Device and method for evaluating slow crack propagation resistance of plastic pipe

Abstract

The invention belongs to the technical field of high polymer materials, and discloses a device and a method for evaluating slow crack propagation resistance of a plastic pipe. The device comprises a point load loading mechanism, a surfactant solution storage tank, a sealable water tank, heating equipment, circulating pressurizing equipment, an electromagnetic valve and a throttling valve, and the point load loading mechanism comprises a point load tool, a collet bracket and an end socket. And the circulating pressurizing equipment is used for pressurizing the interior of the sample and realizing dynamic circulating flow of the surfactant solution between the sample and the surfactant solution storage tank. The device can conveniently and effectively evaluate the point load performance of the pipe, effectively simulate the real stress condition of the pipe, shorten the evaluation period, obtain reliable test data and provide technical basis for pipe construction.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and more specifically, relates to a device and method for evaluating the slow crack growth resistance of a plastic pipe. Background Art

[0002] For plastic pipes, especially polyethylene pipes, slow crack growth resistance is one of the key evaluation properties. Polyethylene pipes are often used underground when transporting gas or drinking water. When the pipe is in contact with the soil, the stones in the soil will cause local stress concentration on the pipe, which is the point load performance, and is also a kind of slow crack growth resistance of the pipe.

[0003] Point load test simulates the actual buried application environment of pipes. For example, pipes may be subjected to concentrated loads from rocks or other hard objects. Even with the standard installation method of PE pipes with sand landfill, the conditions of the cushion layer are difficult to control very accurately, and in trenchless construction, it is impossible to use a sand cushion layer. There are many types of trenchless construction techniques, including pipe jacking, pipe bursting, horizontal directional drilling, etc., which are widely used in the construction of metal pipes. In recent years, technicians have also widely applied trenchless construction technology to the construction and laying of plastic pipes. Therefore, the application of trenchless construction technology in the laying and installation of plastic pipes has put forward an urgent need for the evaluation of the point load resistance performance of plastic pipes.

[0004] Therefore, in order to evaluate the point load performance of polyethylene pipes, it is urgent to develop a device and method for evaluating the slow crack growth resistance of plastic pipes. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and to propose a device and method for evaluating the slow crack growth resistance of plastic pipes. The device of the present invention can conveniently and effectively evaluate the point load performance of pipes, effectively simulate the actual stress conditions of pipes, shorten the evaluation cycle, obtain reliable test data, and provide a technical basis for pipe construction.

[0006] In order to achieve the above-mentioned object, the present invention provides, on one hand, a device for evaluating the slow crack growth resistance of a plastic pipe, the device comprising a point load loading mechanism, a surfactant solution storage tank, a sealable water tank, a heating device, a circulating pressurizing device, a solenoid valve and a throttle valve;

[0007] The point load loading mechanism comprises a point load tool, a bottom bracket and a sealing head; the point load tool and the bottom bracket are arranged in the closable water tank, the bottom bracket is arranged below the point load tool, the point load tool is used to form a notch with a depth less than the wall thickness of the sample on the outer wall of the sample, and fix the sample in the closable water tank together with the bottom bracket; the sealing head is used to seal the two ends of the sample;

[0008] One end pipeline of the solenoid valve and one end pipeline of the throttle valve are both connected to the surfactant solution storage tank; the other end pipeline of the solenoid valve and the other end pipeline of the throttle valve are both connected to the inside of the sample through a cap at one end of the sample;

[0009] The interior of the sample is connected to the surfactant solution storage tank through the other end cap, the cap outlet pipeline, the circulating pressurizing device and the circulating pipeline in sequence;

[0010] The circulating pressurizing device is used to pressurize the interior of the sample and realize the dynamic circulation flow of the surfactant solution between the sample and the surfactant solution storage tank;

[0011] The temperature increasing device is used to increase the temperature inside and outside of the sample.

[0012] According to the present invention, preferably, the solenoid valve is used to realize the switching between the circulation function and the pressurizing function of the circulation pressurizing device.

[0013] According to the present invention, preferably, the throttle valve is used to control the pressure applied by the circulating pressurizing device to the interior of the sample.

[0014] According to the present invention, preferably, the device is a plurality of sets, and the plurality of sets of devices are operated simultaneously. In the present invention, as a preferred embodiment, Figure 2 As shown, the device comprises two sets, and is arranged at front and rear workstations.

[0015] According to the present invention, preferably, the base bracket is a V-shaped base bracket.

[0016] According to the present invention, preferably, the device further comprises a sample and point load lifting mechanism, which is used to realize the removal and entry of the point load loading mechanism and the sample into the closable water tank, such as Figure 2 , Figure 4 shown.

