Testing device and method for graphite heat exchanger

Abstract

The invention provides a testing device and method for a graphite heat exchanger, and relates to the technical field of testing devices.The testing device comprises the graphite heat exchanger, the graphite heat exchanger comprises a tank body, two sealing plates and a heat exchange pipe, the two sealing plates are both fixedly installed in the tank body, and the tank body and the two sealing plates are combined to form a sealed heat exchange cavity; the number of the heat exchange pipes is multiple, and the multiple heat exchange pipes sequentially penetrate through the two sealing plates. According to the testing device and method for the graphite heat exchanger provided by the invention, through the arrangement of the bottom plate, the placement frame, the tank body, the sealing plate, the heat exchange pipe, the pressure measuring pipe, the first air pressure sensor, the communication box, the piston pipe, the second air pressure sensor and the driving structure, multiple mutually independent spaces in the graphite heat exchanger can be tested at the same time; mutual verification comparison testing can be carried out, the leakage position and the internal leakage condition can be rapidly determined, operation is easy and convenient, and the testing work efficiency is high.

Description

Technical Field

[0001] The present invention relates to the technical field of testing devices, and in particular to a testing device and method for a graphite heat exchanger. Background Art

[0002] Graphite heat exchanger is a heat exchange device that uses graphite as a heat transfer element. Due to its excellent thermal conductivity, good corrosion resistance and high temperature stability, graphite has been widely used in chemical, petroleum, pharmaceutical and other industrial fields. Its working principle is that two media with different temperatures flow in graphite blocks or pipes, and heat is transferred from the high-temperature medium to the low-temperature medium through the conduction of graphite materials.

[0003] Before a graphite heat exchanger leaves the factory and after long-term use, it is usually necessary to test its sealing performance in order to ensure the operating safety and heat exchange efficiency of the graphite heat exchanger. When conducting a sealing test, it is usually necessary to seal the air outlets of each independent space in the graphite heat exchanger, and then pass fluid from the air inlet for pressurization to test the sealing performance of the graphite heat exchanger. However, since there are at least two independent spaces in a graphite heat exchanger, it is necessary to inject fluid into two or even more independent spaces for sealing performance testing, which is cumbersome. Summary of the invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a testing device and method for a graphite heat exchanger.

[0005] The present invention provides a testing device and method for a graphite heat exchanger, comprising a graphite heat exchanger, wherein the graphite heat exchanger comprises a tank body, a sealing plate and a heat exchange tube, wherein the number of the sealing plates is two, the two sealing plates are fixedly installed in the tank body, and the tank body and the two sealing plates are combined to form a sealed heat exchange chamber, the number of the heat exchange tubes is multiple, the multiple heat exchange tubes pass through the two sealing plates in sequence, and the openings at both ends of the heat exchange tubes are located outside the heat exchange chamber; It also includes a base plate, on which two placement racks are fixedly mounted, and the graphite heat exchanger is placed on the two placement racks. One end of the heat exchange tube is detachably connected to a pressure measuring tube, and a No. 1 air pressure sensor is installed at the end of the pressure measuring tube. A connecting box is fixedly mounted on the base plate, and a connecting cavity is opened in the connecting box. A plurality of piston tubes connected to the connecting cavity are fixedly connected to the connecting box. The number of the piston tubes is the same as that of the heat exchange tubes and are arranged one by one. The connecting cavity of the connecting box is connected to the air outlet of the base plate, and a No. 2 air pressure sensor is installed at the air inlet of the base plate. A piston is slidably mounted in the piston tube, and a driving structure for driving the piston to slide in the piston tube is installed on the base plate.

[0006] Preferably, a mounting plate No. 1 is detachably mounted on one end of the tank body, and the plurality of pressure measuring tubes are fixedly mounted on the mounting plate No. 1.

[0007] Preferably, a No. 2 mounting plate is detachably mounted on one end of the tank body away from the pressure measuring tube, and the plurality of piston tubes are fixedly mounted on the No. 2 mounting plate.

[0008] Preferably, an air outlet pipe is fixedly mounted on the bottom plate, the air outlet pipe is connected to the heat exchange chamber, a connecting pipe is fixedly mounted on the connecting box, the connecting pipe is connected to the connecting cavity, and a connecting hard pipe is connected between the air outlet pipe and the connecting pipe.

