Device and method for testing stress and strain of polyethylene pipeline under high-temperature working condition

Abstract

The invention discloses a stress-strain test device and method for a polyethylene pipeline under a high-temperature working condition. The device comprises a constant-temperature and constant-humidity test box, a sealing clamp, a pressure gauge, an air pump, a bridge box, a resistance strain gauge and a data acquisition terminal, the constant-temperature and constant-humidity test box is used for adjusting temperature and simulating high-temperature working The sealing clamps are arranged at the two ends of the polyethylene pipeline and used for sealing the pipeline, and the polyethylene pipeline is connected with the pressure gauge and the air pump. A plurality of strain gauges are adhered to the outer surface of the polyethylene pipeline, the strain gauges are connected with a bridge box through a stress test wire terminal seat which is hermetically embedded on the constant-temperature and constant-humidity test box, and the bridge box is sequentially connected with a resistance strain gauge and a data acquisition terminal through data lines. According to the method, the operation condition of the pipeline under the high-temperature working condition is simulated through the device, the stress-strain data of the pipeline are monitored and collected, and the safety performance of the pipeline subjected to fire radiation is evaluated according to the data. The device can be used for carrying out stress-strain test on the polyethylene pipeline under the high-temperature working condition.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline detection and inspection, in particular to a stress-strain test device and method for polyethylene pipelines under high-temperature working conditions. Background Art

[0002] Polyethylene gas pipelines have the advantages of longer life, better corrosion resistance, easier construction, better impact resistance, easy molding and more environmentally friendly than metal pipelines. They have been widely used in urban gas pipeline networks. However, polyethylene gas pipelines are prone to stress concentration, creep and damage accumulation during long-term operation due to factors such as internal pressure, temperature, hydrogen permeation, and external damage, which can lead to safety accidents such as leakage or even rupture. During the operation of polyethylene gas pipelines, there is a risk that outdoor fires will cause the polyethylene gas pipelines under the ground to be exposed to fire for a long time. There is also the possibility that the polyethylene gas pipelines will be exposed to heat radiation due to unreasonable distances between parallel thermal pipelines in the later pipeline construction and transformation. Under the influence of thermal stress under long-term high-temperature working conditions, the safety strength level of polyethylene gas pipelines decreases, affecting the normal operation of polyethylene gas pipelines. In order to ensure the stability and quality of polyethylene gas pipelines, whether polyethylene gas pipelines are allowed to continue to be used under the influence of fire heat radiation, it is necessary to conduct stress strain monitoring tests on polyethylene gas pipelines under high temperature to detect whether the stress of polyethylene gas pipelines under high temperature environment can meet the strength requirements during use. Therefore, high-temperature stress strain data is used to conduct safety assessment of polyethylene gas pipelines to ensure the safety of their continued service structures. At present, there are test equipment for stress testing of polyethylene gas pipelines at room temperature. Generally, stress data is obtained by testing the pipeline on site. There is no stress and strain detection device for measuring polyethylene gas pipelines under high temperature conditions. Summary of the invention

[0003] The present invention aims to provide a high-temperature polyethylene pipeline stress-strain test device and method, which can simulate the operating conditions of the pipeline under high-temperature working conditions, monitor and collect pipeline stress-strain data, and evaluate the safety performance of the fire-radiated pipeline based on the data.

[0004] In order to solve the above technical problems, the specific scheme adopted by the present invention is a high-temperature working condition polyethylene pipeline stress strain test device, including a constant temperature and humidity test box, a sealing fixture, a pressure gauge, an air pump, a bridge box, a resistance strain gauge and a data acquisition terminal; the constant temperature and humidity test box is used to hold the polyethylene pipeline and simulate the high temperature working condition by adjusting the temperature; the sealing fixture is arranged at both ends of the polyethylene pipeline for sealing the pipeline, and the polyethylene pipeline is connected to the pressure gauge and the air pump;

[0005] Several strain gauges are bonded to the outer surface of the polyethylene pipe. The strain gauges are connected to the bridge box through a stress test wire terminal seat sealed and embedded on the side wall of the constant temperature and humidity test chamber. The bridge box is connected to the resistance strain gauge and the data acquisition terminal in turn through data cables.

