Stretching and fixing device and method for aging detection of polyethylene gas pipeline

Abstract

According to the stretching and fixing device and method for aging detection of the polyethylene gas pipeline, polyethylene pipes with different diameters are clamped through an inner clamping plate and an outer clamping plate, and the adaptability of the device is effectively improved; the slippage phenomenon of a pipeline in the stretching process is detected through the covering effect of the polyethylene pipe on the array type light dependent resistor, the array type light dependent resistor calculates the slippage distance of the polyethylene pipe by detecting the change of the length of the array type light dependent resistor irradiated by the lamp strip, and therefore on one hand, the clamping force is enhanced by increasing the current of the electromagnetic pad; and on the other hand, compensation is carried out by adjusting the movement length of the sliding seat to be equal to the slippage distance, so that the pressure load borne by the pipeline is kept unchanged, and the accuracy of experimental parameters is ensured.

Description

Technical Field

[0001] The present invention relates to a stretching and fixing device and method for aging detection of polyethylene gas pipelines, and in particular to a stretching and fixing device and method for aging detection of polyethylene gas pipelines applied in the field of detection equipment. Background Art

[0002] Due to its light weight, easy construction, excellent toughness, corrosion resistance, simple maintenance, and low cost, PE materials are widely used in urban natural gas transmission and water supply. Since the 1960s, advancements in PE material processing and manufacturing have led to the evolution of PE pipe materials from PE63, PE80, to PE100, and their molecular weight distribution has also undergone numerous stages (from unimodal, bimodal, to multimodal). Furthermore, the various performance properties of PE pipe materials have been continuously improved, and their safety performance has also been continuously enhanced. As buried PE pipelines continue to age over time, their aging rate is also increasing, making PE pipeline aging a safety issue that needs to be addressed. Traditional aging methods for polyethylene gas pipelines often involve placing the pipelines directly in an artificial accelerated aging test chamber, as exemplified by the accelerated aging test apparatus and life prediction method for buried polyethylene gas pipelines (publication number CN108120827B).

[0003] Of course, existing aging detection equipment is also used for tensile testing, but existing pipeline stretching equipment does not have a tensile fixing function. It only clamps the pipeline in a universal testing machine for tensile testing, which makes it difficult to simulate the pipeline conditions under long-term operating pressure loads. As a result, the variable parameters of the polyethylene gas pipeline accelerated aging test lack pressure loads, resulting in large experimental errors. In addition, the fixing devices of the existing stretching equipment cannot be well adaptively adjusted according to the slippage of the pipeline during the stretching process. Summary of the Invention

[0004] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is how to adaptively adjust and compensate for the slippage problem during the pipeline stretching process.

[0005] To solve the above problems, the present invention provides a stretching and fixing device and method for aging detection of polyethylene gas pipelines, comprising a base plate, fixed plates fixedly connected to both ends of the base plate, a slide slidably connected to the upper surface of the base plate, a screw rod symmetrically fixedly connected between the two fixed plates and passing through the slide rod, two limit rods arranged parallel to and located inside the screw rod, and a servo motor mounted on one of the fixed plates and with its output end connected to the screw rod, wherein the slide rod and the side wall opposite to one of the fixed plates are fixedly connected to fixing units arranged at the same level; The fixing unit includes a fixing seat, a light shield fixedly connected to the side of the fixing seat, a cross-shaped slide groove opened on the side wall of the fixing seat, multiple inner and outer plywoods arranged concentrically inside the cross-shaped slide groove, a positioning column fixedly connected at the center of the fixing seat, a telescopic device 1 with multiple output ends connected to the outer plywood installed on the side wall of the light shield, and a telescopic device 2 with multiple output ends connected to the inner plywood installed inside the positioning column.

[0006] In the above-mentioned stretching fixture for aging detection of polyethylene gas pipelines, the pipeline is clamped at multiple locations by inner and outer plates, and the inner and outer plates can be adaptively adjusted according to the diameter of the pipeline. The detection function of the array-type photoresistor is used to monitor the slippage distance of the polyethylene pipe during the stretching process, and can perform self-compensation to ensure that the simulation of the long-term operating pressure load of the pipeline does not change, effectively improving the accuracy of the experiment.

