For atmospheric-pressure vessels containing highly hazardous toxic substances, which type of flange should be used: type A, type B, or long-neck butt-weld flanges?
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Dear sea friends: There is a gas collection tank here, containing highly hazardous substances. The nominal diameter of the container is DN800, and the height is 1.2m ； The operating pressure is at atmospheric pressure, and the operating temperature is 60°C. I have the following questions and would appreciate your guidance: (1) Since the working pressure is at atmospheric level and the container holds highly hazardous materials, it cannot be designed and manufactured in accordance with NB47003.1. The design, manufacturing, inspection, and acceptance of this container are carried out in accordance with GBT150-2011; the design pressure is set at 0.01 MPa, and the nominal thickness, as calculated using SW6, is 8 ； Is this design reasonable? ? ? (2) Due to practical requirements, the upper head and the cylinder need to be designed as a detachable structure; therefore, should pipe flanges or pressure vessel flanges be used? (3) If a pressure vessel flange is chosen, what type should be selected? Type A, Type B, long-neck butt welding? This container operates at atmospheric pressure! ! !
For gas collection tanks at atmospheric pressure, there is no need to worry about strength; the main concern is sealing. It depends on what type of gas is used and how permeable it is. It is better not to use pipe flanges for the equipment’s flanges – pressure vessel flanges should be used instead. As for whether they should be of type A, type B, or weld-type, that’s hard to say. In addition to the equipment flanges, attention also needs to be paid to pipe flanges and fasteners
It is recommended to use pressure vessel flanges for butt welding.
For design, manufacturing, and inspection, GB/T150 shall still be followed. The design pressure is set at 0.1 MPa; flanges are selected according to those used for containers. There is no clear specification regarding whether a necked flange is required, and it is up to the designers to decide.
Still, design, manufacturing, and inspection shall be carried out in accordance with standards related to 150; the design pressure should be set at 0.1. Pressure vessel flanges should be used, while for pipe connections, necked butt-welded flanges are appropriate, as specified in 7.2.4 of HG/T20583