[0006] As another optimization scheme of the above-mentioned high-temperature polyethylene pipeline stress-strain testing device: the sealing fixture includes a sealing end cover, a flange bushing, a sealing bushing and a plurality of segmented clamps, and adjacent segmented clamps are fixedly connected by bolts and nuts; the end of the sealing end cover is folded outward to form an end cover sealing surface, and the flange bushing and the sealing bushing are arranged in sequence from the inside to the outside on the clamp sealing surface opposite to the side where the end cover sealing surface and the segmented clamp are fitted; corresponding light holes are opened on the end cover sealing surface and the clamp sealing surface, and a screw is respectively passed through the corresponding light holes between the sealing clamps at both ends of the polyethylene pipe, and anti-loosening nuts are respectively installed at both ends of the screw.

[0007] As another optimization scheme of the above-mentioned high-temperature polyethylene pipe stress-strain test device: the number of segmented clamps is three, the number of corresponding screws is three, the screws are 20 steel double-headed screws, and the surface of the screws is electro-galvanized.

[0008] As another optimization scheme of the above-mentioned high-temperature polyethylene pipe stress-strain test device: the polyethylene pipe is connected to the air pump through the charging and discharging pipelines that pass through the constant temperature and humidity test chamber through a seal, and the charging and discharging pipelines connecting the polyethylene pipe and the air pump are connected with a pressure reducing valve and a stop valve in sequence; the polyethylene pipe is connected to the pressure gauge through the pressure pipeline that passes through the constant temperature and humidity test chamber through a seal.

[0009] As another optimization scheme of the above-mentioned high-temperature polyethylene pipeline stress-strain testing device: a sealing end cover at one end of the polyethylene pipeline is provided with a charging and discharging hole for connecting the charging and discharging pipeline and a pressure hole for connecting the pressure pipeline, and a safety valve is installed on the sealing end cover at the other end of the polyethylene pipeline.

[0010] As another optimization scheme of the above-mentioned high-temperature polyethylene pipe stress-strain test device: a sealing structure is arranged on one side wall of the constant temperature and humidity test box, and the sealing structure is provided with two sealing connection holes for the pressure pipeline and the charging and discharging gas pipeline to pass through respectively.

[0011] As another optimization scheme of the above-mentioned high-temperature polyethylene pipe stress-strain test device: the stress test wire terminal seat includes a terminal seat embedded in the wall of one side of the constant temperature and humidity test chamber, and a plurality of terminal posts are respectively arranged on the inner and outer sides of the terminal seat.

[0012] As another optimization scheme for the above-mentioned high-temperature polyethylene pipe stress-strain test device: a tray is arranged in the constant temperature and humidity test chamber, two V-shaped supports for supporting the polyethylene pipe are arranged side by side on the tray, and a lifting part for supporting the polyethylene pipe to rise or fall is arranged at the bottom of the support.

[0013] As another optimization scheme of the above-mentioned high-temperature polyethylene pipeline stress-strain testing device: rollers are respectively installed on the V-shaped support at the position where it contacts the polyethylene pipeline.

[0014] A stress-strain test method for polyethylene pipelines under high-temperature working conditions, which simulates the operating conditions of polyethylene pipelines under high-temperature working conditions through the above-mentioned test device, monitors and collects stress-strain data of polyethylene pipelines, and evaluates the safety performance of polyethylene pipelines subjected to fire radiation based on the stress-strain data.

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

[0016] 1. In the present invention, the sealing of the polyethylene pipe is ensured by the sealing clamps arranged at both ends of the polyethylene pipe. The polyethylene pipe is connected to the air pump through the sealing clamps, and the polyethylene pipe is connected to the pressure gauge. Several strain gauges bonded to the outer surface of the polyethylene pipe are connected to the bridge box through the stress test wire terminal seat. The bridge box is connected to the resistance strain gauge through the data line. The resistance strain gauge can collect the strain value of the polyethylene pipe at high temperature, and the resistance strain gauge transmits the data to the data acquisition terminal through the data line. Stress data can be obtained from the collected micro-strain data. By adjusting the temperature of the constant temperature and humidity test box, the high-temperature working condition of the polyethylene pipe placed therein is simulated, and then the safety performance of the pipeline is evaluated through the obtained temperature stress data.

