Method for evaluating long-term service performance of flexible composite pipe

Abstract

The application discloses a long-term service performance evaluation method of a flexible composite pipe, and comprises the following steps: obtaining the limit pressure of the flexible composite pipe at the current service time and the limit time required to reach the limit pressure; obtaining the safe working pressure of the flexible composite pipe under the specific working condition environment at the long-term service time and the residual service time; establishing a linear relationship between the working pressure and the service time through the above parameters; selecting at least one test time between the limit time and the residual service time, and obtaining the maximum working pressure at the test time according to the linear relationship; loading the test time and the maximum working pressure at the test time on the flexible composite pipe to perform a survival test, if the survival test is passed, the flexible composite pipe meets the long-term service requirement, otherwise, the flexible composite pipe does not meet the long-term service requirement. The method reduces the workload, is high in operability, and can quickly respond to the long-term service performance of the flexible composite pipe under different working condition conditions in an oil and gas field.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of long-term service performance evaluation of flexible composite pipe, and relates to a long-term service performance evaluation method of flexible composite pipe. BACKGROUND

[0002] In recent years, the ground carbon steel pipelines of oilfield development have failed frequently, and the main cause of failure is internal corrosion. The typical failure mode of internal corrosion is H2S+CO2 coexisting electrochemical corrosion. Flexible composite high-pressure conveying pipe (hereinafter referred to as flexible composite pipe) has excellent corrosion resistance, fewer connection joints, and is convenient for transportation, installation and maintenance; good bending performance, suitable for desert terrain laying; low hydraulic friction, wear-resistant, and delay waxing and scaling. With the above advantages, the application of flexible composite pipe has become one of the important means to solve the corrosion problem, and has been widely used in domestic and foreign oil and gas field water injection and gathering and transportation fields. Flexible composite pipe has been applied in the fields of oil and gas mixed transportation, water injection and water transportation, oil gathering and transportation, and gas gathering and transportation in the western oilfield. The pressure distribution of flexible composite pipe in the field of oil and gas mixed transportation is 0.2-10 MPa; the temperature distribution is 5-80℃, mainly concentrated in 15-60℃. In the field of water injection and water transportation, the pressure distribution is 0.1-24 MPa, mainly concentrated in 0.1-24 MPa; the temperature distribution is 15-80℃, mainly concentrated in 20-60℃. In the field of oil gathering and transportation, the pressure distribution is 0.1-13 MPa, mainly concentrated in 0.1-2 MPa, and the temperature distribution is 20-65℃, mainly concentrated in 20-60℃. In the field of gas gathering and transportation, the pressure distribution is 0.2-14 MPa; the temperature distribution is 20-65℃, mainly concentrated in 10-50℃, mainly concentrated in 15-35℃. In summary, flexible composite pipe has been widely used in oilfield sites, and the application of flexible composite pipe has greatly solved the corrosion problem in oilfield sites. However, the service conditions of flexible composite pipe are complex, and the service pressure and temperature range are wide, in order to meet the needs of oilfield production, higher requirements are put forward for the long-term safe service of flexible composite pipe. Therefore, it is of great significance to establish a method for quickly evaluating the long-term service performance of flexible composite pipe for the safe operation of flexible composite pipe.

[0003] The reference standard API 15S 5.3.3, the MPR of PFR shall be determined by a series of creep rupture tests at the evaluation test temperature and constant pressure. The test shall be conducted according to Procedure B as specified in ASTM D2992-12, the data points with failure time less than 10h shall be excluded from the regression calculation, the detailed test scheme is shown in Table 1. The temperature of the evaluation test is selected by the manufacturer, shall not be lower than the design temperature of the product under any application condition, the recommended evaluation test temperature is 65℃ (polyethylene composite pipe reinforced by polyester fiber). The allowed failure mode is tensile rupture of the reinforcement. If the failure mode is not tensile rupture of the reinforcement during the evaluation test, such as the pipe body is pulled out from the joint or sleeve, the test result shall be discarded when calculating the average value or using the data plot, the part of data collection in the pressure rating evaluation test of flexible composite pipe in the prior art is shown in Table 2. Figure 1 .

