A control method for a hot-rolling dry oil system when on-site instruments fail

Abstract

The present invention relates to a control method for on-site instrument failures in a hot-rolled dry oil system, belonging to the technical field of hot continuous rolling sheet production methods. The technical solution of the present invention is as follows: a limit value is set for the switching value of the pump station pressure switch SP2, and the first-level programmable controller collects the two switching values of the pump station pressure switch. When the pump station pressure is greater than the set value, the newly added control point first controls the pipeline to supply oil in the reverse direction. When the output value of the SP2 switching quantity is higher than the limit value within the set time, the pump station motor automatically stops oil transportation. The beneficial effects of the present invention are as follows: it improves the stability of the operation of the automatic control system, avoids the occurrence of production stoppage accidents, and at the same time reduces the medium consumption of the production line; there is no need for manual intervention, and the system processes faults more quickly and reliably.

Description

Technical Field

[0001] The present invention relates to a control method for a hot-rolled dry oil system when on-site instruments fail, and belongs to the technical field of hot continuous rolling sheet production methods. Background Art

[0002] There are 18 dry oil pump stations throughout the hot continuous rolling dry oil lubrication system, which inject dry oil lubrication into high-speed running equipment such as rolling mills, roller tables, and coiling machines during production to reduce equipment wear. According to different equipment operating characteristics, different lubrication cycles and commutation lubrication times are set for the primary programmable logic controllers (PLCs) of different dry oil pump stations. All dry oil pump stations throughout the line are divided into two pipelines, namely Pipeline A and Pipeline B, to transport dry oil to equipment such as rolling mills. A pressure gauge is installed at the end of each pipeline (i.e., the end of the pipeline before entering the rolling mill or the roller table) to detect the pipeline pressure. The installation location of the pressure detection instrument at the end of the dry oil system pipeline has a large amount of water vapor and equipment vibration on-site, and the operating environment is relatively harsh. The pressure gauge often has short circuit or open circuit faults. At this time, the detected pressure of the pressure gauge is always 0 or the maximum range of 360 bar. The condition of "the pressure difference between the oil supply pipeline and the pipeline to be replaced is greater than 70 bar" is set in the primary programmable logic controller (PLC) as the condition for the system to change the pipeline for oil supply. When the pressure gauge fails, this condition cannot be met, the pipeline cannot be normally commutated, the system always supplies oil with one pipeline, the pipeline pressure gradually increases, and the pipeline bursts after exceeding the pipeline pressure-bearing capacity, resulting in a large waste of dry oil. At the same time, it is impossible to supply oil to the operating equipment, causing equipment wear and seriously affecting the normal production of the hot rolling production line. Currently, the dry oil systems of domestic similar production lines all control the dry oil commutation and oil supply based on the pressure difference of the end pressure gauge. When the pressure gauge fails, accidents such as excessive pressure pipeline breakage, shutdown, and steel piling often occur, and it is necessary to stop the machine to replace the pressure gauge, which affects the safe operation of the equipment and restricts the efficient production of the hot rolling line. Summary of the Invention

[0003] The purpose of the present invention is to provide a control method for a hot-rolled dry oil system when on-site instruments fail. By designing a new pump station pressure switch to control the pipeline commutation and oil supply automatic system, when the pressure gauge fails, the system automatically switches to using the pump station pressure switch to detect the system pressure for system start and stop control, ensuring the normal production of hot rolling when the pressure gauge at the end of the dry oil pipeline fails; by designing a pump station centralized dry oil addition time control mode, on the basis of the original high liquid level detection control to stop adding dry oil, the dry oil addition time is synchronously detected, which can effectively prevent a large amount of dry oil from overflowing from the oil tank due to abnormal high liquid level detection of the ultrasonic level gauge; improving the stability of the automatic control system operation, avoiding the occurrence of production stoppage accidents, and at the same time reducing the medium consumption of the production line; without manual intervention, the system processes faults more quickly and reliably. After the flowmeter fails, an automatic alarm screen pops up on the human-machine interface (HMI) in the relevant area, which can prompt the corresponding technical personnel to promptly handle the equipment fault, effectively solving the above problems existing in the background art.

