Full-size homogeneous non-metallic pipe gas permeability test sample and pretreatment method

Abstract

The application discloses a full-size homogeneous nonmetal pipe gas permeability test sample and a pretreatment method, and belongs to the technical field of gas permeability test. The pretreatment method adopts the form of oil medium immersion, drying and vacuum extraction, eliminates the moisture, volatile substances and attached oil stains of the pipe raw material and the sample in the manufacturing process, fills and extracts the gas and impurities in the intermolecular gap of the polymer material. At the same time, the sample is calibrated and controlled in each stage to avoid the loss of additives and the change of performance of the sample caused by excessive cleaning and vacuum extraction. The immersion process of the application utilizes the similar compatible principle to efficiently fuse the oil medium with the oil stains and impurities in the nonmetal pipe sample, and the oil medium, the oil stains and the impurities are taken out in the drying and vacuum extraction process, and then the rapid and deep cleaning of the nonmetal pipe sample is completed.

Description

Technical Field

[0001] This invention belongs to the field of gas permeability testing technology, specifically relating to a full-size homogeneous non-metallic pipe gas permeability testing sample and a pretreatment method. Background Technology

[0002] Currently, non-metallic pipes with excellent corrosion resistance and no risk of hydrogen embrittlement are becoming an important development trend for the gathering and transportation of H2S-containing natural gas, CO2 transportation, and new energy (H2) transportation. Reinforced composite pipes with flexible thermoplastic linings are among the important non-metallic pipe materials used in these gas transportation fields. Solid-walled homogeneous thermoplastic pipes, such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polyvinylidene fluoride (PVDF), are in direct contact with the transported gas, acting as an important barrier against corrosion and erosion. However, during use, the free movement of gas molecules inevitably leads to adsorption, diffusion, and other permeation phenomena on their surface. On the one hand, gas permeation can cause "bubbling" failure on the inner surface of thermoplastic pipes; on the other hand, gas permeating along the wall thickness can also create leakage safety hazards. Therefore, the permeation of gas media into thermoplastics is the fundamental cause of material failure, thus affecting the safe operation of pipelines. Therefore, testing the gas permeability of full-size homogeneous lined pipes and evaluating their gas permeability resistance has become a necessary means for the design and selection of non-metallic gas transmission pipes.

[0003] The patent "Test Device and Method for Gas Permeability Performance of Full-Size Non-Metallic Pipes" (ZL201310694098.0) discloses a test device and method for the gas permeability performance of full-size non-metallic pipes. This method employs the differential pressure principle. First, a sealed full-size non-metallic pipe is placed into a split-type metal test chamber. Then, the metal test chamber is closed and sealed, and connected to a gas supply system. A vacuum pump is used to evacuate the space between the pipe and the metal chamber to a set vacuum level (≤20 Pa). Test gas is then introduced into the test pipe and pressurized. The pressure changes within the metal chamber are collected in real time to characterize the amount of gas permeating through the pipe under specific conditions, and the gas permeability coefficient of the full-size non-metallic pipe is calculated. The above-mentioned patented methods provide clear guidance for gas permeability testing of full-size homogeneous non-metallic pipes. However, in actual operation, it has been found that due to a series of reasons, such as the large size of the non-metallic pipe test samples, the presence of moisture and volatile substances in the raw materials, the existence of molecular gaps (pores, free volume, etc.) in the polymer materials themselves, and the adhesion of oil and moisture to the samples during the manufacturing process, small molecule volatile components and self-contained gases continuously escape from the full-size homogeneous non-metallic pipe samples during the vacuuming process. This makes it extremely time-consuming to achieve the basic condition of a vacuum degree ≤20Pa (usually about one month), resulting in a long test cycle, heavy load on vacuum pumps and other equipment, and a series of adverse effects. Therefore, how to invent a rapid and efficient pretreatment method for gas permeability testing samples of full-size homogeneous non-metallic pipes without affecting the test results, and significantly shorten the vacuuming time in the gas permeability testing process, has become an urgent technical problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a gas permeability test sample and pretreatment method for full-size homogeneous non-metallic pipes. This solves the problem that in the prior art, before the full-size homogeneous non-metallic pipes reach the test conditions, the polymer material itself has certain molecular gaps and impurities, resulting in a long vacuum time and low testing efficiency for the permeability performance of full-size homogeneous non-metallic pipes.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A pretreatment method for a full-size homogeneous non-metallic pipe gas permeability test sample includes the following steps:

[0007] S1, the full-size homogeneous non-metallic pipe sample and the corresponding standard sample are immersed in oil medium and then dried;

[0008] S2, determine the weight loss rate of the standard sample by measuring the mass change of the standard sample before and after drying. If the weight loss rate of the standard sample meets the first set range, proceed to S3; otherwise, repeat S1.

