ASME Pressure Vessel Code – General Fluids

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Regarding the classification of pipelines, the American standard ASME Pressure Vessel Code ANSI/ASME B31.3 categorizes the fluids transported through pipelines in chemical plants and refineries into four types: Class D, Class M, high-pressure fluids, and general fluids, based on the properties of the fluids being transported and the consequences of leaks. (1) Class D fluids: 1) Transport fluids that are non-flammable, non-toxic, and harmless to humans; 2) The design pressure shall not exceed 1.035 MPa; 3) The design temperature ranges from -29°C to 186°C. (2) Class M fluids 1) If even a small amount of this fluid leaks into the environment during transportation and is inhaled by humans or comes into contact with their bodies, it can cause severe poisoning, and there is no cure possible after coming out of contact with it. (3) High-pressure fluids 1) generally refer to fluid media with pressures exceeding PN420 in ASME B16.5 (grade 2500), but are not limited to such pressures. (4) General fluids refer to all fluids other than those of category D, category M, and high-pressure fluids. According to the above definition, cryogenic fluids and flammable fluids with 42 MPa > P > 1.035 MPa are classified as “general fluids”; it seems to me that these fluids aren’t really general fluids