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The pressure rating of a pipeline refers to the maximum operating pressure level that the pipeline system can withstand; this rating is typically determined by factors such as the medium transported by the pipeline, as well as the material and manufacturing process of the pipeline itself. Its main purpose is to ensure that the pipeline system operates safely and reliably, without causing damage to production or the environment. The determination of the pressure class is the core of pressure pipeline design, a prerequisite for layout and stress verification, and an important factor affecting the capital investment in pressure pipelines as well as their reliability. The pressure rating of pipes includes two aspects: the nominal pressure rating of the standard fittings (expressed in terms of nominal pressure) and the wall thickness class (expressed in terms of wall thickness grade). Typically, the pressure rating of a pipe is a parameter determined by both the nominal pressure rating and the wall thickness rating of the standard fittings. When determining the pressure rating of a pipeline, the following factors need to be considered: the properties of the medium transported by the pipeline (such as flow rate, density, viscosity, temperature, pressure, and other parameters), the material and manufacturing process of the pipeline itself (such as the material used for the pipeline, internal coatings, manufacturing standards, etc.), the external pressures or loads that the pipeline system must withstand (such as seismic forces, wind loads, support loads, etc.), as well as the required safety factors and service life (such as lifespan, stress levels, fatigue, cracks, etc.). Based on these parameters and the actual engineering requirements, systematic calculations and analyses can be carried out to determine the pressure rating required for the pipeline. At the same time, it is also necessary to take into account the provisions of relevant standards and regulations, as well as the actual conditions on site and safety requirements. I. Determination of pipeline pressure class: In engineering practice, process operation parameters should not be used directly as the design criteria for pressure pipelines. Factors such as fluctuations in process operations, the influence of connected equipment, and environmental effects must be taken into account; a certain safety margin is applied to these process operation parameters to serve as the design criteria. The design conditions mentioned here mainly refer to the design pressure and design temperature. 1.1 Determination of design pressure: The design pressure of the pipeline shall be no lower than the pressure under the most severe conditions during normal operation, which are determined by the internal pressure (or external pressure) and temperature. Most severe conditions: refer to the conditions that result in the maximum wall thickness or the highest nominal pressure class for pipes and pipe components. Taking into account factors such as the hydrostatic column pressure of the medium, the design pressure should generally be slightly higher than the maximum operating pressure under the most severe conditions caused by external pressure and temperature. The design pressure of pipelines should take into account the internal and external pressures as well as temperature factors under the most severe conditions; for safety reasons, the design pressure is generally set slightly higher than the maximum operating pressure. When determining the design pressure, we can follow the practices used for pressure vessels by applying a margin factor to ensure ease of operation and safety. a. Under normal circumstances, the design pressure for pipe components is determined by applying a safety factor to the corresponding operating pressure. Under normal circumstances, the design pressure of pipeline components is determined as follows: operating pressure Pw (MPa), design pressure P (MPa); if Pw ≤ 1.8, then P = Pw + 0.18; otherwise, P = 1.8