[0009] S3, Vacuum treatment is performed on the dried full-size homogeneous non-metallic pipe samples and standard samples;

[0010] S4. Determine the vacuum weight loss rate of the standard sample by measuring the mass change of the standard sample before and after vacuuming. If the vacuum weight loss rate of the standard sample meets the second set range, the preprocessing ends; otherwise, repeat S3.

[0011] A further improvement of the present invention is that:

[0012] Preferably, in S1, the standard sample is an arc-shaped piece, which is obtained by cutting from a sample of the same specification as the full-size homogeneous non-metallic pipe sample; the arc length of the arc-shaped piece is 1 / 4 or 1 / 2 of the circumference of the full-size homogeneous non-metallic pipe sample, and the length is 10-15cm; the sample of the same specification and the full-size homogeneous non-metallic pipe sample have the same size, wall thickness and material.

[0013] Preferably, in S1, during the oil medium immersion treatment, the oil medium completely immerses the full-size homogeneous non-metallic pipe sample and the standard sample; the oil immersion temperature is room temperature to 60°C, the oil immersion time is 24 to 48 hours, and the oil immersion pressure is 0 to 7 MPa.

[0014] Preferably, in S2, the formula for calculating the weight loss rate of the standard sample during drying is:

[0015] Standard sample drying weight loss rate (%) = ((M1 –M2) / M1)) *100 (1)

[0016] M1—refers to the mass of the standard sample after immersion in oil medium;

[0017] M2 refers to the dry weight of the standard sample after immersion in oil medium and continuous drying in a 90℃ oven until the mass remains unchanged.

[0018] Preferably, in S3, the formula for calculating the vacuuming time is:

[0019]

[0020] In the formula:

[0021] t — refers to the vacuuming time (min);

[0022] α—refers to the material coefficient of full-size homogeneous non-metallic pipes;

[0023] V—refers to the internal volume (L) of a full-size homogeneous non-metallic pipe;

[0024] S—refers to the vacuum pump's pumping speed (L / min);

[0025] p1 — refers to the initial pressure (Pa);

[0026] p2 — refers to the target vacuum level (Pa);

[0027] T — refers to temperature (K).

[0028] Preferably, in S4, the formula for calculating the vacuum weight loss rate of the standard sample is:

[0029] Standard sample vacuum weight loss rate (%) = ((M2 –M3) / M2)) *100 (3)

[0030] In the formula:

[0031] M2—refers to the dry weight of the standard sample after immersion in oil medium and continuous drying in a 90℃ oven until the mass remains unchanged;

[0032] M3 refers to the dry weight of the dried standard sample after vacuuming.

[0033] Preferably, in S2, the first setting range is 1-3%; in S4, the second setting range is 0.5-1.5%.

[0034] Preferably, before S1, the full-size homogeneous non-metallic tubular sample is wiped with an organic solvent on its inner surface, outer surface, and cross-section.

[0035] Preferably, after S4, when the time interval between the vacuum-treated full-size homogeneous non-metallic pipe sample and the gas permeability test is >4 hours, the vacuum-treated full-size homogeneous non-metallic pipe sample is immersed in a polymer curing agent for treatment.

[0036] A full-size homogeneous non-metallic pipe gas permeability test sample prepared by any of the above pretreatment methods.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] This invention discloses a pretreatment method for testing the gas permeability of full-size homogeneous non-metallic pipe samples. This pretreatment method employs oil-medium immersion, drying, and vacuuming to eliminate moisture, volatile substances, and adhering oil contaminants from the pipe raw materials and manufacturing process, while filling and extracting gases and impurities within the molecular gaps of the polymer material. The immersion method utilizes the principle of "like dissolves like," as the oil-medium can efficiently fuse with oil and impurities in the non-metallic pipe sample. These impurities are then carried out during drying and vacuuming, resulting in rapid and thorough cleaning of the non-metallic pipe sample. Throughout the pretreatment process, standard samples are used to calibrate key stages such as oil-medium immersion and vacuuming, avoiding excessive cleaning and vacuuming that could lead to sample additive loss and performance changes, thus preserving the essential characteristics of the treated sample.

