My company builds switchboards. Most of the fastners used in the assembly are grade 8.8 bolts, nuts and belville washers. Calculations on each joint have been made to determine the clamping force and associated torque on each bolt/nut assembly. Bearing in mind the various forces that could be experienced within the board and inparticular the short circuit loads that could occur. None of the applied torque on the various size fastners exceed 65% of the fastner's proof load stress which is well below the yield point.
The assembly of the boards are done at two locations and a number of fasterners that have been torqued up at the first assembly location have to be removed to continue the assembly at the second location. The practice has been to throw away the fastners that were tightened originally. It seems a waste and having looked at the removed bolts for any signs of distortion I want to recommend the reuse of these bolts. The bolt supplier and manufacturer recommend that these bolts should be replaced. I was wondering if anybody has any views on this or other way of making sure that these high tensile bolt are OK for reuse.
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