CN111551464A - Accelerated test method for testing aging performance of non-metallic material for oil and gas transmission - Google Patents
Accelerated test method for testing aging performance of non-metallic material for oil and gas transmission Download PDFInfo
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Abstract
An accelerated test method for testing the ageing performance of non-metallic material for oil-gas transmission includes such steps as creating the test conditions for simulating the actual running state of non-metallic material in oil-gas environment, developing the accelerated exposure test by high-temp high-pressure reactor, measuring the physical, mechanical and heat-resistant properties before and after the exposure test, and comparing the variation of non-metallic material before and after the accelerated exposure test to determine the qualified technical index of non-metallic material or judge its adaptability or boundary condition. The invention provides an accelerated test method for testing the aging performance of a non-metallic material for oil and gas transmission. The test method is simple and feasible, the test period is short, the actual running state of the non-metallic material in the oil-gas environment is comprehensively considered, the performance index of the sample test is comprehensive, the accuracy of the test result is high, and the method can be directly used for guiding the material selection of the non-metallic material for oil-gas transmission.
Description
Technical Field
The invention relates to the technical field of testing and verifying the aging performance of a non-metallic material, in particular to an accelerated test method for testing the aging performance of the non-metallic material for oil and gas transmission.
Background
In recent years, the oil field medium environment is increasingly harsh, the water content and the temperature gradually rise, and Cl is added-、CO2、H2The content of corrosive media such as S and the like is increased, and great risk is brought to the application of the steel pipe. The nonmetal and composite material pipe has excellent corrosion resistance, so that the nonmetal and composite material pipe is an important solution for solving the corrosion problem of the oil field gathering and transportation pipe network. The non-metallic material in direct contact with the oil-gas medium is mainly a high-molecular polymer material. Like other polymer materials used in various industrial products, polymer materials used in the oilfield field also face significant aging problems. Especially in the complex and harsh oil and gas conveying working condition environments of oil, gas, water, high temperature, high pressure and the like, under the dynamic action of irregular changes of temperature, pressure, medium components and the like, the aging process of a non-metallic material is rapidly accelerated, so that the service life of the pipe is obviously shortened, and great challenges are brought to the safe and long-term operation of an oil field gathering and transportation pipe network. Therefore, the aging performance of the non-metallic material in the oil and gas conveying environment is researched, the quality safety of the non-metallic pipe for oil and gas conveying is controlled for determining the aging rule of the material, and the use of the pipe is ensuredThe lifetime has a very important role.
The aging and anti-aging of polymer materials have become an important research field of polymer science and technology. In recent years, China has made a lot of researches on the aspects of polymer aging and anti-aging, and has made intensive researches on the aging rules and mechanisms of various polymer materials such as plastics, rubber, composite materials and the like and made many achievements. The most common accelerated aging test methods used today are oven accelerated aging tests and wet heat aging tests. The research on artificial accelerated aging and actual natural aging shows that the results of the oven accelerated aging and the actual natural aging are most similar, so the accelerated aging research mainly takes an oven accelerated aging method for increasing the temperature. The heat resistance of a test specimen is evaluated by suspending the test specimen in a heat aging test chamber under given conditions (e.g., temperature, wind speed, etc.) and periodically observing and measuring changes in appearance and properties of the specimen. At present, in the research aspect of the accelerated aging test method of materials, new aging test methods such as an artificial climate accelerated aging test, an ozone accelerated aging test, a smoke corrosion test, an artificial mildew resistance test and the like are sequentially provided. However, in all the above aging test methods, only the influence of conditions such as a single medium type (e.g. hot air, ozone, smoke, etc.), a single environmental factor (e.g. temperature, time), a single failure mode (e.g. brittle failure), etc. on the aging performance of the polymer material is considered. As mentioned above, the oil field pipeline transportation conditions are quite complex: the conveying medium has various types (different oil products, various gas components and various water components), complex environmental working conditions (temperature, pressure and time coordination action), variable external loads (temperature fluctuation, pressure circulation and external force action), and various failure modes (creep toughness failure, slow crack brittle failure and material deterioration failure). Therefore, the aging process of the high polymer material in contact with the oil-gas medium cannot be comprehensively evaluated by adopting the traditional aging performance evaluation method, the comprehensive aging performance evaluation method under the condition of simulating the actual operation of the non-metal material must be established by comprehensively considering the comprehensive environment effect of the oil-gas transmission working condition, and the accurate test and judgment on the comprehensive aging performance of the non-metal material in contact with the oil-gas medium can be made.
Disclosure of Invention
The invention provides an accelerated test method for testing the aging performance of a non-metallic material for oil gas transmission, aiming at the defects of the prior art. In addition, an envelope curve of a change rule curve can be drawn through a series of high-temperature high-pressure autoclave exposure test results, so that the qualification range of key performance indexes of the non-metallic material under a simulated working condition environment and service working condition boundary conditions such as the highest operation temperature, critical gas partial pressure and the like can be determined.
In order to achieve the purpose, the invention is realized by the following technical scheme:
an accelerated test method for testing the ageing performance of non-metallic material for oil-gas transmission features that the test conditions for simulating the actual running state of non-metallic material in oil-gas environment are created, and a high-temperature high-pressure kettle is utilized to carry out an accelerated exposure test, and the physical properties, the mechanical properties, the heat resistance and the degradation behaviors before and after the exposure test are measured, so as to draw a performance change rule map of the physical properties, the mechanical properties, the heat resistance and the degradation behaviors of the nonmetal small sample before and after different accelerated exposure test periods, by constructing an envelope tangent to different map curves, taking a longitudinal coordinate value corresponding to the position of the tangent point as a technical index for determining the qualification of the corresponding performance of the non-metallic material in an oil-gas working condition environment, if any single performance of the non-metallic material is greater than the longitudinal coordinate value corresponding to the position of the tangent point, the non-metallic material is unqualified, and if all the performances of the non-metallic material are less than the longitudinal coordinate value corresponding to the position of the tangent point, the non-metallic material is qualified.
