Appendix A to HG/T 21574-2008 \"Technical Requirements for Lugs and Related Engineering in Chemical Equipment\"
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Hello everyone. On page 75 of Appendix A of HG/T 21574-2008 \"Technical Requirements for Lugs and Related Engineering in Chemical Equipment\", there is a phrase that mentions \"the side length of the square attachment when a gasket is used\" or \"the side length of the square attachment when no gasket is used\". What does this mean? Does anyone know what this phrase is intended to convey? Those who know please speak up; please avoid posting irrelevant comments. Thank you
The lifting lugs must be subject to local stress calculations in accordance with WRC107; the WRC107 criteria applicable to heads are only valid for square attachments, not for rectangular ones. However, whether there is a shimming plate or not, the contact surface between the lifting lugs and the head is rectangular. HG/T 21574 adopts the method of using the square root of the rectangle’s length X width as the side length of the equivalent square, followed by the calculation of local stress. Of course, it is unclear what the equivalence of this conversion method is like, but since standards are recommended, they must have undergone certain testing. These are just my personal opinions; I welcome everyone’s feedback
I personally think your explanation is very reasonable; thank you for your reply