Rapid detection method for sealing defect construction site of waterproof and moistureproof container

Abstract

The method aims to solve the problems that an Internet of Things detection device or some mechanical structures are deployed in an outdoor waterproof and moistureproof container, the sealing positions are many, the sealing structure is complex, and installation and sealing performance detection of the container need to be carried out on a construction site. According to the method, a differential pressure digital twinborn model without sealing defects is established according to the characteristic that the air pressure in a cavity changes along with the gas quantity when the capacity of the cavity of the container is constant, and is compared with a differential pressure value of the container in the exhaust process measured in real time by a differential pressure sensor; and when the actually measured differential pressure value is obviously smaller than and deviates from the differential pressure digital twinborn value without the sealing defect within a period of time and the deviation value reaches a judgment threshold value given by an engineering specification, indicating that the container has the sealing defect which cannot be ignored, thereby constructing a sealing defect detection system of the waterproof and moistureproof container. The invention provides a method for quickly detecting the sealing defect of a waterproof and moistureproof container by utilizing negative pressure on a construction site.

Description

Technical Field

[0001] This invention relates to a non-destructive, rapid on-site detection method for sealing defects in waterproof and moisture-proof containers. Outdoor IoT detection devices or certain specialized mechanical structures need to be placed inside waterproof and moisture-proof containers. These containers have multiple sealing points and complex sealing structures, requiring on-site installation, sealing treatment, and sealing performance testing. This invention provides a rapid on-site detection method for sealing defects in waterproof and moisture-proof containers using negative pressure. Background Technology

[0002] To ensure the safe and stable operation of IoT testing devices or certain mechanical structures outdoors, these devices need to be deployed in sealed, waterproof, and moisture-proof protective containers. These devices and the waterproof and moisture-proof containers (hereinafter referred to as containers) often need to be installed or assembled on-site, with multiple sealing points and complex sealing structures. After the devices are deployed on-site, the sealing performance of the containers needs to be tested. Generally, sealing performance testing is conducted in a laboratory, while on-site testing currently relies mainly on visual inspection for sealing defects. After visual inspection and operation, and following a period of rain and / or significant changes in external humidity, the container is checked for water ingress or humidity changes to determine if there are any sealing defects, and these defects are repaired. For environments where personnel cannot easily access, or where moisture (water ingress) would degrade the performance of the protected device, it is desirable to avoid observing sealing defects after commissioning and then repairing them. Instead, it is desirable to quickly perform non-destructive testing on the container's sealing defects before (or after) the IoT testing devices are installed, promptly identifying and repairing sealing defects before commissioning. This invention provides a rapid detection method for sealing defects in waterproof and moisture-proof containers at outdoor construction sites. Summary of the Invention

[0003] This invention provides a rapid on-site detection method for sealing defects in waterproof and moisture-proof containers using negative gas pressure. This method is applicable to the rapid on-site detection of sealing defects in waterproof and moisture-proof containers with constant volume. At a certain temperature, when the volume of the container cavity (hereinafter referred to as the cavity) is constant, the amount of gas inside the cavity decreases, and the gas pressure inside the cavity also decreases according to a certain pattern. This characteristic is used to establish a differential pressure digital twin model under a defect-free state. After the container and the protected device are sealed on-site, only one easily sealed threaded mounting hole (or threaded sealing process hole) is left. This hole can be easily sealed using a sealing gasket and threads. During on-site sealing defect detection, a negative pressure suction probe is connected through this hole. After detection, the threaded mounting hole of the cover is sealed with a sealing gasket (or sealant). A vacuum pump with a certain exhaust volume is used to extract gas from the cavity through the negative pressure exhaust probe. The exhaust process is controlled by a detection and exhaust control circuit to ensure that the negative pressure inside the cavity is within a safe range to prevent new sealing defects. A gas differential pressure sensor is used to measure the differential pressure between the gas pressure inside the exhaust chamber and atmospheric pressure in real time during the exhaust process. The real-time measured differential pressure value is compared with the corresponding value in a differential pressure digital twin model without sealing defects. The sealing performance of the container is evaluated by determining whether the real-time measured differential pressure value deviates significantly from the digital twin value without sealing defects over a period of time during the exhaust process.