[0007] As a further improvement of the present application, the outer splint includes two inner and outer concentric friction pads, and an elastic edge seal is fixedly connected between the two friction pads.

[0008] As a further improvement of the present application, the inner wall of the outer friction pad is fixedly connected to a magnetic pad, and the inner wall of the inner friction pad is fixedly connected to an electromagnetic pad, and the electromagnetic pad generates magnetism that repels the magnetic pad when energized.

[0009] As a further improvement of the present application, the outer splint further includes an elastic membrane fixedly connected to both ends of the elastic edge seal, and the elastic membrane and the elastic edge seal form a closed space, and the closed space is filled with a saturated electrorheological fluid.

[0010] As another improvement of the present application, a plurality of light strips distributed at equal intervals are fixedly embedded in the side wall of the outer plate facing the inner plate, and a plurality of array-type photoresistor components distributed at equal intervals are fixedly embedded in the side wall of the inner plate facing the outer plate, and the plurality of light strips and array-type photoresistor components are opposite to each other.

[0011] As another improved supplement to the present application, the fixing unit also includes a slip distance measurement module connected to the array photoresistor signal, a current regulation module connected to the electromagnetic pad signal, a compensation module connected to the servo motor, and an on-off power control module connected to the electrorheological fluid signal.

[0012] As another improved supplement to the present application, laser rangefinders with built-in transmitters and receivers are respectively installed at the ends of the two positioning columns, and the fixing unit also includes a start-stop control module connected to the servo motor signal, and a calibration module connected to the receiver signal.

[0013] As another improvement of the present application, the fixing unit further includes a slippage comparison module connected to the array photoresistor signal, and an alarm connected to the slippage comparison module is installed on the fixing unit.

[0014] As another improvement of the present application, a scale is further provided on the upper surface of the base plate, and the numerical reading lines of the scale are painted with a fluorescent agent.

[0015] A method for using a stretching fixture for detecting aging of a polyethylene gas pipeline, comprising: S1. First, clamp the two ends of the polyethylene tube for testing between the inner and outer clamping plates on the two fixing units. Activate the first and second telescopic devices to push the inner and outer clamping plates toward each other, thereby clamping the inner and outer walls of the polyethylene tube. S2. Then, the two servo motors are started to rotate the screw rods, which causes the slide to slide until it reaches the pre-calculated stretching distance. During this period, the inner and outer plates maintain the stretching state on the polyethylene tube, simulating the pressure load of the polyethylene tube under long-term operation. S3. When the stretching is just started, the electromagnetic pad is energized to generate magnetism that repels the magnetic pad, thereby increasing the holding force on the polyethylene tube and preventing the polyethylene tube from falling off from the fixing unit when the stretching is just started. S4. During or after stretching, when the polyethylene tube slips a short distance from the clamping of the inner and outer clamping plates, the length of the array photoresistor element covered by the polyethylene tube decreases, while the length illuminated by the light strip increases. The slippage distance measurement module calculates the slippage distance of the polyethylene tube by measuring the exposed length of the array photoresistor element. On the one hand, the current regulation module is triggered to increase the power supply current to the electromagnetic pad to increase the clamping force. On the other hand, the compensation module is triggered to start the servo motor to drive the slide to move a distance equal to the slippage distance to compensate for the slippage length of the polyethylene tube. S5. During the stretching process and after the stretching stops, if irregular slippage occurs at one end of the polyethylene tube, the lengths of the multiple array-type photoresistors on the same inner clamping plate covered by the polyethylene tube are different, and the slippage comparison module triggers the alarm after analysis and comparison. At the same time, after the stretching is completed, the laser rangefinder monitors the distance between the slide and the fixed plate in real time. Once a change occurs, the calibration module is triggered to drive the servo motor to restore the slide to its position.

