一：Preface：
Because the high-speed wire rod production line uses a large amount of high-pressure water to cool the cooling water, it is inevitable that it will enter the lubrication system of finishing mill Moisture in oil (free water, emulsified water and dissolved water) will bring the following adverse effects: the formation of damaged oil film will deteriorate the lubrication effect, and the bearing corrosion will affect the normal life of transmission equipment; Promote the oxidation and deterioration of oil products and accelerate the corrosion of organic acids to metals: make additives hydrolyze and fail; The fluidity of oil products becomes worse at low temperature; Gas resistance produced by vaporization at high temperature affects the cycle; Lead to the increase of oil viscosity; In addition, because the water content in the oil exceeds the standard, it will also lead to a large number of bubbles in the oil tank, and the floating oil suction port will suck empty and other faults.
二：Current situation:
At present, the main measures adopted are how to reduce water inflow and filter out the water that has entered the lubricating oil effectively The commonly used double lubricating oil tank is equipped with one oil tank connected to lubricate the lubricating oil in the other oil tank, so as to restore the stability of additives such as wear resistance, heat resistance, oxidation resistance, foam resistance and rust prevention in lubricating oil, provide sufficient and necessary standing time and conditions for external circulation filtration separation for settling and separating water and impurities in lubricating oil. On-site application of oil-water separation, oil-water separator has better water removal effect when water is free or slightly emulsified, and the separation effect is not ideal when oil emulsification is serious. At this time, heating vacuum oil-water separation equipment will be a more effective water removal method Therefore, it is necessary not only to prevent water from entering the lubrication system as much as possible, but also to try to prevent the entered water from forming emulsion with oil Therefore, it is required to take timely measures to reduce the possibility of floating liquid formation when cooling water is found to enter.
At present, the off-line analysis method-distillation sampling test (GB/T260) is still used to measure the water content in lubricating oil Off-line monitoring technology has been gradually replaced by on-line monitoring technology in many application fields because of the need to sample first and then analyze, which is not only laborious, time-consuming and costly, but also has a time lag in the return of measurement results Accurate on-line measurement of water content in lubricating oil, monitoring the changing trend of water content in lubricating oil, and preventing the water content in lubricating oil from increasing significantly in a short time due to cooler leakage and gasket leakage, etc., which will cause major equipment accidents, have great practical significance for guiding production.
三：Failure mechanism analysis of lubricating oil in finishing mill:
Finishing mill is generally used in oil film bearing oil commonly used brand T100 # Shell T22O # and so on The industrial monitoring center of Baosteel obtained the following conclusions from the analysis of the causes of bearing failure caused by lubricating oil from the change of lubricating oil performance after a large amount of water entered the lubricating system of wire rod high-speed rolling mill
1) Elastohydrodynamic lubrication theory (EHD) By analyzing and discussing the minimum oil film thickness required for bearing lubrication, it can be found that the density of lubricating oil is diluted by water, which makes the dynamic viscosity η 0 of lubricating oil decrease and the minimum oil film thickness become smaller for the oil film bearing oil used in high-speed wire rod rolling mill.
2) According to the results of four-ball wear spot test of lubricating oil with different water content, it can be found that when the water content of oil film bearing oil exceeds 0.5%, the probability of bearing failure will increase greatly. If the water content exceeds 1%, it is very likely that rolling bearing failure will occur in a short time.
3) The forms of bearing failure caused by large amount of lubricating oil entering water are surface fatigue pitting corrosion and rust, in which pitting corrosion is caused by the formation of lubricating oil film thickness and the decline of lubricating oil extreme pressure performance, while rust is caused by free water in lubricating oil. In this state, if the mechanical equipment stalls for a period of time, the rust will become more serious.
四：Selection of sensors：
At present, on-line monitoring of water content in lubricating oil is mainly based on the large difference of dielectric constant between oil and water, and the change of dielectric constant after oil-water mixing is measured to determine the water content in oil At present, the accuracy of detection results is generally low, and many aspects need to be further improved A Sensor for on-line Monitoring of Moisture Content of Lubricating Oil by Electrochemical Impedance Spectroscopy (EIS) Small volume, light weight, reliable structure, convenient use, fast response and low price.
The preliminary laboratory test in this project shows that the sensor can accurately measure the water content and other oxidative pollution of lubricating oil on line, so as to accurately measure the quality of lubricating oil The sensor with thread connection can be widely used in real-time monitoring of lubricating oil quality of gearbox, pump and steam turbine of various large and medium-sized power machinery.
五：Design of sampling position
5.1 Principle of sampling
a.Be representative and authentic
b.It is necessary to carry the information when the lubrication system of the equipment is in a balanced state to the maximum extent
c.Eliminate contamination by factors other than lubrication system of equipment
5.2 Location of sampling
5.2.1Fuel tank
If the sensor installed in the mailbox is used for sampling, the upper or lower part of the fuel tank should not be sampled, and the middle part of the fuel tank should be considered for sampling.
The specific design needs to be based on the actual situation of the site.
5.2.2 pipeline
If the sensor is installed in the lubrication pipeline, it should be considered not to install it in the oil return pipeline before and after the filter, but also to install it in the external circulation pipeline.
The specific design needs to be based on the actual situation of the site.
六：Specific application
6.1；In cooperation with Baosteel Industrial Testing Company, on-line lubricating oil moisture content monitoring of finishing mill lubrication system in Baosteel has been carried out
6.2；The on-line lubricating oil moisture content monitoring system of finishing mill lubrication system produced in cooperation with Guangzhou Machinery Research Institute has been applied in iron and steel enterprises
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