Aggregate soft particle tester and use method thereof

Abstract

The invention discloses an aggregate soft particle tester and a use method thereof. According to the tester, aggregate does not need to be pressurized one by one on a testing machine, crushed particles do not need to be selected for the pressurized aggregate, the tester can be operated automatically, the loading process is controlled by a controller, and the requirement of constant-speed loading can be met; the tester has data calculation and storage functions, and can directly calculate and display the content of the soft particles in the aggregate. By using the tester, the test time of the aggregate soft particles can be shortened, and the working efficiency is improved. Meanwhile, the influence on the result caused by impact damage of sample particles due to non-uniform speed in the loading process is avoided; through the square hole sieve, the phenomenon that particles with slight corner falling are judged to be soft particles can be effectively avoided; therefore, the accuracy of test results is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aggregate particle determination, and in particular relates to an aggregate soft particle determination instrument and a use method thereof. Background Art

[0002] The weak particles in the aggregate mainly affect the strength and durability of the concrete. The higher the content of the weak particles in the aggregate, the lower the strength of the concrete. Secondly, due to the poor volume stability of the weak particles, the durability of the concrete is poor. Therefore, the content of the weak particles in the aggregate needs to be strictly controlled.

[0003] According to the "Test Procedure for Sand and Gravel Aggregates for Hydraulic Concrete" DL / T5151-2014, "Test Procedure for Hydraulic Concrete" SL / T352-2020 and "Test Procedure for Highway Engineering Aggregates" JTG 3432-2024, the steps for the weak particle test are as follows: select an appropriate amount of representative aggregates, process them according to the requirements of the specifications, and screen them according to different particle sizes; select the number of particles required by the specifications, weigh and record them; pressurize each particle according to the compressive load corresponding to different particle sizes; the crushed particles are weak particles, and after removing them, weigh the mass of the remaining unbroken particles; the weak particle content value corresponding to each particle size can be calculated according to the weak particle content calculation formula.

[0004] Crushed particles refer to particles that are obviously broken and do not include particles with slightly chipped corners.

[0005] In summary, the existing practice requires pressurizing the aggregates one by one. According to different specifications, the minimum number of tests is 100 particles. The test workload is large and it takes a lot of time to pressurize each particle. Secondly, if the pressurization load is not well controlled during the pressurization process, the sample particles will be damaged by impact, resulting in larger values ​​measured in the test, which will affect the judgment of the aggregate quality.

[0006] The patent document with the announcement number CN112113845A discloses an aggregate weak particle tester, which has the following structure: the support column is fixedly connected to the center position of the rear side of the bottom plate surface, the limit nut is screwed into the appropriate position of the upper threaded structure of the support column, and then the pressure device is placed on the upper part of the support column, and the pressure device is moved down to the limit nut by adjusting the up and down moving handle on the pressure device. The pressure device also includes a pressure handle and a slider, the front of the slider is fixedly connected to a fixed plate, the force gauge is fixedly connected to the fixed plate, and the lower part of the force gauge is provided with a screw-type pressure sensor, and the pressure plate is connected to the pressure sensor by a nut welded at the center position of its upper surface; a pressure plate is placed at the axial position directly below the pressure plate, and the pressure plate is fixedly connected to the bottom plate by a hexagon socket screw, and a circular collar is placed at the center of the pressure plate. The invention does not set a weighing component, and it fails to solve the technical problem of avoiding judging particles with slightly off corners as weak particles.

[0007] The patent document with the announcement number CN109632626A discloses a measuring needle and a measuring method for the content of weak particles in concrete coarse aggregate, and relates to a measuring needle and a measuring method for the content of weak particles. The purpose is to solve the problems of poor operability and large errors in the determination of the content of weak particles. The measuring needle is composed of a connecting rod and a measuring head; the measuring head is a cylinder, one end face of the measuring head is a concave spherical surface, the outer circumferential surface of the upper end of the connecting rod is provided with a thread, and the lower end of the connecting rod is fixedly connected to the plane end of the measuring head. Measuring method: the measuring needle is installed on the chuck of the penetration resistance meter, a supporting platform is placed below, a concrete coarse aggregate particle is placed on the supporting platform and pressure is applied. The invention combines the penetration resistance meter to measure the content of weak particles in concrete coarse aggregate, and can ensure that the applied pressure control range is within 0 to 1000N. The invention also does not set a weighing component. If it is necessary to test samples of different particle sizes, repeated measurements are carried out because the structure for holding aggregates is fixed and it is not convenient to remove excess aggregates. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides an aggregate soft particle measuring instrument and a use method thereof.