[0004] (1) Differential pressure inside and outside the cavity and sealing performance

[0005] This method can detect sealing defects in temperatures ranging from -55℃ to 150℃, and the gases involved can be approximated as ideal gases, based on the ideal gas law:

[0006]

[0007] Where P: pressure; V: standard specific volume of air, V = 0.7727 m³ 3 / kg; m: amount of substance; Rg: gas constant (gas constant of air Rg=0.287J / kg); T: absolute temperature.

[0008] Utilizing exhaust volume A vacuum pump (L / min) vents (evacuates) the chamber under test, with a gas discharge rate of m. x The relationship with time t is shown in formula (2), where Standard density of air .

[0009]

[0010] If the tested cavity has no sealing defects (no air intake), as the exhaust time t increases, the amount of residual gas m in the cavity will increase. x Corresponding air pressure Px (Hereinafter referred to as residual pressure) and gas discharge rate m x Relationship:

[0011]

[0012] Where m0 is the amount of gas in the cavity in the initial state, and the corresponding gas pressure inside the container is atmospheric pressure. Therefore, we can obtain

[0013]

[0014] At this time, the pressure difference between the gas inside the cavity and the gas outside the cavity (atmospheric pressure) is called differential pressure P. c This can be described using formula (4):

[0015]

[0016] Formula (4) is a differential pressure model for the tested cavity without sealing defects during the exhaust process.

[0017] If the cavity being tested has a sealing defect, gas will enter through the sealing defect while gas is being extracted. This will cause a difference between the differential pressure change detected in real time by the gas differential pressure sensor during the exhaust process and the formula (4). Let P be the differential pressure detected in real time by the gas differential pressure sensor during the exhaust process (referred to as the measured differential pressure). cs If it is indicated, then it must be true that:

[0018]

[0019] (2) Differential pressure digital twin model without sealing defects during exhaust process

[0020] The rated exhaust capacity of the air pump is As the remaining air pressure P in the cavity x The decrease (differential pressure P) C As the pressure increases, the exhaust volume δ of the pump will also decrease. The exhaust volume δ and the differential pressure P C It exhibits a certain degree of nonlinearity. To ensure that negative pressure does not cause new sealing defects, the maximum differential pressure generated within this negative pressure range in this test method is P. CM Exhaust flow rate and differential pressure P C The relationship can be approximated by linear characteristics. Therefore, when the container has no sealing defects, the exhaust volume δ and the differential pressure P... C The relationship can be expressed by formula (6), where P CM Determined by engineering construction specifications.

[0021]

[0022] Formula (4) can be further expressed as formula (7).

[0023]

[0024] The solution can be found to be:

[0025]

[0026] Formula (7) is used as the differential pressure digital twin model of the test cavity without sealing defects during the exhaust process (hereinafter referred to as differential pressure digital twin model).

[0027] (3) Real-time detection of differential pressure inside and outside the cavity during exhaust process

[0028] During the exhaust process, a gas differential pressure sensor is used to measure the pressure difference between the gas inside the chamber and the gas outside the chamber (atmospheric pressure) in real time. If the sensitivity of the gas differential pressure sensor is Sn (the sensitivity Sn of the gas differential pressure sensor is a constant), the output signal P of the gas differential pressure sensor... s The measured pressure difference P between the cavity and atmospheric pressure cs The relationship is (If it is a digital sensor, the differential pressure measurement value can be read directly, in which case Sn can be considered as 1). The output signal of the gas differential pressure sensor is a directly measurable signal. This is achieved by measuring the output signal P of the gas differential pressure sensor. s This allows us to obtain the measured differential pressure P of the tested cavity. cs As shown in formula (8):

[0029]

[0030] (4) Identification and judgment of sealing defects

[0031] The differential pressure value P measured in real time by the differential pressure sensor during the exhaust process of the tested cavity. cs (t) and the digital twin value P generated at the corresponding time point of the differential pressure digital twin model. c (t) is compared, when the measured pressure difference P over a period of time is... cs If (t) is significantly smaller than and deviates from the differential pressure digital twin value without sealing defects described by formula (7), and the deviation value reaches the judgment threshold given by the engineering specification, then it can be determined that there is a non-negligible sealing defect.

