What are the requirements for steel plates when designing liquid ammonia storage tanks? Such as carbon equivalent, surface hardness value, etc.? Please answer!
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What are the requirements for steel plates when designing liquid ammonia storage tanks? Such as carbon equivalent, surface hardness value, etc.? Please answer!
Liquid ammonia easily causes stress corrosion in low-alloy steel. High-strength steel plates must be supplied at least under normal conditions. The hardness of materials and welds must be controlled. The equipment must undergo post-weld heat treatment as a whole. Material toughness reserves must be sufficient. The grains must be fine. The residual stress in welds must be controlled. In the final analysis, it is to prevent the initiation and expansion of cracks. See HG 20581 7.8.4, which specifies specific requirements for the selection of materials for liquid ammonia stress corrosion environments.
Q345R is used for liquid ammonia. It is in the normalized state. I have never seen any requirements for the material hardness. The main purpose is to prevent stress corrosion. For details, please see the six-page book.
There are no mandatory requirements for carbon equivalent and surface hardness in GB150.
Our unit uses Q245R (normalizing or normalizing + tempering), mainly considering stress corrosion and material hardness.； The ammonia refrigeration industry basically uses Q245R
My unit uses Q345R for everything, and liquid ammonia is not only used for refrigeration, it is used in many places in the chemical industry.
Well, different industries have different requirements. Another reason why Q245R is mainly used in the ammonia refrigeration industry is that using Q345R requires heat treatment.