【Common Issues in Haichuan Pipeline Design】When is it necessary to install dual check valves?

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Under what circumstances is it necessary to install dual check valves? The main function of check valves is to prevent the backflow of fluid, ensuring that it can only flow in one direction and thus protecting the safety of pipeline systems and equipment. However, in many cases, it is necessary to install double check valves. 1. When the pressure difference at the outlet of a centrifugal pump is greater than 4.0 MPa: In accordance with Article 11.7 of the \"Design Code for Process Piping in Refining Units\" (SH/T 3122-2013), for centrifugal pumps whose outlet and inlet pressure difference exceeds 4.0 MPa, it is advisable to install double isolation valves as well as double check valves of different types on the pump’s outlet pipeline. 2. Outlet pipeline of centrifugal hydrogen compressor: Article 12.6 of the \"Code for Design of Process Piping in Refining Units\" (SH/T 3122-2013) stipulates that on the outlet pipeline of centrifugal hydrogen compressors with an operating pressure (absolute) of 4.0 MPa or higher, a double check valve or a check valve combined with a fire-safe emergency shut-off valve should be installed. 3. Backflow prevention devices for potable water systems: The \"Design Code for Building Water Supply and Drainage\" (GB50015-2019) stipulates that in potable water systems, at locations such as two or more inlet pipes connecting to different sections of the urban pipeline network, the inlet pipes of pressure-boosting equipment used for direct water extraction, the inlet pipes used to fill pressurized containers, and the starting points of fire-fighting water pipelines, backflow prevention devices must be installed to prevent backflow contamination. Protective backflow prevention devices typically consist of a dual-check valve structure.