Questions regarding the calculation of SP lugs in HG/T 21574-2018
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A few days ago I downloaded HG/T 21574-2018 from a forum; thank you. I tried to carry out calculations for SP lugs. The new standard includes checks for compressive stress, as well as requirements regarding the dimensional fit between the pins and the lug holes. I have a few questions now and I hope an expert can help answer them. ①In the calculations for the side wall plate lugs, why isn’t the weld between the gusset plate and the cylinder checked? This was taken into account in the old standards, and the meanings of the symbols G, LSP, and HSP are explicitly stated at the beginning of section A.2; yet these symbols are not used in the subsequent calculations. ② In the denominator of the formula in appendix A.2.6, there is a symbol b – its meaning is unknown, and its origin could not be found
This post was last edited by zjq1962 on 2018-12-16 at 15:47. Based on the formula derivation, the value of b should equal Lsp – G. It cannot be proven that the shear area of the weld between the gusset plate and the cylinder is greater than that of the weld between the lug plate and the gusset plate; therefore, the shear stress check for the weld connecting the gusset plate to the cylinder is also necessary. The values of Hsp and Lsp are only used when calculating the shear stress of the gusset plate welds.
Thank you. In actual calculations, if the value of b is determined using Lsp-G, I’m not sure whether it will be accepted by the reviewers. Alas, with such a small issue above, those working on the design don’t know where to start.
Yes, the lack of rigor in setting standards makes things difficult for designers.
Must the SP-type lifting lugs be calculated, or can the load be selected directly? Is the calculation done by hand? Except for the SP type, any other that meets the requirements can be chosen directly, right?
Since the minimum thickness standards for the head and cylinder are calculated according to WRC107, and the SP lugs do not fall within this calculation model, they are not taken into account in our design. We only use stress analysis for calculations when the equipment is heavy.
This post was last edited by Mengmeng199081 on 2019-5-23 09:28. In formula A.2.6-2, the value of 8r in the denominator refers to the four r corners under the lug plate; each r corner has two sides, so together they amount to 8r, right? ? ? ? This calculation formula is really annoying. It’s not rigorous where it should be, and it overthinks things where rigor isn’t needed. Only a Virgo can be the editor of standards. . . . . . . . I don’t have any OCD.
According to Appendix A of HG/T21574-2018, A.1.4 Check on the strength of the lifting lug head: tensile stress and shear stress are equal. Is that not right?
This post was last edited by zhangjuhua on 2020-5-19 09:30. If b=Lsp-G, then is 2L1 redundant? Also, in A.1.3.5, the value of the compressive stress seems to be quite high. What does dr mean in A.1.3.5?
This post was last edited by meiszp on 2021-5-28 09:43. I just read this standard today and would like to share my understanding. b, 2L1 is used to calculate all welds in a week. dr is the pin diameter, as specified in 2.2.1.
How should we understand the formula for calculating compressive stress?