[0016] In summary, the inner and outer splints are used to clamp polyethylene tubes of different diameters, which effectively improves the adaptability of the device. The covering effect of the polyethylene tube on the array photoresistor is used to detect the slippage of the pipeline during the stretching process. The array photoresistor calculates the slippage distance of the polyethylene tube by detecting the change in the length of itself illuminated by the light strip. On the one hand, the clamping force is strengthened by increasing the current of the electromagnetic pad to effectively prevent the polyethylene tube from slipping further. On the other hand, compensation is performed by adjusting the slide to move a length equal to the slippage distance, thereby keeping the pressure load on the pipeline unchanged and ensuring the accuracy of the experimental parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a three-dimensional diagram of the fixing device according to the first embodiment of the present application; Figure 2 This is a three-dimensional diagram of the fixing unit of the first embodiment of the present application; Figure 3 This is a three-dimensional exploded view of the fixing unit of the first embodiment of the present application; Figure 4 This is a distribution diagram of the light strip and array-type photoresistor components of the second embodiment of the present application; Figure 5 A side sectional view of an outer splint according to a second embodiment of the present application; Figure 6 This is a side sectional view of an inner splint according to a second embodiment of the present application; Figure 7 This is a schematic diagram of detecting a polyethylene tube before and after slippage according to the second embodiment of the present application; Figure 8 This is a schematic diagram of the polyethylene tube according to the second embodiment of the present application when irregular slippage occurs.

[0018] Description of the numbers in the figure: 1 base plate, 2 fixed plate, 3 slide, 4 screw rod, 5 limit rod, 6 servo motor, 7 fixed unit, 8 fixed seat, 801 cross slide, 9 light shield, 10 inner splint, 11 outer splint, 1101 friction pad, 1102 elastic edge banding, 1103 magnetic pad, 1104 electromagnetic pad, 1105 elastic film, 1106 electrorheological fluid, 12 telescopic device 1, 13 positioning column, 14 telescopic device 2, 15 light strip, 16 array photoresistor, 17 laser rangefinder, 18 ruler. DETAILED DESCRIPTION

[0019] Two implementation modes of the present application are described in detail below with reference to the accompanying drawings.

[0020] The first implementation method: like Figure 1As shown, it includes a base plate 1, fixed plates 2 fixedly connected to both ends of the base plate 1, a slide 3 slidably connected to the upper surface of the base plate 1, a screw 4 symmetrically fixedly connected between the two fixed plates 2 and passing through the slide 3, two limit rods 5 arranged parallel to and located on the inner side of the screw 4, and a servo motor 6 installed on one of the fixed plates 2 and connected to the screw 4 at its output end (the specific model is selected according to actual needs). The slide 3 and the opposite side walls of one of the fixed plates 2 are fixedly connected with fixed units 7 arranged at the same level. When performing aging testing, the two ends of the polyethylene tube are respectively clamped on the two fixed units 7, and then the servo motor 6 drives the screw 4 to move the slide 3, thereby stretching the polyethylene tube, thereby simulating the load of the polyethylene tube under long-term operating pressure; like Figure 2 、 3 As shown, the fixing unit 7 includes a fixing seat 8, a light shield 9 fixedly connected to the side of the fixing seat 8, a cross-shaped slide groove 801 opened on the side wall of the fixing seat 8, a plurality of inner plywood 10 and outer plywood 11 slidably connected to the concentric circle inside the cross-shaped slide groove 801, a positioning column 13 fixedly connected at the center of the fixing seat 8, a telescopic device 12 with multiple output ends connected to the outer plywood 11 is installed on the side wall of the light shield 9, and a telescopic device 2 14 with multiple output ends connected to the inner plywood 10 is installed inside the positioning column 13. The driving source of the telescopic device 12 and the telescopic device 2 14 can be electric or hydraulic. The specific driving source is selected according to actual needs and is not described in detail here. By adjusting the movement of the inner plywood 10 and the outer plywood 11 by the telescopic device 12 and the telescopic device 2 14, polyethylene pipes of different diameters can be clamped and fixed, thereby effectively improving the adaptability of the fixing device; This embodiment uses multiple groups of inner clamps 10 and outer clamps 11 to clamp the polyethylene pipe wall at multiple points, effectively improving the uniformity of load distribution during the stretching process. Moreover, the positions of the inner clamps 10 and outer clamps 11 can be flexibly moved to fix polyethylene pipes of different diameters, thereby effectively improving the adaptability of the fixing device.