The invention further improves the following steps: the non-metallic material is a thermoplastic, thermoset, elastomer or composite.
The invention further improves the following steps: the method for establishing the test conditions for simulating the actual running state of the non-metallic material in the oil-gas environment comprises the following steps: test medium, test pressure, test temperature, test period and test state.
The invention further improves the following steps: the test temperature is determined by the difference between the test temperature and the maximum allowable use temperature, and the difference between the test temperature and the maximum allowable use temperature is obtained by the following formula:
in the formula:
α -time-temperature conversion coefficient;
tLife-design life;
tTesttest time for 50% reduction in tensile modulus of the specimen;
Δ T-the difference between the test temperature and the maximum allowable use temperature.
The invention further improves the following steps: when the non-metallic material is polyethylene material, taking alpha as 0.11; the default value for alpha is 0.05 when the non-metallic material is a multi-layer material composed of two or more materials, or when a non-ductile failure mode occurs in the non-metallic material.
The invention further improves the following steps: the physical properties comprise the weight change of the non-metallic material, and the adsorption weight gain and the leaching weight loss of the non-metallic material are respectively measured; the adsorption weight gain refers to the weight difference between the wet weight of the non-metal material after the exposure test and the dry weight of the fully dried non-metal material, and the leaching weight loss refers to the weight difference between the dry weight of the fully dried non-metal material after the exposure test and the dry weight of the non-exposed sample; the calculation formulas of the adsorption weight gain rate and the leaching weight loss rate are as follows:
adsorption weight gain (%) ((M)2–M3)/M1))*100………………(2)
Leaching weight loss ratio (%) ((M)3–M1)/M1))*100………………(3)
In the formula:
M1the dry weight of the non-metallic material before the exposure test when the non-metallic material is continuously dried in an oven at 90 ℃ until the weight is unchanged;
M2after finger Exposure testWet weight of non-metallic material;
M3and means the dry weight of the non-metallic material after the exposure test when the non-metallic material is continuously dried in an oven at 90 ℃ until the weight is unchanged.
The invention further improves the following steps: also included is the determination of the degradation performance before and after the exposure test.
The invention further improves the following steps: the degradation performance is measured by a structural component test of infrared spectrum, a heat weight-differential heat resistance test, an X-ray photoelectron spectrum test, a static thermal mechanical test or a dynamic thermal mechanical test.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides an accelerated test method for testing the aging performance of a non-metallic material for oil and gas transmission. The test sample does not need to adopt a real-object pipe, the test method is simple and feasible, the test period is short, the actual running state of the non-metal material in the oil-gas environment and three possible failure modes are comprehensively considered, the performance index of the sample test is comprehensive, the accuracy of the test result is high, and the method can be directly used for guiding the material selection of the non-metal material for oil-gas transmission.
2. The technical indexes of the acceptability of different non-metallic materials in different oil and gas transmission working condition environments can be determined by utilizing the accelerated test method provided by the invention; and determining service working condition boundary conditions such as the highest operating temperature, the critical gas partial pressure and the like of the non-metallic material in the oil and gas transmission working condition environment.
3. The accelerated test method for testing the aging performance of the non-metallic material for oil and gas transmission provided by the invention has the advantages that the tested performance indexes are very comprehensive, the test result can completely ensure the safety and reliability of the application of the non-metallic material in an oil and gas environment, and an important foundation is laid for predicting the service life of the non-metallic material by an extrapolation method.
Furthermore, the invention fully considers the dual influence of the exposure test medium on the sample adsorption and leaching, and provides effective support for comprehensively analyzing the influence of the test medium on the physical processes of sample swelling, leaching and the like by simultaneously measuring the adsorption weight gain and the leaching weight loss of the sample.
Drawings
FIG. 1 is a graph showing the behavior change after exposure test and a representative envelope curve of polyethylene pipe.
FIG. 2 shows the IR spectrum change before and after the exposure test of polyethylene pipe. Wherein 1 is an unexposed sample; 2 is the specimen after 2 days of exposure; 3 is the specimen after 21 days of exposure; and 4 is the sample after 56 days of exposure.
FIG. 3 shows the IR spectrum change before and after the FRP pipe exposure test. Wherein 5 is an unexposed sample; and 6 is the sample after exposure.
Detailed Description
The present invention is further illustrated by the following specific examples.
According to the invention, through establishing a test condition for simulating the actual running state of the non-metallic material in an oil-gas environment, carrying out an accelerated exposure test by using a high-temperature high-pressure kettle, comprehensively considering the influence of various failure modes, measuring the physical properties, mechanical properties, heat resistance and degradation properties of the sample before and after the exposure test, and drawing a property change rule map of the physical properties, mechanical properties, heat resistance and degradation behaviors of the non-metallic small sample before and after different accelerated exposure test periods. By constructing envelope lines tangent to different atlas curves, referring to performance change judgment indexes mentioned in relevant standards, and taking longitudinal coordinate values corresponding to tangent point positions as technical indexes for determining the qualification of corresponding performances of the non-metallic material in an oil-gas working condition environment, if any single performance of the non-metallic material is greater than the longitudinal coordinate value corresponding to the tangent point position, the non-metallic material is unqualified, and if all performances of the non-metallic material are less than the longitudinal coordinate value corresponding to the tangent point position, the non-metallic material is qualified.
