Hello forum participants,

I understand the reasoning behind the tabulated allowable stress values in the B31.1 and 31.3 Codes; the lesser of (a) one quarter of the ultimate (b) five eights of yield (c) 1% strain in 100,000 hours (or .1% in 10,000 hours or .01% in 1,000 hours) (d) the average of three samples that rupture in 100,000 hours etc … My question is “what is the historic basis for the 1% strain and what is the historic basis for the 100,000 hours”?

This was posted by me when I got my hands on a computer on Christmas eve while visiting my daughter and her husband. I figured that this post would solicit some decent replies !! I can understand the 1% creep strain; if the piping distorted 1% it could in many instances compoimise the piping system's functionality. But again, what is the historic significance of the 100,000 hours ??