[0004] The technical solution of the present invention is: a control method for a hot-rolled dry oil system when on-site instruments fail, including the following steps:

[0005] (1) The first-level programmable controller detects the fault signal of the working state of the pressure gauge at the end of the dry oil system pipeline in each scan cycle;

[0006] (2) When the system detects a fault in the pressure gauge at the end of the pipeline, it automatically switches to a newly designed pump station pressure switch to control the automatic pipeline reversing oil supply system;

[0007] (3) Reset the digital control value of the pressure switch SP2 of the dry oil pump station, and the first-level programmable controller collects the digital input point of SP2;

[0008] (4) When the first-level programmable controller collects a high-pressure alarm of the pump station pressure switch, the newly added control point first controls the pipeline to reverse the oil supply;

[0009] (5) Set different circulating oil supply operation times and operation cycles according to the process characteristics of different pump station oil supply equipment;

[0010] (6) When the first-level programmable controller collects a high-pressure alarm of the pump station pressure switch that lasts for more than the set time, the system judges that the on-site pipeline is blocked. To prevent the pipeline from bursting, the oil supply motor of the pump station automatically stops running;

[0011] (7) When the first-level programmable controller collects a low oil tank liquid level, on the basis of detecting that the dry oil stops refueling at a high liquid level, a time relay is used to synchronously control the stop of refueling to avoid a large amount of dry oil overflow and waste caused by a detection error of the ultrasonic liquid level gauge at a high liquid level.

[0012] In the step (1), the working state of the pressure gauge at the end of the dry oil system pipeline is detected in the first-level programmable controller; when the measured pressure of the pressure gauge at the end of the pipeline is constantly 0 or the maximum value of 600 bar, the system judges that the end pressure gauge is faulty.

[0013] In the step (2), when the first-level programmable controller system detects that the displayed value of the end pressure gauge is constantly 0 or the maximum value of 600 bar for 5 seconds, the system judges that the on-site pressure gauge is faulty, outputs the fault signal of this pump station, and uses this signal to stop the two pipeline pressure difference detection signals and the original system-designed pipeline automatic reversing oil supply function; at the same time, use this fault occurrence signal to automatically start the newly designed pump station pressure switch to control the pipeline reversing oil supply mode.

[0014] In the step (3), reset the values of the two digital quantities of the pump station pressure switch. The original control system uses the digital quantity SP2 as the interlock condition for the pump station motor to stop running, and stops the pump station motor when this digital quantity detects high pressure.

[0015] In step (4), the value of the SP2 digital input being on is adjusted. Different on - time settings are made when the SP2 digital input has a high pressure. When the SP2 digital input is on, it is first used for the switching of the pipeline's reverse - flow oil supply function. After the pipeline is switched, if the pressure switch continuously alarms for high pressure, the system determines that the oil - supply pipeline is blocked and automatically stops the operation of the oil - supply motor of the pumping station to protect the pipeline equipment.

[0016] In step (5), after the dry - oil system reverses the oil supply according to the set value of the pumping - station pressure switch, different pumping stations set different oil - supply times, cyclic oil - supply times, and stop - operation times according to the operating characteristics and technological features of the oil - supply equipment. During each cycle, dry oil is transported to different equipment different numbers of times.

[0017] In step (6), within one cyclic oil - supply period, the first - level programmable logic controller (PLC) continuously detects the pumping - station pressure switch. The set time is 30 seconds. When the pressure continuously exceeds the set time, this point serves as an interlock condition for starting the pumping - station motor. During each scan cycle, the operating conditions are scanned and judged. When the pressure continuously exceeds the set value, the operation of the pumping - station motor is stopped in a timely manner.