The purpose of the accelerated test is to determine the technical index of the non-metallic material qualification or judge the applicability or the applicable boundary conditions of the non-metallic material by comparing and analyzing the comprehensive performance change of the sample before and after the exposure test. In the present invention, it is desirable that the measurement of all the performance parameters of the sample after the end of the exposure test is completed within not more than 4 hours. In the performance test of the invention, besides the basic physical and chemical performance test requirements, the degradation performance test of the non-metallic material is added. The sample degradation performance test mainly comprises structural component analysis of infrared spectrum and thermogravimetric-differential thermal resistance analysis, and can also comprise other degradation performance characterization means of high molecular materials such as X-ray photoelectron spectroscopy analysis, static thermomechanical analysis or dynamic thermomechanical analysis.
Non-metallic materials include thermoplastics, thermosets, elastomers, and composites, among others.
The method for establishing the test conditions for simulating the actual running state of the non-metallic material in the oil-gas environment comprises the following steps: test medium, test pressure, test temperature, test period and test state.
The test temperature is determined by the difference between the test temperature and the maximum allowable use temperature, and the difference between the test temperature and the maximum allowable use temperature is obtained by the following formula:
in the formula:
α -time-temperature conversion coefficient;
tLife-design life;
tTesttest time for 50% reduction in tensile modulus of the specimen;
Δ T-the difference between the test temperature and the maximum allowable use temperature.
When the non-metallic material is polyethylene material, taking alpha as 0.11; the default value for alpha is 0.05 when the non-metallic material is a multi-layer material composed of two or more materials, or when a non-ductile failure mode occurs in the non-metallic material.
The physical properties comprise the weight change of the non-metallic material, and the adsorption weight gain and the leaching weight loss of the non-metallic material are respectively measured; the adsorption weight gain refers to the weight difference between the wet weight of the non-metal material after the exposure test and the dry weight of the fully dried non-metal material, and the leaching weight loss refers to the weight difference between the dry weight of the fully dried non-metal material after the exposure test and the dry weight of the non-exposed sample; the calculation formulas of the adsorption weight gain rate and the leaching weight loss rate are as follows:
adsorption weight gain (%) ((M)2–M3)/M1))*100………………(2)
Leaching weight loss ratio (%) ((M)3–M1)/M1))*100………………(3)
In the formula:
M1the dry weight of the non-metallic material before the exposure test when the non-metallic material is continuously dried in an oven at 90 ℃ until the weight is unchanged;
M2-refers to the wet weight of the non-metallic material after the exposure test;
M3and means the dry weight of the non-metallic material after the exposure test when the non-metallic material is continuously dried in an oven at 90 ℃ until the weight is unchanged.
The degradation performance is measured by adopting a structural component test of infrared spectrum, a heat weight-differential heat resistance test, an X-ray photoelectron spectrum test, a static thermal mechanical test or a dynamic thermal mechanical test.
Specifically, the method for testing the aging performance of the non-metallic material under the oil-gas working condition environment comprises the following steps:
preparation of sample S1: intercepting a test sample from a non-metal pipe, processing the test sample into a standard sample meeting related performance tests (such as tensile performance), and adjusting the state of the sample according to standard requirements;
s2 test conditions determine:
1) test medium: when the unknown material is applied to a working condition environment, a standardized test medium can be established by referring to a relevant standard (such as NACE TM 0298-; when the material is applied in a working condition environment, the test medium components such as oil medium (kerosene, diesel oil and the like) and water component (Cl) can be simulated and established according to the analysis result of the components of the conveying medium-Content, pH, etc.), determining the gas composition (type, content, partial pressure), etc.
2) Test pressure: when an unknown material is applied to a working condition environment, the total pressure at room temperature can be set to be 6-10 MPa; when the known material is applied to a working condition environment, the highest design pressure of the pipe in service can be set as a test pressure.
3) Test temperature: the invention adopts a method of raising temperature to carry out accelerated aging test on the non-metallic material. The test temperature should be higher than the maximum allowable use temperature of the material, and the temperature difference can be calculated by the following formula:
in the formula:
α -time-temperature conversion coefficient; when polyethylene material is adopted, taking alpha as 0.11; the default value for alpha is 0.05 for other polymeric materials, or for multilayer materials composed of two or more materials, or when a non-ductile failure mode occurs.
tLifeDesign lifetime in hours (h);
tTesttest time for 50% reduction in tensile modulus of the test specimen (i.e. test specimen subjected to t)TestAfter the test time of (a), the tensile modulus decreases by 50%, which is considered to be an acceptable threshold for a decrease in material properties) in hours (h);
Δ T-the difference between the test temperature and the maximum allowable use temperature.
Typically, the test temperature should be at least 20 ℃ higher than the maximum allowable use temperature of the material.
4) And (3) test period: the exposure test should be performed in at least 3 test periods, such as 3-10 days, 11-20 days, etc.
5) And (3) test states: static or stirring dynamic.