[0017] Another aspect of the present invention provides a method for evaluating the slow crack growth resistance of a plastic pipe, the method using the device comprising the following steps:

[0018] S1: forming a notch on the outer wall of the sample, wherein the depth of the notch is less than the wall thickness of the sample;

[0019] S2: fixing the sample obtained in step S1 in the closable water tank, sealing both ends of the sample, and allowing the surfactant solution to dynamically circulate between the sample and the surfactant solution storage tank;

[0020] S3: Filling the closable water tank with water; evaluating the slow crack growth resistance of the plastic pipe, including:

[0021] The temperature of the closable water tank is raised, and after the internal and external temperatures of the sample reach predetermined temperatures and stabilize, pressure is applied to the interior of the sample using the cyclic pressurizing device. After the internal pressure of the sample reaches a predetermined pressure, timing is started until the sample is destroyed, and the destruction time is recorded.

[0022] According to the present invention, preferably, the point load tool adopts a constant displacement loading method to form a notch on the outer wall of the sample with an accuracy of 0.005-0.01 mm.

[0023] According to the present invention, preferably, the depth of the notch is 8-9 mm.

[0024] According to the present invention, preferably, the sample is at least one of a polyethylene pipe, a polypropylene pipe and a polybutylene pipe.

[0025] According to the present invention, preferably, the mass concentration of the surfactant solution is 1.5-2.5%.

[0026] According to the present invention, preferably, the surfactant in the surfactant solution is at least one of nonylphenol polyoxyethylene ether, hexadecyltrimethylammonium oxide, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide, dodecyl / tetradecyl dimethylamine oxide and sodium stearate.

[0027] According to the present invention, preferably, the predetermined temperature is 20-95° C.; and the predetermined pressure is 0.1-1.6 MPa.

[0028] The beneficial effects of the technical solution of the present invention are as follows:

[0029] The device of the present invention can conveniently and effectively evaluate the point load performance of the pipe, effectively simulate the actual stress condition of the pipe, shorten the evaluation cycle, obtain reliable test data, and provide a technical basis for pipe construction.

[0030] The device of the present invention can realize the dynamic circulation flow of the surfactant solution between the sample and the surfactant solution storage tank, so that the concentration of the surfactant solution in the sample can be evenly distributed, accelerating the destruction of the sample. In the comparative example, the setting without dynamic circulation flow will cause the surfactant solution to separate in the sample, and the surfactant solution will sink to the bottom of the sample, making it impossible to control the surfactant concentration in the upper part of the sample, resulting in untrue evaluation results. Therefore, the device and method of the present invention can ensure the authenticity of the evaluation results.

[0031] The device of the present invention comprises multiple sets, so multiple stations can be operated simultaneously.

[0032] The device of the present invention also includes a sample and point load lifting mechanism, which facilitates the removal and entry of the point load loading mechanism and the sample into the water tank.

[0033] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0035] Figure 1 The schematic diagram of the principle of a device for evaluating the slow crack growth resistance of a plastic pipe provided by the present invention is shown.

[0036] Figure 2 The figure shows a side view of a device for evaluating the slow crack growth resistance of a plastic pipe provided by the present invention. (“1990” means the highest height of the device is 1990 cm; “1410” means the width of the device is 1410 cm)

[0037] Figure 3 The figure shows a point load loading mechanism of a device for evaluating the slow crack growth resistance of a plastic pipe provided by the present invention.

[0038] Figure 4 A front view of a device for evaluating the slow crack growth resistance of a plastic pipe provided by the present invention is shown.

[0039] Figure 5 A physical picture of a V-shaped bottom bracket of a plastic pipe slow crack growth resistance performance evaluation device provided by the present invention is shown.

[0040] The following are the descriptions of the reference numerals:

[0041] 1: Point load loading mechanism; A: End cap; B: Closeable water tank; C: Surfactant solution storage tank; D: Specimen; E: Circulating pressurizing equipment; F: Point load tool; G: V-type bottom bracket; H: Solenoid valve; I: Throttle valve; J: End cap outlet pipeline; K: Circulating pipeline; 2: Specimen and point load lifting mechanism. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0043] Example 1

[0044] This embodiment provides a device for evaluating the slow crack growth resistance of a plastic pipe. Figure 2 As shown, the device is composed of 2 sets, with front and rear stations arranged, such as Figure 1 , 4 As shown, each device includes a point load loading mechanism 1, a surfactant solution storage tank C, a closable water tank B, a heating device (not shown), a circulating pressurizing device E, a solenoid valve H and a throttle valve I;