[0021] The second implementation method: This embodiment further improves the fixing unit 7 based on the first embodiment to compensate for the slippage distance of the polyethylene tube and ensure that the pressure load does not change during the stretching process. The rest of the parts remain the same as the first embodiment. like Figure 5As shown, the outer splint 11 includes two concentric inner and outer friction pads 1101 (friction-resistant polyurethane material is preferred, and other materials can also be selected according to actual needs), and an elastic edge seal 1102 is fixedly connected between the two friction pads 1101, a magnetic pad 1103 is fixedly connected to the inner wall of the outer friction pad 1101, and an electromagnetic pad 1104 (made of electromagnetic material) is fixedly connected to the inner wall of the inner friction pad 1101, and the electromagnetic pad 1104 generates magnetism that repels the magnetic pad 1103 when energized. When the polyethylene tube is stretched just after starting, the sudden change in its stress makes it resist the stretching force. At this time, the polyethylene tube is most likely to slip off the fixing unit 7. Therefore, when the stretching is just started, the electromagnetic pad 1104 is energized to generate magnetism that repels the magnetic pad 1103, thereby increasing the pressure of the outer clamping plate 11 on the polyethylene tube, thereby increasing the friction force, thereby effectively preventing the polyethylene tube from slipping off during the stretching start-up phase. This also indirectly increases the clamping force of the fixing device, effectively improving the stability of the polyethylene tube. like Figure 5 As shown, the outer splint 11 also includes an elastic film 1105 fixedly connected to both ends of the elastic edge sealing 1102, and the elastic film 1105 and the elastic edge sealing 1102 form a closed space, and the closed space is filled with a saturated electrorheological fluid 1106. The elastic edge sealing 1102 is to cooperate with the electromagnetic pad 1104 to repel the magnetic pad 1103. After the electromagnetic pad 1104 and the magnetic pad 1103 remain stable, the electrorheological fluid 1106 is energized to harden it, thereby improving the stability of the entire outer splint 11 to prevent the outer splint 11 from repeatedly changing during the stretching process and affecting the clamping stability of the polyethylene tube. In addition, when the positions of the magnetic pad 1103 and the electromagnetic pad 1104 change, since the elastic film 1105 is elastic, the electrorheological fluid 1106 will always maintain a saturated state in the closed space, so that the electrorheological fluid 1106 can also adapt to the changes of the outer splint 11, thereby not affecting the stabilization effect. like Figure 4 、 6As shown in Figure 7, the side wall of the outer plywood 11 facing the inner plywood 10 is fixedly inlaid with a plurality of equally spaced light strips 15, and the side wall of the inner plywood 10 facing the outer plywood 11 is fixedly inlaid with a plurality of equally spaced array-type photoresistors 16. Its specific structure is composed of a plurality of photoresistor elements connected in series, and each photoresistor element can work independently. Whenever the polyethylene tube slips, a different number of photoresistor elements can be exposed, thereby detecting the light signal emitted by the light strip 15. The plurality of light strips 15 and the array-type photoresistor elements 16 are opposite to each other in pairs, and the light emitted by the light strip 15 is irradiated on the array-type photoresistor element 16 and detected by it. Since the array-type photoresistor element 16 is distributed in an array, the light signal can be detected according to the number of photoresistor elements that can detect the light signal. The length of the arrayed photoresistor 16 covered by light can be measured by counting the number of light-sensitive resistors. The specific calculation method is as follows: before the polyethylene tube slips, the arrayed photoresistor 16 is covered by the tube wall. After the polyethylene tube slips, multiple photoresistor elements are exposed. Since the lengths of two adjacent photoresistor elements are fixed and known, the sum of the lengths of the newly exposed photoresistor elements is the distance D that the polyethylene tube slipped. In this way, the arrayed photoresistor 16 can control the movement of the slide 3 to compensate for the slippage based on this distance D. In addition, if only one end of the polyethylene tube slips, the compensation distance of the slide 3 is D. If both ends of the polyethylene tube slip, the compensation distance of the slide 3 is the sum of the slippage distances at both ends. The fixing unit 7 also includes a slippage distance measuring module connected to the array photoresistor element 16 signal, a current regulating module connected to the electromagnetic pad 1104 signal, a compensation module connected to the servo motor 6, and an on-off control module connected to the electrorheological fluid 1106 signal. The slippage distance measuring module obtains the slippage distance D of the polyethylene tube by the sum of the lengths of the newly exposed multiple photoresistor elements. Then, the slippage distance measuring module triggers the current regulating module to increase the current of the electromagnetic pad 1104, thereby increasing the clamping force on the polyethylene tube and preventing further slippage of the polyethylene tube. On the other hand, the slippage distance measuring module triggers the compensation module to control the servo motor 6 