[0009] Preferably, an air intake pipe is fixedly mounted on the bottom plate, the air intake pipe is communicated with the heat exchange chamber, and the second air pressure sensor is fixedly mounted on the end of the air intake pipe.

[0010] Preferably, the driving structure comprises a piston rod, an electric slide rail and a driving disk; the number of the piston rods is the same as the number of the pistons and they are arranged in one-to-one correspondence, one end of the piston rod passes through the connecting box and is fixedly connected to the piston, the electric slide rail is fixedly mounted on the bottom plate, and the driving disk is fixedly mounted on the slider of the electric slide rail; When the driving plate slides, the driving plate can drive the piston rod to move laterally.

[0011] Preferably, the driving structure also includes an electric push rod; the number of the electric push rods is the same as the number of the piston rods and is arranged in one-to-one correspondence, and the multiple electric push rods are fixedly mounted on the driving disk, and the output shaft of the electric push rod is fixedly connected to the end of the piston rod away from the piston.

[0012] A test method for a graphite heat exchanger test device, the test method is as follows: Step 1: Install the graphite heat exchanger on the rack and fix it, and install the test device and the graphite heat exchanger; Step 2: The electric slide rail drives the driving plate to move, and the driving plate drives the piston rod and the piston to move, and the piston slides in the piston tube; Step 3: As the piston slides, record the value changes of multiple pressure sensors No. 1 and No. 2. Step 4: Multiple electric push rods gradually work to record the value changes of multiple No. 1 pressure sensors and No. 2 pressure sensors.

[0013] Preferably, in the step, it is necessary to compare whether the changes in the values ​​recorded by the plurality of No. 1 air pressure sensors are consistent.

[0014] Preferably, in the step, it is necessary to compare whether the value changes recorded by multiple No. 1 air pressure sensors are consistent, and when each electric push rod is replaced, it is necessary to compare and record the value changes of the No. 2 air pressure sensor.

[0015] The present invention provides a testing device and method for a graphite heat exchanger, which have the following beneficial effects: by arranging a bottom plate, a placement rack, a tank body, a sealing plate, a heat exchange tube, a pressure measuring tube, a No. 1 air pressure sensor, a connecting box, a piston tube, a No. 2 air pressure sensor and a driving structure, a plurality of mutually independent spaces in a graphite heat exchanger can be tested simultaneously, mutual verification and comparative tests can be performed, and the location of the leak and the situation of the internal leak can be quickly determined; the operation is simple and convenient, and the test work efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a schematic diagram of the overall structure of a testing device for a graphite heat exchanger.

[0017] Figure 2 A side cross-sectional view of a testing device for a graphite heat exchanger proposed by the present invention.

[0018] Figure 3 The present invention provides a cross-sectional view of the connection between a pressure measuring tube and a heat exchange tube in a testing device for a graphite heat exchanger.

[0019] Figure 4 The present invention provides a cross-sectional view of the connection between a piston tube and a heat exchange tube in a testing device for a graphite heat exchanger.

[0020] Figure 5 This is a cross-sectional view of a driving structure in a testing device for a graphite heat exchanger proposed by the present invention.

[0021] In the figure: 1. bottom plate; 2. placement rack; 3. tank body; 4. sealing plate; 5. heat exchange tube; 6. pressure measuring tube; 7. No. 1 air pressure sensor; 8. connecting box; 9. piston tube; 10. No. 2 air pressure sensor; 11. piston; 12. No. 1 mounting plate; 13. No. 2 mounting plate; 14. outlet pipe; 15. connecting pipe; 16. connecting hard pipe; 17. inlet pipe; 18. piston rod; 19. electric slide rail; 20. drive plate; 21. electric push rod. DETAILED DESCRIPTION

[0022] Reference Figure 1-Figure 5The present invention proposes a testing device for a graphite heat exchanger, including a graphite heat exchanger, the graphite heat exchanger including a tank body 3, a sealing plate 4 and a heat exchange tube 5, the number of the sealing plates 4 is two, the two sealing plates 4 are fixedly installed in the tank body 3, and the tank body 3 and the two sealing plates 4 are combined to form a sealed heat exchange chamber, the two sealing plates 4 and the tank body 3 constitute the shell of the graphite heat exchanger, the number of the heat exchange tube 5 is multiple, the multiple heat exchange tubes 5 all pass through the two sealing plates 4 in sequence, the openings at both ends of the heat exchange tube 5 are both located outside the heat exchange chamber, the middle section of the heat exchange tube 5 is located in the heat exchange chamber, and the structure of the graphite heat exchanger is the prior art.