[0009] The present invention is achieved through the following technical solutions.

[0010] The present invention provides an aggregate soft particle measuring instrument, which comprises a test box and a control system. The test box is connected to the control system. A loading component, a screening component and a weighing component are sequentially arranged in the test box from top to bottom. The loading component, the screening component and the weighing component are electrically connected to the control system respectively.

[0011] Preferably, the loading assembly includes a loading pressure head and a pressure plate, the loading pressure head is connected to the inner wall of the test box through a hydraulic cylinder system, the pressure plate is connected to the inner wall of the test box, a pressure rod is arranged on the loading pressure head, a box door is arranged on one side of the test box, a handle is arranged on the box door, and the box door is hinged to the test box.

[0012] Preferably, a sample particle position point is set on the pressure plate, and the sample particle position point is set in the form of an arc-shaped through hole. The maximum sizes of the sample particle position point include 10mm, 16mm, 20mm, 31.5mm and 40mm respectively. The force measuring range of the hydraulic cylinder system is 0-1000N, the accuracy is 10N, and the displacement stroke is not less than 50mm.

[0013] Preferably, the screening assembly includes a square hole sieve and a support, the square hole sieve is connected to the top of the support, the square hole sieve has a nominal particle size of 10 mm, 16 mm, 20 mm, 31.5 mm and 40 mm, and the support is arranged on the hopper of the weighing assembly.

[0014] Preferably, the weighing assembly includes a weighing platform and a hopper, the weighing platform is arranged at the bottom of the test box, the hopper is arranged above the weighing platform, the hopper is connected to the inner wall of the test box, the maximum range of the weighing platform is 5kg, and the sensitivity is not greater than 1g.

[0015] Preferably, the control system comprises a touch screen, a power switch and a data interface, and the touch screen, the power switch and the data interface are arranged on the front of the control system, and a battery is arranged in the control system.

[0016] A method for using an aggregate soft particle measuring instrument comprises the following steps:

[0017] 1) Prepare and make test samples, and process the samples according to different regulations;

[0018] 2) According to the particle size of the sample, select and install the pressure plate and square hole sieve of appropriate size, open the measuring instrument box door, and install them in the corresponding positions of the loading area and screening area;

[0019] 3) Turn on the power switch of the analyzer, and the status light of the analyzer will light up, indicating that the analyzer is working normally; pour the sample to be tested into the pressure plate and close the analyzer box door; enter the main interface of the control system and operate the control system through the touch screen;

[0020] 4) Enter the procedure selection interface. After selecting the procedure, click the return button to enter the main interface;

[0021] 5) Enter the information entry interface, enter the sample number, tester, test time, and initial quality information of the sample to be tested, and click the return button to enter the main interface;

[0022] 6) Click the Start Test button to enter the Start Test interface. At the same time, the system performs the measurement steps in the order of loading, screening and weighing. According to the entered sample particle size, the system automatically matches the corresponding loading speed and controls the loading of the loading head through the hydraulic cylinder system. After the loading is completed, the pressure plate is separated from the disconnection point, so that all the particles on the pressure plate fall into the square hole sieve.

[0023] Start the support vibration screening mode to make the square hole screen vibrate, and the particles under the screen are collected on the weighing platform through the hopper; after the screening is completed, the weighing platform automatically weighs and records the mass of the particles under the screen. After completion, click the return button to enter the main interface;

[0024] 7) If it is necessary to test samples of different particle sizes, repeat steps 2) to 6) to conduct the soft particle test of the next particle size sample;

[0025] 8) After all the particle size samples are tested, the measuring instrument will automatically calculate the mass and content of weak particles in each grade of samples; if it is a continuous grading, the measuring instrument will automatically calculate the proportion of different particle sizes, and calculate and display the sum of the product of the proportion of different particle sizes and the content of weak particles, which is the content of weak particles in the continuous grading. Click the return button to enter the main interface;

[0026] 9) Click the data export button to enter the data output interface; this interface records and displays all test data, and you can choose to export all or part of the data or delete the data according to your needs; when exporting data, you need to connect the external storage device at the data interface, select the data to be exported, and click the data export button to copy the relevant data generated during the test to the external storage device.