S3 exposure test: placing the sample after the state adjustment into a high-temperature high-pressure autoclave, and developing an exposure test strictly according to the operation flow of the high-temperature high-pressure autoclave;
and (S4) performance test:
1) and (3) testing physical properties:
a) appearance: observing the color change and the transparency change of the sample after the exposure test, and observing whether phenomena such as foaming, cracking, cracks and the like exist;
b) volume: measuring the volume change of the test specimen with reference to ASTM D792-2008;
c) weight: the sample weight change is a comprehensive representation of the adsorption weight gain and leaching weight loss during the exposure test. The sample adsorption weight gain and leaching weight loss should be measured separately. Adsorption weight gain refers to the sample after exposure testWet weight M2Relative to the dry weight M of the completely dried sample3Weight difference therebetween, leaching weight loss means the dry weight M of the completely dried sample after the exposure test3Dry weight M of non-development exposed sample1The weight difference therebetween. The calculation formulas of the adsorption weight gain rate and the leaching weight loss rate are as follows:
adsorption weight gain (%) ((M)2–M3)/M1))*100………………(2)
Leaching weight loss ratio (%) ((M)3–M1)/M1))*100………………(3)
In the formula:
M1dry weight in grams (g) when the sample was oven dried continuously in an oven at 90 ℃ until the weight remained unchanged before the exposure test;
M2-refers to the wet weight of the sample after exposure test in grams (g);
M3dry weight in grams (g) when the sample after the exposure test is dried in an oven at 90 ℃ until the weight is unchanged;
the sample weight should be measured simultaneously for the adsorption weight gain (formula (2)) and the leaching weight loss (formula (3)).
a) Hardness: the hardness of the test specimens was tested according to the relevant standard specifications.
2) Mechanical properties: testing mechanical performance indexes such as tensile strength, elongation at break, modulus and the like of the sample after the exposure test according to relevant standards;
3) heat resistance: testing heat resistance indexes such as Vicat softening temperature, thermal deformation temperature, glass transition temperature, oxidation induction time and the like of the sample after the exposure test according to related standards;
4) degradation performance: infrared spectroscopic analysis, thermogravimetric-differential thermal analysis (TG-DSC) and the like of the exposure test sample are carried out, and the structural components and the pyrolysis process change of the high molecular material are researched.
Results summary of S5: and (5) sequentially measuring various performance indexes of the sample after different test periods according to the requirements of the step S4, and drawing a relation graph of various performance changes and the test periods so as to obtain the aging performance change rule of the non-metal material in different test periods.
Analysis of results at S6: comprehensively analyzing the appearance, volume, weight, hardness, tensile strength, elongation at break, modulus, Vicat softening temperature, thermal deformation temperature, glass transition temperature, infrared spectrogram, thermogravimetry-differential thermal curve and other change conditions of the sample before and after the exposure test, constructing an envelope tangent to each index change curve, referring to the performance change judgment index mentioned in the relevant standard, taking the longitudinal coordinate value corresponding to the position of the tangent point as the qualification technical index for determining the corresponding performance of the non-metal material in the oil-gas working condition environment, if any single performance of the non-metal material is greater than the longitudinal coordinate value corresponding to the position of the tangent point, the non-metal material is unqualified, and if all the performances of the non-metal material are less than the longitudinal coordinate value corresponding to the position of the tangent point, the non.
According to the constructed envelope tangent to each index change curve, the change range of the non-metallic material aging performance index suitable for the simulated environment working condition is determined.
The following are specific examples.
Example 1: clear the technical index of the qualification of polyethylene pipe under the condition of known oil gas working condition
(1) Sample preparation: according to the requirements of GB/T8804.3-2003, a dumbbell-shaped tensile specimen was cut out from a polyethylene pipe as a sample for exposure test, and a 25 mm. times.25 mm block-shaped specimen was cut out as a specimen for measuring weight and volume change. All exposed samples were conditioned for 40h in a standard laboratory environment (23 ℃, 50% relative humidity).
(2) And (3) determining test conditions:
1) test medium: the high-temperature autoclave simulation test conditions were established according to the working conditions provided by the user, as shown in table 1.
TABLE 1 simulation test conditions for polyethylene pipe high-temperature and high-pressure autoclave
2) Test temperature: assuming that the maximum allowable service temperature of the polyethylene pipe in the oil and gas transmission field is 65 ℃, the design service life is 20 years, namely tLifeTest time t 175200h and predicted 50% reduction in tensile modulusTestSelecting time-temperature conversion coefficient α as 0.11 when the temperature is 1000h, substituting the parameters into formula (1), and calculating to obtain the temperature difference of 20.4 DEG C
Thus, the test temperature of this example was determined to be 65+20.4 — 85.4 ℃.
3) And (3) test period: 6 test periods are selected, which are respectively as follows: 2 days, 7 days, 14 days, 21 days, 35 days and 56 days.
4) And (3) test states: the sample was placed statically in the kettle.
(3) Carrying out an exposure test: placing the sample after the state adjustment into a high-temperature high-pressure autoclave, and developing an exposure test strictly according to the operation flow of the high-temperature high-pressure autoclave;
(4) and (3) performance testing:
1) performance testing of the samples before exposure testing:
testing physical properties:
the dimensions of each specimen were measured with a vernier caliper to an accuracy of 0.02mm the mass of each specimen was measured with a balance to an accuracy of 1mg, in particular, the dry weight M of a 25mm × 25mm block sample before the exposure test was dried continuously in an oven at 90 ℃ until the weight remained unchanged was measured with a balance1To the nearest 1 mg;
measurement of mass m in air before immersion of other samples by Water replacement method with reference to NACE TM02961And mass m in deionized water (or absolute ethanol)3；
The samples were tested for shore hardness as specified in ASTM D1708-13.
Testing mechanical properties: the tensile properties of the test specimens, including the tensile breaking strength, elongation and modulus of elasticity of the material, were measured according to the specifications of GB/T8804.3-2003 and were tested using 5 parallel test specimens.
Testing heat resistance: testing the Vicat softening temperature of the sample according to the regulation of GB/T1633-2000; testing the heat distortion temperature of the test sample according to the specification of GB/T1634.2-2004; according to the provisions of GB/T19466.6-2009, the samples were tested for oxidation induction time (isothermal OIT) or oxidation induction temperature (dynamic OIT). The test should be performed using 3 parallel samples.