[0039] Furthermore, when the sample needs to be left to stand for a period of time before use, the entire pipe sample is immersed in a polymer curing agent to form a curing film on its surface, thereby sealing the pipe after the treatment. Using a polymer curing film for sealing can prevent external gas from penetrating in and keep the surface clean, avoiding recontamination of the sample before the gas permeability performance test. Attached Figure Description

[0040] Figure 1 This is a flowchart of the testing process for the present invention. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings:

[0042] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] The first aspect of the present invention provides a pretreatment method for a full-size homogeneous non-metallic pipe gas permeability test sample, the pretreatment method specifically including the following steps:

[0044] S1. Obtain a standard sample of the same material, size, and specification for gas permeability testing. This standard sample, along with a full-size homogeneous non-metallic pipe sample, is then immersed in an oil medium. The immersed pipe sample and the standard sample are dried at 90°C, and the oil immersion process is controlled by the change in the mass of the standard sample. During the oil immersion process, the swelling effect of the oil medium dissolves and extracts oil and impurities from the pipe sample. The drying process then rapidly cleans the sample at the molecular level.

[0045] It should be noted that the standard sample of this invention is an arc-shaped sheet, 10-15 cm in length, uniformly cut along the axial direction of the pipe used for gas permeability testing, representing 1 / 4 or 1 / 2 of its circumference. The pipe used for gas permeability testing is a sample of the same material, size, and wall thickness as the heterogeneous full-size pipe sample to be tested. By setting up the standard sample, it is convenient to conduct comparative tests and evaluations with samples taken concurrently, and it can represent the wall thickness, size, and characteristics of the full-size pipe sample, ensuring comparability of the test results with those of the full-size pipe sample.

[0046] In some embodiments of the present invention, the oil medium may be kerosene or diesel oil.

[0047] In some embodiments of the present invention, the oil medium immersion temperature range is room temperature to 60°C, the immersion time is 24-48h, and during the oil immersion process, the sample is placed in an autoclave or a closed high-pressure chamber, and nitrogen or other inert gas is introduced into the autoclave or closed high-pressure chamber to reach an immersion pressure of 0-7MPa.

[0048] In some embodiments of the present invention, the specific soaking process is as follows: using an oil bath or pressure vessel of appropriate volume, placing the pre-cleaned full-size homogeneous non-metallic pipe sample and the prepared standard sample into it, pouring in sufficient diesel or kerosene to completely soak all the samples, and then starting the oil medium soaking treatment.

[0049] In some embodiments of the present invention, the specific drying process is as follows: After the oil medium soaking is completed, the full-size homogeneous non-metallic pipe sample and the standard sample are taken out. After wiping off the residual oil medium on the inner and outer surfaces of the standard sample, the mass of the standard sample is weighed, which is M1. Subsequently, the standard sample is continuously dried in a 90°C oven until its mass remains unchanged, and the mass of the standard sample is weighed, which is M2.

[0050] S2: Determine the weight loss rate of the standard sample by measuring the mass change of the standard sample before and after drying. If the weight loss rate of the standard sample meets the first set range, proceed to S3; otherwise, repeat S1. The first set range is 1 to 3%.

[0051] Specifically, the standard sample drying weight loss rate is calculated using the following formula (1). If the standard sample drying weight loss rate is 1-3%, proceed to the next step; if the standard sample drying weight loss rate is <1%, continue the oil medium immersion treatment process of S1 until the standard sample drying weight loss rate reaches 1-3%. As described above, the drying process may continue multiple times. In this data setting, if the standard sample drying weight loss rate is <1%, it means that the mass change during the drying process is small, and some attached oil medium, gas, impurities, etc. have not been fully dried and removed; if the standard sample drying weight loss rate is >3%, it indicates that the drying degree is too large, causing some beneficial additives in the pipe to precipitate, which will affect the true performance of the sample. Therefore, the optimal drying weight loss rate determined through a large amount of experimental data is 1-3%.