[0004] Table 1 MPR failure point distribution (reference ASTM D2992-12)

[0005] Failure time (h) Failure point Design failure point 10～1000 At least 4 11 1000～6000 At least 3 3 More than 6000 At least 3 3 More than 10000 At least 1 1 Total number At least 18 18

[0006] The specific embodiment of the prior art is:

[0007] a) 65℃ water pressure burst strength test is carried out on the test sample pipe, and the ultimate strength value is obtained;

[0008] b) according to the ultimate strength value, the pressure value corresponding to the failure time of 10-1000h is deduced, and 11 failure points of two specifications are collected within two months;

[0009] c) according to the distribution of 10-1000h failure points, the regression curve is preliminarily drawn, and the corresponding relationship between the subsequent test time and pressure distribution is calculated, and the pressure value corresponding to the subsequent test failure point is given;

[0010] d) 6000-10000h test point collection work is carried out, a total of 3 points;

[0011] e) 1000-6000h test point collection work is carried out, a total of 3 points.

[0012] The above implementation steps and the attached Figure 1 It can be seen that the pressure rating evaluation test specified in API 15S includes the collection of 18 effective data points, and the longest test time is 10000 hours, so the evaluation method has huge workload, long test period and uncontrollable effective data in the test process. SUMMARY

[0013] In view of the problems in the prior art, the application provides a long-term service performance evaluation method of a flexible composite pipe, so that long-term service performance evaluation of the flexible composite pipe can be completed in a shorter time.

[0014] The application is realized by the following technical scheme:

[0015] A long-term service performance evaluation method of a flexible composite pipe comprises the following steps:

[0016] S1: Obtain the limit pressure at the current service time of the flexible composite pipe and the limit time required to reach the limit pressure; obtain the maximum working pressure at the limit service time of the flexible composite pipe and the remaining service time;

[0017] S2: Establish a linear relationship between the maximum working pressure and the service time of the flexible composite pipe within the service time by using the limit pressure at the current service time, the limit time required to reach the limit pressure, the maximum working pressure at the limit service time and the remaining service time obtained in step S1;

[0018] S3: Select at least one test time between the limit time required to reach the limit pressure and the remaining service time, and obtain the maximum working pressure of the flexible composite pipe at the test time by using the linear relationship established in step S2;

[0019] S4: Perform a survival test on the flexible composite pipe by loading the test time and the maximum working pressure of the flexible composite pipe at the test time obtained in step S3; if the flexible composite pipe passes the survival test, the flexible composite pipe meets the long-term service requirement; otherwise, the flexible composite pipe does not meet the long-term service requirement.

[0020] Preferably, the limit pressure at the current service time of the flexible composite pipe and the limit time required to reach the limit pressure are obtained by using a water pressure burst test.

[0021] Preferably, the maximum working pressure at the limit service time is obtained by using the nominal pressure, the pressure safety factor, the temperature reduction factor and the medium reduction factor of the flexible composite pipe, and specifically:

[0022] MOP=NPR×η×f t ×f f (1)

[0023] In the formula:

[0024] MOP is the maximum working pressure of the flexible composite pipe at the limit service time;

[0025] NPR is the nominal pressure of the flexible composite pipe;

[0026] η is a pressure safety factor of the flexible composite pipe;

[0027] f t is a temperature reduction factor of the flexible composite pipe;

[0028] f f is a medium reduction factor of the flexible composite pipe.

[0029] Preferably, the temperature reduction factor is obtained by a pipe material type of the flexible composite pipe and a maximum allowable service temperature.

[0030] Preferably, the medium reduction factor is obtained by a test medium of the flexible composite pipe, in particular:

[0031] when the test medium is gas, the medium reduction factor is not greater than 0.67;

[0032] when the test medium is liquid hydrocarbon and multiphase fluid, the medium reduction factor is not greater than 0.8;

[0033] when the test medium is water, the medium reduction factor is not greater than 1.

[0034] Preferably, the remaining service time is obtained by an expected life of the flexible composite pipe and a served life, in particular:

[0035] t sy = t yq - t fy (2)

[0036] wherein:

[0037] t sy is a remaining service time of the flexible composite pipe;

[0038] t yq is an expected life of the flexible composite pipe;

[0039] t fy is a served life of the flexible composite pipe.

