Method for inspecting overall radial deformation defect of stress corrosion medium liquefied gas tank truck

Abstract

The present application relates to a kind of stress corrosion medium liquefied gas tank truck overall radial deformation defect inspection method, the method includes the following steps: (1) the total stress of container and the deformation of fender after the deformation of different sizes of tank body rollover is generated;(2) the critical stress σ cc It is stress corrosion threshold value;(3) the relationship between stress corrosion threshold value and total stress is compared, whether the tank body occurs stress corrosion is evaluated;Then according to the relationship between total stress and stress corrosion threshold value, the radial critical deformation amount of fender that tank body does not occur stress corrosion is obtained, and the maximum radial deformation of fender allowed to exist under the condition that tank body meets the strength requirement is calculated;(4) the irregular deformation of tank body after accident is quantified using fender radial deformation;(5) the deformation size after quantification is compared with critical deformation amount, and the corresponding deformation defect inspection method is given.The present application is fast, accurate, and can reduce the risk of inspection.

Description

Technical Field

[0001] This invention relates to the field of inspection and testing, and in particular to a method for inspecting radial deformation defects in liquefied gas tank trucks subjected to stress corrosion. Background Technology

[0002] With the rapid development of the transportation industry and the uneven distribution of natural resources in my country, the use of mobile pressure vessels is becoming increasingly widespread. Mobile pressure vessels are transported over long distances and are greatly affected by road conditions and human factors, making them prone to traffic accidents such as rollovers. Furthermore, liquefied gas tank trucks have a high center of gravity and large mass; during transport, sudden swerving, braking, and rapid turns, the sloshing of the liquid inside the tank causes the tank's center of gravity to shift, reducing the truck's stability and greatly increasing the risk of rollovers or overturning accidents. When a tank truck rolls or overturns, the tank collides with the road surface, causing overall radial deformation of the tank.

[0003] Currently, there is no established standard for inspecting and evaluating the overall radial deformation defects of liquefied gas tank trucks prone to stress corrosion. To ensure the safety of tank truck transportation, all are sent back to the factory for repair. This indiscriminate practice of sending all tank trucks back for repair causes significant economic losses to users and society. Furthermore, it hinders the healthy development of the inspection industry. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a rapid and accurate method for inspecting the overall radial deformation defects of liquefied gas tank trucks subjected to stress corrosion.

[0005] To address the above problems, the present invention provides a method for inspecting the overall radial deformation defects of liquefied gas tank trucks subjected to stress corrosion, comprising the following steps:

[0006] (1) Calculate the total stress of the container and the deformation of the baffle after the tank body overturns and undergoes deformation of different sizes;

[0007] (2) The critical stress σ that causes cracks when liquefied gas medium acts on the tank body of a tank truck, tested according to national and industry standards. cc This is the stress corrosion threshold value;

[0008] (3) Compare the relationship between the stress corrosion threshold value and the total stress to assess whether the tank has undergone stress corrosion; then, based on the relationship between the total stress and the stress corrosion threshold value, determine the critical radial deformation of the baffle plate that the tank will not undergo stress corrosion, i.e., the first critical value L1; and calculate the maximum radial deformation of the baffle plate that is allowed to exist under the condition that the tank meets the strength requirements, i.e., the second critical value L2.

[0009] (4) The irregular deformation of the tank after the accident is quantified by the radial deformation of the baffle plate, and L is used to represent the size of the overall radial deformation of the tank.

[0010] (5) Compare the quantified deformation dimensions with the critical deformation amount and provide the corresponding inspection method for deformation defects.

[0011] The method for inspecting deformation defects in step (5) is as follows:

[0012] When L≤L1, perform a full test;

[0013] When L1 < L ≤ L2, no deformation is treated; after local heat treatment, a comprehensive inspection is performed.

[0014] When L > L2, a qualified unit shall conduct a comprehensive inspection after repair.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. This invention establishes the relationship between deformation, stress corrosion threshold, and strength, and derives the critical deformation amount required for tank safety evaluation. The evaluation is based on the critical deformation amount; by comparing the quantified deformation size with the critical deformation amount, a method for inspecting overall radial deformation defects can be provided.

