Butt joint of elliptical head and cylinder

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This post was last edited by niuchangsheng on 2016-3-8 at 22:28. I have just completed the design of a gas storage tank, with a design pressure of 4.4 MPa, an inner diameter of 1200 mm. The head is made of Q345R steel with a thickness of 18 mm, while the cylinder body is made of Q345R steel with a thickness of 16 mm. For the butt welds, I used an internal alignment; however, the review engineer suggested using external alignment, stating that it makes things easier in the workshop. For boilers, we often use external alignment for butt welds, but the boiler drawings do not specify a minimum formation thickness. In the case of containers, I think it’s necessary to be more precise, especially since the reference point is clearly defined as the inner diameter, and the minimum formation thickness is specified for the head as well. Since the inner diameter remains constant, if we switch to external alignment, would my cylinder body also require an additional dimension corresponding to the minimum formation thickness? Also, the head isn’t thinned in all areas; the end faces might even become thicker (I haven’t seen it in person, it was what the review engineer said). I can’t specify the dimensions of this cylinder from the drawings. Simply put, the measurements are determined on-site during manufacturing, and I’m too embarrassed to say anything about it, but I still insist that my drawings remain unchanged. I’d also like to hear everyone’s opinions here. Have you all encountered this situation as well? How did you handle it? Thank you all for sharing your insights! Additional note: The company has available Q345R steel plates in three thicknesses – 16, 18, and 20 millimeters. However, none of these thicknesses is sufficient to construct the entire container. After calculations, it was determined that plates with a thickness of 16 millimeters can be used for the cylinder section, as their strength meets the requirements. In theory, 16-millimeter thick plates could also be used for the end caps, but considering the minimum required thickness for proper forming, plates with a thickness of 18 millimeters must be used. I’m currently going through all these diagrams, and no one has anything more to say about this issue. By using the one-month break during the New Year to work on these diagrams slowly, my efforts weren’t in vain.