Testing degradation performance: testing the infrared spectrum of the sample by using a Fourier infrared spectrometer; the thermogravimetry-differential thermal (TG-DSC) curve of the test specimens was tested using a differential scanning calorimeter.
2) Performance testing of the samples after exposure test:
after the exposure test for each test cycle was completed, the test was slowly stopped according to the high temperature autoclave procedure to prevent damage to the exposed sample, and then the sample was removed. After drying the samples with cotton cloth or filter paper, the material performance parameters were measured at room temperature. After the soaking test is finished, the measurement of the performance parameters of the sample is preferably finished within 4 hours, and if the measurement cannot be finished within 4 hours, the sample is stored in the same liquid medium (normal pressure and normal temperature) as the soaking test.
Testing physical properties:
after the exposure test is finished, the sample is visually checked for damage to the outside, and the damage to the outside includes but is not limited to the following forms: cracks, delamination, swelling, bubbling, etc., and if necessary, cutting to check for structural changes in the interior of the specimen. The location and number of lesions should be recorded;
after the exposure test is finished, the size of each sample is measured to be 0.02mm by using a vernier caliper. And calculating the length change rate of each sample before and after soaking by adopting a formula (5):
the mass of each sample was measured to the nearest 1mg by a balance, in particular, the wet weight (mass of sample after wiping dry with cotton cloth or filter paper) M of a block sample of 25mm × 25mm after the exposure test was measured by a balance2And a dry weight M of the mixture which is dried continuously in an oven at 90 ℃ until the weight is unchanged3Calculating the adsorption weight gain rate of a 25mm × 25mm block sample by adopting a formula (2), and calculating the leaching weight loss rate of a 25mm × 25mm block sample by adopting a formula (3);
measuring mass m of other samples soaked in air by adopting water replacement method according to reference standard NACE TM02962And mass m in deionized water (or absolute ethanol)4And calculating the volume change rate of each sample before and after soaking by adopting a formula (6):
the samples were tested for shore hardness as specified in ASTM D1708-13.
Testing mechanical properties: the tensile properties of the test specimens, including the tensile breaking strength, elongation and modulus of elasticity of the material, were measured according to the specifications of GB/T8804.3-2003 and were tested using 5 parallel test specimens. The rate of change was calculated as compared to the measurements before the exposure test. The tensile break strength can also be replaced by the tensile yield strength.
Testing heat resistance: testing the Vicat softening temperature of the sample according to the regulation of GB/T1633-2000; testing the heat distortion temperature of the test sample according to the specification of GB/T1634.2-2004; according to the provisions of GB/T19466.6-2009, the samples were tested for oxidation induction time (isothermal OIT) or oxidation induction temperature (dynamic OIT). The rate of change was calculated as compared to the measurements before the exposure test.
Testing degradation performance: the infrared spectrum of the sample after the exposure test is tested by a Fourier infrared spectrometer, and the thermogravimetry-differential thermal (TG-DSC) curve of the sample after the exposure test is tested by a differential scanning calorimeter and compared with the measured value before the exposure test.
(5) And (4) summarizing the results: and sequentially measuring various performance indexes of the samples after different test periods (2 days, 7 days, 14 days, 21 days, 35 days and 56 days), and drawing a relation graph of various performance changes and the test period so as to obtain an aging performance change rule of the polyethylene material in different test periods under the known oil gas working condition, as shown in figure 1.
(6) And (4) analyzing results:
by comprehensively analyzing the changes of the polyethylene sample before and after the exposure test, such as volume, weight, hardness, tensile strength, elongation at break, vicat softening temperature, and other parameters, as shown in fig. 1, the polyethylene sample has stable change area of various performance parameters after the exposure test for 21 days.
By analyzing the infrared spectrogram of the polyethylene sample under various test conditions (see fig. 2, in fig. 2, 1 is an unexposed sample, 2 is a sample after being exposed for 2 days, 3 is a sample after being exposed for 21 days, and 4 is a sample after being exposed for 56 days), it can be seen that the infrared spectrogram of the sample does not change obviously, which indicates that the structural components of the sample do not change obviously after different test periods, and proves that the molecular structure of the polyethylene material is kept intact in the simulated exposure test environment.
And the appearance, the thermogravimetry-differential thermal curve and the like of the polyethylene sample are basically unchanged under various analysis conditions.
In summary, through the analysis, it is possible to construct an envelope tangent to each map curve according to the variation of the performance index shown in fig. 1, and determine tangent point data of each envelope, that is, it is possible to determine the technical indicators of the acceptability of the selected polyethylene pipe in the aging performance under the known oil and gas conditions (see table 1) as follows (see table 2):
TABLE 2 polyethylene aging Performance acceptability technical index (for this example)
Remarking: if the indexes listed in the table 2 are exceeded, the selected polyethylene pipe is not suitable for the oil-gas working condition environment in the table 1.
Example 2: make clear of the applicability of the new glass fiber reinforced plastic pipe material under the oil gas working condition
(1) Sample preparation: according to the requirements of GB/T1447-. All exposed samples were conditioned for 80h in a standard laboratory environment (23 ℃, 50% relative humidity).
(2) And (3) determining test conditions:
1) test medium: reference may be made to NACE TM 0298-2003, where a standard oilfield acidic water environment is selected as a simulated test environment for the FRP pipe, as shown in Table 3.