[0023] like Figure 1 and Figure 2As shown, it also includes a bottom plate 1, on which two placement racks 2 are fixedly installed, and the graphite heat exchanger is placed on the two placement racks 2. One end of the heat exchange tube 5 is detachably connected to a pressure measuring tube 6, and a sealing structure (sealing ring, sealing gasket, etc.) is arranged between the pressure measuring tube 6 and the heat exchange tube 5 to ensure the sealing of the space in the heat exchange tube 5. A No. 1 air pressure sensor 7 is installed at the end of the pressure measuring tube 6, and the end of the pressure measuring tube 6 away from the heat exchange tube 5 is in a blocked state. The No. 1 air pressure sensor 7 is used to measure the air pressure change in the heat exchange tube 5. A connecting box 8 is fixedly installed on the bottom plate 1, and a connecting cavity is opened in the connecting box 8. The connecting box 8 A plurality of piston tubes 9 connected to the connecting cavity are fixedly connected on the top, the number of piston tubes 9 and heat exchange tubes 5 is the same and they are arranged one by one, the connecting cavity of the connecting box 8 is connected to the air outlet of the bottom plate 1, and a No. 2 air pressure sensor 10 is installed at the air inlet of the bottom plate 1, and a piston 11 is slidably installed in the piston tube 9, and the space in the plurality of heat exchange tubes 5 and the heat exchange chamber are separated by the piston 11 to form a plurality of independent spaces, and a driving structure for driving the piston 11 to slide in the piston tube 9 is installed on the bottom plate 1. When performing a sealing test, the driving structure drives the plurality of pistons 11 to slide synchronously at the same time, and as the piston 11 The space in the piston tube 9 is squeezed by the movement, but the gas volume remains unchanged, and the air pressure in the heat exchange tube 5 increases. The air pressure changes in the multiple heat exchange tubes 5 are detected by multiple No. 1 air pressure sensors 7. Assuming that there are 3 heat exchange tubes 5, the air pressure in the first heat exchange tube 5 is A1, the air pressure in the second heat exchange tube 5 is A2, the air pressure in the third heat exchange tube 5 is A3, and the air pressure in the heat exchange chamber is B. When the three pistons 11 are driven to slide synchronously at the same time, when A1=A2=A3 (there is a certain difference, set the difference), it means that the sealing performance of the three heat exchange tubes 5 is consistent and there is no leakage. (In actual situations, there are many heat exchange tubes 5, and it is unlikely that all of them leak. When a leak occurs, the leakage conditions of each heat exchange tube 5 will not remain consistent, so it is judged that the heat exchange tube 5 is not leaking). Assuming that A1=A2>A3, the third heat exchange tube 5 leaks, and its sealing performance fails. The sealing performance of multiple heat exchange tubes 5 can be tested at the same time, and the value change of the air pressure B in the heat exchange chamber can be recorded. The value of the air pressure B in the heat exchange chamber gradually decreases. When the value decreases below the set value, it means that there is a problem with the sealing performance of the heat exchange chamber.

[0024] like Figure 2 and Figure 3 As shown in the figure, one end of the tank body 3 is detachably mounted with a mounting plate No. 12, and a plurality of pressure measuring tubes 6 are fixedly mounted on the mounting plate No. 12. During installation, it is convenient to dock and install the plurality of pressure measuring tubes 6 and the plurality of heat exchange tubes 5, thereby improving work efficiency.

[0025] like Figure 2 and Figure 4As shown in the figure, the end of the tank body 3 away from the pressure measuring tube 6 is detachably mounted with a No. 2 mounting plate 13, and multiple piston tubes 9 are fixedly mounted on the No. 2 mounting plate 13, which facilitates the docking installation of the piston tube 9 and the heat exchange tube 5, simplifies the testing work, and improves the work efficiency.

