Why does GB20801.1-2020 exclude plastic pipes from the category of pressure pipes?
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1.3 The industrial metal pressure pipelines referred to in this section (hereinafter referred to as “pressure pipelines”) include those belonging to process units, auxiliary units, and utility systems within the site boundary. This section applies to pressure pipelines that meet the following conditions: a) the maximum operating pressure is 0.1 MPa (gauge pressure) or higher, the medium is a gas, liquefied gas, steam, or a liquid that is flammable, explosive, toxic, corrosive, with a maximum operating temperature equal to or higher than its standard boiling point, and the nominal diameter is 50 mm or larger. 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 pipeline components 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. 1.4 This section does not cover the following areas: a) specific requirements for the modification, inspection, testing, maintenance, and repair of pressure pipelines in service ； b) Pipes with a nominal pressure of PN420 or higher ； c) Non-metallic pipes or their lining layers.
According to the provisions of GB20801.1-2020 Industrial Metal Pressure Piping – Part 1: General Rules for Pipeline Design, plastic pipes are excluded from the category of pressure pipes, as this standard is primarily applicable to industrial metal pressure pipes. Due to their properties and materials, plastic pipes differ significantly from metal pipes, which gives rise to certain unique issues and requirements in terms of design, installation, operation, and maintenance. Therefore, to ensure the safety and reliability of industrial metal pressure pipelines, plastic pipes are excluded from the scope of pressure pipelines under this standard. Plastic pipes may need to be designed and used in accordance with the requirements of other relevant standards or specifications. .