[0027] Preferably, in step 1), the sample is processed according to different regulations. For example, for the DL standard and the SL standard, the aggregate needs to be soaked in water for more than 8 hours, and after being taken out, the water film on the surface of the particles is wiped off with a wrung wet towel, and the aggregate is sieved into three particle sizes of 5-10 mm, 10-20 mm and 20-40 mm, and the needle-like particles are selected, and the rest are used as samples to be tested;

[0028] According to the JTG standard, the aggregate is soaked in water, and the surface of the particles is quickly scrubbed with a wire brush. After repeated rinsing until the water is visually clear, it is drained and dried at 105℃±5℃ until the surface is dry. The drying time does not exceed 4h. After cooling to room temperature, it is sieved into three particle sizes of 4.75-9.5mm, 9.5-16mm and 16-31.5mm as the samples to be tested. When a certain particle size in the sample is less than 10%, the particles of this particle size will not be tested.

[0029] Preferably, in the step 3), the power switch of the measuring instrument is turned on, and the status light of the measuring instrument is on, indicating that the measuring instrument is working normally; the sample to be tested with a weight of m1 is poured into the pressure plate, and the sample is moved by hand to fill the sample particle position points on the pressure plate, and the excess sample is taken out and weighed after its weight m2; the measuring instrument box door is closed; the main interface of the control system is entered, and the control system is operated through the touch screen;

[0030] Preferably, in step 4), after entering the procedure selection interface, the measuring instrument includes three options: JTG 3432-2024, DL / T5151-2014 and SL / T 352-2020. After the procedure version is invalidated, the system will automatically update the latest version of the procedure.

[0031] The beneficial effects of the present invention are:

[0032] The use of the present invention can shorten the test time of aggregate soft particles and improve work efficiency; at the same time, on the one hand, it avoids the influence of uneven loading speed on the results when using manual loading; on the other hand, it avoids the phenomenon of judging particles with slightly chipped corners as soft particles, thereby improving the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the present invention;

[0034] Figure 2 It is a front view structural schematic diagram of the present invention;

[0035] Figure 3 It is a schematic diagram of the structure of region A of the present invention;

[0036] Figure 4 It is a structural schematic diagram of the pressure plate of the present invention;

[0037] Figure 5 It is a structural schematic diagram of the sample particle position point of the present invention;

[0038] Figure 6 is a schematic diagram of a menu page of a display screen of the present invention;

[0039] Figure 7 is a schematic diagram of a protocol selection page of the present invention;

[0040] Figure 8 It is a schematic diagram of the information entry page of the present invention;

[0041] Fig. 9 is a schematic diagram of a test page of the present invention;

[0042] Fig.10 is a schematic diagram of a test result page of the present invention;

[0043] Fig.11 is a schematic diagram of a test result page of the present invention;

[0044] Fig.12 is a schematic diagram of a data output page of the present invention;

[0045] In the figure: 11-loading pressure head, 111-pressure rod, 12-pressure plate, 13-sample particle position point, 14-disconnection point, 15-hydraulic cylinder system, 21-square hole screen, 22-support, 31-weighing table, 32-hopper, 4-touch screen, 5-power switch, 6-data interface, 7-box door, 8-handle. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0047] Example:

[0048] like Figures 1 to 12 As shown, an aggregate weak particle measuring instrument includes a test box and a control system. The test box is connected to the control system. A loading component, a screening component and a weighing component are sequentially arranged in the test box from top to bottom. The loading component, the screening component and the weighing component are electrically connected to the control system respectively. The external dimensions of the test box are 900mm×400mm×600mm. The control system can be arranged in the test box for protection. The material of the test box is stainless steel. The main functions of the control system include procedure selection, information entry, automatic loading of sample particles, automatic screening of loaded particles, automatic weighing of screened particles, automatic calculation and display of weak particle content at each level of the sample, automatic calculation and display of weak particle content of the continuously graded sample, and export or deletion of data.

