Oil film bearing lubricating oil flow precision control oil supply method

Abstract

The application discloses an oil film bearing lubricating oil flow precision control oil supply method, comprising the following control steps: calculating the normal rotating speed of the variable frequency pump group in the steady state; setting the overflow pressure value at the same time; one of the variable frequency pumps operates at the normal rotating speed in the normal state; when the total oil flow of the oil film bearing is greater than the total oil flow in the optimal state of the oil film bearing operation, the lubricating oil supplement level of the pressure tank decreases, and the pump operates at the rotating speed of the normal rotating speed+5% when the level is lower than the low level of the pressure tank; the pump operates at the normal rotating speed+5% if the pressure tank is still at the low level; the pump is accelerated to the normal rotating speed+10% if the pressure tank is not at the low level and not at the working level; the pump is accelerated to the normal rotating speed+5% if the pressure tank is not at the low level and not at the working level; and the pump returns to the normal rotating speed if the pressure tank is at the working level. The application can solve the problems of poor precision and stability of the oil film bearing oil supply oil flow, and poor stability of the module rolling mill under large bearing capacity.

Description

Technical Field

[0001] This invention relates to the field of steel manufacturing equipment technology, and in particular to a precise oil supply method for oil film bearing lubricating oil in a module mill of a high-speed bar and wire rod production line for finishing and reducing sizing mills. Background Technology

[0002] In high-speed bar and wire rod production lines, the finishing and sizing mills all include cantilever roll modular mills using oil film bearings. The stable control of these oil film bearings directly determines the production stability and cost of the production line. The stability and load-bearing capacity of the modular mill's oil film bearings directly restrict the production of high-speed bar and wire rod, especially with the rise of high-speed bar production in recent years. Some initially constructed production lines often face limited design capacity of the modular mill's oil film bearings and a limited range of product specifications. As production lines need to expand their production processes, especially with the application of controlled rolling and controlled cooling technologies, the load-bearing capacity required for low-temperature rolling modular mills is greater, which can easily lead to insufficient safety factors for the oil film bearings, resulting in poor system stability.

[0003] The usual design solutions to these problems are increasing the kinematic viscosity of the oil in the oil film bearings or increasing the bearing size. However, this approach requires significant investment. Our company's high-speed bar mill reducing oil station has a tank capacity of 40 cubic meters per tank. Assuming 85% capacity is used for filling, the two high-speed bar mills (four tanks in total) require 136 cubic meters, totaling 122 tons. At a market price of 20,800 yuan per ton, the cost would be 2,537,600 yuan. Furthermore, increasing the kinematic viscosity at low temperatures leads to large pressure fluctuations and oil flow fluctuations in the oil film bearings, negatively impacting system stability. Therefore, increasing the kinematic viscosity by changing the oil not only incurs substantial financial costs but may also fail to completely resolve the current issues. Increasing the width-to-diameter ratio of the oil film bearings would require upgrading the modular rolling mill, further increasing costs and raising the issue of spare parts consumption, significantly increasing overall investment.

[0004] The company's high-speed bar production line reducing mill system can meet production needs but lacks stability. Therefore, the entire modular mill system was systematically tracked and data analyzed. A series of trial runs were also conducted during downtime. The results showed that the oil film bearing operates more stably when the oil supply is stable and the oil volume is large. Therefore, precise and stable control of the oil flow of the oil film bearing can solve the problem of poor stability of the modular mill under high load.

[0005] Our company currently has an oil film bearing lubrication system in the finishing and sizing mill of the high-speed bar production line. The oil station uses industrial frequency pumps, and each pump supplies a fixed amount of oil. If the oil pump supply exceeds the total lubrication oil required by the system, the oil will accumulate in the system pipeline, causing the system pressure to rise and resulting in overflow near the oil supply port. When the system overflows, the overflow rate cannot be precisely controlled, which may lead to fluctuations in the oil film bearing supply. This instability in the oil film layer of the bearing makes it highly susceptible to roller box burnout.

