Optimize the design of the sealed sampler in the device to comprehensively improve leak prevention at the source

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Optimize the device design to comprehensively improve leak prevention at the source (V) Optimize design for preventing and controlling leaks. During the design phase, it is necessary to fully identify and assess leakage risks, and take measures at the source to control the hazards caused by leaks. Advanced process routes should be selected as much as possible to reduce potential leakage points such as equipment seals and pipeline connections, and to lower process conditions such as operating pressure and temperature. When designing discharge valves such as those at the outlets and sampling points of equipment and pipelines, measures such as the use of blind flanges, plug valves, pipe caps, and double valves should be employed to reduce the risk of leaks. For processes involving highly toxic or extremely toxic substances, a sealed sampling system should be used, and sealed designs must be adopted for the safe pressure relief of toxic and flammable gases. \"Guidelines for the Safe Production Management of Phosgene and Phosgenated Products\" (Safety Supervision Administration Office, Document No. Guan San [2014] 104), 6.3.5.2: Routine sampling refers to the sampling points and sampling frequency specified in the sampling plan for the production workshop. For those liquid samples, such as phosgene solutions, sampling should be done in a sealed manner, with the sealed sampling box connected to the phosgene destruction ventilation system. It is necessary to ensure that the ventilation system is working properly when sampling. To avoid purging before sampling, the sampling valve should be able to close completely. It is preferable for the sampler to be able to control the amount of sample taken, in order to prevent a large quantity of product from entering the collection tank. There should be a written procedure that has been approved for safety purposes to guide the sampling process. According to Clause 3.1.14 of the \"Design Code for Purified Terephthalic Acid Plants\" (GB 51205-2016), sampling of flammable liquids such as p-xylene, acetic acid, methyl acetate, and azeotropes should be carried out using a closed sampling method. According to the \"Coking Safety Standards\" (GB 12710-2024), 7.1.18: For media that pose extreme or high hazards, as well as Class A flammable gases, a closed-loop sampling system should be employed. Article 8.6.3 of the \"Standards for the Control of Unorganized Emissions of Volatile Organic Compounds\" (GB 37822-2019) stipulates that the sampling and connection systems for gaseous VOCs and volatile organic liquids shall comply with one of the following requirements: a) Use an online sampling and analysis system ； b) Adopt a closed-loop sampling connection system ； c) The sampling connection system is connected to the VOCs waste gas collection and treatment system ； d) Use a sealed container for storage, and record the amount of sample recovered. According to 5.12.1 of the \"Safety Specifications for the Production of Phosgene and Phosgenated Products\" (GB 19041-2024), for gas media with acute toxicity inhalation categories 1 or 2 in phosgene and phosgenation plants, for liquid media with acute toxicity inhalation categories 1 or 2 and a working temperature higher than their standard boiling points, and for gas/liquid media with acute toxicity through skin absorption in categories 1 or 2, a closed-loop sampler should be used for on-site sampling and analysis. The classification of acute toxicity categories is carried out in accordance with the provisions of GB 30000.18. According to the \"Safety Management Standards for Fine Chemical Enterprises\" (AQ 3062-2025), 9.2.3 states that for devices and storage tanks involving flammable gases, liquefied hydrocarbons, as well as substances with acute toxicity classified as Category 1 or Category 2, a closed sampling system must be used for sampling. The condensate (residual liquid) from these storage tanks should be discharged into a dedicated collection system in a closed manner. According to the \"Technical Specifications for Chlorine Safety in Chemical Enterprises\" (GB 11984-2024), 5.1.2 states that chlorine should be sampled in a sealed manner; analysis should be carried out in a fume hood, with a supervisor present. \"Technical Specifications for Process Reengineering of Fluorination Reactions Using Hypergravity\" (GB/T 44900-2024) 6.3.7 When sampling high-risk substances such as hydrogen fluoride or hydrofluoric acid is involved, a sealed sampling device shall be used. According to the \"Specifications for Safe Production Management of Cyanides\" (GB 45189-2025), section 5.13 states that the transportation temperature of hydrocyanic acid should not exceed 20 ℃; insulation measures should be applied to the pipelines, and a circulating extraction method should be used for these pipelines. A closed-loop sampling system should be installed for hydrogen cyanide sampling. \"Code for Design of Tank Areas in Petrochemical Storage and Transportation Systems\" (SH/T 3007-2014) 5.1.12 For storage tanks holding liquids with toxicity grades I and II, sealed samplers shall be used. \"Code for Process Design of Petrochemical Units\" (SH/T 3121-2022) 9.1.1 The selection of closed/open sampling systems shall comply with the following provisions: a) The design of the sampling system shall ensure the safety of the sampling process, and protective measures shall be provided for media harmful to human health. b) Pollution of the surrounding environment should be avoided during sampling. c) A sealed sampling system should be used for the following media: 1) Media whose toxicity level is classified as moderate, high, or extremely high according to GBZ/T 230 ； 2) According to GB50160 and GB50016, the fire hazard is classified as Class A flammable gases, or Class A, A-B, and B flammable liquids. d) Materials containing malodorous substances should preferably use a sealed sampling system. e) When an open sampling system is used, Class B media should be cooled below their flash point. \"Code for Design of Layout of Metal Piping in Petrochemical Industries\" (SH 3012-2011) 7.2 Layout of Sampling Pipes 7.2.1 The layout of sampling ports on gas pipelines shall comply with the following provisions: a) Sampling ports on horizontal pipelines shall be located at the top of the pipeline ； b) On a vertical pipe, when the medium flows from bottom to top, the sampling port should be located on the side of the pipe at an angle of 45° upward; when the medium flows from top to bottom, the sampling port should be located on the side of the pipe ； C) The sampling port on a gas pipeline containing a solid medium should be located on the vertical part of the pipeline, with the sampling tube extending into the center of the pipeline. 7.2.2 The arrangement of sampling ports on liquid pipelines shall comply with the following provisions: a) Sampling ports on horizontal pipelines for pressure transmission shall be located at the top or side of the pipeline ； The sampling port of a liquid pipeline containing a solid medium should be located on the side of the pipeline ； On horizontally flowing pipes, sampling ports should be located at the bottom of the pipe; b) on vertically flowing pipes, sampling ports should be placed on the side of the pipe where the medium flows from bottom to top. When the medium flows from top to bottom, sampling points should not be installed, as this ensures that the liquid fills the sampling tube completely. 7.2.3 Closed-loop sampling should be employed for the following media: a) extremely hazardous and highly hazardous media ； b) Class A flammable gases ； c) Liquefied hydrocarbons. 7.2.4 Sampling ports shall not be located on vibrating equipment or pipelines; otherwise, vibration reduction measures shall be taken. 7.2.5 Sampling pipes for combustible gases, liquefied hydrocarbons, and combustible liquids shall not be led into the laboratory. \"Code for the Design of Process Piping in Refining Units\" (SH/T 3122-2013) 16.8 For sampling toxic media, closed-loop systems as well as purging and displacement measures shall be employed. According to the \"Design Code for Occupational Safety and Health in Petrochemical Enterprises\" (SH/T 3047-2021), 8.2.1.2: For materials that pose extreme or high levels of hazard, sealed sampling devices should be used, and such devices should be installed in locations that facilitate their use. Clause 18.2.4.7 of the \"Specifications for the Design of Pipeline Layout in Chemical Processing Plants\" (HG/T 20549.5-1998) stipulates that for media for which air isolation is required during sampling, sampling pipes shall be installed in accordance with process requirements, such as by using sealed samplers or sampling cylinders filled with nitrogen. In summary, the media that require sealed sampling are: (1) media with highly toxic or severe toxicity ； Determining extremely hazardous and highly hazardous media according to GBZ/T 230 ； According to GB30000.18, the acute toxicity is classified as Category 1 or Category 2 substances ； (2) Flammable gases (Classes A and B), liquefied hydrocarbons ； (3) Class A and Class B liquids. It should be noted that Category C liquids do not require sealed sampling.