[0017] 2. The safety valve, pressure reducing valve and stop valve provided in the present invention can monitor and regulate the pressure in the polyethylene pipe in real time during the test, prevent the test device from overpressure, and ensure the safety and reliability during the test.

[0018] 3. In the present invention, the polyethylene pipe can be sealed by passing the screw through the sealing end caps respectively arranged at the ends of the polyethylene pipe and the corresponding segmented clamps respectively clamped on the end walls of the polyethylene pipe to ensure the sealing performance of the polyethylene pipe. The segmented clamps are arranged in sections for easy disassembly and assembly.

[0019] 4. In the present invention, the polyethylene pipe is placed on a V-shaped support, and a roller is provided on the V-shaped support to adjust the polyethylene pipe 360°, which is convenient for bonding the strain gauge. In addition, the lifting member provided at the bottom of the support can adjust the distance between the polyethylene pipe and the constant temperature and humidity test chamber, which is convenient for bonding and arranging the strain gauge. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the main structure of the present invention;

[0021] Figure 2 Figure a is a schematic diagram of the structure in which the sealing clamp is installed at the end of the polyethylene pipe; Figure b is a schematic diagram of the connection structure between the segmented clamps.

[0022] Figure numerals: 1. Constant temperature and humidity test chamber, 101. Sealing structure, 102. Tray, 103. Support, 2. Pressure gauge, 3. Pressure reducing valve, 4. Stop valve, 5. Air pump, 6. Charging and discharging pipelines, 7. Pressure pipeline, 8. Sealing fixture, 801. Sealing end cover, 8011. Pressure hole, 8012. Charging and discharging holes, 802. Screw, 803. Mounting hole, 804. Flange bushing, 805. Lock nut, 806. Segmented clamp, 807. Sealing bushing, 808. Bolt and nut, 809. Light hole, 9. Strain gauge, 901. Wire, 10. Safety valve, 11. Stress test wire terminal seat, 1101. External wire, 12. Polyethylene pipe, 13. Bridge box, 14. Resistance strain gauge, 15. Data acquisition terminal. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further elaborated in detail below in conjunction with specific embodiments. The parts not described in detail in the following embodiments of the present invention, such as the structure and function of the pressure reducing valve, the stop valve, the air pump, the pressure gauge, the safety valve, the strain gauge, the bridge box, the resistance strain gauge, the data acquisition terminal, and the structure and temperature regulating function of the constant temperature and humidity test box, etc., should be understood as the prior art known or should be known to those skilled in the art.

[0024] like Figure 1 As shown, a stress strain test device and method for polyethylene pipelines under high temperature working conditions include a constant temperature and humidity test box 1, a sealing fixture 8, a pressure gauge 2, a pressure reducing valve 3, a stop valve 4, an air pump 5, a bridge box 13, a resistance strain gauge 14, and a data acquisition terminal 15. The constant temperature and humidity test box 1 can accommodate a polyethylene pipeline 12, and the constant temperature and humidity test box 1 is a test box that can adjust the temperature within a temperature range of -40°C to 180°C. The polyethylene pipeline 12 is placed in the constant temperature and humidity test box 1, and the temperature can be adjusted by the constant temperature and humidity test box 1 to simulate the working conditions of the polyethylene pipeline 12 under high temperature working conditions.

[0025] The sealing fixture 8 is arranged at both ends of the polyethylene pipe 12 and can seal the polyethylene pipe 12. The sealing fixture 8 comprises sealing end caps 801 respectively arranged at the two ends of the polyethylene pipe 12, segmented clamps 806 respectively clamped on the pipe walls of the two ends of the polyethylene pipe 12, and screws 802 for connecting and fixing the sealing end caps 801 at both ends.