[0006] Our existing oil supply system supplies not only the oil film bearings but also other bearings and gears in the modular rolling mill system. When the oil supply system is unstable, a large amount of oil can easily flow to other bearings and gears besides the oil film bearings, resulting in low oil flow to the oil film bearings.

[0007] The pneumatic control valve used in the oil supply system is difficult to guarantee when its accuracy is abnormal. At the same time, the cooling water temperature and the external ambient temperature have a certain impact on the control valve. Summary of the Invention

[0008] The problem to be solved by the present invention is to provide a method for precise control of the lubricating oil flow in oil film bearings, so as to solve the problem of poor accuracy and stability of the oil flow in existing oil film bearings, which leads to poor stability of the modular rolling mill under high load.

[0009] To solve the above problems, the technical solution of the present invention is as follows: The oil supply method for precise control of lubricating oil flow in oil film bearings includes using an oil supply system to precisely control the lubricating oil in oil film bearings; the oil supply system includes an oil tank connected to an oil pump group via pipeline, an oil film bearing oil supply port, and oil supply ports for other bearings; there are two oil tanks connected in parallel; the oil pump group includes a variable frequency pump group consisting of two variable frequency pumps connected in parallel for supplying oil film bearings and a fixed frequency pump group consisting of two fixed frequency pumps connected in parallel for lubricating lubrication points outside the oil film bearings; the variable frequency pump group and the fixed frequency pump group are connected in parallel; the oil pump group is connected in parallel between the two oil tanks. The variable frequency pump set is connected in series with two-stage filters, an oil film bearing cooling control device, a pressure tank and an oil film bearing oil supply port. The power frequency pump set is connected to the first-stage filter and then to the other bearing oil supply ports. The oil film bearing cooling control device includes a water inlet pipe connected to multiple branch pipes and then connected to a cooler. The water outlet pipe of the cooler is equipped with a pneumatic control regulating valve. The oil inlet pipe of the cooler is connected to the two-stage filter. The first branch pipe is connected to a manual regulating valve, and the other branch pipes are connected to solenoid valves. The control process includes the following steps: Find the total oil flow under optimal operating conditions of the oil film bearing, which equals the oil supply of the oil station, and calculate the normal steady-state speed n of the variable frequency pump set; at the same time, set the overflow pressure value; Under normal conditions, one of the variable frequency pumps operates at its normal speed n%. When the total oil flow in the oil film bearing exceeds the total oil flow under optimal operating conditions, the lubricating oil level in the pressure tank decreases. When the level is lower than the low level in the pressure tank, the pump speed increases to (n+5)%. If the pressure tank level does not drop to the low level, the pump speed remains at n%. When the pump speed is (n+5)%, if the pressure tank is still at the low level, the pump speed increases to (n+10)%. If the pressure tank is neither at the low level nor the working level, the pump speed is (n+5)%. If the pressure tank is at the working level, the pump returns to n%. If the speed of one of the variable frequency pumps keeps fluctuating and cannot be stabilized within an hour, then a system malfunction should be considered. When the oil pump set is restarted after a fault repair, one of the variable frequency pumps will run at full frequency, and the variable frequency pump will be put into variable frequency control with the working liquid level of the pressure tank as the target.

[0010] A more specific embodiment of the above technical solution could be: the air inlet pipe of the pressure tank is split into two paths after passing through an air filter. One path passes through a manual ball valve and is connected to the outlet pneumatic butterfly valve and the oil outlet pipe. The other path is connected in sequence to the air inlet solenoid valve, the regulating valve, and the parallel booster valve, and then to the air inlet at the top of the pressure tank. The oil inlet pipe of the pressure tank is connected to the oil outlet pipe of the cooler of the oil film bearing cooling control device. The end of the oil outlet pipe of the pressure tank is connected to the oil supply port of the oil film bearing and then to the oil tank.

[0011] Furthermore: the pressure tank is equipped with a level switch, and the pressure tank overflow valve is installed on the oil return pipe at the top of the pressure tank.

[0012] Furthermore: the two-stage filter comprises two filter groups connected in series.

[0013] Furthermore, an oil filter is connected in series between the two oil tanks.