[0040] Preferably, the linear relationship in the step S2 is in particular:

[0041]

[0042] wherein,

[0043] x is a logarithmic value of a service time of the flexible composite pipe;

[0044] y is a logarithmic value of a maximum working pressure in the service time of the flexible composite pipe;

[0045] x1 is a logarithmic value of the limit time required to reach the limit pressure at the current service time;

[0046] y1 is a logarithmic value of the limit pressure of the flexible composite pipe at the current service time;

[0047] x2 is a logarithmic value of the remaining service time of the flexible composite pipe;

[0048] y2 is a logarithmic value of the maximum working pressure of the flexible composite pipe at the limit service time;

[0049] The base number of the logarithmic value is 10.

[0050] Preferably, the test time selected in the step S3 is 1000h.

[0051] Preferably, the test temperature of the survival test in the step S4 is 0-100 DEG C, and the test medium is any one of water, oil, multiphase flow or gas.

[0052] Preferably, the flexible composite pipe comprises a polyester industrial filament reinforced polyethylene composite pipe, a polyester industrial filament reinforced crosslinked polyethylene composite pipe, a polyester industrial filament reinforced heat-resistant polyethylene composite pipe and an aramid filament reinforced polyvinylidene fluoride composite pipe.

[0053] Compared with the prior art, the present application has the following beneficial technical effects:

[0054] The present application provides a long-term service performance evaluation method of a flexible composite pipe, which takes the limit pressure of the flexible composite pipe at the current service time and the limit time required to reach the limit pressure as a group of data, takes the maximum working pressure of the flexible composite pipe at the limit service time and the remaining service time as a group of data, obtains the linear relationship of the long-term service performance of the flexible composite pipe through linear fitting of the two groups of data, selects at least one test time in the service period, obtains the maximum working pressure at the test time by combining the linear equation, and performs a survival test by using the test time and the maximum working pressure at the test time, thereby verifying the long-term service performance of the flexible composite pipe. The method greatly reduces the workload, has strong operability, can quickly respond to the long-term service performance of the flexible composite pipe under different working conditions in oil and gas fields, and provides strong support for the long-term safe service of the flexible composite pipe in oil and gas fields.

[0055] Further, the limit pressure of the flexible composite pipe at the current service time and the limit time required to reach the limit pressure are obtained by using a water pressure burst test, which is convenient to operate and reliable in result.

[0056] Further, the long-term safe operation of the pipeline is fully considered, the pressure safety factor is introduced on the basis of the nominal pressure, the temperature reduction factor is introduced considering that the lining material of the flexible composite pipe is greatly affected by temperature, and the medium reduction factor is introduced considering that the medium is different during the operation and test of the flexible composite pipe, so that the nominal pressure of the flexible composite pipe is corrected by parameters such as the medium reduction factor, the simulated result is more in line with the actual situation, and the result is more reliable.

[0057] Further, the test time in step S3 is 1000h, and the long-term service capability of the flexible composite pipe can be more accurately reflected. BRIEF DESCRIPTION OF DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0059] Figure 1 Part of the data collection in the pressure grade evaluation test of the flexible composite pipe in the prior art;

[0060] Figure 2 The linear relationship between the maximum working pressure in the service time of the flexible composite pipe and the service time established in the present application;

[0061] Figure 3 The linear relationship between the maximum working pressure in the service time of the flexible composite pipe and the service time established in the present application. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0063] Therefore, the detailed description of the embodiments of the present application provided in the drawings below is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0064] It should be noted that like reference numerals and characters refer to like elements throughout the several views of the drawings, and that, unless otherwise indicated, like reference numerals and characters in different figures indicate like elements throughout the several views of the drawings.

