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summary: Pipelines are composed of pipes, fittings and valves. In production, only if the pipelines are smooth and the valves are properly adjusted can production run normally. This article introduces the general requirements for chemical pipeline layout and how to train students to disassemble and assemble pipelines. keywords: Pipeline disassembly and assembly is to meet the requirements of cultivating high-skilled talents in the chemical industry and improve the overall quality of students. Since 2000, our college has introduced the practical teaching content of chemical pipeline assembly and disassembly to the five-year higher vocational classes majoring in chemical engineering. After years of practice, good results have been achieved, so it has been officially implemented in the process major of the Department of Chemical Engineering since 2005. 1. The significance and characteristics of the chemical pipeline assembly and disassembly training 1. To cultivate students' ability to read pictures, students are required to list equipment and instruments based on the piping system diagram provided by the instructor, and draw three views based on the on-site devices that have been assembled by each group. 2. Train students to master the use of commonly used tools. 3. Cultivate students' spirit of unity and cooperation, and be able to perform pipeline assembly, pressure testing, flushing and disassembly operations in groups. 4. Able to perform system trial operation and parking operations. 2. Basic requirements for chemical pipeline assembly and disassembly 1. General requirements for chemical pipeline layout: When laying out and installing pipelines, the main considerations are the convenience and safety of installation, maintenance, and operation, while minimizing infrastructure costs. Comprehensive considerations are also based on the characteristics of production, the layout of equipment, and the properties of materials. 1.1 When installing chemical pipelines, various pipelines should be laid in parallel to facilitate the sharing of pipe racks. They should be as straight as possible, with fewer turns and fewer intersections, so as to save pipe materials and reduce resistance, while striving to be neat and beautiful. ； 1.2 To facilitate operation, installation and maintenance, parts and valves on parallel pipelines should be installed staggered ； 1.3 Pipes should be installed horizontally and vertically. The deviation of horizontal pipes should not be greater than 15mm/10m, and the deviation of vertical pipes should not be greater than 10mm/10m. ； 1.4 After the pipeline is installed, the strength and tightness test should be carried out according to regulations. ； 1.5 The height of the pipeline from the ground shall be in order to facilitate maintenance, but when passing through the sidewalk, the lowest point shall not be less than 2m from the ground. 2. Installation requirements for common pipe fittings, valves, and flow meters: 2.1 The rotameter is used to measure the fluid flow in the piping system, and its installation has strict requirements. It must be installed vertically in the pipe system. If it is tilted, it will affect the accuracy of the measurement, and in severe cases, the rotor will not be able to rise. There should be corresponding straight pipe sections before and after the rotameter. The front section should have a straight pipe section of 15 to 20 days, and the rear section should have a straight pipe section of about 5 days (d is the inner diameter of the pipe) to ensure the stability of the flow. 2.2 Assembly and disassembly of valves: The stop valve has a simple structure and is easy to adjust the flow, but the resistance is large. When installing, the fluid should flow upward from the lower part of the valve disc in order to reduce resistance and make it easier to open. In the closed state, the valve stem and stuffing box are not in contact with the medium to prevent the valve stem from being corroded. The gate valve has good sealing performance and small fluid resistance, but it is not suitable for transporting liquid pipelines containing crystals and suspended solids. 2.3 The movable joint is a common pipe fitting in the piping system. When closing the piping system, it should be installed last. When dismantling the piping system, the movable joint should be started first. 3. The general principle of pump pipeline layout is to ensure good suction conditions and convenient maintenance. 3.1 In order to increase the allowable suction height of the pump, the suction pipeline should be as short and straight as possible to reduce resistance. The diameter of the suction pipeline should not be smaller than the diameter of the pump suction inlet. 3.2 No pipelines are arranged above the pump, which is conducive to pump maintenance. 3. Organization and implementation of chemical pipeline assembly and disassembly training 1. The instructor explains the key points of the training accordingly and divides the students into groups. ； 2. Organize students to watch teaching videos on chemical pipelines so that students can have a certain perceptual understanding of chemical pipelines. ； 3. Each training group will list equipment, pipe fittings, instruments, etc. based on the piping system diagram provided by the teacher, and receive corresponding materials and tools, etc. ； 4. Accurately process galvanized pipes according to the requirements of the piping system diagram ； The instructor explains how to use cutters, reamers, etc. 5. Assemble the pipeline. Each team assembles the pipeline according to the requirements of the piping system diagram. ； When assembling, the location of the equipment should be determined first, and then the pipelines can be assembled. Specifically, the centrifugal pump, high-level tank, etc. should be determined first, and then the piping can be carried out. 6. Check whether each pipe fittings and valves are installed accurately according to the piping system diagram. ； 7. Carry out water flushing and hydraulic pressure test on the pipeline. Keep the pressure above 4 kgf (gauge pressure) and check the sealing performance of each connection. ； 8. Conduct trial operation and shutdown of the pipeline system. When driving, you should prime the pump first, then turn on the motor, and then open the outlet valve. When parking, the outlet valve should be closed first, and then the motor should be stopped. 9. Correctly master the removal of pipelines. Instruments, unions, valves, etc. should be disassembled first, and then pipe fittings and accessories should be disassembled. 10. After the pipeline is removed, refer to the equipment and instrument list and return the instruments, pipe fittings, tools and consumables in good condition. In addition, in order to deepen students' understanding of common valves, equipment, etc. Our college is also equipped with several common valves, multi-stage pumps, metering pumps, etc., allowing students to understand their structures and working principles and deepen their understanding of theoretical knowledge. Through the above operations, students' hands-on efforts are improved and lay a good foundation for entering the workplace in the future.