[0018] In step (7), the ultrasonic level gauge of the dry - oil pumping - station tank detects the tank level. When the level is low, the automatic dry - oil adding function is started, and when the high level is detected, adding dry oil to the tank is stopped. When the ultrasonic level gauge is affected by dry - oil impurities or other factors and has an incorrect high - level detection, the dry - oil adding time - control function is applied. When the low - level detection starts the automatic dry - oil adding, an automatic timer starts. After reaching the set time, whether the high level is detected or not, the system automatically stops adding dry oil, avoiding a large waste of dry oil.

[0019] The beneficial effects of the present invention are as follows: By designing a new automatic system for controlling the pipeline's reverse - flow oil supply with a pumping - station pressure switch, when the pressure gauge fails, the system automatically switches to using the pumping - station pressure switch to detect the system pressure for system start - stop control, ensuring the normal production of hot - rolling when the pressure gauge at the end of the dry - oil pipeline fails. By designing a centralized dry - oil adding time - control mode for the pumping station, on the basis of the original high - level detection control to stop adding dry oil, the dry - oil adding time is simultaneously detected, which can effectively prevent a large amount of dry oil from overflowing from the tank due to abnormal high - level detection by the ultrasonic level gauge. It improves the stability of the operation of the automatic control system, avoids the occurrence of production - stop accidents, and at the same time reduces the consumption of media on the production line. Without manual intervention, the system processes faults more quickly and reliably. After a flowmeter failure occurs, an automatic alarm screen pops up on the human - machine operation interface in the relevant area, which can prompt the corresponding technical personnel to handle the equipment fault in a timely manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the working flow chart of the present invention. Detailed implementation mode

[0021] In order to make the purpose, technical solution and advantages of the invention implementation cases clearer, the following will combine the attached drawings in the implementation cases to clearly and completely describe the technical solutions in the implementation cases of the present invention. Obviously, the described implementation cases are a small part of the implementation cases of the present invention, rather than all the implementation cases. Based on the implementation cases in the present invention, all other implementation cases obtained by those of ordinary skill in the art without creative labor belong to the protection scope of the present invention.

[0022] A control method for a hot-rolled dry oil system when on-site instruments fail, comprising the following steps:

[0023] (1) The first-level programmable controller detects the fault signal of the working state of the pressure gauge at the end of the dry oil system pipeline in each scan cycle;

[0024] (2) When the system detects a fault in the pressure gauge at the end of the pipeline, it automatically switches to a newly designed pump station pressure switch to control the automatic pipeline commutation oil supply system;

[0025] (3) Reset the switch quantity control value of the pressure switch SP2 of the dry oil pump station, and the first-level programmable controller collects the switch quantity input point of SP2;

[0026] (4) When the first-level programmable controller collects a high-pressure alarm of the pump station pressure switch, the newly added control point first controls the pipeline to change the direction of oil supply;

[0027] (5) Set different circulating oil supply operation times and operation cycles according to the process characteristics of different pump station oil supply equipment;

[0028] (6) When the first-level programmable controller collects a high-pressure alarm of the pump station pressure switch that lasts for more than the set time, the system judges that the on-site pipeline is blocked. To prevent the pipeline from bursting, the oil supply motor of the pump station automatically stops running;

[0029] (7) When the first-level programmable controller collects a low oil tank liquid level, on the basis of detecting that the dry oil stops refueling at a high liquid level, a time relay is used to synchronously control the stop of refueling to avoid the problem of a large amount of dry oil overflow and waste caused by a detection error of the ultrasonic liquid level gauge at a high liquid level.

[0030] In the step (1), the working state of the pressure gauge at the end of the dry oil system pipeline is detected in the first-level programmable controller; when the measured pressure of the pressure gauge at the end of the pipeline is constantly 0 or the maximum value of 600 bar, the system judges that the end pressure gauge is faulty.

[0031] In step (2), when the display value of the terminal pressure gauge in the first-level programmable controller system remains constant at 0 or the maximum value of 600 bar for 5 seconds, the system determines that the on-site pressure gauge has failed, outputs the failure signal of this pumping station, and uses this signal to stop the two pipeline pressure difference detection signals and the pipeline automatic commutation oil supply function designed in the original system; at the same time, uses this failure occurrence signal to automatically start the newly designed pumping station pressure switch to control the pipeline commutation oil supply mode.