[0032] Assume that during the exhaust process, the measured pressure difference value P in the tested cavity is... cs (t) and differential pressure digital twin P c The deviation of (t) is e(t) (abbreviated as deviation e(t)), as shown in formula (9):

[0033]

[0034] When the cavity being tested has no sealing defects, the deviation e(t) is very small, almost approaching 0. However, due to the presence of zero-mean random noise in the sensor output signal... Therefore, the deviation signal also contains noise, i.e. To avoid misjudgment, the average deviation during the exhaust gas detection time period from 0 to t is used. When judging sealing defects, the influence of zero-mean random interference, including power frequency interference, can be basically eliminated when t>10 seconds.

[0035]

[0036] The sealing performance of the container can be tested by obtaining the output value Y according to the sealing criterion formula (11). Y=1 indicates the presence of a non-negligible sealing defect, where E TH It is the discrimination threshold determined by the engineering construction specifications, E TH >0.

[0037]

[0038] This invention is implemented as follows:

[0039] The main feature of this method is its ability to rapidly detect sealing defects in waterproof and moisture-proof containers at the construction site using negative gas pressure. Based on the characteristic that the gas pressure inside the container changes with the gas volume when the container volume is constant, a differential pressure digital twin model without sealing defects is established. This model is compared with the differential pressure value measured in real time during the container's exhaust process using a gas differential pressure sensor. If the measured differential pressure value is significantly less than and deviates from the differential pressure digital twin value without sealing defects over a period of time, and the deviation reaches the judgment threshold given by the engineering specifications, then the container is judged to have a non-negligible sealing defect. A rapid detection system for sealing defects in waterproof and moisture-proof containers is thus constructed. Figure 1 As shown, Figure 1 middle Sensor mounting holes or process holes for containers negative pressure exhaust probe For probe sealing ring For endotracheal connector negative pressure airway A T-connector with a buffer chamber Vacuum pump For sensor air tube For testing and exhaust control circuit For lithium batteries, the rapid detection device for sealing defects mainly consists of... Tee connector with buffer chamber vacuum pump Sensor tubing Detection and exhaust control circuit Lithium battery configuration; detection and exhaust control circuit It consists of hardware and software. The hardware mainly consists of an embedded processor and a differential pressure sensor, while the software algorithm determines the sealing status of the waterproof and moisture-proof container being tested.

[0040] (1) After the on-site construction is completed, the sealing performance test is carried out. The tested container is installed through the sensor mounting hole of the container. and probe sealing ring Install negative pressure exhaust probe endotracheal connector With negative pressure exhaust probe endotracheal connector connection;

[0041] (2) The process of the rapid detection system for sealing defects of waterproof and moisture-proof containers is as follows: Figure 2 As shown, after the rapid sealing defect detection device is powered on, the system initializes and starts the differential pressure sensor and timer. The system then sets... and , where R g T, V, , P is a constant, and P is set according to the engineering construction specifications. CM , Discrimination threshold E TH Then, the key scanning program is invoked;

[0042] (3) When the seal detection button is pressed, the seal detection program is invoked;

[0043] (4) Sealing detection procedure, using sampling period T S (T) S (Not exceeding 10ms), collect the differential pressure values ​​P of gas differential pressure sensors at N points within time t. cs (t k And use the formula to calculate the differential pressure digital twin value P. c (t k )and Save the results and calculate the differential pressure deviation. mean According to the sealing test criterion formula, the sealing performance test output value Y is obtained. Y=1 indicates that there is a non-negligible sealing defect, and Y=0 indicates that there is no non-negligible sealing defect. The result is then uploaded and the program jumps to the display subroutine.

[0044]

[0045]

[0046]

[0047] (5) When the end button is pressed, the seal detection end program is called and the program jumps to the display subroutine;

[0048] (6) When no key is pressed, the no-operation function maintains its original working state and jumps to the display subroutine;

[0049] (7) Display subroutine to display running status and sealing test results. After execution, jump to keyboard scanning program and repeat the above steps until power is cut off.

[0050] This method targets waterproof and moisture-proof containers deployed outdoors by IoT detection devices or certain mechanical structures, where there are multiple sealing locations and complex sealing structures, requiring on-site installation and sealing performance testing. Based on the characteristic that the gas pressure inside the container changes with the gas volume when the container's volume is constant, this method constructs a rapid detection system for sealing defects in waterproof and moisture-proof containers. A gas differential pressure sensor measures the container's exhaust process in real time (i.e., the gas differential pressure sensor outputs a real-time signal), comparing this signal with the corresponding time-point signal generated by the constructed digital twin model. If the measured pressure difference value is significantly less than and deviates from the differential pressure digital twin value without sealing defects over a certain period, it indicates that the container has a non-negligible sealing defect. This invention provides a rapid on-site detection method for sealing defects in waterproof and moisture-proof containers using negative pressure, enabling rapid sealing performance testing on-site. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the sealing detection structure of the present invention.