[0052] The formula for calculating the weight loss rate of the standard sample during drying is as follows:

[0053] Standard sample drying weight loss rate (%) = ((M1–M2) / M1))*100…............…(1)

[0054] In the formula:

[0055] M1—refers to the mass of the standard sample after immersion in oil medium;

[0056] M2 refers to the dry weight of the standard sample after immersion in oil medium and continuous drying in a 90℃ oven until the mass remains unchanged.

[0057] The M2 value of the standard sample in the process of calculating the drying weight loss rate is the value of the full-size homogeneous non-metallic pipe sample after being soaked in oil medium and continuously dried in a 90℃ oven until the mass remains unchanged.

[0058] S2 involves vacuuming the dried, full-size homogeneous non-metallic pipe samples and standards. This vacuuming process further removes residues and gases from intermolecular spaces and cavities after the oil medium has escaped, achieving rapid and deep cleaning once again.

[0059] Specifically, the dried, full-size homogeneous non-metallic pipe samples and standard samples are placed in a vacuum chamber and subjected to vacuuming. The vacuuming time can be calculated using the following formula:

[0060] During the vacuum extraction process, the vacuuming time can be calculated using the following formula:

[0061]

[0062] In the formula:

[0063] t—vacuuming time (min);

[0064] α—Material coefficient for full-size homogeneous nonmetallic tubular materials;

[0065] V—Inner volume of a full-size homogeneous non-metallic pipe (L);

[0066] S—vacuum pump pumping speed (L / min);

[0067] p1—Initial pressure (Pa);

[0068] p2—Target vacuum level (Pa); this value varies depending on the material.

[0069] T — Temperature (K).

[0070] The material coefficient α for full-size homogeneous thermoplastic pipes is 1.2 to 1.6; the material coefficient α for ceramic pipes is 0.8 to 1.2; and the material coefficient α for rubber pipes is 1.0 to 1.5.

[0071] S4. The vacuuming process is controlled by the change in the mass of the standard sample. The vacuum weight loss rate of the standard sample is determined by the change in the mass of the standard sample before and after vacuuming. If the vacuum weight loss rate of the standard sample meets the second set range, the preprocessing ends. Otherwise, S3 is repeated. The second set range is 0.5 to 1.5%.

[0072] After the vacuuming process is completed, the standard sample is taken out and weighed as M3. The vacuum weight loss rate of the standard sample is calculated using formula (2). If the vacuum weight loss rate of the standard sample is 0.5-1.5%, proceed to the next step; if the vacuum weight loss rate of the standard sample is <0.5%, continue the vacuuming process in step S4 until the vacuum weight loss rate of the standard sample reaches 0.5-1.5%. At this point, the full-size homogeneous non-metallic pipe sample can enter the gas permeability testing process.

[0073] Standard sample vacuum weight loss rate (%) = ((M2–M3) / M2))*100…............…(3)

[0074] In the formula:

[0075] M1—refers to the mass of the standard sample after immersion in oil medium;

[0076] M2 refers to the final dry weight of the standard sample after immersion in oil medium and continuous drying in a 90℃ oven until the mass remains unchanged.

[0077] M3—Dry weight of the dried standard sample after vacuuming.

[0078] The selection of 0.5% to 1.5% is the same as described above after oil impregnation. It is necessary to ensure that vacuuming creates a certain weight loss to ensure that some gases and impurities continue to be removed, while controlling the degree to avoid excessive extraction and loss of beneficial additives or even fillers.

[0079] In the above process, the standard sample drying weight loss rate and standard sample vacuum weight loss rate are used to control the oil medium immersion treatment and vacuuming process, respectively, to avoid excessive treatment and vacuuming that could cause sample additive loss or performance changes.

[0080] In some embodiments of the present invention, before S1, a preliminary cleaning is performed on the full-size homogeneous non-metallic pipe sample before the oil medium immersion process. Specifically, an organic solvent is used to wipe and clean the inner and outer surfaces and cross-section of the full-size homogeneous non-metallic pipe sample to complete the preliminary cleaning.

[0081] Preferably, the organic solvent is alcohol or acetone, which can wash away grease, oil stains, or other dust, powder or other minute impurities from the inner and outer surfaces and cross-sectional surfaces of the full-size homogeneous non-metallic pipe sample.

[0082] In some embodiments of the present invention, the full-size homogeneous non-metallic pipe is a homogeneous solid-wall material pipe such as a thermoplastic pipe, ceramic pipe, or rubber pipe.

