管径的确定 当流体的流量已知时，管径的大小取决于允许的流速或允许的摩擦阻力（压力降）。流速大时管径小，但压力降值增大。因此，流速大时可以节省管道基建投资，但泵和压缩机等动力设备的运行能耗费用增大。此外，如果流速过大，还有可能带来一些其他不利的因素。因此管径应根据建设投资、运行费用和其他技术因素综合考虑决定。
Pipe-diameter determination When the flow rate of fluid is known, the size of pipe diameter depends on the allowable flow rate or allowable friction resistance (pressure drop). When the flow rate is high, the diameter of the tube is small, but the pressure drop increases. Therefore, when the flow rate is high, the investment of pipeline infrastructure can be saved, but the running energy consumption of power equipment such as pumps and compressors increases. In addition, if the flow rate is too high, there may be some other adverse factors. Therefore, the pipe diameter should be determined according to the construction investment, operation cost and other technical factors.
管道 - 管道的联接 管子、管子联接件、阀门和设备上的进出接管间的联接方法，由流体的性质、压力和温度以及管子的材质、尺寸和安装场所等因素决定，主要有螺纹联接、法兰联接、承插联接和焊接等4种方法:①螺纹联接：主要适用于小直径管道。联接时，一般要在螺纹联接部分缠上氟塑料密封带或涂上厚漆、绕上麻丝等密封材料，以防止泄漏。在1.6兆帕以上压力时，一般在管子端面加垫片密封。这种联接方法简单，可以拆卸重装，但须在管道的适当地方安装活接头，以便于拆装。②法兰联接：适用的直径范围较大。联接时根据流体的性质、压力和温度选用不同的法兰和密封垫片，利用螺栓夹紧垫片保持密封。在需要经常拆装的管段处和管道与设备相联接的地方大都采用法兰联接。③承插联接：用于铸铁管、 混凝土管、 陶土管及其联接件之间的联接，只适用于在低压常温条件下工作的给水、排水和煤气管道。联接时，一般在承插口的槽内先填入麻丝、棉线或石棉绳，然后再用石棉水泥或铅等材料填实，还可在承插口内填入橡胶密封环，使其具有较好的柔性，容许管子有少量的移动。④焊接联接：这种联接的强度和密封性最好，适用于各种管道，省工省料，但拆卸时必须切断管子和管子联接件。
The connection methods between pipe-to-pipe connection pipes, pipe connectors, valves and equipment are determined by fluid properties, pressure and temperature, material, size and installation site of pipes. There are four main methods: threaded connection, flange connection, socket connection and welding. It is mainly suitable for small diameter pipelines. When joining, it is necessary to wrap fluoroplastic sealing tape or coat thick paint, wrap hemp wire and other sealing materials on the threaded joint part to prevent leakage. When the pressure is above 1.6 MPa, gaskets are usually added to the end face of the pipe. This connection method is simple and can be disassembled and reassembled, but the loose joint must be installed in the proper place of the pipeline for disassembly and assembly. (2) Flange connection: the applicable diameter range is large. Different flanges and sealing gaskets are selected according to the nature of the fluid, pressure and temperature, and the gaskets are clamped by bolts to keep the sealing. Flange connection is mostly used in pipeline sections which need to be disassembled and assembled frequently and in places where pipelines are connected with equipment. (3) Socket connection: It is used for the connection between cast iron pipe, concrete pipe, clay pipe and its connectors. It is only suitable for water supply, drainage and gas pipeline working under low pressure and normal temperature. When connecting, linen, asbestos or asbestos rope is usually filled in the socket slot first, then filled with asbestos cement or lead, and rubber sealing ring can also be filled in the socket to make it more flexible and allow the pipe to move a little. (4) Welding connection: This connection has the best strength and sealability. It is suitable for all kinds of pipelines and saves labour and material. However, when disassembling, it is necessary to cut off the pipe and its connecting parts.