[0065] In the description of the embodiments of the present application, it should be noted that the orientation or position relationship indicated by the terms "upper", "lower", "horizontal", "inner" and the like is based on the orientation or position relationship shown in the drawings or the orientation or position relationship in which the product of the present application is usually placed, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0066] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0067] In the description of the embodiments of the present application, it should also be noted that, unless otherwise specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0068] The present application will be described in further detail below with reference to the accompanying drawings:

[0069] Embodiment 1

[0070] A method for evaluating the long-term service performance of a flexible composite pipe, comprising the following steps:

[0071] S1: Obtain the limit pressure P of the flexible composite pipe to be evaluated at the current service time burst and the limit time t required to reach the limit pressure burst , to obtain a set of data (t burst , P burst ); Obtain the maximum working pressure MOP of the flexible composite pipe at the limit service time and the remaining service time t sy , to obtain a set of data (t sy , MOP). Specifically, the following steps are taken:

[0072] S1.1: cut the test sample from the flexible composite pipe section, and process it into a standard sample conforming to the water pressure blasting, hydrostatic pressure test, and adjust the sample state according to the standard requirements. At the service temperature, the water pressure blasting test is used to obtain the limit pressure P of the flexible composite pipe at the current service time burst and the limit time t required to reach the limit pressure burst . The embodiment takes DN150 PN6.4 MPa type I flexible composite pipe as an example, the blasting pressure is 36 MPa, and the blasting time is 60 s (0.017 h), that is, t burst = 0.017 h, P burst = 36 MPa.

[0073] S1.2: Obtain the maximum working pressure at the limit service time through the nominal pressure, pressure safety factor, temperature reduction factor and medium reduction factor of the flexible composite pipe, specifically:

[0074] MOP = NPR x η x f t x f f (1)

[0075] In the formula:

[0076] MOP is the maximum working pressure of the flexible composite pipe at the limit service time, in units of megapascal (MPa);

[0077] NPR is the nominal pressure of the flexible composite pipe, in units of megapascal (MPa);

[0078] η is the pressure safety factor of the flexible composite pipe, which is 1.5;

[0079] f t is the temperature reduction factor of the flexible composite pipe;

[0080] f f is the medium reduction factor of the flexible composite pipe.

[0081] The flexible composite pipe in the application is divided into five types, which are polyester industrial filament reinforced polyethylene composite pipe (type I), polyester industrial filament reinforced cross-linked polyethylene composite pipe (type II), polyester industrial filament reinforced heat-resistant polyethylene composite pipe (type III), aramid filament reinforced polyvinylidene fluoride composite pipe (type IV) and other types (type V). The temperature reduction factor is obtained by the pipe type and the highest allowable service temperature of the flexible composite pipe. The selection of the temperature reduction factor should comply with the provisions of Table 2, Table 3 and Table 4. For other types (type V) of pipe, the temperature reduction factor is provided by the manufacturer when the long-term service performance evaluation is carried out by the application.

[0082] Table 2 Temperature reduction factor of type I and type III composite pipes at different service temperatures

[0083] Temperature t, °C 20＜t≤30 30＜t≤40 40＜t≤50 50＜t≤60 60＜t≤70 Temperature reduction factor 0.95 0.90 0.86 0.81 0.7

[0084] Table 3 Temperature reduction factor of Type II composite pipe at different service temperatures

[0085] Temperature t, °C 20＜t≤50 50＜t≤60 60＜t≤70 70＜t≤75 Temperature reduction factor 1 0.90 0.82 0.70

[0086] Table 4 Temperature reduction factor of Type IV composite pipe at different service temperatures

[0087] Temperature t, °C 20＜t≤70 70＜t≤80 80＜t≤90 90＜t≤100 100＜t≤110 Temperature reduction factor 1 0.97 0.95 0.9 0.88

[0088] The medium reduction factor is obtained by the test medium of the flexible composite pipe, specifically:

[0089] When the test medium is gas, the medium reduction factor is not greater than 0.67;

[0090] When the test medium is liquid hydrocarbon and multiphase fluid, the medium reduction factor is not greater than 0.8;

[0091] When the test medium is water, the medium reduction factor is not greater than 1.

[0092] For a DN150 PN6.4 MPa Type I flexible composite pipe, it is known that the nominal pressure NPR thereof is 6.4 MPa, the maximum allowable service temperature is 65℃, and the test medium is water, then the maximum working pressure of the flexible composite pipe at the limit service time = nominal pressure * pressure safety factor * temperature reduction factor * medium reduction factor, that is, MOP = 6.4 x 1.5 x 0.7 x 1 = 6.72 MPa.