[0045] The point load loading mechanism 1 comprises a point load tool F, a V-shaped bottom bracket G and a sealing head A; the point load tool F and the V-shaped bottom bracket G are arranged in the closable water tank B, the V-shaped bottom bracket G is arranged below the point load tool F, the point load tool F is used to form a notch with a depth less than the wall thickness of the sample D on the outer wall of the sample D, and fix the sample D in the closable water tank B together with the V-shaped bottom bracket G; the sealing head A is used to seal the two ends of the sample D;

[0046] One end pipeline of the solenoid valve H and one end pipeline of the throttle valve I are both connected to the surfactant solution storage tank C; the other end pipeline of the solenoid valve H and the other end pipeline of the throttle valve I are both connected to the interior of the sample D through the end cap A of the sample D;

[0047] The interior of the sample D is connected to the surfactant solution storage tank C through the other end cap A, the cap outlet pipeline J, the circulating pressurizing device E and the circulating pipeline K in sequence;

[0048] The circulating pressurizing device E is used to pressurize the interior of the sample D and realize the dynamic circulation flow of the surfactant solution between the sample D and the surfactant solution storage tank C. Figure 1 As shown; the solenoid valve H is used to switch the circulation function and the pressurizing function of the circulation pressurizing device E; the throttle valve I is used to control the pressure of the circulation pressurizing device E to pressurize the inside of the sample D;

[0049] The temperature increasing device is used to increase the temperature of the inside and outside of the sample D.

[0050] like Figure 2 , 3 As shown in , 4, the device also includes a sample and point load lifting mechanism 2, which is used to realize the removal and entry of the point load loading mechanism 1 and the sample D into the closable water tank B.

[0051] Example 2

[0052] This embodiment provides a method for evaluating the slow crack growth resistance of a plastic pipe. The samples are 3 PE100 pipes of different qualities with a DN of 110, numbered as sample 1# (brand p6006), sample 2# (brand YGH041T), and sample 3# (prepared by directly adding carbon black to the original color material, which is an unqualified product).

[0053] This embodiment adopts the device described in Embodiment 1, and includes the following steps:

[0054] S1: using the point load tool F to adopt a constant displacement loading method (with an accuracy of 0.01 mm) to form a notch on the outer wall of the sample D, the depth of the notch is 8.8 mm, which is less than the wall thickness of the sample D;

[0055] S2: fix the sample D obtained in step S1 in the closable water tank B, seal both ends of the sample D, and allow the surfactant solution (mass concentration is 2%) to dynamically circulate between the sample D and the surfactant solution storage tank C;

[0056] S3: Fill the closable water tank B with water; evaluate the slow crack growth resistance of the plastic pipe, including:

[0057] The temperature of the closable water tank B is raised, and after the internal and external temperatures of the sample D reach a predetermined temperature of 80°C and stabilize, pressure is applied to the interior of the sample D using the cyclic pressurizing device E. After the internal pressure of the sample D reaches a predetermined pressure of 0.8 MPa, timing is started until the sample is destroyed, and the destruction time is recorded.

[0058] Example 3

[0059] This embodiment provides a method for evaluating the slow crack growth resistance of a plastic pipe. The samples are 3 PE100 pipes of different qualities with a DN of 110, numbered as sample 4# (brand p6006), sample 5# (brand YGH041T), and sample 6# (prepared by directly adding carbon black to the original color material, which is an unqualified product).

[0060] This embodiment adopts the device described in Embodiment 1. The difference between this embodiment and Embodiment 2 is that the predetermined temperature is 60° C. and the predetermined pressure is 1.0 MPa.

[0061] Comparative Example 1

[0062] This comparative example provides a method for evaluating hydrostatic pressure. The samples are 3 PE100 pipes of different qualities of DN110, numbered as sample 7# (brand P6006), sample 8# (brand YGH041T), and sample 9# (prepared by directly adding carbon black to the color material, which is an unqualified product).

[0063] The only difference between this comparative example and Example 1 is that after the surfactant solution (mass concentration is 2%) is injected into the sample D, the surfactant solution does not dynamically circulate between the sample D and the surfactant solution storage tank C, but is only statically stored in the sample.

[0064] Comparative Example 2

[0065] This comparative example provides a method for evaluating hydrostatic pressure. The samples are 3 PE100 pipes of different qualities of DN110, numbered as sample 10# (brand P6006), sample 11# (brand YGH041T), and sample 12# (prepared by directly adding carbon black to the color material, which is an unqualified product);

[0066] The only difference between this comparative example and Example 1 is that after the surfactant solution (mass concentration is 2%) is injected into the sample, the surfactant solution does not dynamically circulate between the sample and the surfactant solution storage tank, but is only statically stored in the sample.

[0067] The predetermined temperature is 60°C; and the predetermined pressure is 1.0 MPa.

[0068] The failure time of the samples of the above-mentioned Examples 2-3 and Comparative Examples 1-2 is shown in Table 1.