[0026] like Figure 1 , Figure 2 , Figure 3 and Figure 5 As shown in the figure, an air outlet pipe 14 is fixedly installed on the tank body 3, and the air outlet pipe 14 is connected to the heat exchange chamber. A connecting pipe 15 is fixedly installed on the connecting box 8, and the connecting pipe 15 is connected to the connecting cavity. A connecting hard pipe 16 is connected between the air outlet pipe 14 and the connecting pipe 15. The heat exchange chamber and the connecting cavity are connected by the connecting hard pipe 16 to ensure that the space in the heat exchange chamber remains unchanged. When the piston 11 is slid, it is ensured that the space in the heat exchange chamber and the heat exchange tube 5 are in a mutually related state (the movement of the piston 11 will simultaneously change the pressure in the heat exchange tube 5 and the pressure in the heat exchange chamber).

[0027] like Figure 1 , Figure 2 and Figure 4 As shown in the figure, an air intake pipe 17 is fixedly installed on the tank body 3, and the air intake pipe 17 is connected to the heat exchange chamber. The No. 2 air pressure sensor 10 is fixedly installed at the end of the air intake pipe 17. The air pressure in the heat exchange chamber is detected by the No. 2 air pressure sensor 10, so as to judge whether the tank body 3 is leaking according to the value of the detected air pressure B.

[0028] like Figure 1 , Figure 2 , Figure 4 and Figure 5 As shown in , the driving structure includes a piston rod 18, an electric slide rail 19 and a driving disk 20; the number of piston rods 18 is the same as the number of pistons 11 and is arranged one by one. One end of the piston rod 18 passes through the connecting box 8 and is fixedly connected to the piston 11. The diameter of the piston rod 18 is smaller than the inner diameter of the piston tube 9. The electric slide rail 19 is fixedly mounted on the base plate 1, and the driving disk 20 is fixedly mounted on the slider of the electric slide rail 19. When the driving disk 20 slides, the driving disk 20 can drive the piston rod 18 to move laterally. In the actual test process, the driving disk 20 is driven to slide by the operation of the electric slide rail 19. When the driving disk 20 moves, it pushes multiple piston rods 18 to move synchronously, so that the piston rod 18 pushes the piston 11 to slide in the piston tube 9, thereby changing the air pressure in multiple independent spaces in the graphite heat exchanger, and then comparing and verifying with each other to determine whether the sealing performance of the graphite heat exchanger is qualified.

[0029] In actual situations, there may be many leakage situations. For example, there are two situations regarding the leakage position of the third heat exchange tube 5. One is that the leakage occurs at a position inside the heat exchange chamber, and the second is that the leakage occurs at a position outside the heat exchange chamber. When judging the leakage position of the third heat exchange tube 5, when the leakage position of the third heat exchange tube 5 is inside the heat exchange chamber, during the above operation, the air pressure inside the third heat exchange tube 5 increases more slowly than the air pressure inside the first heat exchange tube 5 and the second heat exchange tube 5, and the air pressure inside the heat exchange chamber decreases more slowly than in the normal state. In addition, there is a leakage in the heat exchange chamber, and additional operations are required for judgment. The specific operations are as follows.

