Regarding the selection of bolts in HG/T20614-2009
Thread Content
HG/T20614-2009 specifies that for grades of 1.6 MPa or less, with operating temperatures ranging from -20 to 300°C, hex head bolts of grade 8.8 according to GB/T5782 can be used. However, it is curious to know what considerations lead to the prohibition of using bolts of grade 8.8 per GB/T5783 in such cases
Bolts of grade 8.8 according to GB/T5783 are not permitted to be used in HG/T20614-2009, mainly due to considerations regarding the strength and ductility of such bolts. Although both GB/T5782 and GB/T5783 belong to the 8.8 grade, their design standards and mechanical properties differ. Bolts in accordance with GB/T5782 are more suitable for low- and high-temperature environments, and thus fit the usage conditions specified in that standard; whereas bolts in accordance with GB/T5783 may perform less well under certain specific conditions, posing potential safety risks. Therefore, it is specified to use bolts in accordance with GB/T5782 to ensure the safety and reliability of the system. .
GB/T 5783 refers to hex head bolts with full threads, and they should be of a higher grade than the hex head bolts specified in GB/T 5782. It seems that GB/T 5782 can be used, and GB/T 5783 should also work. Doesn’t HG/T20614-2009 also specify that for flammable and toxic media, specialized chemical full-threaded bolts should be used?
Fully threaded ones should be better, right? They’re all grade 8.8, so there shouldn’t be any issues with strength