[0093] S1.3: The remaining service time is obtained by the expected life of the flexible composite pipe and the served years, specifically:

[0094] t sy = t yq -t fy (2)

[0095] In the formula:

[0096] t sy is the remaining service time of the flexible composite pipe;

[0097] t yq is the expected life of the flexible composite pipe;

[0098] t fy is the served years of the flexible composite pipe.

[0099] The expected life of the flexible composite pipe in the industry is 20 years, if it is a new pipe, the remaining service time is 20 years, that is, t sy= 20 x 365 x 24h = 175200h; if the service life is 4 years, the remaining service time t sy = 20 - 4 = 16 years, i.e. t sy = 16 x 365 x 24h = 140160h, which can be accurate to months.

[0100] S2: Establish a linear relationship between the maximum working pressure and the service time of the flexible composite pipe within the service time of the flexible composite pipe by the limit pressure at the current service time of the flexible composite pipe obtained by step S1, the limit time required to reach the limit pressure, the maximum working pressure of the flexible composite pipe at the limit service time, and the remaining service time, and the linear relationship is specifically:

[0101]

[0102] The linear relationship is seen in Figure 2 , wherein,

[0103] x is the logarithmic value of the service time of the flexible composite pipe;

[0104] y is the logarithmic value of the maximum working pressure within the service time of the flexible composite pipe;

[0105] x1 is the logarithmic value of the limit time t burst required to reach the limit pressure;

[0106] y1 is the logarithmic value of the limit pressure P burst at the current service time of the flexible composite pipe;

[0107] x2 is the logarithmic value of the remaining service time t sy ; and

[0108] y2 is the logarithmic value of the maximum working pressure MOP at the limit service time;

[0109] The base of the logarithmic value is 10.

[0110] In this embodiment, t burst = 0.017h, P burst = 36MPa, t sy = 140160h, and MOP = 6.72MPa. That is, the parameters required for evaluating the long-term service performance of the flexible composite pipe in Table 5 are obtained.

[0111] Table 5 Parameters required for evaluating the long-term service performance of the flexible composite pipe

[0112] Parameter <![CDATA[t burst (h)]]> P burst (MPa) <![CDATA[t sy (h)]]> MOP (MPa) Value 0.017 36 140160 6.72

[0113] The specific process of obtaining the linear relationship is as follows:

[0114] S2.1: The two sets of data (tburst , P burst ) and (t sy , MOP) are taken as the logarithm with base 10, we get:

[0115]

[0116] That is, according to the logarithm with base 10 of the abscissa and ordinate values of the two sets of data (0.017, 36) and (140160, 6.72), we get: (-1.770, 1.556), (5.147, 0.827).

[0117] S2.1: Substitute the two sets of data (x1, y1) and (x2, y2) into y = ax + b to get:

[0118] y1 = ax1 + b (3.1)

[0119] y2 = ax2 + b (3.2)

[0120] Further deduce:

[0121]

[0122] That is, the equation of the fitted straight line is:

[0123]

[0124] According to the two sets of data (-1.770, 1.556) and (5.147, 0.827), we get the linear equation of DN150 PN6.4 MPa Type I flexible composite pipe at 65℃:

[0125] y = -0.101x + 1.318 (3.3)

[0126] S3: Select at least one test time between the limit time required to reach the limit pressure and the remaining service time, and obtain the maximum working pressure of the flexible composite pipe at the test time through the linear relationship established in step S2;

[0127] The test time selected in this step is 1000h; the test temperature range is usually between 0-100℃; the test medium is water, oil or multiphase flow, gas;

[0128] According to the above obtained formula 3.3, the maximum working pressure at 1000h at the corresponding temperature is obtained, that is:

[0129]

[0130] y = 1.015

[0131] That is,

[0132] Therefore, the maximum working pressure P of the DN150 PN6.4 MPa flexible composite pipe at 1000h is 10.35 MPa. 1000h

[0133] Therefore, it can be known that the maximum working pressure of the DN150 PN6.4 MPa flexible composite pipe at 1000h under the theoretical condition is 10.35 MPa at 65 DEG C.