to drive the slide 3 to move a distance equal to the slippage distance D, thereby compensating for the stretched length of the polyethylene tube and ensuring that the pressure load does not change significantly, thereby effectively improving the accuracy of the experimental parameters. In addition, while adjusting the current of the electromagnetic pad 1104, the on-off control module also de-energizes the electrorheological fluid 1106 to match the position changes of the electromagnetic pad 1104 and the magnetic pad 1103. A laser rangefinder 17 with a built-in transmitter and receiver is installed at the end of each of the two positioning posts 13 (the specific model is selected according to actual needs). The fixed unit 7 also includes a start-stop control module connected to the servo motor 6 signal, and a calibration module connected to the receiver signal. The transmitter and receiver are distributed on the two positioning posts 13. When the slide 3 stops moving, the polyethylene tube begins to enter a stationary state. During this process, the laser rangefinder 17 monitors the distance between the two fixed units 7 in real time. If the distance between the two fixed units 7 changes due to mechanical failure or other factors of the slide 3, the receiver immediately triggers the calibration module, and then the calibration module triggers the start-stop control module to allow the servo motor 6 to drive the slide 3 to return to its original position, so as to avoid changing the pressure load of the polyethylene tube and affecting the accuracy of the experiment. like Figure 8 As shown, the fixing unit 7 also includes a slippage comparison module connected to the array photoresistor 16 signal, and an alarm connected to the slippage comparison module is installed on the fixing unit 7. There are many cases of polyethylene tube slippage, which are mainly two types. One is synchronous slippage of the port, and the other is asynchronous slippage of the port. In this case, the port of the polyethylene tube will appear as an inclined surface. In this case, the pressure load of the entire polyethylene tube is no longer balanced, and there is a risk of rupture of the pipeline. Therefore, a timely alarm is required, and the slippage comparison module can analyze and compare the slippage distance D detected by each array photoresistor 16. When the analysis shows that the distance D detected by multiple array photoresistors 16 on the same inner plywood 10 is different or the distance D detected by the array photoresistors 16 between different inner plywood 10 is also different, it indicates that the polyethylene tube has undergone irregular slippage, and the alarm is immediately triggered to remind the experimenter to check in time; like Figure 1 As shown, a scale 18 is further provided on the upper surface of the base plate 1, and the numerical reading lines of the scale 18 are painted with a fluorescent agent. The scale 18 facilitates the experimenter to check the stretching distance of the polyethylene tube, and the fluorescent agent can effectively enhance the conspicuousness of the scale 18; How to use the tensile fixture for aging detection of polyethylene gas pipelines: S1. First, clamp the two ends of the polyethylene tube for testing between the inner and outer clamping plates 10 and 11 on the two fixing units 7. Activate the telescopic device 12 and the positioning column 13 to push the inner and outer clamping plates 10 and 11 toward each other, thereby clamping the inner and outer walls of the polyethylene tube. S2. Next, the two servo motors 6 are started to rotate the screw 4, thereby sliding the slide 3 until the slide 3 slides to the pre-calculated stretching distance. During this period, the inner and outer clamping plates 10 and 11 maintain the stretching state on the polyethylene tube, thereby simulating the pressure load of the polyethylene tube under long-term operation. S3. When the stretching is just started, the electromagnetic pad 1104 is energized to generate magnetism that repels the magnetic pad 1103, thereby increasing the holding force on the polyethylene tube and preventing the polyethylene tube from falling off from the fixing unit 7 when the stretching is just started. S4. During or after stretching, when the polyethylene tube slips a short distance from the clamping of the inner and outer clamping plates 10 and 11, the length of the arrayed photoresistor 16 covered by the polyethylene tube decreases, while the length illuminated by the light strip 15 increases. The slippage distance measuring module calculates the slippage distance of the polyethylene tube by measuring the exposed length of the arrayed photoresistor 16. On the one hand, the current regulating module is triggered to increase the power supply current to the electromagnetic pad 1104 to increase the clamping force. On the other hand, the compensation module is triggered to start the servo motor 6 to drive the slide 3 to move a distance equal to the slippage distance to compensate for the slippage length of the polyethylene tube. S5. During the stretching process and after the stretching stops, if irregular slippage occurs at one end of the polyethylene tube, the lengths of the multiple array-type photoresistors 16 on the same inner clamping plate 10 covered by the polyethylene tube are different, and the slippage comparison module triggers the alarm after analysis and comparison. At the same time, after the stretching is completed, the laser rangefinder 17 monitors the distance between the slide 3 and the fixed plate 2 in real time. Once a change occurs, the calibration module is triggered to drive the servo motor 6 to restore the slide 3 to its position.