[0083] In some embodiments of the present invention, S4 is followed by S5, which involves immersing the full-size homogeneous non-metallic pipe sample, after vacuum treatment, in a polymer film-forming agent solution, followed by curing and sealing the sample. This curing and sealing process prevents sample re-contamination and gas infiltration, ensuring the pre-treatment state remains unchanged before testing.

[0084] Specifically, when the time between the extraction process and the subsequent gas permeation test is more than 4 hours, the entire sample of the full-size homogeneous non-metallic pipe should be immersed in a polymer curing agent to form a curing film on its surface and thus preserve the pre-treated pipe condition.

[0085] Preferably, the soaking time is 1-2 hours, and after soaking, the product is air-dried naturally.

[0086] Preferably, the polymer curing agent is an acrylate or vinyl ester curing agent, etc.

[0087] When formally testing the gas permeability of full-size homogeneous non-metallic pipes, the protective film formed by the polymer curing agent can be destroyed by heating and cooling. Then, vacuuming can quickly remove the protective film and carry out the gas permeability test.

[0088] As a preferred embodiment of the present invention, the method mainly includes four stages of treatment: the first stage is to wipe and clean the inner and outer surfaces and cross-sections of the full-size homogeneous non-metallic pipe sample with solvents such as alcohol and acetone; the second stage is to remove moisture, volatile substances and attached oil stains from the pipe raw materials and samples during the manufacturing process by immersion in oil medium and drying; the third stage is to extract gas and impurities in the intermolecular spaces of the non-metallic material by vacuum extraction; and the fourth stage (optional) is to impregnate the entire pipe sample with a polymer curing agent to form a curing film on its surface and then seal the treated pipe state.

[0089] A full-size homogeneous non-metallic pipe sample is impregnated entirely with a polymer curing agent. The cured protective film then seals the pretreated sample. During the formal testing of the gas permeability of the full-size homogeneous non-metallic pipe, the sample is placed in a gas permeability testing device as described in patent ZL 201310694098.0. The heating and cooling functions of this device break down the protective film formed by the polymer curing agent. A vacuum is then applied to quickly remove the protective film, making the sample suitable for gas permeability testing.

[0090] The following specific examples further illustrate this point:

[0091] Example 1: Pretreatment of full-size polyethylene pipe gas permeability test samples without the need for rest

[0092] (1) Primary cleaning treatment: Use solvents such as alcohol and acetone to wipe and clean the inner and outer surfaces and cross-section of the full-size homogeneous polyethylene pipe sample;

[0093] (2) Oil medium immersion treatment:

[0094] 1) Preparation of standard samples:

[0095] A 10cm section of polyethylene pipe is cut and uniformly cut into strips of 1 / 4 circumference along the pipe axis to serve as a standard sample.

[0096] 2) Oil immersion:

[0097] A suitable oil bath was used to place pre-cleaned, full-size homogeneous polyethylene pipe samples and prepared standard samples inside. Sufficient diesel fuel was poured in to completely immerse all samples. Subsequently, oil medium immersion treatment was initiated at room temperature for 48 hours and at atmospheric pressure.

[0098] (3) Drying treatment:

[0099] After the oil medium soaking is completed, the full-size homogeneous polyethylene pipe sample and the standard sample are taken out. After wiping the residual oil medium on the inner and outer surfaces of the standard sample, the mass of the standard sample is weighed and is M1. Then the standard sample is continuously dried in a 90℃ oven until the mass remains unchanged, and the mass of the standard sample is weighed and is M2. The drying weight loss rate of the standard sample is calculated by formula (1). If the drying weight loss rate of the standard sample is 1-3%, the next step is carried out; if the drying weight loss rate of the standard sample is <1%, the oil medium soaking process is continued until the drying weight loss rate of the standard sample reaches 1-3%, and the final M2 value of the standard sample is recorded. At this time, the full-size homogeneous polyethylene pipe sample after oil medium soaking is continuously dried in a 90℃ oven until the mass remains unchanged.

