Surface inspection issues of welded joints between heat exchange tubes and composite tube sheets
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The heat exchange tubes are made of stainless steel, while the tube sheet is a composite plate with a stainless steel coating. Does the welding joint between the heat exchange tubes and the tube sheet count as a welding joint of the coating on a composite plate? Article 7 of 3.2.10.2.2.4 on page 24 of the code requires that the clad weld joints of composite steel plates be subject to surface inspection; requirement similar exists in item f of 10.4 on page 336 of GB150. As I understand it, the clad weld joints of composite plates refer to those that are formed when composite plates are welded to each other – I’m not sure if this is correct
For the welding joint between the heat exchange tube and the tube sheet, the drawings should also require PT testing; therefore, your question has nothing to do with whether the tube sheet is made of a composite material.
The standards do not require surface inspection of all weld joints between the heat exchange tubes and the tube sheet; if the design drawings do not specify such an requirement, then it is probably not necessary to carry out such inspection