[0026] The port side wall of the sealing end cap 801 is folded outward at an angle of 90° to form the end cap sealing surface. The sealing end cap 801 and the end cap sealing surface are integrally cast with stainless steel material, and three light holes 809 are evenly distributed on the end cap sealing surface. Correspondingly, the material of the segmented clamp 806 is stainless steel, and the segmented clamp 806 is a three-section structure that is easy to disassemble and assemble. The three segments of the segmented clamps 806 are fixedly connected by bolt and nut 808 fastening structures. The segmented clamp 806 is vertically distributed on the pipe wall at the port of the polyethylene pipe 12, and the side of the clamp sealing surface away from the polyethylene pipe 12 is the clamp sealing surface that can fit with the end cap sealing surface, and the clamp sealing surface is provided with light holes 809 corresponding to the positions of the light holes 809 on the end cap sealing surface.

[0027] The screw 802 is a steel double-headed screw 802, and the surface of the screw 802 is electro-galvanized to prevent high-temperature corrosion. The number of screws 802 is three corresponding to the number of light holes 809. Both ends of the screw 802 are provided with threads. The two ends of any screw 802 pass through the two sealing end caps 801 and the light holes 809 on the corresponding segmented clamps 806, and then are tightened and fixed by the anti-loosening nut 805. The anti-loosening nut 805 is made of metal stainless steel that can prevent the nut from loosening when the pressure is increased or decreased. The screw 802 cooperates with the anti-loosening nut 805 to prevent the sealing end cap 801 from falling off the port of the polyethylene pipe 12 when the internal pressure of the polyethylene pipe 12 increases.

[0028] like Figure 2 As shown, a flange bushing 804 and a sealing bushing 807 are sequentially arranged from the inside to the outside on one side of the segmented clamp 806 opposite to the clamp sealing surface, and the pipe wall of the polyethylene pipe 12 port can be clamped in the clamping space surrounded by the flange bushing 804 and the sealing bushing 807. The sealing bushing 807 is made of polytetrafluoroethylene, and is fixed to the end of the polyethylene pipe 12 by a bolt and nut 808 fastening structure, and an interference fit is adopted between the segmented clamp 806. The material of the flange bushing 804 is polytetrafluoroethylene, which can avoid rigid contact with the polyethylene pipe 12 to damage the pipe. When the screw 802 is tightened, the flange bushing 804 can play a tightening role on the polyethylene pipe 12. The sealing bushing 807 and the flange bushing 804 work together to clamp and seal the polyethylene pipe 12.

[0029] The sealing end cap 801 at the left end of the polyethylene pipe 12 is provided with a pressure hole 8011 and a charging and discharging hole 8012, and the sealing end cap 801 at the right end of the polyethylene pipe 12 is provided with a mounting hole 803, through which the safety valve 10 is mounted on the polyethylene pipe 12. The pressure hole 8011 is connected to the pressure gauge 2 through the pressure pipeline 7, and the pressure gauge 2 can monitor, adjust, and display the pressure in the polyethylene pipe 12 in real time.

[0030] The charging and discharging holes 8012 are connected to the pressure reducing valve 3, the stop valve 4, and the air pump 5 in sequence through the charging and discharging pipeline 6. The air pump 5 is an electric charging pump. The air pump 5 pressurizes the polyethylene pipe 12 to be tested and inflates it to the test pressure value. The stop valve 4 can be closed after reaching the test pressure to ensure that the pressure in the polyethylene pipe 12 remains unchanged, or the stop valve 4 can be opened to quickly relieve the pressure of the polyethylene pipe 12. The pressure reducing valve 3 can fine-tune the pressure in the polyethylene pipe 12 during the test. When the pressure exceeds the test pressure, the pressure reducing valve 3 is opened to reduce the pressure of the polyethylene pipe 12 to the test pressure value.

[0031] A sealing structure 101 (sealing plug) is embedded on the left wall of the constant temperature and humidity test box 1. The sealing structure 101 is installed on the constant temperature and humidity test box 1 by means of a high-temperature sealant that is resistant to high temperatures. Two sealing connection holes are opened on the sealing structure 101. The pressure pipeline 7 is sealed through one of the sealing connection holes and then connected to the pressure gauge 2. The charging and discharging gas pipeline 6 is sealed through the other sealing connection hole and then connected to the pressure reducing valve 3, the stop valve 4, and the air pump 5 in sequence. The setting of the sealing structure 101 can ensure the sealing performance of the constant temperature and humidity test box 1.

