Questions regarding bolt calculations
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I’ve been learning about *bolts recently, and it’s useful to apply that knowledge in the field; however, the issues related to data are quite confusing. In general, bolts of grade 4.8 and 8.8 are used in field applications; these have a tensile strength of 400 N/mm2 (400 MPa) and 800 N/mm2 (800 MPa) respectively. Even when calculated based on yield strength, the values are 320 and 640. The stress levels in pipelines in the field are 1.6 MPa and 2.5 MPa. So, is it really necessary to use bolts of such high grades? It’s possible that high temperatures may reduce the tensile strength of the bolts, but it’s likely there won’t be any problems. So, what theory is used to select the bolts for pipelines? Thank you, I hope everyone can help me out with some advice.
The selection of bolts should be based on strength calculations and torque calculations to choose the appropriate bolts. Simply put, when selecting bolts for flanges, you can refer to the fastener section in HG20592-20635. For torque calculations, you may want to check this post: http://bbs.hcbbs.com/viewthread.php?tid=204743
Could someone please explain what formula is used for calculating strength? Why is there such a large margin? Thank you