Has anyone seen the strength calculation document?
Thread Content
I don’t quite understand. The Special Inspection Agency stated that the wall thickness-to-strength ratio calculated in our drawings for the imported equipment was too high, and requested that we revise the strength calculation documents. I took a look at the strength calculation sheet provided by the foreign party; there was a line that read, “Weights and dimensions are only for calculation, the definitive data are shown on the drawing.” Does this mean that the wall thickness calculated in the strength calculation sheet represents the minimum required wall thickness, and it is used solely for calculation purposes? The actual cylinder thickness matches the specifications on the drawings. Since the specific strength calculation shows a higher value, as long as the minimum thickness requirement is met, there is no problem. It’s not necessary for the wall thickness specified in the drawings to be the same as that calculated in the strength calculations, right? Can I explain it to the Special Inspection Agency this way?
The thickness in the drawings must be the same as that specified in the strength calculation sheet. If you use a thicker cylinder wall, you need to take into account the critical temperature of some materials, as the allowable stress decreases as the thickness increases.
It’s right if it’s large; it’s wrong if it’s smaller than the calculation sheet
The special inspection institute follows a 150-based approach, out of concern about stress skipping issues. The calculation sheet should ideally match the actual wall thickness.
Under special calculation conditions, the cylinder thickness is greater than that specified in the calculation sheet, and thus the cylinder thickness fails the verification. For example, for Q345R, the allowable stress at the same temperature differs between 18mm and 16mm. So it depends on the situation: if the thickness of the cylinder and the thickness specified in the calculation sheet are in the same range, then it’s okay ； If they are not in the same category, then the thickness of the book cover must be calculated to be the same as the thickness of the cylinder.
I’m really confused – there are still people who make such requests. The wall thickness indicated on the drawings represents the actual nominal thickness of the equipment; if the thickness and other dimensions shown on the drawings do not match those of the actual equipment, then there is indeed a problem. The dimension requirements specified on the drawings mean that the manufacturing unit shall design and produce according to these requirements. What’s the reason to ask for a revision of the calculation sheet?
Would the manufacturer be foolish enough to increase the thickness to the point where the allowable stress is reduced? The thicker the plate, the more expensive it is.
There is a change in the allowable stress of the Q345R 16mm steel plate. What the original poster is trying to say is that the thickness calculated according to the diagram is much greater than that in the strength-to-thickness calculation sheet. His calculations indicate that the estimation is based only on the minimum thickness. If the self-weight load of the equipment needs to be taken into account, it will affect the subsequent calculations, right?
A large wall thickness for the cylinder body should not be a problem, but there might be issues with span length for the head.
Take a close look to see if there is thickening due to corrosion margin, etc.; the calculated thicknesses used abroad may differ from those used domestically.
The calculated value represents the minimum wall thickness; the actual thickness is the calculated value plus a corrosion allowance, with an additional slight increase to ensure safety.