[0032] A stress test lead terminal seat 11 is embedded on the right wall of the constant temperature and humidity test chamber 1. The stress test lead terminal seat 11 includes a wiring terminal seat embedded on the wall of the constant temperature and humidity test chamber 1. The wiring terminal seat is sealed and fixed on the constant temperature and humidity test chamber 1 by high-temperature sealant. The wiring terminal seat is an epoxy resin casting structure, and a plurality of pure copper terminals are respectively arranged on the inner and outer sides of the wiring terminal seat facing the polyethylene pipe 12 and the bridge box 13.

[0033] A number of strain gauges 9 are bonded to the outer surface of the polyethylene pipe 12. The strain gauges 9 are high-temperature temperature-compensated strain gauges 9. The glue with which the strain gauges 9 are bonded to the polyethylene pipe 12 is high-temperature resistant. The strain gauges 9 can collect strain data of the polyethylene pipe 12 at high temperatures. The number of bonded strain gauges 9 is determined according to test requirements.

[0034] The strain gauge 9 is connected to the inner terminal of the corresponding stress test wire terminal seat 11 through the wire 901 set at its end, and the terminal outside the stress test wire terminal seat 11 is connected to the bridge box 13 through the external wire 1101. The bridge box 13 is connected to the resistance strain gauge 14 used to collect the strain value of the polyethylene pipe 12 at high temperature through the data line. The resistance strain gauge 14 can collect the strain value of the polyethylene pipe 12 at high temperature. The resistance strain gauge 14 transmits the data to the data acquisition terminal 15 through the data line. The stress data can be obtained through the collected micro-strain data. The high-temperature working condition of the polyethylene pipe 12 placed in the constant temperature and humidity test box 1 is simulated by adjusting the temperature, and the pipeline safety performance is evaluated through the obtained temperature stress data.

[0035] Further, such as Figure 1 As shown, the bottom of the constant temperature and humidity test box 1 is provided with moving wheels for facilitating the adjustment of its position, and a tray 102 is fixed inside the constant temperature and humidity test box 1, and the tray 102 is arranged at a position below the middle of the constant temperature and humidity test box 1. Two V-shaped supports 103 for supporting the polyethylene pipe 12 are arranged side by side on the tray 102, and lifting parts for driving the polyethylene pipe 12 to rise or fall are respectively arranged on the two supports 103 directly below the polyethylene pipe 12, and the lifting parts can be a driving mechanism that can rise or fall, such as a lifting cylinder, and the lifting cylinder can adjust the distance between the polyethylene pipe 12 and the constant temperature and humidity test box 1, so as to facilitate the arrangement of the strain gauge 9.

[0036] Furthermore, rollers are installed on the V-shaped support 103 at the position where it contacts the polyethylene pipe 12. The rollers can adjust the polyethylene pipe 12 by degrees to facilitate the bonding of the strain gauge 9. In addition, the support 103 and the rollers are both made of polytetrafluoroethylene. The support 103 and the rollers made of polytetrafluoroethylene have good wear resistance and lubricity, and will not wear or bump when in contact with the polyethylene pipe 12.

Claims

1. A high temperature polyethylene pipe stress strain test device, characterized by: The invention comprises a constant temperature and humidity test box (1), a sealing fixture (8), a pressure gauge (2), an air pump (5), a bridge box (13), a resistance strain gauge (14) and a data acquisition terminal (15); the constant temperature and humidity test box (1) is used to contain a polyethylene pipe (12) and simulate a high temperature working condition by adjusting the temperature; the sealing fixture (8) is arranged at both ends of the polyethylene pipe (12) to seal the pipe, and the polyethylene pipe (12) is connected to the pressure gauge (2) and to the air pump (5); A plurality of strain gauges (9) are bonded to the outer surface of a polyethylene pipe (12); the strain gauges (9) are connected to a bridge box (13) via a stress test lead terminal seat (11) sealed and embedded on a side wall of a constant temperature and humidity test chamber (1); and the bridge box (13) is connected to a resistance strain gauge (14) and a data acquisition terminal (15) in sequence via data cables.