[0100] (4) Vacuum extraction process:

[0101] 1) Vacuuming process:

[0102] The dried, full-size homogeneous polyethylene pipe samples and standard samples were placed in a vacuum chamber and vacuumed at room temperature. The vacuuming time was calculated using the following formula:

[0103]

[0104] In the formula:

[0105] t—vacuuming time (min);

[0106] α—Material coefficient for full-size homogeneous polyethylene pipe, taken as 1.2;

[0107] V—The internal volume (L) of a full-size homogeneous polyethylene pipe, calculated from the sample pipe diameter, wall thickness, and length;

[0108] S—vacuum pump pumping speed (L / min), determined based on the vacuum pump;

[0109] p1—Initial pressure (Pa), taken as atmospheric pressure;

[0110] p2 — Vacuum degree (Pa), value is 30Pa;

[0111] T—Temperature (K), valued at 273K.

[0112] 2) Standard sample vacuum weight loss rate control

[0113] After the vacuum treatment is completed, the standard sample is taken out and weighed as M3. The vacuum weight loss rate of the standard sample is calculated by formula (2). If the vacuum weight loss rate of the standard sample is 0.5-1.5%, the next step is carried out; if the vacuum weight loss rate of the standard sample is <0.5%, the vacuum treatment process is continued until the vacuum weight loss rate of the standard sample reaches 0.5-1.5%. At this time, the pretreatment of the full-size homogeneous polyethylene pipe sample is completed, and then the gas permeability test process is started.

[0114] Example 2: Pretreatment of full-size alumina ceramic pipe samples for gas permeability testing that need to be stored

[0115] (1) Primary cleaning treatment: Use solvents such as alcohol and acetone to wipe and clean the inner and outer surfaces and cross-section of the full-size homogeneous alumina ceramic tube sample;

[0116] (2) Oil medium immersion treatment:

[0117] 1) Preparation of standard samples:

[0118] A 15cm section of alumina ceramic pipe is cut and uniformly cut into strips of 1 / 2 circumference along the pipe axis to serve as the standard sample.

[0119] 2) Oil immersion:

[0120] A pressure vessel of suitable volume was used to place the pre-cleaned, full-size homogeneous alumina ceramic tube sample and the prepared standard sample inside. Sufficient kerosene was poured in to completely immerse all the samples. Subsequently, an oil medium immersion treatment was initiated at a temperature of 60℃ for 36 hours and an immersion pressure of 2 MPa.

[0121] (3) Drying treatment:

[0122] After the oil medium immersion is completed, the full-size homogeneous alumina ceramic pipe sample and the standard sample are taken out. After wiping the residual oil medium on the inner and outer surfaces of the standard sample, the mass of the standard sample is weighed and is M1. Then the standard sample is continuously dried in a 90℃ oven until the mass remains unchanged, and the mass of the standard sample is weighed and is M2. The drying weight loss rate of the standard sample is calculated by formula (1). If the drying weight loss rate of the standard sample is 1-3%, the next step is carried out; if the drying weight loss rate of the standard sample is <1%, the oil medium immersion process is continued until the drying weight loss rate of the standard sample reaches 1-3%, and the final M2 value of the standard sample is recorded. At this time, the full-size homogeneous alumina ceramic pipe sample after oil medium immersion is continuously dried in a 90℃ oven until the mass remains unchanged.

[0123] (4) Vacuum extraction process:

[0124] 1) Vacuuming process:

[0125] The dried, full-size homogeneous alumina ceramic pipe samples and standard samples were placed in a vacuum chamber and vacuumed at 60°C. The vacuuming time was calculated using the following formula:

[0126]

[0127] In the formula:

[0128] t—vacuuming time (min);

[0129] α—Material coefficient for full-size homogeneous alumina ceramic pipe, taken as 0.9;

[0130] V—The internal volume (L) of the full-size homogeneous alumina ceramic tube is calculated from the sample tube diameter, wall thickness, and length;

[0131] S—vacuum pump pumping speed (L / min), determined based on the vacuum pump;

[0132] p1—Initial pressure (Pa), taken as atmospheric pressure;

[0133] p2 — Vacuum degree (Pa), value is 20Pa;

[0134] T—Temperature (K), valued at 333K.

[0135] 2) Standard sample vacuum weight loss rate control

[0136] After the vacuum treatment is completed, the standard sample is taken out and weighed as M3. The vacuum weight loss rate of the standard sample is calculated by formula (2). If the vacuum weight loss rate of the standard sample is 0.5-1.5%, the next step is carried out; if the vacuum weight loss rate of the standard sample is <0.5%, the vacuum treatment process is continued until the vacuum weight loss rate of the standard sample reaches 0.5-1.5%.

