and the bearing box of the rolling mill on the machine was a high-pressure metal rubber hose. To check whether the distributor was over-oiled during online operation, the hose needed to be disassembled, which was time-consuming and laborious, greatly prolonging the inspection time and reducing the inspection effect. Therefore, through communication with the hose manufacturer, the hose was improved. Under the condition of maintaining the overall length unchanged, an additional 100 mm of specially treated, highly resistant to bending, high-pressure transparent pipe was added to the high-pressure hose. One end of the pipe is connected by threads, and the other end is connected by a sleeve. After being put into use, it achieved full visualization, and it was immediately obvious whether there was oil in the pipe.

1.3 Improvement of the Filter Rod

The original filter rod for the rod was a Φ6.35mm rod with a common one end thread and a conical thread at the other end. It could only be screwed with one Φ6.35mm oil and gas quick-change head. In order to enable a certain rolling mill to achieve temporary external pipe lubrication when the first or second distributor was damaged, without affecting the oil and gas flow direction, a specific angle Φ6.35mm three-way with the ability to simultaneously connect 2 Φ6.35mm oil and gas quick-change heads was studied.

2. Improvement Effects

After the implementation of the above improvement plan, practical tests have proved that the lubrication system of the rolling mill bearings is very stable. The online operation of the rolling mill bearings ensures a long-term good lubrication effect, prolongs the service life of the bearings, reduces the occurrence rate of online bearing burnout, and at the same time reduces cost consumption while increasing equipment operation rate and the hourly output of the rolling line.

(1) After using the direct-flow distributor, the phenomenon of distributor blockage or abnormal damage has been significantly reduced. Moreover, it can ensure the smooth passage of oil and gas through the distributor and to each lubrication point even under low pressure or low temperature conditions, achieving the required oil and gas lubrication effect for the normal operation of the rolling mill bearings over a long period.

(2) After the visual pipeline for rolling mill oil and gas lubrication was designed, tested, and manufactured, it was officially put into use in the Vanadium Extraction Steel Rolling No. 1 Plant in February 2013. After one year of practical use, the results were obvious. When workers conduct inspections, they no longer need to plug and unplug the quick-change head for inspection. They only need to check if the transparent tube is filled with oil. This increases the accuracy of judgment, shortens the inspection time, reduces spare part wear, avoids the occurrence of bearing burnout due to distributor damage, lowers production costs, and improves equipment operation rate.

(3) The use of specially designed three-way valves was initially only for emergency use when the first or second distributor was damaged and could not supply oil normally. However, the effect was still very obvious. It avoided multiple bearing burnout accidents. For example, when a sudden accident such as an un-flooding distributor on a rolling mill base or a broken base oil pipe was discovered during inspection, and due to the short parking time, there was no opportunity to handle it. At this time, by connecting a specially designed three-way valve, a separate external connection pipe could be connected from the nearest oil source to ensure the supply of oil. Additionally, manual oil replenishment through the external connection pipe could also be achieved.

3 Conclusion

By implementing the above improvement measures, the Rolling One Plant of the Vanadium Alloy Steel Section has significantly reduced the bearing burn accidents in the online rolling machines, improved the operation rate and hourly output, and to some extent reduced the cost consumption, thus achieving considerable benefits. However, during the usage process, some problems were also exposed, and further optimization and improvement are still needed. For example: When the temperature is very low in winter, the lubricating oil becomes viscous and has poor fluidity. It does not flow smoothly through the distributor, affecting the lubrication effect. If the external force is too large, the high-pressure transparent rubber hose is prone to being kinked, causing pipeline blockage.