[0030] like Figure 1 , Figure 2 and Figure 5 As shown in , the driving structure also includes an electric push rod 21; the number of the electric push rods 21 is the same as the number of the piston rods 18 and is arranged one by one. The multiple electric push rods 21 are fixedly installed on the driving disk 20, and the output shaft of the electric push rod 21 is fixedly connected to the end of the piston rod 18 away from the piston 11. After the above work, the third heat exchange tube 5 with a sealing performance failure can be tested. At this time, the electric push rod 21 corresponding to the qualified heat exchange tube 5 is selected to work, and the electric push rod 21 drives the corresponding piston rod 18 and piston 11 to move, and records the value change of the No. 1 air pressure sensor 7 on the corresponding heat exchange tube 5, and records the value change of the No. 2 air pressure sensor 10 at the same time, and then resets the electric push rod 21, drives the piston rod 18 and piston 11 to reset, and then the electric push rod 21 corresponding to the third heat exchange tube 5 works to push the corresponding piston rod 18 and piston 11 to move, and records the value change of the corresponding No. 1 air pressure sensor 7 and the value change of the No. 2 air pressure sensor 10. At this time, there are multiple situations, as follows: The first is that a section of the third heat exchange tube 5 located in the heat exchange chamber leaks, and the tank body 3 does not leak. When the piston 11 moves (compressing the gas in the heat exchange tube 5), the amount of gas in the heat exchange chamber and the heat exchange tube 5 remains unchanged, and the pressure drop rate in the third heat exchange tube 5 slows down (compared with the normal heat exchange tube 5 under the same operating state), and the pressure drop rate in the heat exchange chamber will also decrease accordingly. Assume that the drop rate is C. The second type is that a section of the third heat exchange tube 5 located in the heat exchange chamber leaks, and the tank body 3 leaks, driving the piston 11 to slide in the corresponding piston tube 9 (compressing the gas in the heat exchange tube 5), and the air pressure drop speed in the third heat exchange tube 5 slows down, and the drop speed in the heat exchange chamber is C-, the air pressure in the heat exchange chamber decreases, and the gas in the third heat exchange tube 5 enters the heat exchange chamber. In addition, the outside air will also enter the tank body 3 through the leak under the action of the air pressure; The third type is that a section of the third heat exchange tube 5 outside the heat exchange chamber leaks, and the tank body 3 does not leak. When the piston 11 moves (compressing the gas in the heat exchange tube 5), the pressure rise rate in the third heat exchange tube 5 slows down, and the pressure reduction rate in the heat exchange chamber remains at a normal speed. The fourth type is that a section of the third heat exchange tube 5 outside the heat exchange chamber leaks, and the tank body 3 leaks. When the piston 11 moves (compressing the gas in the heat exchange tube 5), the pressure rise rate in the third heat exchange tube 5 slows down, and the pressure decrease rate in the heat exchange chamber slows down (when this situation occurs, it is necessary to drive the piston 11 corresponding to the normal heat exchange tube 5 to move. Since the heat exchange chamber and the heat exchange tube 5 are relatively closed in a normal state, their internal volumes remain unchanged. When the piston 11 moves, although the air is compressed, the added spatial volume of the two does not change, and it can be determined by calculation whether the tank body 3 is leaking). The above operation is simple and convenient, and can simultaneously test the sealing conditions of multiple independent spaces in the graphite heat exchanger, quickly determine which independent space is leaking (including internal leakage), facilitate staff to repair it, and improve the efficiency of detection work.

[0031] The specific test method is as follows: Step 1: Install the graphite heat exchanger on the placement rack 2 and fix it, and install the test device and the graphite heat exchanger; Step 2: The electric slide rail 19 drives the driving disc 20 to move, and the driving disc 20 drives the piston rod 18 and the piston 11 to move, and the piston 11 slides in the piston tube 9; Step 3: As the piston 11 slides, the value changes of the multiple No. 1 air pressure sensors 7 and the No. 2 air pressure sensors 10 are recorded, and it is necessary to compare whether the value changes recorded by the multiple No. 1 air pressure sensors 7 are consistent.

[0032] Step 4: Multiple electric push rods 21 gradually work to record the value changes of multiple No. 1 air pressure sensors 7 and No. 2 air pressure sensors 10. It is necessary to compare whether the value changes recorded by multiple No. 1 air pressure sensors 7 are consistent. When each electric push rod 21 is replaced, it is necessary to compare and record the value changes of No. 2 air pressure sensor 10. In actual operation, for example, when testing the same batch of graphite heat exchangers, the normal sealing air pressure will be around the standard value.

[0033] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A testing device for a graphite heat exchanger, characterized in that: Comprising a graphite heat exchanger, the graphite heat exchanger comprising a tank body (3), a sealing plate (4) and a heat exchange tube (5), the number of the sealing plates (4) being two, the two sealing plates (4) being fixedly mounted in the tank body (3), and the tank body (3) and the two sealing plates (4) being combined to form a sealed heat exchange chamber, the number of the heat exchange tubes (5) being multiple, the multiple heat exchange tubes (5) each passing through the two sealing plates (4) in sequence, and the openings at both ends of the heat exchange tube (5) being located outside the heat exchange chamber; It also includes a base plate (1), on which two placement racks (2) are fixedly mounted, and the graphite heat exchanger is placed on the two placement racks (2); one end of the heat exchange tube (5) is detachably connected to a pressure measuring tube (6), and a first air pressure sensor (7) is installed at the end of the pressure measuring tube (6); a connecting box (8) is fixedly mounted on the base plate (1), and a connecting cavity is opened in the connecting box (8); a plurality of piston tubes (9) connected to the connecting cavity are fixedly connected to the connecting box (8), and the number of the piston tubes (9) is the same as that of the heat exchange tubes (5) and they are arranged one by one; the connecting cavity of the connecting box (8) is connected to the air outlet of the base plate (1), and a second air pressure sensor (10) is installed at the air inlet of the base plate (1); a piston (11) is slidably mounted in the piston tube (9), and a driving structure for driving the piston (11) to slide in the piston tube (9) is installed on the base plate (1).