[0022] Compared with the existing technology, this embodiment can monitor the slippage phenomenon of the polyethylene tube during the stretching process and can also compensate for it. In this way, the polyethylene tube can be stretched to a pre-calculated stretching distance and the long-term pressure load on the polyethylene tube will not change, thereby effectively improving the accuracy of the experiment.

[0023] In view of current actual needs, the protection scope of the above-mentioned implementation mode adopted in this application is not limited to this. Various changes made within the knowledge scope of technical personnel in this field without departing from the concept of this application still fall within the protection scope of the present invention.

Claims

1. A stretching fixture for polyethylene gas pipeline aging detection, characterized by: The invention comprises a base plate (1), fixed plates (2) fixedly connected to both ends of the base plate (1), a slide seat (3) slidably connected to the upper surface of the base plate (1), a screw rod (4) symmetrically fixedly connected between the two fixed plates (2) and passing through the slide seat (3), two limit rods (5) arranged parallel to the screw rod (4) and located on the inner side thereof, and a servo motor (6) mounted on one of the fixed plates (2) and having an output end connected to the screw rod (4), and the side walls opposite to the slide seat (3) and one of the fixed plates (2) are fixedly connected to fixing units (7) arranged at the same level; The fixing unit (7) includes a fixing seat (8), a light shield (9) fixedly connected to the side of the fixing seat (8), a cross-shaped slot (801) provided on the side wall of the fixing seat (8), a plurality of inner clamping plates (10) and outer clamping plates (11) slidably connected to the inside of the cross-shaped slot (801) and arranged concentrically, a positioning column (13) fixedly connected at the center of the fixing seat (8), a telescopic device (12) having a plurality of output ends connected to the outer clamping plates (11) installed on the side wall of the light shield (9), and a telescopic device (14) having a plurality of output ends connected to the inner clamping plates (10) installed inside the positioning column (13).

2. A stretching and fixing device for aging detection of polyethylene gas pipelines according to claim 1, characterized in that: The outer clamping plate (11) comprises two inner and outer concentric friction pads (1101), and an elastic sealing edge (1102) is fixedly connected between the two friction pads (1101).

3. The stretching and fixing device for aging detection of polyethylene gas pipelines according to claim 2, characterized in that: The inner wall of the outer friction pad (1101) is fixedly connected to a magnetic pad (1103), and the inner wall of the inner friction pad (1101) is fixedly connected to an electromagnetic pad (1104), and the electromagnetic pad (1104) generates magnetism that repels the magnetic pad (1103) when energized.

4. The stretching and fixing device for aging detection of polyethylene gas pipelines according to claim 2, characterized in that: The outer splint (11) further comprises an elastic membrane (1105) fixedly connected to both ends of the elastic edge seal (1102), and the elastic membrane (1105) and the elastic edge seal (1102) enclose a closed space, and the closed space is filled with a saturated electrorheological fluid (1106).