[0134] S4: The maximum working pressure of the flexible composite pipe at the test time and the test time under the theoretical condition is subjected to a survival test, if the flexible composite pipe passes the survival test, the flexible composite pipe meets the long-term service requirement, otherwise, the flexible composite pipe does not meet the long-term service requirement.

[0135] In this embodiment, the hydrostatic pressure test, i.e. the survival test, is carried out at 1000h and 10.35 MPa, and the result is that the flexible composite pipe passes the survival test under the condition, and the flexible composite pipe meets the long-term service requirement.

[0136] The application provides a long-term service performance evaluation method of a flexible composite pipe. The temperature correction coefficient is determined by the type of the flexible composite pipe corresponding to the service temperature, the medium correction coefficient is determined by the service medium condition, the long-term service working pressure corresponding to 20 years is deduced, the limit strength corresponding to the burst time is obtained through the short-term burst test at the service temperature. The long-term service performance fitting curve and the linear equation of the flexible composite pipe are deduced through linear fitting of the above two groups of data, and the survival test pressure at 1000h is calculated.

[0137] The application comprehensively considers that the long-term service performance of different pipe materials is different under different service temperatures, and the flexible composite pipe is divided into (I-V type) according to the temperature resistance difference of different types of flexible composite pipes, and the temperature reduction coefficient f of different types of flexible composite pipes is different. t Meanwhile, the application comprehensively considers the long-term safe operation of the pipeline, introduces a safety factor of 1.5 times on the basis of the nominal pressure; considers that the lining material of the flexible composite pipe is greatly affected by temperature, and therefore introduces the temperature reduction coefficient f t ; considers that the medium is different in the operation process and the test process of the flexible composite pipe, and introduces the medium reduction coefficient f f . The long-term service performance evaluation test method of the flexible composite pipe is established according to the long-term safe service engineering application background of the oil and gas field environment.

[0138] ​The application establishes a relatively harsh indoor accelerated survival test method, through obtaining the burst limit time and pressure of different types of flexible composite pipes at corresponding service temperatures and the maximum working pressure corresponding to the long-term service time, using linear fitting to obtain the long-term service curve and equation, obtaining the survival test pressure corresponding to 1000h, and quickly judging the long-term service performance of the flexible composite pipe through 1000h survival test.

[0139] The application effectively overcomes the defects of long test period and complicated workload of API 15S pressure rating evaluation test, greatly reduces the workload, has strong operability, can quickly respond to the long-term service performance of the flexible composite pipe under different working conditions in the oil and gas field, and provides strong support for the long-term safe service of the flexible composite pipe in the oil and gas field. In addition, the method of the application can also be used for long-term service performance evaluation of non-metal pipes such as glass steel pipes, PE pipes and plastic alloy pipes used in the oil and gas field.

[0140] Example 2

[0141] Taking DN150 PN6.4 MPa type I composite pipe as an example, according to the 1000h survival test pressure calculation method of SY / T 6794-2010 (API 15S), the pipe is a new pipe, t burst = 0.017h, P burst = 17.1 MPa. In the water system test, at 65 DEG C, the maximum working pressure of the flexible composite pipe at the limit service time is equal to the nominal pressure * the pressure safety factor * the temperature reduction factor * the medium reduction factor, i.e. MOP = 6.4 * 1.5 * 0.7 * 1 = 6.72 MPa, after 20 years. That is, the parameters required for evaluating the long-term service performance of the flexible composite pipe in Table 6 are obtained.

[0142] Table 6 Calculation parameters required for evaluating the long-term service performance of the flexible composite pipe

[0143] Parameter <![CDATA[t burst (h)]]> P burst (MPa)

[00100] (h) sy (h) MOP (MPa) Value 0.017 17.1 175200 6.72

[0144] Linear equation solving: according to two groups of data (0.017, 17.1) and (175200, 6.72), log 10 ) is obtained (-1.770, 1.233), (5.244, 0.8274), and the fitting straight line equation is determined as y = -0.05783x + 1.1307. According to the linear equation, the test pressure of the DN150 PN6.4 MPa flexible composite pipe at 65 DEG C for 1000h is 9.06 MPa, and after 1000h, the pipe is scrapped after 9.06 MPa hydrostatic test, so it does not meet the long-term service requirement.