[0069] Table 1

[0070]

[0071] It can be seen that the device of the present invention can realize the dynamic circulation flow of the surfactant solution between the sample and the surfactant solution storage tank, so that the concentration of the surfactant solution in the sample can be evenly distributed, accelerating the destruction of the sample. However, the setting of the lack of dynamic circulation flow in Comparative Example 1-2 will cause the surfactant solution to separate in the sample, and the surfactant solution will sink to the bottom of the sample, making it impossible to control the surfactant concentration in the upper part of the sample, resulting in untrue evaluation results. Therefore, the device and method of the present invention can ensure the authenticity of the evaluation results.

[0072] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A device for evaluating the slow crack growth resistance of plastic pipes, characterized in that: The device comprises a point load loading mechanism, a surfactant solution storage tank, a sealable water tank, a temperature raising device, a circulating pressurizing device, a solenoid valve and a throttle valve; The point load loading mechanism comprises a point load tool, a bottom bracket and a sealing head; the point load tool and the bottom bracket are arranged in the closable water tank, the bottom bracket is arranged below the point load tool, the point load tool is used to form a notch with a depth less than the wall thickness of the sample on the outer wall of the sample, and fix the sample in the closable water tank together with the bottom bracket; the sealing head is used to seal the two ends of the sample; One end pipeline of the solenoid valve and one end pipeline of the throttle valve are both connected to the surfactant solution storage tank; the other end pipeline of the solenoid valve and the other end pipeline of the throttle valve are both connected to the inside of the sample through a sealing head at one end of the sample; The interior of the sample is connected to the surfactant solution storage tank through the other end cap, the cap outlet pipeline, the circulating pressurizing device and the circulating pipeline in sequence; The circulating pressurizing device is used to pressurize the interior of the sample and realize the dynamic circulation flow of the surfactant solution between the sample and the surfactant solution storage tank; The temperature increasing device is used to increase the temperature inside and outside of the sample.

2. The device for evaluating the slow crack growth resistance of plastic pipes according to claim 1, wherein: The solenoid valve is used to realize the switching between the circulation function and the pressurization function of the circulation pressurization equipment; The throttle valve is used to control the pressure applied by the circulating pressurizing device to the interior of the sample.

3. The device for evaluating the slow crack growth resistance of a plastic pipe according to claim 1, wherein: The device comprises multiple sets, and the multiple sets of devices operate simultaneously.

4. The device for evaluating the slow crack growth resistance of a plastic pipe according to claim 1, wherein: The bottom bracket is a V-shaped bottom bracket.

5. The device for evaluating the slow crack growth resistance of a plastic pipe according to claim 1, wherein: The device also includes a sample and point load lifting mechanism, which is used to realize the removal and entry of the point load loading mechanism and the sample into the closable water tank.

6. A method for evaluating the slow crack growth resistance of a plastic pipe, characterized in that: The method adopts the device described in any one of claims 1 to 5, and comprises the following steps: S1: forming a notch on the outer wall of the sample, wherein the depth of the notch is less than the wall thickness of the sample; S2: fixing the sample obtained in step S1 in the closable water tank, sealing both ends of the sample, and allowing the surfactant solution to dynamically circulate between the sample and the surfactant solution storage tank; S3: Filling the closable water tank with water; Evaluation of slow crack growth resistance of plastic pipes, including: The temperature of the closable water tank is raised, and after the internal and external temperatures of the sample reach predetermined temperatures and stabilize, pressure is applied to the interior of the sample using the cyclic pressurizing device. After the internal pressure of the sample reaches a predetermined pressure, timing is started until the sample is destroyed, and the destruction time is recorded.

7. The method for evaluating the slow crack growth resistance of a plastic pipe according to claim 6, wherein: The point load tool adopts a constant displacement loading method to form a notch on the outer wall of the sample with an accuracy of 0.005-0.01mm; The depth of the notch is 8-9 mm.

8. The method for evaluating the slow crack growth resistance of a plastic pipe according to claim 6, wherein: The sample is at least one of a polyethylene pipe, a polypropylene pipe and a polybutylene pipe.

9. The method for evaluating the slow crack growth resistance of a plastic pipe according to claim 6, wherein: The mass concentration of the surfactant solution is 1.5-2.5%; The surfactant in the surfactant solution is at least one of nonylphenol polyoxyethylene ether, hexadecyl trimethyl ammonium oxide, sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate, hexadecyl trimethyl ammonium bromide, dodecyl / tetradecyl dimethyl amine oxide and sodium stearate.

10. The method for evaluating the slow crack growth resistance of a plastic pipe according to claim 6, wherein: The predetermined temperature is 20-95° C.; the predetermined pressure is 0.1-1.6 MPa.

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