[0049] The loading assembly includes a loading head 11 and a pressure plate 12. The loading head 11 is connected to the inner wall of the test box through a hydraulic cylinder system 15. The pressure plate 12 is connected to the inner wall of the test box. A pressure rod 111 is arranged on the loading head 11. 100 pressure rods 111 can be arranged or other numbers can be arranged as needed. A box door 7 is arranged on one side of the test box. A handle 8 is arranged on the box door 7. The box door 7 is hinged to the test box.

[0050] The pressure plate 12 is provided with sample particle position points 13, the number and positions of the sample particle position points 13 correspond to the pressure rod 111, the sample particle position points 13 are provided as arc-shaped through holes, the maximum sizes of the sample particle position points 13 include 10mm, 16mm, 20mm, 31.5mm and 40mm respectively, the force measuring range of the hydraulic cylinder system 15 is 0-1000N, the accuracy is 10N, and the displacement stroke is not less than 50mm.

[0051] The screening component includes a square hole screen 21 and a support 22. The square hole screen 21 and the support 22 are connected at the top. The square hole screen has a nominal particle size of 10 mm, 16 mm, 20 mm, 31.5 mm and 40 mm. The support 22 is arranged on the hopper 32 of the weighing component. The support 22 is used to provide vibration so that the sample in the square hole screen 21 is vibrated and screened. The use of the square hole screen 21 can effectively avoid judging particles with slightly off corners as weak particles.

[0052] The weighing assembly includes a weighing platform 31 and a hopper 32. The weighing platform 31 is arranged at the bottom of the test box, and the hopper 32 is arranged above the weighing platform 31. The hopper 32 is connected to the inner wall of the test box. The maximum range of the weighing platform 31 is 5kg, and the sensitivity is not greater than 1g. The function of the hopper 32 is to collect the particles sieved out by the square hole sieve 21 on the weighing platform 31, so as to weigh the mass of the sieved particles.

[0053] The control system includes a touch screen 4, a power switch 5 and a data interface 6, wherein the touch screen 4, the power switch 5 and the data interface 6 are arranged on the front of the control system, and a storage battery is arranged in the control system.

[0054] A method for using an aggregate soft particle measuring instrument comprises the following steps:

[0055] 1) Prepare and make test samples, and process the samples according to different regulations. For example, for DL ​​standard and SL standard, the aggregate needs to be soaked in water for more than 8 hours, and then wipe off the water film on the surface of the particles with a wrung wet towel, and sieve into three particle sizes of 5-10mm, 10-20mm and 20-40mm. Pick out the needle-like particles, and the rest are used as samples to be tested;

[0056] According to the JTG standard, the aggregate is soaked in water, and the surface of the particles is quickly scrubbed with a wire brush. After repeated rinsing until the water is visually clear, it is drained and dried at 105℃±5℃ until the surface is dry. The drying time does not exceed 4h. After cooling to room temperature, it is sieved into three particle sizes of 4.75-9.5mm, 9.5-16mm and 16-31.5mm as the samples to be tested. When a certain particle size in the sample is less than 10%, the particles of this particle size will not be tested.

[0057] 2) According to the particle size of the sample, select and install the pressure plate 12 and the square hole sieve 21 of appropriate size, open the measuring instrument box door 7, and install them at the corresponding positions of the loading area and the screening area;

[0058] 3) Turn on the power switch 5 of the measuring instrument, and the status light of the measuring instrument lights up, indicating that the measuring instrument is working normally; pour the sample to be tested with a mass m1 into the pressure plate 12, move the sample by hand to make it occupy the sample particle position point 13 on the pressure plate 12, and take out the excess sample and weigh its mass m2; close the measuring instrument box door 7; enter the main interface of the control system, and operate the control system through the touch screen 4;

[0059] 4) Enter the procedure selection interface. The measuring instrument includes three options: JTG 3432-2024, DL / T5151-2014 and SL / T 352-2020. After the procedure version is invalidated, the system will automatically update the latest version of the procedure. After selecting the procedure, click the return button to enter the main interface;

[0060] 5) Enter the information entry interface, input the sample number, tester, test time, initial mass of the sample to be tested (m1-m2) and sample particle size information, click the return button to enter the main interface;