2. A testing device for a graphite heat exchanger according to claim 1, characterized in that: A first mounting plate (12) is detachably mounted on one end of the tank body (3), and a plurality of pressure measuring tubes (6) are fixedly mounted on the first mounting plate (12).

3. A testing device for a graphite heat exchanger according to claim 2, characterized in that: A second mounting plate (13) is detachably mounted on one end of the tank body (3) away from the pressure measuring tube (6), and the plurality of piston tubes (9) are fixedly mounted on the second mounting plate (13).

4. A testing device for a graphite heat exchanger according to claim 1, characterized in that: An air outlet pipe (14) is fixedly mounted on the tank body (3), the air outlet pipe (14) being in communication with the heat exchange chamber; a connecting pipe (15) is fixedly mounted on the connecting box (8), the connecting pipe (15) being in communication with the connecting chamber; a connecting hard pipe (16) is in communication between the air outlet pipe (14) and the connecting pipe (15).

5. The testing device for graphite heat exchanger according to claim 1, characterized in that: An air intake pipe (17) is fixedly mounted on the tank body (3), the air intake pipe (17) is in communication with the heat exchange chamber, and the second air pressure sensor (10) is fixedly mounted at the end of the air intake pipe (17).

6. A testing device for a graphite heat exchanger according to claim 1, characterized in that: The driving structure comprises a piston rod (18), an electric slide rail (19) and a driving disk (20); the number of the piston rods (18) is the same as the number of the pistons (11) and they are arranged in a one-to-one correspondence; one end of the piston rod (18) passes through the connecting box (8) and is fixedly connected to the piston (11); the electric slide rail (19) is fixedly mounted on the bottom plate (1); and the driving disk (20) is fixedly mounted on a slider of the electric slide rail (19); When the driving plate (20) slides, the driving plate (20) can drive the piston rod (18) to move laterally.

7. A testing device for a graphite heat exchanger according to claim 6, characterized in that: The driving structure further comprises an electric push rod (21); the number of the electric push rods (21) is the same as the number of the piston rods (18) and they are arranged in a one-to-one correspondence; the plurality of electric push rods (21) are fixedly mounted on the driving disk (20); and the output shaft of the electric push rod (21) is fixedly connected to the end of the piston rod (18) away from the piston (11).

8. A method for testing a graphite heat exchanger testing device, using a testing device for a graphite heat exchanger according to any one of claims 1 to 7, characterized in that: The test method is as follows: Step 1: Install the graphite heat exchanger on the placement rack (2) and fix it, and install the test device and the graphite heat exchanger; Step 2: The electric slide rail (19) drives the driving plate (20) to move, and the driving plate (20) drives the piston rod (18) and the piston (11) to move, and the piston (11) slides in the piston tube (9); Step 3: As the piston (11) slides, the value changes of the plurality of air pressure sensors No. 1 (7) and No. 2 (10) are recorded. Step 4: The plurality of electric push rods (21) gradually work to record the value changes of the plurality of No. 1 air pressure sensors (7) and No. 2 air pressure sensors (10).

9. A testing device and method for a graphite heat exchanger according to claim 8, characterized in that: In step 3, it is necessary to compare whether the changes in the values ​​recorded by the multiple No. 1 air pressure sensors (7) are consistent.

10. A testing device and method for a graphite heat exchanger according to claim 8, characterized in that: In step 4, it is necessary to compare the value changes recorded by the plurality of No. 1 air pressure sensors (7) to see whether they are consistent. When each electric push rod (21) is replaced, it is necessary to compare and record the value changes of the No. 2 air pressure sensor (10).

Images