On the definition and classification of pressure pipelines

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According to clause 1.3 of the latest GB/T 20801.1-2020 regarding the definition of pressure pipelines, it states: 1.3 The industrial metal pressure pipelines referred to in this part (hereinafter referred to as “pressure pipelines”) include those belonging to process units, auxiliary units, and utility systems within the plant area. This section applies to pressure pipelines that meet the following conditions: a) The maximum operating pressure is greater than or equal to 0.1 MPa (gauge pressure); the medium is gas, liquefied gas, steam, or a liquid that is flammable, explosive, toxic, corrosive, with a maximum operating temperature greater than or equal to its standard boiling point; and the nominal diameter is greater than or equal to 50 mm. Except for pipes with a nominal diameter of less than 150 mm and a maximum operating pressure of less than 1.6 MPa (gauge pressure), as well as the pipes that form part of the equipment used for transporting non-toxic, non-flammable, and non-corrosive gases. b) Pressure pipelines other than those listed in 1.5. 1.5 The areas where this section does not apply are as follows: a) **Pipelines in equipment and nuclear facilities ； b) Pipelines for exploration and extraction equipment of oil, natural gas, geothermal energy, etc ； c) Pressure pipelines on mobile equipment such as railway locomotives, automobiles, ships, aerospace vehicles, etc ； d) GA class long-distance pipelines ； e) GB-class public pipelines ； f) GCD-type power pipelines ； g) Internal pipes of boilers, pressure vessels, and heating furnaces, as well as external connection ports of equipment ； h) Pipelines for transporting non-toxic, non-flammable, and non-corrosive fluids, with a design pressure of less than 0.1 MPa (gauge pressure) but not less than atmospheric pressure. Based on these two points, a normal-temperature water pipeline with a diameter of DN200 and a design pressure of 1.2 MPa should fall under the category of pressure pipelines described in 1.3b). Points 4.1 and 4.2 state: 4.1 The “pressure pipelines” listed in 1.3a) are classified into GC1 level and GC2 level according to their degree of hazard and safety requirements: a) Pressure pipelines that meet one of the following conditions shall be classified as GC1 level: 1) Pressure pipelines that transport media with an acute toxicity level of Category 1 as specified in the “Catalogue of Hazardous Chemicals (2015 edition)”, gas media with an acute toxicity level of Category 2, or liquid media with an acute toxicity level of Category 2 whose operating temperature is higher than their standard boiling point. 2) Pressure pipelines that transport flammable gases classified as Category A or B, or flammable liquids of Category A (including liquefied hydrocarbons) as specified in GB50160—2008 and GB50016—2014, and whose design pressure is 4.0 MPa or greater. 3) Pressure pipelines that transport fluids other than those mentioned in the first two items, with a design pressure of 10.0 MPa or more, or a design pressure of 4.0 MPa or more and a design temperature of 400 °C or higher. b) Pressure pipelines (including refrigeration pipelines) that meet the following conditions shall be classified as GC2 grade: those whose medium has a toxicity or flammability hazard level, and whose design pressure and design temperature are lower than those specified in 4.1a) (GC1 grade) pressure pipelines. 4.2 1.3b) Pressure pipelines listed therein that meet the following conditions shall be classified as GC3 grade: pressure pipelines that transport non-toxic, non-flammable, and non-corrosive liquid media, with a design pressure of less than or equal to 1.0 MPa and a design temperature higher than –20 °C but not higher than 185 °C. Note: GC3-class pipes are not suitable for pressure pipes listed in 1.3a). So, what grade should the aforementioned circulating water pipeline belong to? As stated in clause 4.1, water is a non-toxic and non-flammable liquid, and should not fall under GC1 or GC2. According to clause 4.2, if the design pressure is greater than 1.0 MPa and it does not fall under category GC3, then even if the design pressure is less than 1.0 MPa it can still be classified as GC3; but if the pressure is greater than 1.0 MPa, it cannot be classified as GC3 at all? I seek the master’s guidance