[0061] 6) Click the Start Test button to enter the Start Test interface. At the same time, the system performs the measurement steps in the order of loading, screening and weighing. According to the entered sample particle size, the system automatically matches the corresponding loading speed, controls the loading of the loading pressure head 11 through the hydraulic cylinder system 15, and inserts the pressure rod 111 into the sample particle position point 13 to ensure uniform loading without impact damage to the sample. After loading is completed, the pressure plate 12 is separated from the disconnection point 14, so that all the particles on the pressure plate 12 fall into the square hole sieve 21;

[0062] Start the vibration screening mode of the support 22 to make the square hole screen 21 vibrate, and the particles under the screen are collected on the weighing platform 31 through the hopper 32; after the screening is completed, the weighing platform 31 automatically weighs and records the mass of the particles under the screen. During the test, the entire test process can be intuitively understood through the touch screen 4, such as the parameter values ​​of the loading speed, the pressurized load, and the displacement stroke. At the same time, the process record displays the entire test step flow, records and displays the test time, and the information of the relevant data records. After completion, click the return button to enter the main interface;

[0063] 7) If it is necessary to test samples of different particle sizes, repeat steps 2) to 6) to conduct the soft particle test of the next particle size sample;

[0064] 8) After all the particle size samples are tested, the measuring instrument will automatically calculate the mass and content of weak particles in each grade of samples; if it is a continuous grading, the measuring instrument will automatically calculate the proportion of different particle sizes, and calculate and display the sum of the product of the proportion of different particle sizes and the content of weak particles, which is the content of weak particles in the continuous grading. Click the return button to enter the main interface;

[0065] 9) Click the data export button to enter the data output interface; this interface records and displays all test data, and you can choose to export all or part of the data or delete the data according to your needs; when exporting data, you need to connect the external storage device U disk at the data interface 6, select the data to be exported, and click the data export button to copy the relevant data generated during the test to the external storage device U disk. The data interface 6 can be a USB interface.

Claims

1. An aggregate soft particle measuring instrument, characterized in that: The test box comprises a test box and a control system, wherein the test box is connected to the control system, wherein a loading component, a screening component and a weighing component are sequentially arranged in the test box from top to bottom, and the loading component, the screening component and the weighing component are electrically connected to the control system respectively.

2. The aggregate soft particle measuring instrument according to claim 1, characterized in that: The loading assembly comprises a loading pressure head (11) and a pressure plate (12); the loading pressure head (11) is connected to the inner wall of the test box through a hydraulic cylinder system (15); the pressure plate (12) is connected to the inner wall of the test box; a disconnection point (14) is provided on the pressure plate (12); a pressure rod (111) is provided on the loading pressure head (11); a box door (7) is provided on one side of the test box; a handle (8) is provided on the box door (7); and the box door (7) is hinged to the test box.

3. An aggregate weak particle measuring instrument as claimed in claim 2, characterized in that: The pressure plate (12) is provided with a sample particle position point (13), the sample particle position point (13) is provided in the form of an arc-shaped through hole, the maximum values ​​of the sizes of the sample particle position point (13) are 10 mm, 16 mm, 20 mm, 31.5 mm and 40 mm, respectively, the hydraulic cylinder system (15) has a force measuring range of 0-1000 N, an accuracy of 10 N, and a displacement stroke of not less than 50 mm.

4. The aggregate soft particle measuring instrument according to claim 1, characterized in that: The screening component comprises a square hole screen (21) and a support (22), wherein the square hole screen (21) and the support (22) are connected at the top, the square hole screen has a nominal particle size of 10 mm, 16 mm, 20 mm, 31.5 mm and 40 mm, and the support (22) is arranged on a hopper (32) of a weighing component.

5. The aggregate soft particle measuring instrument according to claim 1, characterized in that: The weighing assembly comprises a weighing platform (31) and a hopper (32); the weighing platform (31) is arranged at the bottom of the test box; the hopper (32) is arranged above the weighing platform (31); the hopper (32) is connected to the inner wall of the test box; the maximum measuring range on the weighing platform (31) is 5kg, and the sensitivity is not greater than 1g.

6. The aggregate soft particle measuring instrument according to claim 1, characterized in that: The control system comprises a touch screen (4), a power switch (5) and a data interface (6); the touch screen (4), the power switch (5) and the data interface (6) are arranged on the front of the control system; and a storage battery is arranged in the control system.