5. The stretching and fixing device for aging detection of polyethylene gas pipelines according to claim 1, characterized in that: A plurality of equally spaced light strips (15) are fixedly inlaid on the side wall of the outer clamping plate (11) facing the inner clamping plate (10), and a plurality of equally spaced array photoresistors (16) are fixedly inlaid on the side wall of the inner clamping plate (10) facing the outer clamping plate (11), wherein the plurality of light strips (15) and array photoresistors (16) are opposed to each other.

6. The stretching and fixing device for aging detection of polyethylene gas pipelines according to claim 5, characterized in that: The fixing unit (7) further comprises a slippage distance measuring module connected to the array photoresistor (16) signal, a current regulating module connected to the electromagnetic pad (1104) signal, a compensation module connected to the servo motor (6), and an on / off control module connected to the electrorheological fluid (1106) signal.

7. The stretching and fixing device for aging detection of polyethylene gas pipelines according to claim 1, characterized in that: The ends of the two positioning columns (13) are respectively equipped with laser rangefinders (17) with their own transmitters and receivers. The fixing unit (7) also includes a start-stop control module connected to the servo motor (6) signal, and a calibration module connected to the receiver signal.

8. The stretching and fixing device for aging detection of polyethylene gas pipelines according to claim 5, characterized in that: The fixing unit (7) further comprises a slippage comparison module connected to the array photoresistor element (16) by signal, and an alarm connected to the slippage comparison module is installed on the fixing unit (7).

9. The stretching and fixing device for aging detection of polyethylene gas pipelines according to claim 1, characterized in that: The upper surface of the base plate (1) is also provided with a scale (18), and the numerical reading lines of the scale (18) are painted with a fluorescent agent.

10. The method for using the stretching and fixing device for aging detection of polyethylene gas pipelines according to claim 1, characterized in that: A method for using the stretching and fixing device for aging detection of polyethylene gas pipelines according to any one of claims 1 to 9: S1. First, clamp the two ends of the polyethylene tube for testing between the inner clamping plate (10) and the outer clamping plate (11) on the two fixing units (7), start the telescopic device (12) and the positioning column (13) to push the inner clamping plate (10) and the outer clamping plate (11) toward each other, thereby clamping the inner and outer walls of the polyethylene tube; S2. Then, the two servo motors (6) are started to drive the screw (4) to rotate, thereby sliding the slide (3) until the slide (3) slides to the pre-calculated stretching distance. In the subsequent stage, the inner clamping plate (10) and the outer clamping plate (11) maintain the stretching state of the polyethylene pipe, thereby simulating the pressure load of the polyethylene pipe under long-term operation; S3. When the stretching is just started, the electromagnetic pad (1104) is energized to generate magnetism that repels the magnetic pad (1103), thereby increasing the holding force on the polyethylene tube and preventing the polyethylene tube from falling off the fixing unit (7) when the stretching is just started. S4. When the polyethylene tube slips a short distance from the clamping of the inner clamping plate (10) and the outer clamping plate (11) during stretching and after stretching stops, the length of the array photoresistor (16) covered by the polyethylene tube decreases, while the length illuminated by the light strip (15) increases. The slippage distance measurement module calculates the slippage distance of the polyethylene tube by measuring the exposed length of the array photoresistor (16). On the one hand, the current regulation module is triggered to increase the power supply current to the electromagnetic pad (1104) to increase the clamping force. On the other hand, the compensation module is triggered to start the servo motor (6) to drive the slide (3) to move a distance equal to the slippage distance to compensate for the slippage length of the polyethylene tube. S5. During the stretching process and after the stretching stops, if irregular slippage occurs at one end of the polyethylene tube, the lengths of the multiple array-type photoresistors (16) on the same inner clamping plate (10) covered by the polyethylene tube are different, and the slippage comparison module triggers the alarm after analysis and comparison. At the same time, after the stretching is completed, the laser rangefinder (17) monitors the distance between the slide (3) and the fixed plate (2) in real time. Once a change occurs, the calibration module is triggered to drive the servo motor (6) to restore the slide (3) to its position.

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