【2025 Specification Requirements】The regulatory basis for installing dual valves in chemical plants

This post was last edited by The one on 2025-12-29 09:47. According to SH 3012-2011 \"Code for Design of Layout of Metal Piping in Petrochemical Industries\", 8.1.7: For pipelines carrying extremely hazardous media, double valves should be installed for discharge or emptying, and the flow should be directed into a closed recovery system. 8.1.8 Except for extremely hazardous media, the exhaust outlets for toxic gases shall meet environmental protection requirements, and toxic liquids shall not be discharged into sewers. 8.1.9 For pipelines carrying highly hazardous media, dual valves should be installed for venting or draining; when a single valve is used, a blind flange and a flange cover shall be added. 8.1.10 Double valves shall be provided for the venting or draining of high-pressure pipelines; when a single valve is used, a blind flange and a flange cover shall be installed. 8.1.11 For the drain at the lowest point of combustible gas pipelines that are operated continuously, a double valve should be installed, and the liquid discharged therefrom should be sent to a sealed system; for the drain of combustible gas pipelines that is used only during startup and shutdown, a single valve may be sufficient, along with a plug, pipe cap, or flange cover. When a shut-off valve is installed for draining on pipelines carrying flammable liquids and vapors, a plug, pipe cap, or flange cover should be placed at the end of the pipeline. 9.4.1 When semi-fixed nitrogen purging is required in the device, a nitrogen connection should be provided at the hose station, along with a double valve.

SH/T 3007-2014 \"Code for Design of Tank Areas in Petrochemical Storage and Transportation Systems\" 5.3.7 A main isolation valve should be installed near the tank base at the inlet and outlet pipes of the storage tank, and an operating valve should also be installed on each of these inlet and outlet pipes. The drain pipe of the storage tank should be equipped with a double valve.  6.4.4 Anti-freezing measures shall be taken for the bottom pipeline of liquefied hydrocarbon storage tanks in cold regions. A double valve should be installed on the dehydration pipeline of the liquefied hydrocarbon tank.

HG/T 20570.18-1995 \"Technical Specifications for the Design of Process System Engineering\" 2.0.3.1 For storage tanks holding liquefied petroleum gas, other flammable, toxic, valuable liquids, highly corrosive substances such as concentrated sulfuric acid and caustic soda, as well as substances with special requirements (such as those with unpleasant odors that cause severe environmental pollution), two valves in series should be installed on the pipes leading from the bottom of the tank to other equipment. Regardless of whether there are valves near those other devices, these two valves are necessary; one of them should be located right next to the tank’s connection port. When the tank has a large capacity or is located at a significant distance, it is advisable that this valve be a remotely controlled one. To reduce the number of valves, where operation permits, several pipes are combined and connected to a single outlet. The drain valve of the container containing the aforementioned medium should also be a dual-valve design. The sampling valve and drain valve on the aforementioned medium pipeline should have dual valves installed or not, depending on the frequency of operation and other conditions. 2.0.3.2 For equipment that needs to be shut down during operation of the unit for maintenance, cleaning, or regeneration, a double valve arrangement should be used, with an inspection valve installed between the two valves. When the device is disconnected from the system, both valves close and the check valve opens. 2.0.3.3 Utility material pipelines should, as much as possible, not be fixedly connected to process material pipelines; instead, they should be connected using quick connectors via hose stations. When direct connection is required for operation, a double-valve connection should be used, with a check valve installed in between; this check valve opens when feeding is stopped, or it can be sealed with a lead seal. Add a check valve in situations where pressure may fluctuate. 2.0.3.5 Double valves shall be installed upstream of the connection points between hydrocarbons, toxic and hazardous chemicals, and other process materials, as well as on the vent and drain pipes.

SH 3136-2003 \"Code for Design of Spherical Storage Tanks for Liquefied Hydrocarbons in Petrochemical Industries\" 6.3 Two isolation valves shall be installed on the water cut-off valve of spherical liquefied petroleum gas storage tanks, and a direct water cut-off method is preferred.

SH 3009-2013 \"Code for Design of Flammable Gas Emission Systems in Petrochemical Industries\" 5.5.5: Subject to the requirement of safe emission of flammable gases, switching operations can be carried out between multiple flares； The switching connecting pipe between torches should be installed in front of the water seal tank, and it should be equipped with double isolation valves and blind flanges.

GB/T 20801.3-2020 \"Code for pressure pipelines – Industrial pipelines – Part 3: Design and calculation\": B.5.1.6 For pipelines carrying substances of acute toxicity categories 1 and 2, relief or drainage devices shall be installed, along with double valves, and the discharged fluids shall be directed into a closed recovery system. B.5.1.8 For pipelines carrying acutely toxic substances of Category 1 and Category 2, dual valves should be provided for venting or draining; when a single valve is used, a blind flange or flange cover should be installed. B.5.1.9 Double valves should be provided for the venting or draining of high-pressure pipelines; when a single valve is used, a blind flange or flange cover should be installed. B.5.1.10 For the drainage at the lowest point of combustible gas pipelines in continuous operation, a double valve should be installed. The liquid discharged should be sent to a closed system. Combustible gas pipelines should be drained only during startup and shutdown; in such cases, a single valve suffices, along with a plug, pipe cap, or flange cover.

This post was last edited by The one on 2025-12-29 09:47. “Code for Pressure Piping – Industrial Piping, Part 6: Safety Protections” GB/T 20801.6-2020 7.4.11 When utility pipes such as steam, air, and nitrogen are connected to GC1-grade or GC2-grade pipes, the following requirements shall be met: a) Check valves shall be installed on the utility pipes that are in continuous use, along with isolation valves at their bases； b) Two isolation valves shall be installed on the utility pipes used intermittently, with a check valve placed between the two valves.

GB 50016-20185 \"Code for Fire Protection Design of Buildings\".4.15 For boilers and diesel generators installed within buildings, their fuel supply pipelines shall comply with the following requirements: 1. Automatic and manual shut-off valves shall be installed on the pipelines both before they enter the building and inside the equipment room

The last edit to this post was made by The one on 2025-12-29 09:48. According to SH/T 3024-2017 \"Code for Environmental Protection Design in Petrochemical Industries\", 10.2.4 requires that pipelines carrying highly hazardous materials should be equipped with dual valves and connected to a closed recovery system； The discharge of other toxic media can use a single valve with a flange cover. For the discharge of high-pressure fluid medium pipelines, a dual-valve system or a single valve with a flange cover should be used; for the discharge of other fluid medium pipelines, a single valve with a flange cover should be employed. 10.2.10 Centrifugal pumps and rotary pumps used for transporting process materials should preferably be equipped with mechanical seals. For centrifugal pumps and rotary pumps used to transport toxic media, seal-less pumps should be chosen, and the sealing standard should be elevated. Centrifugal pumps or rotary pumps used to transport toxic and hazardous media should be equipped with bottom drain valves, which should be designed as a dual-valve system.

HG/T 20512-2014 \"Code for Design of Instrument Piping and Wiring\" 6.0.7 When the pressure class is greater than or equal to PN160 and the root valve is a double-valve type, the instrument drain valve should be designed as a double valve or as a single valve with a pipe cap.