[0014] Furthermore: the variable frequency pump set is connected to the main overflow valve and then to the two-stage filter, and the power frequency pump set is connected to the main overflow valve and then to the first-stage filter.

[0015] By adopting the above technical solution, the present invention has the following advantages compared with the prior art: This method for precisely controlling the lubricating oil flow of the oil film bearing employs a parallel oil tank system, with one tank in operation and the other as a backup. A variable frequency pump unit supplies oil to the oil film bearing, while a fixed frequency pump supplies oil to bearings at other lubrication points. This avoids fluctuations in the oil supply to other bearings affecting the oil film bearing's supply, achieving a balance between oil supply and demand at the oil station. The oil supplied to the oil film bearing undergoes two-stage filtration to ensure the high cleanliness requirements of the oil. A specially designed cooling control device for the oil film bearing ensures minimal oil temperature fluctuations. A pressure tank is added before the oil film bearing's supply port, achieving both stable pressure supply and providing emergency oil supply in case of pump unit malfunction. Combined with optimized control parameters, this effectively ensures large, precise, and stable control of the oil flow to the oil film bearing, guaranteeing the stability of the oil film layer during unit operation and consequently ensuring the stability of the modular rolling mill. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention; Figure 2 yes Figure 1 Enlarged view of point A; Figure 3 yes Figure 1 Enlarged view of point B; The diagram shows the following components: oil tank 1, variable frequency pump set 2, fixed frequency pump set 3, oil filter 4, main overflow valve 5, filter set 6, water inlet pipe 7, water outlet pipe 8, cooler 9, pneumatic control regulating valve 10, solenoid valve 11, manual regulating valve 12, cooler oil inlet pipe 13, cooler oil outlet pipe 14, pressure tank 15, air filter 16, manual ball valve 17, outlet pneumatic butterfly valve 18, oil outlet pipe 19, inlet solenoid valve 20, regulating valve 21, booster valve 22, pressure tank overflow valve 23, level switch 24, oil film bearing oil supply port 29, and other bearing oil supply ports 30. Detailed Implementation

[0017] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings: A method for precisely controlling the lubricating oil flow in oil film bearings involves using an oil supply system to precisely control the lubricating oil flow. The oil supply system includes, for example,... Figure 1 , Figure 2 , Figure 3 As shown, it consists of four parts: an oil station, a filter, a water cooling system, and a pressure tank.

[0018] The gas station consists of two oil tanks 1 connected in parallel. One tank (20) supplies oil to the oil film bearing, while the other tanks (30) supply oil to other bearings. The oil pump assembly comprises two parallel variable frequency pumps (2) for supplying oil to the oil film bearing, and two parallel fixed frequency pumps (3) for lubricating external lubrication points of the oil film bearing. The variable frequency pump assembly 2 and the fixed frequency pump assembly 3 are connected in parallel between the two oil tanks. An oil filter 4 is connected in series between the two oil tanks. Both the variable frequency pump assembly 2 and the fixed frequency pump assembly 3 have a main pipe overflow valve 5 connected to their main pipes, which are then connected to a two-stage filter and a first-stage filter, respectively. The variable frequency pump assembly 2 has its own overflow valve. By connecting the two oil tanks 1 in parallel, one for operation and one for standby, and using the variable frequency pump assembly 2 to supply oil to the oil film bearing and the fixed frequency pump assembly 3 to supply oil to other bearings, fluctuations in oil supply to these other bearings are avoided, thus achieving a balance between oil supply and demand at the gas station. Both variable frequency pump set 2 and fixed frequency pump set 3 consist of two pumps, one in use and one on standby.

