Design issues for liquid ammonia storage tanks
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Seeking advice from fellow engineers: When designing a liquid ammonia storage tank with a pressure of 2.16 MPa and a temperature of 50°C, can Q345R be used for the tank shell heads, while S30408 is used for the nozzles and flanges? The counterargument that comes to mind is the issue of post-weld heat treatment. Due to stress corrosion, overall post-weld heat treatment is required, but austenitic stainless steels are generally not heat-treated. Rule 150 stipulates that the heat treatment temperature for low-alloy steel shall not exceed 400°C, while the heat treatment temperature for austenitic stainless steel should be higher than this value. Sea friends, please help come up with some ideas!
The description is incorrect; according to regulation 150, the temperature inside and outside the furnace must not exceed 400℃
Analysis and design of austenitic stainless steel nozzles requiring post-weld heat treatment
Reference shall be made to Clause 6.0.9, Sub-clause 6 of HG/T20585-2011 for implementation.
The temperature for heat treatment – 400°C is not sufficient. There’s no problem; equipment made of stainless steel composite panels often requires post-weld heat treatment.
400 should be the temperature inside and outside the furnace; I made a mistake.
The question is, why choose stainless steel? Wouldn’t carbon steel work just as well?
Stainless steel is in stock, but the lead time is too short; I want to object
Here’s how it works: first, the design temperature for this storage tank is 50°C, and the design pressure corresponds to the saturated vapor pressure at that temperature. Operation should take place under conditions of low temperature and low pressure; generally, for such equipment, Q345R material is chosen considering the low-temperature stress conditions. Theoretically, using stainless steel fittings seems fine, but based on engineering experience, welding of dissimilar steels should be avoided as much as possible, even at low temperatures or in the presence of stress corrosion; therefore, the use of stainless steel fittings is not recommended. As for heat treatment, it can actually be solved.
A friend said the same thing: try to avoid welding dissimilar steels when in contact with the medium.