I have a very large fabricated pipe spool (some 40Tonnes) which as it cannot be broken down further requires to be lifted whole and becuse of it's weight we cannot safely use soft slings. The intention is to weld lifting lugs onto the piping, where possible via re-inforced trunnion type attachments [to try and introduce the loads into the 'pressure' shell gradually].
My question is - can I use the specified yield strength of the material [A671 CC65; Ys=35ksi]as a basis for design for the lift, or am I, since the spool has been designed under B31.3 limited to the basic allowable stress [21.7ksi] or even the 1.33 x S allowed for occasional loads.
To be frank I would only intend to use 0.6 x Ys = 21KSi, and even then with a minimum 5:1 SF, but this has had me wondering, if the B31 code would cover this potentially high stress/ low cycle operation, bearing in mind the future use this piping will see.