Issues related to the calculation of expansion joints in heat exchangers according to national standards
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When calculating a heat exchanger for a certain operating condition, the metal wall temperature is 143 degrees for the shell and 0 degrees for the tubes. The question is: when the tube sheet and tubes are welded together, it’s not necessary to use expansion joints; however, when other methods such as expansion fitting or seal welding are used, it is indicated that expansion joints are required. What is the reason for this? With such a large temperature difference, expansion joints must be used in all cases when performing calculations according to ASME standards.
Whether to use expansion joints is certainly related to the temperature difference between the shell and the tube side, but it’s not necessary to use expansion joints just because there is a large temperature difference; otherwise, what’s the point of performing such precise calculations?