[0145] Example 3

[0146] DN65 PN6.4 MPa Type I composite pipe as an example, according to the SY / T 6794-2010 (API 15S) 1000h survival test pressure calculation method, the pipeline has been in service for 3 years, t burst = 0.017h, P burst = 34.7MPa. In the water system test, at 65℃, the maximum working pressure of flexible composite pipe at the limit service time is = nominal pressure * pressure safety factor * temperature reduction factor * medium reduction factor, i.e. MOP = 6.4 * 1.5 * 0.7 * 1 = 6.72MPa. That is, the parameters required for evaluating the long-term service performance of flexible composite pipe in Table 7 are obtained.

[0147] Table 7 Example 3 calculation parameters required for evaluating the long-term service performance of flexible composite pipe

[0148] Parameter <![CDATA[t burst (h)]]> P burst (MPa)

[00100] (h) sy (h) MOP (MPa) Value 0.017 34.7 148920 6.72

[0149] Linear equation solution: according to two groups of data (0.017, 34.7) and (148920, 6.72) take the logarithm of 10 to get (-1.770, 1.540) and (5.173, 0.827), which determines the fitting straight line equation as: y = -0.1027x + 1.358. As shown in the attached Figure 3 figure, according to the linear equation, the corresponding test pressure of the plastic alloy pipe sample after service for 1000h is 11.22MPa. After 1000h, 11.22MPa hydrostatic test, the pipeline passes the survival test, which meets the long-term service requirements.

[0150] Example 4

[0151] DN50 PN32 MPa Type III composite pipe as an example, according to the SY / T 6794-2010 (API 15S) 1000h survival test pressure calculation method, the pipeline is a new pipe, t burst = 0.017h, P burst = 68.21MPa. In the water system test, at 65℃, the maximum working pressure of flexible composite pipe at the limit service time is = nominal pressure * pressure safety factor * temperature reduction factor * medium reduction factor (Type III), i.e. MOP = 32 * 1.5 * 0.7 * 1 = 33.6MPa. That is, the parameters required for evaluating the long-term service performance of flexible composite pipe in Table 8 are obtained.

[0152] Table 8 Example 4 calculation parameters required for evaluating the long-term service performance of flexible composite pipe

[0153] Parameter <![CDATA[t burst (h)]]> P burst (MPa) <![CDATA[t sy (h)]]> MOP (MPa) Value 0.017 68.21 175200 33.6

[0154] Linear equation solving: according to two groups of data (0.017, 68.21) and (175200, 33.6) take logarithm (log 10 ) get (-1.770, 1.834), (5.244, 1.52634) determine fitting straight line equation is: y=-0.0439x+1.7564. According to the linear equation, DN50 PN32 MPa flexible composite pipe at 65 DEG C. 1000h corresponding test pressure is 42.14MPa, after 1000h, 42.14MPa hydrostatic test, the pipeline is scrapped, then does not meet the long-term service requirements.

[0155] Example 5

[0156] DN80 PN16 MPa type II composite pipe as an example, according to SY / T 6794-2010 (API 15S) 1000h survival test pressure calculation method, the pipeline is new, 65 DEG C., t burst =0.017h, P burst =51.7MPa. In water system test, 65 DEG C., 20 years, the maximum working pressure of flexible composite pipe at the limit service time in water system test, 65 DEG C., 20 years, the maximum working pressure of flexible composite pipe at the limit service time = nominal pressure * pressure safety factor * temperature reduction coefficient * medium reduction coefficient, that is, MOP=16*1.5*0.7*1=16.8MPa. That is, the parameters required for evaluating the long-term service performance of flexible composite pipe in table 9 are obtained.

