Material selection for liquid ammonia tanks
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Liquid ammonia as a material source? The dimensional tolerance requirements specify that the material must be at least normalized and tempered ； HG20581 specifies that the material can be normalized or normalized plus tempered. Technically, it should include the requirements from HG20581; so why were the words “normalizing or” omitted?
There’s nothing to do about it – pressure vessel regulations are laws, while HG is just a standard; if it’s a pressure vessel, one must follow the pressure vessel regulations
The Q345R steel plates used for the cylinder and head shall be supplied in the normalized state and meet the requirements of Clause 6.7.4, Paragraph 2, of HG20581-1998. The materials for its main pressure-bearing components are retested in accordance with Article 25 of the Regulations on Safety Supervision of Pressure Vessels. Standards adopted: GB150-1998 \"Steel Pressure Vessels\", \"Technical Requirements for the Manufacture of Steel Chemical Vessels\"; HG20584-1998 \"Regulations for the Safety Inspection of Pressure Vessels\" (1999). Cylinder diameter: Φ3400, wall thickness: δ=28, material: Q345R; Head material: Q345R. Standard number: JB/T4746-2002
Classmates upstairs, the minimum requirements per the tolerance specifications are normalizing plus tempering; see page 128, line 4 of the tolerance specifications: “C. The material must be in a state of normalizing + tempering, annealing, or quenching and tempering.” I really don’t know which one to choose; the prices of the two different types of steel plates differ significantly.
The tolerance specifications represent the minimum requirements and are limited to the main text of the specifications as well as the attachments. The places you mentioned are only for introduction and explanation, and it was also stated that they are excerpts from HG20581, for reference only.
The material for the liquid ammonia tank is 16MnR, while the pipes are made of 20# carbon steel