[0137] (5) Sealing and storage:

[0138] The entire sample of a full-size homogeneous alumina ceramic pipe is impregnated with an ethylene ester curing agent. The cured protective film then seals the pretreated sample. During the formal testing of the gas permeability of the full-size homogeneous alumina ceramic pipe, the sample is placed in a full-size non-metallic pipe gas permeability testing device. Utilizing the device's heating and cooling functions, the sample is heated to 90°C and held for 4 hours, then immediately water-cooled to room temperature. A vacuum is then applied to quickly remove the protective film, making the sample ready for gas permeability testing.

[0139] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pretreatment method for a full-size homogeneous non-metallic pipe gas permeability test sample, characterized in that, Includes the following steps: S1, the full-size homogeneous non-metallic pipe sample and the corresponding standard sample are immersed in oil medium and then dried; In S1, the standard sample is an arc-shaped piece, which is obtained by cutting from a sample of the same specifications as the full-size homogeneous non-metallic pipe sample; the arc length of the arc-shaped piece is 1 / 4 or 1 / 2 of the circumference of the full-size homogeneous non-metallic pipe sample, and the length is 10~15cm; the sample of the same specifications and the full-size homogeneous non-metallic pipe sample are the same in size, wall thickness and material. S2, determine the weight loss rate of the standard sample by measuring the mass change of the standard sample before and after drying. If the weight loss rate of the standard sample meets the first set range, proceed to S3; otherwise, repeat S1. The first setting range is 1~3%; in S4, the second setting range is 0.5~1.5%; S3, Vacuum treatment is performed on the dried full-size homogeneous non-metallic pipe samples and standard samples; The formula for calculating the vacuuming time is: （2） In the formula: t —Refers to the vacuuming time (min); α —Refers to the material coefficient of full-size homogeneous non-metallic pipes; V —Refers to the internal volume (L) of a full-size homogeneous non-metallic pipe. S —Refers to the vacuum pump's pumping speed (L / min); p 1 — refers to the initial pressure (Pa); p 2—Refers to the target vacuum level (Pa); T —Refers to temperature (K); S4. Determine the vacuum weight loss rate of the standard sample by measuring the mass change of the standard sample before and after vacuuming. If the vacuum weight loss rate of the standard sample meets the second set range, the preprocessing ends; otherwise, repeat S3. The formula for calculating the vacuum weight loss rate of the standard sample is as follows: Standard sample vacuum weight loss rate (%) = ((M2–M3) / M2) 100 (3) In the formula: M2—refers to the dry weight of the standard sample after immersion in oil medium and continuous drying in a 90°C oven until the mass remains unchanged; M3 refers to the dry weight of the dried standard sample after vacuuming.

2. The pretreatment method for a full-size homogeneous non-metallic pipe gas permeability test sample according to claim 1, characterized in that, In S1, during the oil medium immersion treatment, the full-size homogeneous non-metallic pipe sample and the standard sample are completely immersed in the oil medium; the oil medium immersion temperature is room temperature to 60℃, the oil medium immersion time is 24 to 48 hours, and the oil medium immersion pressure is 0 to 7 MPa.

3. The pretreatment method for a full-size homogeneous non-metallic pipe gas permeability test sample according to claim 1, characterized in that, In S2, the formula for calculating the weight loss rate of the standard sample during drying is: Standard sample drying weight loss rate (%) = ((M1–M2) / M1) 100(1) M1—refers to the mass of the standard sample after immersion in oil medium; M2 refers to the dry weight of the standard sample after immersion in oil medium and continuous drying in a 90°C oven until the mass remains unchanged.

4. The pretreatment method for a full-size homogeneous non-metallic pipe gas permeability test sample according to claim 1, characterized in that, Before S1, the inner surface, outer surface and cross-section of the full-size homogeneous non-metallic pipe sample were wiped with an organic solvent.

5. The pretreatment method for a full-size homogeneous non-metallic pipe gas permeability test sample according to claim 1, characterized in that, After S4, when the time interval between the vacuum-treated full-size homogeneous non-metallic pipe sample and the gas permeability test is greater than 4 hours, the vacuum-treated full-size homogeneous non-metallic pipe sample is immersed in a polymer curing agent for treatment.

6. A full-size homogeneous non-metallic pipe gas permeability test sample prepared by the pretreatment method described in any one of claims 1-5.

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