[0157] Table 9 calculation parameters required for evaluating the long-term service performance of flexible composite pipe

[0158] Parameter

[00100] (h) burst (h) P burst (MPa)

[00100] (h) sy (h) MOP (MPa) Value 0.017 51.7 175200 16.8

[0159] Linear equation solving: according to two groups of data (0.017, 51.7) and (175200, 16.8) take logarithm (log 10 ) get (-1.770, 1.7135), (5.244, 1.2253) determine fitting straight line equation is: y=-0.0696x+1.5903. According to the linear equation, DN80 PN16 MPa flexible composite pipe at 65 DEG C. 1000h corresponding test pressure is 24.07MPa, after 1000h, 24.07MPa hydrostatic test, the pipeline is normal, then meets the long-term service requirements.

[0160] The above only for the preferred embodiments of the present application, and does not limit the present application, for those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A method for evaluating long-term service performance of a flexible composite pipe, characterized by, The method comprises the following steps: S1: obtaining the limit pressure at the current service time of the flexible composite pipe and the limit time required to reach the limit pressure; obtaining the maximum working pressure at the limit service time of the flexible composite pipe and the residual service time; S2: establishing a linear relationship between the maximum working pressure and the service time of the flexible composite pipe within the service time of the flexible composite pipe by using the limit pressure at the current service time, the limit time required to reach the limit pressure, the maximum working pressure at the limit service time and the residual service time obtained in step S1; S3: selecting at least one test time between the limit time required to reach the limit pressure and the residual service time, and obtaining the maximum working pressure of the flexible composite pipe at the test time by using the linear relationship established in step S2; S4: loading the test time and the maximum working pressure of the flexible composite pipe at the test time obtained in step S3 on the flexible composite pipe, and performing a survival test on the flexible composite pipe; if the flexible composite pipe passes the survival test, the flexible composite pipe meets the long-term service requirement; otherwise, the flexible composite pipe does not meet the long-term service requirement; The limit pressure at the current service time of the flexible composite pipe and the limit time required to reach the limit pressure are obtained by using a water pressure burst test. The maximum working pressure at the limit service time is obtained by using the nominal pressure, the pressure safety factor, the temperature reduction factor and the medium reduction factor of the flexible composite pipe, and is specifically as follows: （1） In the formula: Pmax is the maximum working pressure of the flexible composite pipe at the end of its service life; P is the nominal pressure of the flexible composite pipe; a pressure safety factor for the flexible composite pipe; temperature reduction factor for the flexible composite pipe; a medium reduction factor for the flexible composite pipe; The linear relationship in step S2 is specifically as follows: （3） In the formula, This is the logarithm of the service time of the flexible composite pipe; the maximum working pressure for the flexible composite pipe over its service life; logarithmic value of the limit time required to reach the limit pressure at the current service time; log limit pressure for the current service time of the flexible composite pipe; ln(RT) is the log value of the remaining service time for the flexible composite pipe; log10(maximum working pressure) for the flexible composite pipe at the end of its service life; The base of the logarithmic value is 10.

2. The method for evaluating long-term service performance of a flexible composite pipe according to claim 1, characterized by, The temperature reduction factor is obtained by using the pipe material type and the allowable maximum service temperature of the flexible composite pipe.

3. The method for evaluating long-term service performance of a flexible composite pipe according to claim 1, characterized by, The medium reduction factor is obtained by using the test medium of the flexible composite pipe, and is specifically as follows: When the test medium is a gas, the medium reduction factor is not greater than 0.67; When the test medium is a liquid hydrocarbon and a multiphase fluid, the medium reduction factor is not greater than 0.8; When the test medium is water, the medium reduction factor is not greater than 1.

4. The method for evaluating long-term service performance of a flexible composite pipe according to claim 1, characterized by, The residual service time is obtained by using the expected service life and the served life of the flexible composite pipe, and is specifically as follows: （2） In the formula: remaining service life of the flexible composite pipe; for the expected lifetime of the flexible composite pipe; is the in-service age of the flexible composite pipe.

5. The method for evaluating long-term service performance of a flexible composite pipe according to claim 1, characterized by, The test time selected in step S3 is 1000h.

6. The method of evaluating long-term service performance of a flexible composite pipe according to claim 1, characterized in that, The test temperature of the survival test in step S4 is 0-100℃, and the test medium is any one of water, oil, a multiphase fluid or a gas.

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