[0017] 2. The present invention uses the critical deformation amount as a limit during inspection. By comparing the quantified radial deformation size of the wave deflector with the critical deformation amount, a method for inspecting defects can be quickly provided, thereby reducing economic losses for users and society.

[0018] 3. This invention can be applied to the inspection of accident deformation defects of liquefied gas tank trucks. It not only provides a basis for the inspection of accident deformation defects of liquefied gas tank trucks, but also significantly reduces the inspection risk of tank trucks and ensures the safe operation of tank trucks. Attached Figure Description

[0019] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0020] Figure 1 The radial deformation and total stress of the tank under different collision velocities in the embodiments of the present invention are shown.

[0021] Figure 2 This illustrates the relationship between stress and stress corrosion threshold values ​​in embodiments of the present invention. Detailed Implementation

[0022] Because the ellipticity of the tank body has an error value during the manufacturing of liquefied gas tank trucks, according to the standard GB / T19905-2017 "Liquefied Gas Tank Trucks," "the difference between the maximum and minimum inner diameters on the same cross-section of the cylinder shall not exceed 1% of the inner diameter of that cross-section, and shall not exceed 25 mm." This results in the cylinder itself not being perfectly circular. Therefore, accurately measuring the tank deformation is crucial for estimating the residual stress caused by deformation and evaluating the safety of the tank. This invention proposes to predict the residual stress of the tank through the deformation of the baffle plate, and to quantify the radial deformation of the tank through the deformation of the baffle plate.

[0023] A method for inspecting radial deformation defects in liquefied gas tank trucks subjected to stress corrosion includes the following steps:

[0024] (1) Calculate the total stress of the container and the deformation of the baffle after the tank body overturns and undergoes deformation of different sizes;

[0025] (2) The critical stress σ that causes cracks when liquefied gas medium acts on the tank body of a tank truck, tested according to national and industry standards. cc This is the stress corrosion threshold value;

[0026] (3) Compare the relationship between the stress corrosion threshold value and the total stress to assess whether the tank has undergone stress corrosion; then, based on the relationship between the total stress and the stress corrosion threshold value, determine the critical radial deformation of the baffle plate that the tank will not undergo stress corrosion, i.e., the first critical value L1; and calculate the maximum radial deformation of the baffle plate that is allowed to exist under the condition that the tank meets the strength requirements, i.e., the second critical value L2.

[0027] (4) The irregular deformation of the tank after the accident is quantified by the radial deformation of the baffle plate, and L is used to represent the size of the overall radial deformation of the tank.

[0028] (5) Compare the quantified deformation dimensions with the critical deformation amount, and provide the corresponding inspection method for deformation defects. The inspection method for deformation defects is:

[0029] When L≤L1, perform a full test;

[0030] When L1 < L ≤ L2, no deformation is treated; after local heat treatment, a comprehensive inspection is performed.

[0031] When L > L2, a qualified unit shall conduct a comprehensive inspection after repair.

[0032] Example 1: Inspection of Deformation Defects in Liquefied Petroleum Gas Tanker Trucks After Accidents

[0033] (1) Determine the total stress of the tanker tank and the deformation of the baffle plate.

[0034] The finite element method was used to calculate the total stress of the container and the deformation of the baffle plate after the tank overturned and deformed at different degrees. The calculated total stress and baffle plate deformation after different deformations following a liquefied petroleum gas tanker truck overturning collision are shown below. Figure 1 As shown.

[0035] (2) The critical stress σ that causes cracks when liquefied gas medium acts on the tank body of a tank truck, tested according to national and industry standards. cc This is the stress corrosion threshold value.

[0036] According to GB / T4157-2017 "Laboratory Test Methods for Resistance of Metals to Sulfide Stress Cracking and Stress Corrosion Cracking in Hydrogen Sulfide Environments", the stress corrosion threshold value of the test tank material in liquefied petroleum gas medium is 520 MPa.

