The design pressure is 2.0 MPa, and the fluid in the shell side is liquid ammonia. Is heat treatment required?

It is specified in nb47012 that the storage container needs to be modified

Heat treatment of pressure vessels is a rather complex process, and the decision as to whether it is necessary depends on various factors. After reviewing the NB/T47012 standard, it can be said that this standard is a set of guidelines designed to facilitate the design of refrigeration systems; it seems relatively simple, and its scope of application is likely limited. For your device, aside from 47012, several factors need to be considered. First is the concentration of the medium, liquid ammonia; if it exceeds 99.8% and the operating temperature is above -5 degrees Celsius, it constitutes a stress-corrosion environment, and heat treatment is required. If the medium does not meet the requirements, it is also necessary to check whether the design temperature is low enough and whether it satisfies the requirements for low-temperature pressure vessels; if so, heat treatment is still required. There is also only a design specification with no dimensions specified; the material used is not clear either, and when the thickness of the material reaches a certain level, heat treatment is required. I’m not familiar with the NB/T47012 standard you mentioned. From a brief look, it seems to be applicable only to simple refrigeration units as complete sets; whether it falls within the scope of this standard needs to be determined by oneself. Even if it does meet the requirements of this standard, it still needs to comply with the relevant standards for pressure vessels as well. Therefore, it’s better to disregard this standard when making judgments.

800 fixed tube sheet heat exchanger, material: Q345R

Referring to the third floor, post-weld heat treatment is recommended.

Stress-relief heat treatment is required; I wonder what material the heat exchange tubes are made of?

Post-weld heat treatment is required for the liquid ammonia storage tanks made of Q345R.

The material also matters. Under normal circumstances, low-carbon steel and low-alloy steel require post-weld heat treatment in an ambient ammonia stress corrosion environment.