A common misconception about pressure vessels is that the scope of the ASME Code ends at the face of any nozzle flange, and therefore anything installed after that gasket face does not need to be designed or built per the code rules. While this is true for most flange faces, there are exceptions. Any pressure-retaining cover that is bolted to a flange and intended to stay with the vessel permanently is included in the code scope. Examples of this include manway covers, sight glasses, and removable dip pipes. All of those should be fabricated and tested in accordance with the code. Also, the code includes requirements for a pressure relief device, which may not be attached directly to the vessel. Call Ward with any questions about the ASME Code.