With the development of computer technology and communication technology, SCADA system has demonstrated sufficient advantages in gas pipeline leak detection, which is one of the development directions of the above detection methods. It monitors the pipeline operating status in real time through the pressure, temperature, flow and other parameters measured by sensors along the key points of the pipeline. The central control center uses various algorithms to analyze and process the collected data in real time to achieve gas pipeline leak detection and positioning, and the result information Feedback to the management personnel in the form of graphics so that the management personnel can timely understand the pipeline operation and make corresponding treatment. The system is mainly implemented based on software. In the algorithm, a variety of existing pipeline leak detection and positioning technologies can be used to process the collected data, thereby improving the accuracy and reliability of system monitoring.

With the increasing application of plastic pipes, people increasingly hope to improve the performance of pipes by self-reinforcement technology, especially the circumferential performance of pipes, which is also a hot spot in the field of pipe research for many years. As early as the 1960s, the British Gross used a molding device with a core directly connected to the extruder screw to extrude the pipe. The circumferential performance of the pipe was slightly improved, but it was not obvious that Bevis et al. Adopted the inventive shear The control method was successful when extruding glass fiber reinforced polypropylene pipes, but when used in the self-reinforcement research of pure PP pipe extrusion, the results were disappointing. Zachariades also studied the extrusion of PE pipes through their respective rotating heads. For pure polyolefin pipes, there has never been any report of improvement in circumferential performance. Based on the work done by the predecessors, we have developed an extrusion molding device for bidirectionally reinforced polyolefin pipes in a composite stress field. In the extrusion molding process, in the section where the shear stress field is applied, a circumferential shear stress field is applied to the melt by the rotation and drag of the core sleeve, so that the macromolecules are oriented and crystallized in the circumferential direction. In the axial stretching section, relying on the wedge-shaped flow channel compression to cause the melt to stretch in the axial direction, so that some macromolecules are also oriented in the axial direction. That is, the die has applied a stress field in two directions to the melt, which is called a composite stress field. It is hoped that shear-induced crystallization can fix the orientation of the polymer in the shear field at the melting temperature, and form crystals with axial fiber crystals along the orientation stretching direction to improve the mechanical properties of the pipe in the circumferential and axial directions.

With the further increase in the speed of the mandrel, it decreases. On the contrary, the axial strength shows a downward trend with the rotation speed of the mandrel. If the horizontal line with the strength of 22MPa is selected as a symmetric curve, the curve of the circumferential and axial strength with the rotation speed of the mandrel is almost symmetrical. This is a typical case of anisotropy due to molecular orientation. From the experimental device, during the melt extrusion process, the plastic field of self-reinforced HDPE pipe prepared under the composite stress field of tensile stress along the axial direction is constant, while the circumferential stress field increases with the speed of the core rod. It was enhanced. The change of the circumferential stress field redistributes the degree of orientation of the macromolecules in the circumferential and axial directions, so the strength of the pipe along these two directions also exhibits anisotropy consistent with the degree of orientation. The author believes that the change of the biaxial tensile strength of the ordinary grade HDPE6100M pipe prepared by the composite stress field belongs to the orientation enhancement mode mechanism, and the bidirectional reinforcement of the pipe has not been achieved, and the increase in the circumferential strength is not large, only 13% about. Although the pipes prepared by adding B and C of HMWHDPE under the compound stress field have realized the enhancement of the two-way mechanical properties of the pipe, it is found that the extent of B enhancement is more obvious. According to the analysis, in the temperature field of 130 ℃, the polymer melt B contains only 4% HMWHDPE, the high molecular weight HMWHDPE macromolecules can be well dispersed in the melt, and the density of the dynamic network entanglement points between the molecules is relatively high Low, HMWHDPE macromolecules can easily form nucleus along the flow field direction line under the action of the circumferential shear field. Due to its high molecular weight, the line nucleus can be well retained at a higher temperature of 130 ℃.

The pipe made of ordinary grade HDPE6100M extruded in the composite stress field has a circumferential strength that increases slowly with the increase of the speed of the core rod. It reaches the highest point when the speed of the core rod is 40r / min, about 24.4MPa, and then Under the application of shear, the core can further induce the HDPE6100M macromolecule to fold and crystallize around it. The polymer melt C contains 40% HMWHDPE. The high molecular weight HMWHDPE macromolecules cannot be well dispersed in the melt. It is likely that the HMWHDPE macromolecules are entangled with each other, and the dynamic network entanglement point density between the molecules is relatively high. Many, so it is necessary to form a core under stronger shearing, which can be indirectly proved from Figure 5, that is, the circumferential strength of the B tube sample increases rapidly with the increase of the core rod speed; and C test The circumferential strength of the sample showed a relatively slow increase with the increase of the speed of the mandrel, and the highest point of the strength appeared at a higher mandrel speed (15r / min), so the bidirectional self-reinforcement effect of the final pipe sample C instead The self-reinforced HDPE pipe plastics prepared under the composite stress field without pipe sample B have a good reinforcement effect.

The pipe made of ordinary grade HDPE6100M is extruded through a composite stress field. The maximum circumferential strength of the pipe appears at the speed of the core rod at 40r / min, which is 24.4MPa, which is a 13% improvement over the pipe without the composite stress field. , The axial strength at the corresponding rotation speed is 19.82MPa, which is 9.3% lower than that of the pipe without the composite stress field applied. This is a typical anisotropic situation caused by molecular orientation, which fails to achieve bidirectional reinforcement of the pipe . Adding a small amount of HMWHDPE to the ordinary grade HDPE6100M, the pipe extruded by the compound stress field device can greatly improve the bidirectional tensile strength of the pipe and realize the bidirectional self-reinforcement of the pipe.

In the composite stress field, high molecular weight polyethylene molecules are more likely to retain orientation along the orientation direction, and can form a line core at a higher temperature, and can further induce ordinary molecular weight polyethylene molecules to fold around the line core along the shear flow direction Orientation and crystallization, so that the bidirectional strength of the pipe has been greatly improved. This enhanced mode is an enhanced mode of shear-induced crystallization.

Adding 4% of bidirectional reinforced pipe to ordinary grade HDPE6100M has more excellent bidirectional mechanical properties. Metal-reinforced winding structure wall pipe China has started in the development of metal-reinforced winding structure wall pipe, because of its outstanding advantages, there is a trend of rapid development. The currently used connection method is mainly extrusion torch welding.

The self-developed composite plastic pipe is a reinforced polyethylene pipe developed in China, including steel skeleton plastic composite pipe, perforated steel skeleton plastic composite pipe and steel wire reinforced composite plastic pipe. Docking.

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