[0019] The gas station needs to control the balance between the supply and demand of oil in the system and the consumption at user points. Otherwise, if the supply exceeds the demand, the system will experience pressure buildup and overflow. When the overflow valve opens, the overflow rate cannot be controlled to be exactly how much the supply exceeds the demand. For example, the supply might exceed the demand by 10 m³ / h, but when the system overflow valve opens, 20 m³ / h, 30 m³ / h, or even higher might overflow, disrupting the system's supply and demand balance. During the "steel-biting" period of the modular unit, the oil film layer of the oil film bearing will be unstable due to fluctuations in the oil flow of the oil film bearing. In conventional systems, the oil supply from each pump in the gas station is fixed. If the oil supply from the pump is less than the total lubrication oil required by the system, the oil film bearing will definitely experience oil shortage. It is difficult to make the oil supply from the pump equal to the total lubrication oil required by the system using a fixed-frequency pump. Moreover, the oil film bearing demand will definitely change slightly with changes in a certain variable in the system. In other words, the total demand of the oil film bearing will not be a fixed amount. Therefore, if the gas station uses a fixed-frequency pump, the system's oil supply must be greater than the total demand of the oil film bearing to ensure sufficient oil supply. This can lead to oil buildup in the oil film bearing system, causing pressure increases and triggering overflow valves. When overflow occurs, the overflow rate cannot be precisely controlled, potentially resulting in fluctuations in the oil film bearing supply. This instability in the oil film layer can easily lead to roller box burnout. Therefore, the oil pump supplying the oil film bearing must be designed as a variable frequency pump. The total oil demand of the system's oil film bearings must be calculated and tested, and the pump selection must be based on this demand (matching the operating frequency of the variable frequency pump within its optimal range). Simultaneously, the oil station design must be optimized to prevent overflow during normal operation of the modular rolling mill. The entire system has three safety overflow valves; the overflow sequence of the main pipe overflow valve and the pressure tank overflow valve must be later than the overflow valve of the variable frequency pump unit itself.

[0020] Filter section: Variable frequency pump unit 2 consists of a two-stage filter, an oil film bearing cooling control device, a pressure tank, and an oil film bearing oil supply port 29 connected in series. The two-stage filter comprises two filter groups 6 connected in series. The modular rolling mill oil film bearings have high requirements for oil cleanliness, therefore the oil film bearing oil circuit is designed with a two-stage filter. The industrial frequency pump unit 3 is connected to the first-stage filter, then to the cooling control device for other components, and finally to the oil supply port 30 for other bearings.

[0021] Water cooling section, such as Figure 2 As shown: The oil film bearing cooling control device includes a water inlet pipe 7 connected to six branch pipes in parallel and then connected to a cooler 9. A pneumatic control regulating valve 10 is installed on the water outlet pipe 8 of the cooler 9. The oil inlet pipe 13 of the cooler is connected to a two-stage filter. A manual regulating valve 12 is connected to the first branch pipe, and solenoid valves 11 are connected to the other five branch pipes.

[0022] Other bearing cooling control devices include a cooler 9 connected to two parallel branch pipes after the water inlet pipe 7 is connected to it, a manual regulating valve 12 is connected to one branch pipe, a solenoid valve 11 is connected to the other branch pipe, and the cooler 9 is connected to a primary filter.

[0023] The temperature of the cold water fluctuates with environmental factors. Clearly, the cooling effect on the oil supply temperature differs significantly between cooling water temperatures of 30-40 degrees Celsius in summer and those of around 10 degrees Celsius in winter. Maintaining a constant water temperature on-site is extremely difficult, so controlling the cooling efficiency of the cooling device requires controlling the water flow. Furthermore, the cooling device's temperature control must ensure minimal oil temperature fluctuations. Excessive cooling capacity leading to large oil temperature drops and significant oil flow fluctuations can cause momentary system anomalies. If this anomaly occurs during the rolling mill's steel-biting oil film bearing, fluctuations in the oil film layer can easily cause friction and burn-out of the roll shaft and bearing bearing. Therefore, the total cooling water inlet is controlled in six stages, branching into six thin pipes (1 / 6 of the total inlet volume). One of these pipes is controlled by a manual regulating valve 12, while the remaining five are each controlled by a solenoid valve 11. The amount of cooling water entering the cooler 9 is controlled by selecting the solenoid valve 11 of the branch and adjusting the manual regulating valve 12 based on changes in ambient temperature. To prevent excessive oil temperature fluctuations, a pneumatic control regulating valve 10 was installed on the cooler return water pipe. This valve is equipped with a valve positioner for PID control of the pneumatic control regulating valve 10 to ensure the oil supply temperature is maintained at 42±1°C. Within this temperature range, the oil supply to the oil film bearing is stable and the kinematic viscosity of the oil is optimal.

