Detailed summary of pipeline pressure

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Throughout the entire process of pipeline design, manufacturing, operation, and acceptance, a complete safety logic is established by four key pressure parameters: nominal pressure, operating pressure, design pressure, and test pressure. The definitions, functions, and numerical relationships among these parameters are clear and interrelated, serving as the fundamental basis for pipeline safety. Detailed explanation of the four major pressures. Nominal pressure (PN): It is a nominal pressure grade established to standardize design, manufacturing, and selection; it is a standardized parameter, similar to the \"pressure resistance class\" of pipes. Common values include PN10, PN16, PN25, etc. This pressure is determined based on a reference temperature; in actual use of pipelines, the load-bearing capacity decreases as the temperature of the fluid rises. It serves as a basic grade indicator for pipeline components and does not directly represent the real-time load-bearing capacity. Operating pressure (P): It is the continuous operating pressure that the pipeline system actually experiences during normal operation. It is determined by the production process, the properties of the medium, and the operating conditions, and it varies with changes in temperature, flow rate, and load. It is the original basis for the pipeline pressure system, and all subsequent pressure settings are based on it as a reference. Design pressure (Pe): It is the maximum allowable operating pressure of a pipeline determined during the design phase, and it serves as the key benchmark for the strength design of pipelines. This value is never lower than the operating pressure, and safety margins are taken into account by fully considering factors such as pressure fluctuations, water hammer, and changes in operating conditions. The design pressure directly determines the pipe material, wall thickness, and selection of pipe fittings; it is a key indicator for classifying the safety level of pipes. Test pressure (Ps): It is the pressure used for strength verification and leak testing after the pipeline has been manufactured or installed on-site; it represents the highest pressure that the pipeline is subjected to during its entire life cycle. The standard hydrostatic test pressure is generally 1.5 times the design pressure, while the pneumatic test uses the corresponding value specified in the standards; only by withstanding such pressures can it be determined whether the pipeline can be put into operation safely. Four key differences in pressure. Nominal pressure: Standard for manufacturing classification; fixed grade, with actual load-bearing capacity affected by temperature ； Work pressure: Actual operating load, determined by the process, with dynamic fluctuations ； Design pressure: Design safety threshold, basis for strength calculation, with a safety margin ； Test pressure: acceptance test standard, maximum short-term pressure, to verify safety. The internal connections and core logic of the four major pressures. The numerical iron law: Test pressure > Nominal pressure > Design pressure ≥ Operating pressure. This relationship is the core principle for pipeline design, acceptance, and operation, and it must not be reversed. Complete logical chain: The process first specifies the operating requirements and determines the working pressure → Designers then add a safety margin to this value to establish the design pressure → Based on this design pressure, the appropriate grade is selected, and the nominal pressure is determined to guide manufacturing → After installation, tests are conducted at higher pressures to verify strength and tightness; only after passing these tests can the system be put into use. Key points for industry applications: Industrial pipelines are based on design pressure, with material selection, classification, and testing carried out in strict accordance with relevant standards ； For utility pipelines and long-distance pipelines, factors such as water hammer effects, topographical elevation differences, and the properties of the fluid must be taken into account. At the same time, the requirements for integrity tests need to be strengthened to ensure safety throughout the entire process, from design to operation of these pipelines.