TABLE 3 simulation test conditions for FRP pipe high-temperature autoclave (acid water environment)
2) Test temperature: assuming that the maximum allowable service temperature of the acid anhydride cured glass fiber reinforced plastic pipe in the oil and gas transmission field in the embodiment is 63 ℃, the design service life is 30 years, namely tLifeTest time t 262800h and predicted 50% reduction in tensile modulusTestSelecting time-temperature conversion coefficient α as 0.05 for 2000h, substituting the parameters into formula (1), and calculating to obtain temperature difference of 42.2 deg.C
Thus, the test temperature of this example was determined to be 63+42.2 — 105.2 ℃.
3) And (3) test period: the standard test period was chosen to be 160h, as can be seen in NACE TM 0298-2003.
4) And (3) test states: the sample was placed statically in the kettle.
(3) Carrying out an exposure test: placing the sample after the state adjustment into a high-temperature high-pressure autoclave, and developing an exposure test strictly according to the operation flow of the high-temperature high-pressure autoclave;
(4) and (3) performance testing:
1) performance testing of the samples before exposure testing:
testing physical properties:
the dimensions of each specimen were measured with a vernier caliper to an accuracy of 0.02mm the mass of each specimen was measured with a balance to an accuracy of 1mg, in particular, the dry weight M of a 40mm × 40mm block sample before the exposure test was measured with a balance in an oven at 90 ℃ until the weight remained constant1To the nearest 1 mg;
measurement of mass m in air before immersion of other samples by Water replacement method with reference to NACE TM02961And mass m in deionized water (or absolute ethanol)3；
The samples were tested for Barkel hardness according to GB/T3854-2005.
Testing mechanical properties: the tensile properties of the test specimens, including the tensile breaking strength, elongation and elastic modulus of the material, are measured according to GB/T1447-.
Testing heat resistance: the glass transition temperature of the test specimens was tested according to the provisions of GB/T19466.2-2004. The test should be performed using 3 parallel samples.
Testing degradation performance: testing the infrared spectrum of the sample by using a Fourier infrared spectrometer; the thermogravimetry-differential thermal (TG-DSC) curve of the test specimens was tested using a differential scanning calorimeter.
2) Performance testing of the samples after exposure test:
after the exposure test was completed, the test was slowly stopped according to the high temperature autoclave procedure to prevent damage to the exposed sample, and then the sample was taken out. After drying the samples with cotton cloth or filter paper, the material performance parameters were measured at room temperature. After the soaking test is finished, the measurement of the performance parameters of the sample is preferably finished within 4 hours, and if the measurement cannot be finished within 4 hours, the sample is stored in the same liquid medium (normal pressure and normal temperature) as the soaking test.
Testing physical properties:
after the exposure test is finished, the sample is visually checked for damage to the outside, and the damage to the outside includes but is not limited to the following forms: cracks, delamination, swelling, bubbling, etc., and if necessary, cutting to check for structural changes in the interior of the specimen. The location and number of lesions should be recorded;
after the exposure test is finished, the size of each sample is measured to be 0.02mm by using a vernier caliper. And calculating the length change rate before and after each sample exposure test by adopting a formula (5):
the mass of each sample was measured to the accuracy of 1mg by a balance, in particular, the wet weight (mass of sample after wiping dry with cotton cloth or filter paper) M of a block sample of 40mm × 40mm after the exposure test was measured by a balance2And a dry weight M of the mixture which is dried continuously in an oven at 90 ℃ until the weight is unchanged3(ii) a Using a formula(2) Calculating the adsorption weight gain rate of a 40mm × 40mm block sample, and calculating the leaching weight loss rate of a 40mm × 40mm block sample by adopting a formula (3);
measuring mass m of other samples soaked in air by adopting water replacement method according to reference standard NACE TM02962And mass m in deionized water (or absolute ethanol)4Calculating the volume change rate of each sample before and after soaking by adopting a formula (6);
the samples were tested for Barkel hardness according to GB/T3854-2005.
Testing mechanical properties: the tensile properties of the test specimens, including the tensile breaking strength, elongation and elastic modulus of the material, were measured in accordance with GB/T1447-2005. The rate of change was calculated as compared to the measurements before the exposure test.
Testing heat resistance: the glass transition temperature of the test specimens was tested according to the provisions of GB/T19466.2-2004. The rate of change was calculated as compared to the measurements before the exposure test.
Testing degradation performance: the infrared spectrum of the sample after the exposure test is tested by a Fourier infrared spectrometer, and the thermogravimetry-differential thermal (TG-DSC) curve of the sample after the exposure test is tested by a differential scanning calorimeter and compared with the measured value before the exposure test.
(5) Results summary and analysis: and comparing and analyzing the appearance, size, volume, weight, hardness, tensile strength, elongation at break, modulus, infrared spectrum, TG-DSC curve and other performance index change conditions of the novel glass steel tube sample before and after the exposure test, and judging whether the glass steel tube sample meets the technical indexes of the qualification of the glass steel tube specified in the relevant standard. If any one of the glass fiber reinforced plastic pipes is not in accordance with the specification of the technical index of eligibility, the novel glass fiber reinforced plastic pipe is judged to be not suitable for simulating the oil gas working condition environment. As shown in fig. 3, 5 in fig. 3 is an unexposed sample; 6 is the exposed sample; after the exposure test of the novel glass fiber reinforced plastic pipe in the embodiment, the infrared spectrogram changes obviously, which indicates that the structural components of the polymer resin matrix selected by the glass fiber reinforced plastic change obviously, and although the technical parameters such as appearance, size, weight, tensile property and the like meet the requirements of the technical indexes of acceptability, the selected glass fiber reinforced plastic pipe is still judged to be not suitable for the simulated oil-gas working condition environment.