[0024] Pressure tank section, such as Figure 3As shown: The pressure tank 15 provides both stable oil supply and emergency oil supply in case of abnormal tripping of the oil pump unit. Both functions protect the oil film bearing from fluctuations or abnormalities in oil pressure and flow. The pressure tank 15 has compressed air at the top and lubricating oil at the bottom, allowing adjustment of the oil level using compressed air. The air inlet pipe of the pressure tank splits into two paths after passing through the air filter 16. One path connects to the outlet pneumatic butterfly valve 18 and the oil outlet pipe 19 via a manual ball valve 17. The other path connects sequentially to the inlet solenoid valve 20, regulating valve 21, and parallel booster valve 22 before connecting to the air inlet at the top of the pressure tank. Both the oil inlet and outlet pipes 19 of the pressure tank are equipped with manual regulating valves. A pressure tank overflow valve 23 is installed on the return oil pipe at the top of the pressure tank. The overflow port of the pressure overflow valve connects to the oil tank return port to prevent oil splashing during overflow and to facilitate the recovery of overflowed oil. The pressure tank 15 is equipped with a level switch 24. The oil inlet pipe of pressure tank 15 is connected to the oil outlet pipe 14 of the cooler of the oil film bearing cooling control device, and the end of the oil outlet pipe 18 of pressure tank is connected to the oil supply port 29 of oil film bearing and then connected to oil tank 1.

[0025] A single-electrode solenoid valve is installed next to the inlet solenoid valve 20 to control the supply of compressed air to the pressure tank. A single-electrode solenoid valve is installed next to the outlet pneumatic butterfly valve 18. The single-electrode solenoid valve controls the outlet pneumatic butterfly valve 18. When the solenoid valve is de-energized, the outlet butterfly valve opens, allowing oil from the pressure tank to enter the system. The control system will not close the outlet pneumatic butterfly valve 18 unless the system equipment and related rolling mill equipment are under maintenance and stopped. If the limit switch of the outlet pneumatic butterfly valve 18 does not show that it is open during rolling, then: an alarm is triggered on the main control panel of the rolling mill and steel tapping is stopped; a shutdown timer (3 minutes) is started and the countdown time is displayed on the HMI; the rolled pieces are cleared sequentially; after the billets are cleared or the shutdown timer reaches zero, the rolling mill stops; after the rolling mill equipment stops, the oil supply pump motor is stopped.