[0032] In step (3), the numerical values of the two digital quantities of the pumping station pressure switch are reset. The original control system uses the digital quantity SP2 as the interlock condition for the pumping station motor to stop running. When this digital quantity detects high pressure, the pumping station motor stops running. [[ID=X]]

[0033] In step (4), the on-time value of the SP2 digital quantity being turned on is adjusted. Different on-time values are set when the SP2 digital quantity has high pressure. When the SP2 digital quantity is turned on, it is first used for the switching of the pipeline commutation oil supply function. After the pipeline is switched, if the pressure switch continuously alarms with high pressure, the system determines that the oil supply pipeline is blocked and automatically stops the operation of the pumping station oil supply motor to protect the pipeline equipment.

[0034] In step (5), after the dry oil system commutates and supplies oil according to the set value of the pumping station pressure switch, different pumping stations set different oil supply times, cyclic oil supply times, and stop operation times according to the different operating characteristics and process characteristics of the oil supply equipment, and convey dry oil to different equipment different numbers of times within each cycle.

[0035] In step (6), the first-level programmable controller detects the pumping station pressure switch in real time within a cyclic oil supply period. The set time is 30 seconds. When the pressure continuously exceeds the set time, this point is used as the interlock condition for the pumping station motor to start. In each scan cycle, the operating conditions are scanned and judged. When the pressure continuously exceeds the set value, the pumping station motor is stopped in a timely manner.

[0036] In step (7), the ultrasonic liquid level gauge of the dry oil pumping station tank detects the liquid level in the tank. When the liquid level is low, the automatic dry oil adding function is started, and when the high liquid level is detected, adding dry oil to the tank is stopped; when the ultrasonic liquid level gauge is affected by dry oil impurities or other factors and the high liquid level detection is incorrect, the dry oil adding time control function is used. When the low liquid level is detected and the automatic dry oil adding starts, the timer starts automatically. After reaching the set time, whether the high liquid level is detected or not, the system automatically stops adding dry oil to avoid a large amount of waste of dry oil.

[0037] In practical applications, the present invention sets reasonable limit values for the switch quantities of the pump station pressure switch SP2. The first-level programmable logic controller (PLC) collects the two switch quantities of the pump station pressure switch, sets the value of the pump station pressure switch quantity SP2 to 280 bar, and compiles a control program. The switch quantity input point of SP2 is used for the commutation of the dry oil system and the function of stopping the operation of the pump station motor. When the newly designed control system detects a fault in the pressure gauge at the end of the pipeline in the dry oil system, it automatically collects the pressure of the dry oil pump station. When the pump station pressure is greater than the set value of 280 bar, the newly added control system uses this output point to control the automatic commutation of pipeline A and pipeline B. If the pipeline is not blocked after normal commutation, the system pressure will quickly drop below 280 bar; when the output value of SP2 is continuously higher than 280 bar for 30 seconds, to prevent pipeline rupture caused by excessive pressure, the pump station motor automatically stops oil transportation. This method automatically switches to the commutation oil supply mode controlled by the pump station pressure switch when the pressure gauge at the end of the on-site pipeline fails, without manual operation, and the reliability and stability of the system operation are strong, eliminating equipment wear and the occurrence of steel piling accidents in the rolling mill when the pressure gauge at the end of the pipeline fails.