[0052] Figure 2 This is a flowchart of the sealing detection and control software of the present invention. Detailed Implementation

[0053] Example:

[0054] S1: The embedded processor in the detection and exhaust control circuit is an STM32WB55RG with Bluetooth function, the sensor is a differential pressure sensor XGZP6897D, and the vacuum pump is a 12V miniature DC brushless air pump D35.

[0055] After on-site construction is completed, a sealing performance test is performed. The container under test is tested through the sensor mounting hole on the container. and probe sealing ring Install negative pressure exhaust probe endotracheal connector With negative pressure exhaust probe Connect the endotracheal tube connector.

[0056] S2: Rapid detection system process for sealing defects in waterproof and moisture-proof containers is as follows: Figure 2As shown, after the rapid sealing defect detection device is powered on, the system initializes and starts the differential pressure sensor and timer. The system then sets... and , where R g T, V, , P is a constant, and P is set according to the engineering construction specifications. CM , Discrimination threshold E TH Then, the key scanning program is invoked;

[0057] S3: When the seal detection button is pressed, the seal detection program is invoked;

[0058] S4: Sealing detection procedure, utilizing sampling period T S (T) S =10ms), within a time t=30s, the differential pressure value P of the gas differential pressure sensor is collected at N=3000 points. cs (t k And use the formula to calculate the differential pressure digital twin value P. c (t k )and Save the results and calculate the differential pressure deviation. mean The sealing performance test output value Y is obtained according to the sealing test criterion formula. Y=1 indicates that there is a non-negligible sealing defect, and Y=0 indicates that there is no non-negligible sealing defect. The result is then uploaded and the program jumps to the display subroutine.

[0059]

[0060]

[0061]

[0062] S5: When the end button is pressed, the seal detection end program is called, and the program jumps to the display subroutine.

[0063] S6: When no key is pressed, the no-operation function maintains its original working state and jumps to the display subroutine.

[0064] S7: Display subroutine, displays running status and sealing test results. After execution, it jumps to the keyboard scanning program and repeats the above steps until power is cut off.

Claims

1. A rapid on-site detection method for sealing defects in waterproof and moisture-proof containers, characterized in that, The method includes the following features: The main feature of this method is that it utilizes negative gas pressure at the construction site for rapid detection of sealing defects in waterproof and moisture-proof containers. Based on the characteristic that the gas pressure inside the container changes with the amount of gas when the container cavity capacity is constant, a differential pressure digital twin model without sealing defects is established. This model is then compared with the differential pressure value measured in real time during the container's exhaust process using a gas differential pressure sensor. If the measured differential pressure value is significantly less than and deviates from the differential pressure digital twin value without sealing defects over a period of time, and the deviation reaches the judgment threshold given by the engineering specifications, then the container is judged to have a sealing defect that cannot be ignored. (1) Differential pressure digital twin model, using formula (1) to describe the characteristics of differential pressure change inside and outside the cavity in the absence of sealing defects during the exhaust process. Rg: gas constant (gas constant for air Rg = 0.287 J / kg), T: absolute temperature. Standard density of air V: Standard specific volume of air, V = 0.7727 m³ 3 / kg, P CM The maximum differential pressure that does not cause new sealing defects when the negative pressure inside the cavity is determined by engineering construction specifications. (2) Measured pressure difference P in the measured cavity cs The detection process involves using a gas differential pressure sensor to measure the pressure difference P between the gas inside the chamber and the gas outside the chamber (atmospheric pressure) in real time during the exhaust process. cs (t); (3) Methods for identifying and judging sealing defects: During the exhaust process, the differential pressure sensor measures the differential pressure value P of the cavity in real time. cs (t) and the digital twin value P generated at the corresponding time point of the differential pressure digital twin model. c (t) is compared, when the measured differential pressure value P over a period of time is... cs (t) is significantly smaller than and deviates from the differential pressure digital twin value P without sealing defects. c (t), the sealing performance output value Y can be obtained according to the sealing criterion formula (2), Y=1 indicates that there is a non-negligible sealing defect, where E TH It is the discrimination threshold determined by the engineering construction specifications, E TH >0.

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