[0026] When in use, the control process includes the following steps: Through a series of tests, the total oil flow Qdemand of the oil film bearing under optimal operating conditions was determined to be equal to the oil supply Qsupply of the oil station. The steady-state speed of the variable frequency pump unit was calculated as the normal speed n% (ideally 70%-90% of the pump's full frequency). Simultaneously, the overflow pressure values ​​of the system's three relief valves were set. Based on the pressure tank's technical parameters and the booster pump's output pressure, the set value of pressure tank relief valve 24 was determined to be 1.2 MPa. Considering that the overflow sequence of the main pipe relief valve 5 is later than that of the variable frequency pump unit's own relief valve and that the maximum oil supply pressure of the tracking oil film bearing does not exceed 0.85 MPa, it was set to 0.9 MPa. For the variable frequency pump unit 2's own relief valve, considering filter blockage, the pump pressure equals the system pressure plus the pressure difference between the two-stage filters. Since the combined pressure difference alarm value of the two-stage filters is 0.3 MPa, the overflow value of the variable frequency pump unit's relief valve = 0.85 + 0.3 = 1.15 MPa. A pressure gauge was also installed on the oil pump unit's outlet pipe with a warning value of 1.1 MPa. Under normal conditions, one of the variable frequency pumps in the variable frequency pump set operates at a fixed frequency at n% of its rated speed. Because the total dynamic oil flow Q of the oil film bearing under the optimal conditions (when the rolling mill is in a biting state and under no-load conditions) is not completely consistent with the total oil flow Q under the optimal state, and because the total dynamic oil flow Q of the oil film bearing will also fluctuate when the cooler is cooling or the oil temperature is low, if the oil pressure fluctuation is not significant, the variable frequency pump set continues to operate stably at n% of its rated speed, and the fluctuation of the total dynamic oil flow Q is balanced by the pressure tank. When the total oil flow Q of the oil film bearing is greater than the total oil flow Q_demand (which is the oil supply Q_supply) under optimal operating conditions, lubricating oil is replenished in the pressure tank, causing the pressure tank level to drop. When the level is below the low level of the pressure tank, one of the variable frequency pumps operates at (n+5)% of its speed. If the pressure tank level does not drop to the low level, the pump speed remains at n%. When the pump speed is at (n+5)%, if the pressure tank is still at the low level, the pump speed is increased to (n+10)%, and a warning is issued to check the system. If the pressure tank is neither at the low level nor the working level, the pump speed is increased to (n+5)%. If the pressure tank is at the working level, the pump speed returns to n%. If the speed of one of the variable frequency pumps fluctuates within an hour and cannot be stabilized, it is necessary to check for system abnormalities, air leaks in the pressure tank, large oil temperature fluctuations, etc. If no defects are found, the speed setting value n% and the adjustment value 5% are unreasonable and need to be optimized.

[0027] When restarting the oil film bearing oil supply after a modular rolling mill has shut down its oil station due to maintenance or production stoppage, the oil flow will be slow, especially when the pipelines, equipment, and ambient temperature are all cold. This results in a smaller total dynamic oil flow (Qtotal) and a lower supply (Qsupply) than the oil station's supply (Qsupply). This can easily lead to excessively high supply pressure and excessively high pressure tank levels. Therefore, the oil film bearing oil supply for the modular rolling mill requires variable frequency pumps with variable frequency control for startup: one variable frequency pump starts at full frequency (100% speed), and the variable frequency pump is put into variable frequency control based on the working pressure tank level. After reaching the working pressure tank level, the variable frequency pump maintains constant pressure at 85%-100% speed. Control to ensure the oil film bearing supply pressure is 7.25 bar as the target value; after 100 seconds, the pump will operate at (n% speed) when the oil film bearing supply pressure is (7.2-7.25 bar). Oil film bearing supply pressure: if the oil film bearing supply pressure is lower than 7.0 bar, the pump will operate at (n+5)% speed; if the oil film bearing supply pressure is 7.0-8.5 bar, the pump will operate at n% speed; if the oil film bearing supply pressure is higher than 8.5 bar, the pump speed will be reduced to (n-10)% speed. If the oil film bearing supply pressure is still higher than 8.5 bar after 100 seconds, the pump speed will continue to be reduced to (n-20)% and a warning will be issued to troubleshoot the fault.

[0028] Meanwhile, in the event of a shutdown or oil station closure, the oil film bearing oil supply system of the modular rolling mill needs to run oil in advance to preheat the pipelines and equipment using the oil temperature. The modular rolling mill can only be started after the oil station system has stabilized.

[0029] This method for precisely controlling the lubricating oil flow of the oil film bearing employs a parallel oil tank 1, one for operation and one as a backup. A variable frequency pump 2 supplies oil to the oil film bearing, while a fixed frequency pump 3 supplies oil to bearings at other lubrication points. This avoids fluctuations in the oil supply to the oil film bearing and achieves a balance between oil supply and demand at the oil station. The oil supplied to the oil film bearing undergoes two-stage filtration to ensure the high cleanliness requirements of the oil. A specially designed cooling control device for the oil film bearing ensures minimal oil temperature fluctuations. A pressure tank 15 is added before the oil film bearing supply port, achieving both stable pressure supply and emergency oil supply in case of abnormal tripping of the oil pump unit. Combined with optimized control parameters, this effectively ensures large, precise, and stable control of the oil flow to the oil film bearing, guaranteeing the stability of the oil film layer during unit operation and consequently ensuring the stability of the modular rolling mill.