[0037] (3) Compare the relationship between the stress corrosion threshold value and the total stress to assess whether stress corrosion has occurred in the tank.

[0038] Compare the relationship between total tank stress and stress corrosion threshold value, such as Figure 2 As shown (the horizontal dashed line represents the stress corrosion threshold), stress corrosion does not occur in the tank when the total stress after a collision is less than 520 MPa.

[0039] (4) Based on the relationship between total stress and stress corrosion threshold, the critical radial deformation of the baffle plate that prevents stress corrosion of the tank is shown in Table 1.

[0040] Table 1. Critical deformation amount at which the tank body will not experience stress corrosion

[0041]

[0042] (5) Calculate the maximum radial deformation of the baffle plate that is allowed to exist under the condition that the tank meets the strength requirements, and give the critical deformation amount.

[0043] Table 2 shows the thickness reduction of the tank after collision deformation at different speeds. As can be seen from Table 2, after overall rollover and side overturning, the thickness reduction of the tank is very small due to the strengthening effect of the internal accessories, and the strength fully meets the requirements.

[0044] Table 2. Tank thickness reduction during side rollover and tumble at different impact velocities.

[0045]

[0046] To enhance the safety of the evaluation, the stress after the tank collision should not be too high. For rollover and side-tipping collisions, the second critical value is still controlled by the stress value. The radial deformation of the baffle plate at a collision speed of 6 m / s is taken, and the critical deformation is shown in Table 3.

[0047] Table 3 Second Critical Deformation of Tank

[0048]

[0049] ⑹ The irregular deformation of the tank after the accident is quantified by the radial deformation of the baffle plate, and L is used to represent the size of the overall radial deformation of the tank.

[0050] (7) Compare the quantified deformation size with the critical deformation amount and provide the corresponding inspection method for deformation defects.

[0051] ① Rollover collision deformation inspection:

[0052] When L≤11.4mm, a full inspection is required;

[0053] When 11.4mm<L≤25.9mm, the collision deformation part within the range from the edge of the deformation position at the connection between the cylinder and the head to the first row of baffles, as well as the local area with reinforcement positions, need to be locally heat treated and then fully inspected.

[0054] When L > 25.9 mm, a qualified unit shall conduct a comprehensive inspection after repair.

[0055] ② Tumble collision deformation test:

[0056] When L≤21.4mm, a full inspection is required;

[0057] When 21.4mm<L≤50mm, the collision deformation part within the range from the edge of the deformation position at the connection between the cylinder and the head to the first row of baffles, as well as the local area with reinforcement positions, need to be locally heat treated and then fully inspected.

[0058] When L > 50mm, a qualified unit shall conduct a comprehensive inspection after repair.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for inspecting the overall radial deformation defects of liquefied gas tank trucks subjected to stress corrosion, comprising the following steps: (1) Calculate the total stress of the container and the deformation of the baffle after the tank body overturns and undergoes deformation of different sizes; (2) The critical stress σ that causes cracks when liquefied gas medium acts on the tank body of a tank truck, tested according to national and industry standards. cc This is the stress corrosion threshold value; (3) Compare the relationship between the stress corrosion threshold value and the total stress to assess whether the tank has undergone stress corrosion; then, based on the relationship between the total stress and the stress corrosion threshold value, determine the critical radial deformation of the baffle plate that the tank will not undergo stress corrosion, i.e., the first critical value L1; and calculate the maximum radial deformation of the baffle plate that is allowed to exist under the condition that the tank meets the strength requirements, i.e., the second critical value L2. (4) The irregular deformation of the tank after the accident is quantified by the radial deformation of the baffle plate, and L is used to represent the size of the overall radial deformation of the tank. (5) Compare the quantified deformation dimensions with the critical deformation amount, and provide a corresponding inspection method for deformation defects; the inspection method for deformation defects is as follows: When L≤L1, perform a full test; When L1 < L ≤ L2, no deformation is treated; after local heat treatment, a comprehensive inspection is performed. When L > L2, a qualified unit shall conduct a comprehensive inspection after repair.

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