2. A high temperature polyethylene pipe stress strain test device according to claim 1, characterized in that: The sealing clamp (8) comprises a sealing end cover (801), a flange bushing (804), a sealing bushing (807) and a plurality of segmented clamps (806), wherein adjacent segmented clamps (806) are fixedly connected by bolts and nuts (808); the end of the sealing end cover (801) is folded outward to form an end cover sealing surface, and the flange bushing (804) and the sealing bushing (807) are sequentially arranged from the inside to the outside on the clamp sealing surface opposite to the side where the end cover sealing surface and the segmented clamp (806) are attached; corresponding light holes (809) are provided on the end cover sealing surface and the clamp sealing surface, and a screw rod (802) is respectively inserted into the corresponding light hole (809) between the sealing clamps (8) at both ends of the polyethylene pipe (12), and anti-loosening nuts (805) are respectively installed at both ends of the screw rod (802).

3. A high temperature polyethylene pipe stress strain test device according to claim 2, characterized in that: The number of segmented clamps (806) is three, and the number of corresponding screw rods (802) is three. The screw rods (802) are 20 steel double-headed screw rods (802), and the surface of the screw rods (802) is electro-galvanized.

4. A high temperature polyethylene pipe stress strain test device according to claim 2, characterized in that: The polyethylene pipe (12) is connected to the air pump (5) by sealingly passing through the air charging and discharging pipeline (6) of the constant temperature and humidity test box (1); the air charging and discharging pipeline (6) connecting the polyethylene pipe (12) and the air pump (5) is connected to a pressure reducing valve (3) and a stop valve (4) in sequence; the polyethylene pipe (12) is connected to the pressure gauge (2) by sealingly passing through the pressure pipeline (7) of the constant temperature and humidity test box (1).

5. A high temperature polyethylene pipe stress strain test device according to claim 4, characterized in that: A gas charging and discharging hole (8012) for connecting to a gas charging and discharging pipeline (6) and a pressure hole (8011) for connecting to a pressure pipeline (7) are provided on the sealing end cover (801) at one end of the polyethylene pipe (12), and a safety valve (10) is installed on the sealing end cover (801) at the other end of the polyethylene pipe (12).

6. A high temperature polyethylene pipe stress strain test device according to claim 4, characterized in that: A sealing structure (101) is provided on one side wall of the constant temperature and humidity test box (1), and the sealing structure (101) is provided with two sealing connection holes for the pressure pipeline (7) and the gas charging and discharging pipeline (6) to pass through in a sealed manner.

7. The high temperature working condition polyethylene pipe stress strain testing device according to claim 1, characterized in that: The stress test wire terminal seat (11) comprises a wiring terminal seat embedded in a box wall at one side of a constant temperature and humidity test box (1), and a plurality of wiring posts are respectively arranged on the inner and outer sides of the wiring terminal seat.

8. The high temperature working condition polyethylene pipe stress strain testing device according to claim 1, characterized in that: A tray (102) is arranged in the constant temperature and humidity test box (1), two V-shaped supports (103) for carrying the polyethylene pipe (12) are arranged side by side on the tray (102), and a lifting member for supporting the polyethylene pipe (12) to rise or fall is arranged at the bottom of the support (103).

9. A high temperature polyethylene pipe stress strain testing device according to claim 8, characterized in that: Rollers are respectively installed on the V-shaped support (103) at positions where the V-shaped support (103) contacts the polyethylene pipe (12).

10. A high temperature polyethylene pipe stress strain test method, characterized in that: The operating conditions of the polyethylene pipe (12) under high temperature working conditions are simulated by the test device described in any one of claims 1 to 9, the stress-strain data of the polyethylene pipe (12) are monitored and collected, and the safety performance of the polyethylene pipe (12) exposed to fire radiation is evaluated based on the stress-strain data.

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