Example 3: determining the highest operation temperature of polyethylene pipe under the condition of known oil-gas working condition
(1) Sample preparation: according to the requirements of GB/T8804.3-2003, a dumbbell-shaped tensile specimen was cut out from a polyethylene pipe as a sample for exposure test, and a 25 mm. times.25 mm block-shaped specimen was cut out as a specimen for measuring weight and volume change. All exposed samples were conditioned for 40h in a standard laboratory environment (23 ℃, 50% relative humidity).
(2) And (3) determining test conditions:
1) test medium: the high-temperature autoclave simulation test conditions were established according to the known application conditions of the materials, as shown in table 1.
2) Test temperature: in this embodiment, the critical temperature meeting the qualification criterion is determined by comparing the test results of the simulation tests at different temperatures, that is, the maximum operating temperature of the polyethylene pipe under the oil-gas working condition is determined. In this example, the exposure test temperatures were set at 70 ℃ and 75 ℃ and 80 ℃ first.
3) And (3) test period: the fixed exposure test period was 21 days.
4) And (3) test states: and (4) dynamically stirring the mixture in a high-temperature high-pressure kettle.
(3) Carrying out an exposure test: placing the sample after the state adjustment into a high-temperature high-pressure autoclave, and developing an exposure test strictly according to the operation flow of the high-temperature high-pressure autoclave;
(4) and (3) performance testing:
1) performance testing of the samples before exposure testing:
testing physical properties:
the dimensions of each specimen were measured with a vernier caliper to an accuracy of 0.02mm the mass of each specimen was measured with a balance to an accuracy of 1mg, in particular, the dry weight M of a 25mm × 25mm block sample before the exposure test was dried continuously in an oven at 90 ℃ until the weight remained unchanged was measured with a balance1To the nearest 1 mg;
measurement of mass m in air before immersion of other samples by Water replacement method with reference to NACE TM02961And mass m in deionized water (or absolute ethanol)3；
The samples were tested for shore hardness as specified in ASTM D1708-13.
Testing mechanical properties: the tensile properties of the test specimens, including the tensile breaking strength, elongation and modulus of elasticity of the material, were measured according to the specifications of GB/T8804.3-2003 and were tested using 5 parallel test specimens.
Testing heat resistance: testing the Vicat softening temperature of the sample according to the regulation of GB/T1633-2000; testing the heat distortion temperature of the test sample according to the specification of GB/T1634.2-2004; according to the provisions of GB/T19466.6-2009, the samples were tested for oxidation induction time (isothermal OIT) or oxidation induction temperature (dynamic OIT). The test should be performed using 3 parallel samples.
Testing degradation performance: testing the infrared spectrum of the sample by using a Fourier infrared spectrometer; the thermogravimetry-differential thermal (TG-DSC) curve of the test specimens was tested using a differential scanning calorimeter.
2) Performance testing of the samples after exposure test:
after the exposure test for each test cycle was completed, the test was slowly stopped according to the high temperature autoclave procedure to prevent damage to the exposed sample, and then the sample was removed. After drying the samples with cotton cloth or filter paper, the material performance parameters were measured at room temperature. After the soaking test is finished, the measurement of the performance parameters of the sample is preferably finished within 4 hours, and if the measurement cannot be finished within 4 hours, the sample is stored in the same liquid medium (normal pressure and normal temperature) as the soaking test.
Testing physical properties:
after the exposure test is finished, the sample is visually checked for damage to the outside, and the damage to the outside includes but is not limited to the following forms: cracks, delamination, swelling, bubbling, etc., and if necessary, cutting to check for structural changes in the interior of the specimen. The location and number of lesions should be recorded;
after the exposure test is finished, the size of each sample is measured to be 0.02mm by using a vernier caliper. And calculating the length change rate of each sample before and after soaking by adopting a formula (5):
the mass of each sample was measured to the nearest 1mg using a balance. In particular, measuring violence on a balanceWet weight (mass of sample after wiping with cotton cloth or filter paper) M of 25mm × 25mm block sample after dew test2And a dry weight M of the mixture which is dried continuously in an oven at 90 ℃ until the weight is unchanged3Calculating the adsorption weight gain rate of a 25mm × 25mm block sample by adopting a formula (2), and calculating the leaching weight loss rate of a 25mm × 25mm block sample by adopting a formula (3);
measuring mass m of other samples soaked in air by adopting water replacement method according to reference standard NACE TM02962And mass m in deionized water (or absolute ethanol)4And calculating the volume change rate of each sample before and after soaking by adopting a formula (6):
the samples were tested for shore hardness as specified in ASTM D1708-13.
Testing mechanical properties: the tensile properties of the test specimens, including the tensile breaking strength, elongation and modulus of elasticity of the material, were measured in accordance with the specifications of GB/T8804.3-2003. The rate of change was calculated as compared to the measurements before the exposure test. The tensile break strength can also be replaced by the tensile yield strength.
Testing heat resistance: testing the Vicat softening temperature of the sample according to the regulation of GB/T1633-2000; testing the heat distortion temperature of the test sample according to the specification of GB/T1634.2-2004; according to the provisions of GB/T19466.6-2009, the samples were tested for oxidation induction time (isothermal OIT) or oxidation induction temperature (dynamic OIT). The rate of change was calculated as compared to the measurements before the exposure test.
Testing degradation performance: the infrared spectrum of the sample after the exposure test is tested by a Fourier infrared spectrometer, and the thermogravimetry-differential thermal (TG-DSC) curve of the sample after the exposure test is tested by a differential scanning calorimeter and compared with the measured value before the exposure test.