[0038] The present invention compiles a PLC control program and adds control functions such as automatically popping up an alarm screen in the human-machine interface (HMI), including the following control processes:

[0039] 1. Through the analysis of a large number of first-level ODG data in the production process, it is considered that when the on-site pressure gauge works normally, the pressure value generally reaches about 100 bar to commutate, and the maximum pipeline pressure during normal commutation does not exceed 180 bar; according to the analysis of a large number of data, it is considered that when the pressure gauge at the end is greater than 180 bar, there is a blockage in the oil transportation pipeline, and an abnormal control signal for the output pipeline is sent. When the pressure gauge at the end of the pipeline continuously detects a low pipeline pressure after the dry oil pump station motor is started, and the pressure difference between the two pressure gauges cannot reach 70 bar within the set time and cannot commutate, it is detected that there is an oil leakage point in the oil transportation pipeline, and an abnormal control signal for the output pipeline is also sent. There are two situations for the failure of the pressure gauge at the end of the dry oil system, that is, the instrument is short-circuited and the pressure value is constantly 0, and the instrument is short-circuited and the pressure value shows the maximum value. At this time, the first-level programmable logic controller (PLC) in the control method of the present invention sends out a fault signal for the pressure gauge at the end.

[0040] 2. When the pressure gauge at the end of the grease system fails, the system outputs a control signal. Taking the No. 9 grease pump station as an example, when there is an internal short circuit in the pressure gauge at the end of the B pipeline of the No. 9 grease pump station and the pressure display value is constantly 0, a new program function block is added. When the detected value of the pressure gauge at the end of the pipeline exceeds 180 bar, it is considered that the on-site end pressure gauge is not working properly. This value can not only ensure the normal lubrication of the equipment by the pump station but also avoid the pipeline from bursting due to excessive pressure; a control program is added to the FU_MS015 function block of the FERPLC02 control system. When the system detects that the value of one of the pressure gauges in the A and B pipelines is constantly 0 or the maximum value of 600, a new signal G_VV90NO is output after a 1-second delay, and it is judged that the end pressure gauge is faulty. This signal is used to control the pipeline oil transportation direction change and the start and stop control of the pump station motor.

[0041] 3. In the original system design, the set value of the pump station pressure switch SP2 was 330 bar. Once the pipeline pressure reached 330 bar, the pump station motor stopped, and different equipment stopped running after a certain set time. The new control system re-set this value and the control process, and set the value of the pump station pressure switch SP2 to 280 bar; when the system reports that the fault signal G_VV90NO of the end pressure gauge is 1, the new control system collects the pump station pressure switch quantity in real time. When the system detects that the state of this switch quantity signal is 1, that is, when the pump station pressure is high, the pump station pressure switch is displayed in yellow for alarm on the HMI, and at the same time, this signal is delayed for 30 seconds and output to the signal G_VV90PHIGH2, and this signal is used to control the motor stop interlock signal.

[0042] 4. When the system detects a fault in the end pressure gauge, the fault judgment signal G_VV90NO is used to automatically switch to the grease fault operation mode for normal pipeline direction change and oil transportation. At this time, the pump station motor uses the pressure detected by the pump station pressure switch and automatically stops when the pressure is high. The normally closed point signal of G_VV90NO is applied to the original designed direction change program. At this time, when the on-site instrument fails, the original designed direction change control mode of the system will automatically stop, and the direction change will be carried out according to the set value of the new designed pump station pressure switch.

[0043] 5. When the PLC system collects the high-pressure alarm of the pump station pressure switch, the new control point first controls the direction change, and the oil supply pipeline changes from the A road to the B road; after the pipeline changes the oil supply direction, the high-pressure alarm value of the pump station pressure switch is reset, and the system supplies oil to the equipment through the B pipeline. The actual pressure of the B pipeline continues to rise. When the set value of the pump station pressure switch SP2 detects an alarm again, the new system controls the direction change and changes from the B pipeline to the A pipeline for oil transportation; according to the different equipment process characteristics of the rolling mill, flying shear and roller table, different cycle operation times are set. For example, the No. 9 grease pump station transports grease to the flying shear, and one oil supply cycle is 2 hours, and the pipeline circulates the oil supply 5 times. After completing 5 cycle periods, this operation cycle stops and the motor stops running, and it starts again after 2 hours.