Claims

1. A method for precisely controlling the flow of lubricating oil in an oil film bearing, comprising using an oil supply system to precisely control the lubricating oil in the oil film bearing; said oil supply system comprising an oil tank connected by pipelines to an oil pump assembly, an oil film bearing supply port, and other bearing supply ports, characterized in that: The oil tanks are two and connected in parallel. The oil pump set includes a variable frequency pump set consisting of two variable frequency pumps connected in parallel for supplying oil film bearings and a fixed frequency pump set consisting of two fixed frequency pumps connected in parallel for lubricating lubrication points outside the oil film bearings. The variable frequency pump set and the fixed frequency pump set are connected in parallel, and the oil pump set is connected in parallel between the two oil tanks. The variable frequency pump set is connected in series with two-stage filters, an oil film bearing cooling control device, a pressure tank and an oil film bearing oil supply port. The power frequency pump set is connected to the first-stage filter and then to the other bearing oil supply ports. The oil film bearing cooling control device includes a water inlet pipe connected to multiple branch pipes and then connected to a cooler. The water outlet pipe of the cooler is equipped with a pneumatic control regulating valve. The oil inlet pipe of the cooler is connected to the two-stage filter. The first branch pipe is connected to a manual regulating valve, and the other branch pipes are connected to solenoid valves. The control process includes the following steps: Find the total oil flow under optimal operating conditions of the oil film bearing, which equals the oil supply of the oil station, and calculate the normal steady-state speed n of the variable frequency pump set; at the same time, set the overflow pressure value; Under normal conditions, one of the variable frequency pumps operates at its normal speed n%. When the total oil flow in the oil film bearing exceeds the total oil flow under optimal operating conditions, the lubricating oil level in the pressure tank decreases. When the level is lower than the low level in the pressure tank, the pump speed increases to (n+5)%. If the pressure tank level does not drop to the low level, the pump speed remains at n%. When the pump speed is (n+5)%, if the pressure tank is still at the low level, the pump speed increases to (n+10)%. If the pressure tank is neither at the low level nor the working level, the pump speed is (n+5)%. If the pressure tank is at the working level, the pump returns to n%. If the speed of one of the variable frequency pumps keeps fluctuating and cannot be stabilized within an hour, then a system malfunction should be considered. When the oil pump set is restarted after a fault repair, one of the variable frequency pumps will run at full frequency, and the variable frequency pump will be put into variable frequency control with the working liquid level of the pressure tank as the target.

2. The oil supply method for precise control of lubricating oil flow in oil film bearings according to claim 1, characterized in that: The air inlet pipe of the pressure tank is split into two paths after passing through an air filter. One path passes through a manual ball valve and is connected to the outlet pneumatic butterfly valve and the oil outlet pipe. The other path is connected in sequence to the air inlet solenoid valve, the regulating valve, and the parallel booster valve, and then to the air inlet at the top of the pressure tank. The oil inlet pipe of the pressure tank is connected to the oil outlet pipe of the cooler of the oil film bearing cooling control device. The end of the oil outlet pipe of the pressure tank is connected to the oil supply port of the oil film bearing and then to the oil tank.

3. The oil supply method for precise control of lubricating oil flow in oil film bearings according to claim 2, characterized in that: The pressure tank is equipped with a level switch, and the pressure tank overflow valve is installed on the oil return pipe at the top of the pressure tank.

4. The oil supply method for precise control of lubricating oil flow in oil film bearings according to any one of claims 1 to 3, characterized in that: The two-stage filter consists of two filter groups connected in series.

5. The oil supply method for precise control of lubricating oil flow in oil film bearings according to claim 3, characterized in that: An oil filter is connected in series between the two oil tanks.

6. The oil supply method for precise control of lubricating oil flow in oil film bearings according to claim 4, characterized in that: The variable frequency pump set is connected to the main overflow valve and then to the two-stage filter; the power frequency pump set is connected to the main overflow valve and then to the first-stage filter.

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