(5) And (4) summarizing the results: and sequentially measuring various performance indexes of the samples at different test temperatures (70 ℃, 75 ℃ and 80 ℃), and drawing a relation graph of various performance changes and test periods so as to obtain the aging performance change rule of the polyethylene material under the known oil gas working condition at different test temperatures.
(6) And (4) analyzing results: and comparing and analyzing the appearance, size, volume, weight, hardness, tensile strength, elongation at break, modulus, infrared spectrum, TG-DSC curve and other performance index change conditions of the polyethylene pipe sample before and after the exposure test, and judging whether the polyethylene pipe sample meets the qualification technical indexes shown in the table 2. Stopping the next exposure test if any one of the exposure test temperatures is not in accordance with the specification of the qualified technical index, wherein the temperature is the highest operation temperature of the polyethylene pipe under the oil-gas working condition; otherwise, the temperature can be continuously increased (at intervals of 5 ℃) to carry out an exposure test, and the highest operation temperature of the polyethylene pipe is determined according to the qualification condition of the technical indexes.
The envelope is mainly used for determining the technical index of the qualification of the material under the oil and gas working condition environment, and the embodiment 2 and the embodiment 3 are equivalent to verifying whether the novel material is applicable in a standard oil and gas medium (embodiment 2) or verifying the operation boundary condition of the material, such as the highest operation temperature (embodiment 3), on the premise that the technical index of the qualification is determined through the envelope.
The test method is simple and feasible, has short test period, comprehensively considers the actual running state of the non-metallic material in the oil-gas environment, has comprehensive performance indexes of sample test and high accuracy of test results, and can be directly used for guiding the material selection of the non-metallic material for oil-gas transmission.
Claims (8)
1. An accelerated test method for testing the aging performance of a non-metallic material for oil and gas transmission is characterized by comprising the following steps: establishing test conditions for simulating the actual running state of the non-metallic material in an oil-gas environment, carrying out an accelerated exposure test by using a high-temperature high-pressure kettle, measuring the physical properties, the mechanical properties, the heat resistance and the degradation behaviors before and after the exposure test, and drawing a performance change rule map of the physical properties, the mechanical properties, the heat resistance and the degradation behaviors of the non-metallic small samples before and after different accelerated exposure test periods; by constructing an envelope tangent to different map curves, taking a longitudinal coordinate value corresponding to the position of the tangent point as a technical index for determining the qualification of the corresponding performance of the non-metallic material in an oil-gas working condition environment, if any single performance of the non-metallic material is greater than the longitudinal coordinate value corresponding to the position of the tangent point, the non-metallic material is unqualified, and if all the performances of the non-metallic material are less than the longitudinal coordinate value corresponding to the position of the tangent point, the non-metallic material is qualified.
2. The accelerated test method for testing the aging performance of non-metallic materials for oil and gas transportation according to claim 1, wherein: the non-metallic material is a thermoplastic, thermoset, elastomer or composite.
3. The accelerated test method for testing the aging performance of non-metallic materials for oil and gas transportation according to claim 1, wherein: the method for establishing the test conditions for simulating the actual running state of the non-metallic material in the oil-gas environment comprises the following steps: test medium, test pressure, test temperature, test period and test state.
4. The accelerated test method of testing the aging performance of non-metallic materials for oil and gas transportation of claim 3, wherein: the test temperature is determined by the difference between the test temperature and the maximum allowable use temperature, and the difference between the test temperature and the maximum allowable use temperature is obtained by the following formula:
in the formula:
α -time-temperature conversion coefficient;
tLife-design life;
tTesttest time for 50% reduction in tensile modulus of the specimen;
Δ T-the difference between the test temperature and the maximum allowable use temperature.
5. The accelerated test method of testing the aging performance of non-metallic materials for oil and gas transportation of claim 4, wherein: when the non-metallic material is polyethylene material, taking alpha as 0.11; the default value for alpha is 0.05 when the non-metallic material is a multi-layer material composed of two or more materials, or when a non-ductile failure mode occurs in the non-metallic material.
6. The accelerated test method for testing the aging performance of non-metallic materials for oil and gas transportation according to claim 1, wherein: the physical properties comprise the weight change of the non-metallic material, and the adsorption weight gain and the leaching weight loss of the non-metallic material are respectively measured; the adsorption weight gain refers to the weight difference between the wet weight of the non-metal material after the exposure test and the dry weight of the fully dried non-metal material, and the leaching weight loss refers to the weight difference between the dry weight of the fully dried non-metal material after the exposure test and the dry weight of the non-exposed sample; the calculation formulas of the adsorption weight gain rate and the leaching weight loss rate are as follows:
adsorption weight gain (%) ((M)2–M3)/M1))*100………………(2)
Leaching weight loss ratio (%) ((M)3–M1)/M1))*100………………(3)
In the formula:
M1the dry weight of the non-metallic material before the exposure test when the non-metallic material is continuously dried in an oven at 90 ℃ until the weight is unchanged;
M2-refers to the wet weight of the non-metallic material after the exposure test;
M3and means the dry weight of the non-metallic material after the exposure test when the non-metallic material is continuously dried in an oven at 90 ℃ until the weight is unchanged.
7. The accelerated test method for testing the aging performance of non-metallic materials for oil and gas transportation according to claim 1, wherein: also included is the determination of the degradation performance before and after the exposure test.
8. The accelerated test method of testing the aging performance of non-metallic materials for oil and gas transportation of claim 7, wherein: the degradation performance is measured by a structural component test of infrared spectrum, a heat weight-differential heat resistance test, an X-ray photoelectron spectrum test, a static thermal mechanical test or a dynamic thermal mechanical test.
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