[0044] 6. The set value of the pump station pressure switch also controls the start and stop of the dry oil system motor. If the system detects high pressure, the motor will be stopped simultaneously, and the oil supply to the rolling mill equipment will be stopped, which conflicts with the reverse oil supply. To address this issue, the interlock condition for stopping the motor was modified. It is designed that the pump station start interlock condition adds a high pump station pressure interlock signal. When the pump station pressure is high, an output signal is given after a 1-second delay to control the commutation. At the same time, the high pressure signal is delayed for 30 seconds to output a control signal. The newly added system controls the pump station pressure switch to alarm in red on the HMI screen and simultaneously controls the pump station motor to stop.

[0045] 7. When the liquid level in the fuel pump station tank of the original system design is low, the system automatically injects dry oil into the tank. After the ultrasonic level gauge detects the high liquid level signal of the dry oil, the refueling stops. To improve the operational stability of the system and prevent a large amount of dry oil from overflowing from the tank due to abnormal instrument operation, a refueling time control function is developed based on liquid level detection. When the ultrasonic level gauge in the pump station tank detects that the liquid level low signal VV90FH1A is 1, the system issues a dry oil refueling command G_VV100OIL_REQUEST for the pump station. The centralized fuel pump station sorts the refueling sequences of the 18 dry oil pump stations in the whole line that request refueling. When the corresponding pump station is sorted to the first (taking the 10# dry oil pump station as an example), the system issues a start refueling command G_VV100OIL_REQUEST. The filling valve of this pump station opens to start refueling. When the new control system detects that the filling valve opening signal O_VV92YVS1_A is 1, the filling valve automatically opens, and at this time, the dry oil refueling time starts to be counted; a timing function block is added to the system. When the filling valve of the pump station for refueling is opened and in the automatic mode of the dry oil pump station, two timing function blocks are used, one with a 11-minute delay to close and the other with a 10-minute delay to connect the function block to control the refueling time. A rising edge control is added before the two timing function blocks, otherwise the timing point will be continuously connected. The output of the delay function is finally given to the variable G_VV100_SYSSP_TIM. This variable is applied to the following controls: (1) Applied to the dry oil refueling in the system pump station tank, as a chain condition for dry oil refueling. It is satisfied within 10 minutes of the new variable G_VV100_SYSSP_TIM timing. After the timing variable is connected, the filling valve automatically opens. After the filling valve opens, the system starts timing. Within 10 minutes, the system allows dry oil to be added to the pump station tank; (2) As a chain condition for the opening and closing of the filling valve; the filling valve opens when the ultrasonic level gauge detects a low dry oil level and starts refueling the tank. During the refueling process, if a high liquid level is detected, the motor of the centralized fuel pump station automatically stops; if a high liquid level is not detected all the time, after 10 minutes of the timing function block, the variable G_VV100_SYSSP_TIM gives a command to close the filling valve, and the filling valve automatically closes. (3) As a chain condition for the motor stop of the centralized fuel pump station; after the centralized fuel pump station issues a dry oil refueling command, a set command is generated in the system to wait for dry oil refueling, and the output variable is VV100_FILL_REQ. There is a system dry oil refueling satisfaction point VV100_FILLING_OK in the dry oil refueling reset program. This point is chained with G_VV100_SYSSP_TIM. After the filling valve is opened and the system refuels dry oil for 10 minutes, the system dry oil refueling condition variable VV100_FILLING_OK is no longer satisfied, and the variable VV100_FILLING_OK is reset, and the dry oil refueling of the centralized fuel pump station ends.

