Precautions for containers holding extremely hazardous or highly dangerous toxic substances

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Material 1: When carbon steel and low-alloy steel plates with a thickness of ≥12 mm (excluding the plates of multi-layer pressure vessels) are used to manufacture the main pressure-bearing components of pressure vessels, and the medium contained has an extremely high or high degree of toxicity, ultrasonic testing shall be carried out on each plate. In accordance with NB/T 47013.3-2015, the testing technique level shall be Grade B, and the acceptance level shall be no lower than Grade II. (TSG21-2016 2.2.1.4.1 P8 ； (GB/T150.2-2011 Table 3) 2. It shall not be used for media with an extremely high or high level of toxicity: steel grades 10 and 20 as specified in GB/T8163, and Q345D (GB/T 150.2-2011 5.1.3 P53); as well as steel pipes of categories III and IV as specified in GB/T12771. (GB/T 150.2-2011 5.2.4, p.54) Type VI steel pipes as specified in GB/T 21832. (GB/T 150.2-2011 5.2.7P54) Q235B and Q235C steel plates as specified in GB/T3274-2007. (GB/T 150.2-2011 D.1P87) Design & Structure: 1. For pressure vessels in which the medium is explosive or possesses an extremely high or high level of toxicity, the joints between the nozzles (flanges) and the vessel shell, as well as the joints in jacketed pressure vessels, shall be designed with a fully penetrated structure. (TSG21-2016 3.2.2.2 P21) 2. For pressure vessels containing liquefied petroleum gas, media with an extremely high or high degree of toxicity, and highly permeable media with a moderate degree of hazard, their pipe flanges shall, in accordance with the provisions of the HG/T 20592 series of standards, use at least high-neck butt weld flanges, metal wound gaskets with reinforcing rings, and specialized high-strength bolts. Where such pipe flange sealing combinations cannot be used, the designer shall determine the flange connection design based on the properties of the medium, pressure, and temperature. (TSG21-2016 3.2.5 P22) 3. For containers holding explosive media or media with an extremely high, high, or moderate level of toxicity, a conduit should be installed at the outlet of the discharge device to guide the discharged media to a safe location where it can be properly disposed of; it must not be released directly into the atmosphere. (GB/T 150.1-2011 B.3.10P18) 4. The fragmentation safety device cannot be used alone in situations where the toxicity of the medium is extremely high, highly hazardous, or where flammable gases and liquefied petroleum gas are involved; in such cases it can be used in combination with a safety valve. (GB/T 150.1-2011 B.5.3P19) 5. The method for determining the design pressure of containers specified in Appendix C of GB/T150.1-2011, which relies on verification blasting tests, shall not be used for the design of containers that are extremely or highly hazardous. (GB/T 150.1-2011 C.1.5P27) 6. The empirical design method outlined in Appendix D of GB/T150.1-2011 shall not be used for the design of containers that hold extremely or highly hazardous substances. (GB/T 150.1-2011 D.1.3P30) 7. The lining composite structure in heat exchangers shall not be used in vessels with media of extremely high or high toxicity. (GB/T 151-2014 5.3.3.2P10) 8. Packed-bed heat exchangers are not suitable for applications involving volatile, flammable, explosive, toxic, or valuable media. (GB/T 151-2014 6.11.1.1P43) 9. For spherical tanks containing media with an extremely high or high degree of toxicity, the inlet and outlet openings shall be provided at the top. (GB12337-2014 5.6.5 P25) Manufacturing 1. For pressure vessels containing media with extremely or highly hazardous toxicity, it is necessary to prepare product welding specimens. (TSG21-2016 3.2.4.1 P22) For containers holding media with extremely or highly hazardous toxicity, and those with Class A longitudinal weld joints, product weld specimens shall be prepared for each individual container. GB/T 150.4-20119.1.1.1 P333) 2. Carbon steel and low-alloy steel vessels used to contain media with extremely or highly hazardous toxicity shall undergo post-weld heat treatment. GB/T 150..4-2011 8.2.2.3 P332) 3. For carbon steel or low-alloy steel containers that hold extremely or highly hazardous media, if any welding repairs are carried out after heat treatment, the repaired areas must be subjected to heat treatment again (GB/T150.4-2011 7.4.3 P329). 4. For pressure components made by cold forming of steel plates, when such components hold extremely or highly hazardous media and the degree of deformation exceeds the limits specified in Table 4 of GB/T150.4, appropriate heat treatment must be applied after forming to restore the material’s properties. (GB/T150.4-2011 8.1.1P330) Inspection 1: For containers holding media with extremely high or high toxicity, all Type A and Type B weld joints shall be subjected to radiographic or ultrasonic testing in accordance with the methods specified in the design documents. (TSG21-20163.2.10.2.2.2 P23 ； GB/T 150.4-2011 10.3.1P335) 2. After passing the pressure test, leakage tests shall be conducted on pressure vessels whose medium is extremely or highly toxic, or for which minor leaks are not permitted due to design considerations. (TSG21-2016 3.1.8 P19 ； GB/T 150.1 4.7.2 P15) Note: According to HG 20660-2000, benzene is considered to be of moderate hazard; however, when it comes to airtightness, benzene is treated as having high hazard. 3. Weld joints of pressure vessels containing media with an extremely high or high degree of toxicity hazard require magnetic particle or penetrant testing on their surfaces. (TSG21-2016 3.2.10.2.2.4 P24) In addition to the provisions mentioned above, HG/T 20580~20585-2020 contains additional regulations; some of these are applicable to the six-in-one system and can be used as a reference. 1. For forgings with extremely high or high toxicity to media, they shall meet the requirements of Grade III or Grade IV. (5.4.3 P84) 2. Elbow joints with a change direction angle greater than 17.5° shall not be used in conditions involving severe cycling, or in situations involving extremely hazardous media. (17.1.2 P259) 3. For containers holding explosive media and moderately hazardous media, the PN of the container flange shall not be lower than 0.6 MPa ； For containers whose filling medium is an extremely or highly hazardous medium, as well as a highly permeable medium, the PN of the container flange should not be lower than 1.0 MPa. (4.1.6 P472) 4. For containers holding explosive hazardous media and moderately toxic hazardous media, the nominal pressure class of the container nozzle flange shall be selected to be no less than 1.6 MPa ； For containers holding extremely toxic and highly hazardous media, as well as highly permeable media, the nominal pressure class of the container’s connection flanges should be at least 2 MPa. (4.2.3 P473) 5. For containers holding extremely toxic and highly hazardous media, highly permeable media, or moderately toxic media, the flanges on their connections should be socket weld flanges with a neck. (4.2.4 P473) 6. For vacuum vessels, vessels storing media with an extremely high or high level of toxicity, or liquefied petroleum gas, as well as pressure vessels storing highly permeable media, vessels with medium or high nominal pressures should preferably use manholes with a smaller nominal diameter. (5.5.4 P477) 7. For containers holding extremely or highly hazardous media with a shell wall thickness of 12 mm or more, reinforcement methods involving overall reinforcement or local overall reinforcement elements shall be employed. (6.2.2 P480) 8. Glass tube level gauges and glass float level gauges should not be used when the container holds explosive materials or materials with moderate, high, or extremely high toxicity. (7.1.3 P484) 9. When the container holds explosive materials, or materials that are extremely toxic, highly hazardous, or moderately hazardous due to their strong permeability, fully penetrative welds should be used. (15.9.2 P533) 10. When dealing with flammable or highly toxic media that pose extreme hazards, or when the design pressure is 1.6 MPa or higher, T-connectors should be constructed using seamless extruded tees or by welding thickened pipes together. (5.0.6 P724)