7. A method for using the aggregate soft particle measuring instrument according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) Prepare and make test samples, and process the samples according to different regulations; 2) According to the particle size of the sample, a pressure plate (12) and a square hole sieve (21) of appropriate size are selected and installed, the measuring instrument box door (7) is opened, and the plates are installed at corresponding positions of the loading area and the screening area; 3) Turn on the power switch (5) of the measuring instrument, and the status light of the measuring instrument lights up, indicating that the measuring instrument is working normally; pour the sample to be tested into the pressure plate (12), and close the measuring instrument box door (7); enter the main interface of the control system, and operate the control system through the touch screen (4); 4) Enter the procedure selection interface. After selecting the procedure, click the return button to enter the main interface; 5) Enter the information entry interface, input the sample number, tester, test time, and initial quality of the sample to be tested, and click the return button to enter the main interface; 6) Click the start test button to enter the start test interface, and the system performs the measurement steps in the order of loading, screening and weighing. According to the entered sample particle size, the system automatically matches the corresponding loading speed, and controls the loading of the loading head (11) through the hydraulic cylinder system (15). After the loading is completed, the pressure plate (12) is separated from the disconnection point (14), so that all the particles on the pressure plate (12) fall into the square hole sieve (21); The support (22) is started to vibrate the square hole screen (21), and the particles under the screen are collected on the weighing platform (31) through the hopper (32); after the screening is completed, the weighing platform (31) automatically weighs and records the mass of the particles under the screen, and after completion, click the return button to enter the main interface; 7) If it is necessary to test samples of different particle sizes, repeat steps 2) to 6) to conduct the soft particle test of the next particle size sample; 8) After all the particle size samples are tested, the measuring instrument will automatically calculate the mass and content of weak particles in each grade of samples; if it is a continuous grading, the measuring instrument will automatically calculate the proportion of different particle sizes, and calculate and display the sum of the product of the proportion of different particle sizes and the content of weak particles, which is the content of weak particles in the continuous grading. Click the return button to enter the main interface; 9) Click the data export button to enter the data export interface; this interface records and displays all test data, and you can choose to export all or part of the data or delete the data according to your needs; when exporting data, you need to connect an external storage device at the data interface (6), select the data to be exported, and click the data export button to copy the relevant data generated during the test to the external storage device.

8. The method for using the aggregate soft particle measuring instrument according to claim 7, characterized in that: In the step 1), the sample is processed according to different regulations. For example, according to the DL standard and the SL standard, the aggregate needs to be soaked in water for more than 8 hours, and after being taken out, the water film on the surface of the particles is wiped off with a wrung wet towel, and the aggregate is sieved into three particle sizes of 5-10 mm, 10-20 mm and 20-40 mm, and the needle-like particles are selected, and the rest are used as samples to be tested; According to the JTG standard, the aggregate is soaked in water, the surface of the particles is quickly scrubbed with a wire brush, and rinsed several times until the water is visually clear, then drained and dried at 105℃±5℃ until the surface is dry. The drying time shall not exceed 4h, and the aggregate is cooled to room temperature and sieved into three particle sizes of 4.75-9.5mm, 9.5-16mm and 16-31.5mm as the samples to be tested. When a particle size in the sample is less than 10%, the particles of that particle size will not be tested.

9. The method for using the aggregate soft particle measuring instrument according to claim 7, characterized in that: In the step 3), the power switch (5) of the measuring instrument is turned on, and the status light of the measuring instrument is on, indicating that the measuring instrument is working normally; the sample to be tested with a mass m1 is poured into the pressure plate (12), and the sample is moved by hand so that it fills the sample particle position points (13) on the pressure plate, and the excess sample is taken out and its mass m2 is weighed; the measuring instrument box door (7) is closed; the control system main interface is entered, and the control system is operated through the touch screen (4).

10. The method for using the aggregate soft particle measuring instrument according to claim 7, characterized in that: In the step 4), after entering the procedure selection interface, the measuring instrument includes three options: JTG3432-2024, DL / T 5151-2014 and SL / T 352-2020. After the procedure version is invalidated, the system will automatically update the latest version of the procedure.

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