Claims

1. A control method for a hot rolling dry oil system when on-site instruments fail, characterized in that It includes the following steps: (1) The first-level programmable controller detects the fault signal of the working state of the pressure gauge at the end of the dry oil system pipeline in each scan cycle; (2) When the system detects a fault in the pressure gauge at the end of the pipeline, it automatically switches to the newly designed pump station pressure switch to control the automatic pipeline commutation oil supply system; (3) Reset the switching value control of the pressure switch SP2 of the dry oil pump station, and the first-level programmable controller collects the input point of the SP2 switching value; (4) When the first-level programmable controller collects a high-pressure alarm of the pump station pressure switch, the newly added control point first controls the pipeline to change the oil supply direction; (5) According to the process characteristics of the oil supply equipment of different pump stations, set different circulating oil supply operation times and operation cycles; (6) When the first-level programmable controller collects a high-pressure alarm of the pump station pressure switch that lasts for more than the set time, the system judges that the on-site pipeline is blocked. To prevent the pipeline from bursting, the oil supply motor of the pump station automatically stops running; (7) When the first-level programmable controller detects a low oil level in the fuel tank, based on the detection of the dry oil stop refueling at the high oil level, the time relay is used to synchronously control the stop of refueling to avoid the problem of a large amount of dry oil overflow and waste caused by the misdetection of the ultrasonic level gauge at the high oil level; In step (2), when the first-level programmable controller system detects that the display value of the end pressure gauge is constantly 0 or the maximum value of 600 bar for 5 seconds, the system judges that the on-site pressure gauge has a fault, outputs the fault signal of this pump station, and uses this signal to stop the two pipeline pressure difference detection signals and the original system-designed pipeline automatic commutation oil supply function; at the same time, use this fault occurrence signal to automatically start the newly designed pump station pressure switch to control the pipeline commutation oil supply mode; In step (4), adjust the value of the SP2 switching value when it is turned on. Set different on times when the SP2 switching value is under high pressure. When the SP2 switching value is turned on, it is first used for the switching of the pipeline commutation oil supply function. After the pipeline is switched, if the pressure switch continues to give a high-pressure alarm, the system judges that the oil supply pipeline is blocked and automatically stops the operation of the pump station oil supply motor to protect the pipeline equipment.

2. The control method for a hot rolling dry oil system in case of on-site instrument failure according to claim 1, characterized in that: In step (1), the first-level programmable controller detects the working state of the pressure gauge at the end of the dry oil system pipeline; when the measured pressure of the pressure gauge at the end of the pipeline is constantly 0 or the maximum value of 600 bar, the system judges that the end pressure gauge has a fault.

3. The control method in case of on-site instrument failure of a hot rolling dry oil system according to claim 1, characterized in that: In step (3), reset the values of the two switching values of the pump station pressure switch. The original control system uses the switching value SP2 as the interlock condition for the pump station motor to stop running. When the SP2 switching value detects high pressure, the pump station motor stops running.

4. The control method in case of failure of on-site instruments in a hot rolling dry oil system according to claim 1, characterized in that: In step (5), after the dry oil system changes the oil supply direction according to the set value of the pump station pressure switch, different pump stations set different oil supply times, circulating oil supply times and stop operation times according to the different operation characteristics and process characteristics of the oil supply equipment, and convey dry oil to different equipment different numbers of times in each cycle.

5. The control method in case of failure of on-site instruments in a hot rolling dry oil system according to claim 1, characterized in that: In the step (6), within a cyclic oil supply period, the primary programmable logic controller (PLC) detects the pressure switch of the pump station in real time. The set time is 30 seconds. When the pressure continuously exceeds the set time, this point is used as an interlock condition for starting the pump station motor. During each scan cycle, the operating conditions are scanned and judged. When the pressure continuously exceeds the set value, the operation of the pump station motor is stopped in a timely manner.

6. The control method for a hot rolling dry oil system in case of on-site instrument failure according to claim 1, characterized in that: In the step (7), the ultrasonic level gauge of the dry oil pump station tank detects the tank level. When the level is low, the automatic dry oil adding function is started, and when the high level is detected, adding dry oil to the tank is stopped; when the ultrasonic level gauge is affected by dry oil impurities or other factors and the high level detection is incorrect, the dry oil adding time control function is applied. When the low level is detected and the automatic dry oil adding is started, the timer is automatically started. After reaching the set time, whether the high level is detected or not, the system automatically stops adding dry oil to avoid a large amount of waste of dry oil.

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