Material selection issue
Thread Content
In the design of the tower, with the local average monthly minimum temperature being -23.5 degrees, the reaction tower is designed for normal pressure conditions, and its exterior shell does not have any insulation； The operating temperature of the liquid medium is 50 degrees. The skirt of the tower is made of Q345R; as for the shell of the tower, should it be made of Q235B or Q345R? ； Can Q235B material be used for the flanges of the tower, and material 20 be used for the nozzles?
According to the GB150-2024 pressure vessel standards, the minimum operating temperature for Q235B material is 20 degrees Celsius, while for Q345R material it is -20 degrees Celsius. Considering conservative estimates, based on the operating conditions you described (is it possible to ensure that the temperature remains at 50 degrees all the time?) ) are not very suitable ； As for whether atmospheric-pressure vessels need to be treated as pressure vessels, a comprehensive consideration is required.
Q235B definitely cannot be used in an environment at -20 degrees
You can specify the requirements in the drawings and communicate in writing with the user; first, let the medium flow in to heat up the equipment, and then increase the pressure once the desired temperature is reached. And a thermometer is installed on the wall of the vessel. But why go to the trouble? Safety should be the priority in design. Besides, Q345R isn’t much more expensive than Q235B; saving that little amount could cause problems if something goes wrong