Clause 302.2.2 in ASME B31.3 states that "...piping component having same allowable stress as the straight pipe shall be rated using not more than 87.5% of nominal thickness of seamless pipe..." - I would like to know the exact interpretation of this. Does this mean the thickness of pipe fittings like elbow, tees, reducers should be more than the mating pipe thickness by 12.5%.
Also there is a mismatch of mill tolerance (M.T) between pipe and fittings when we use pipes welded from rolled plates (like ASTM A 671 , A672 or A 358) as in these cases the M.T for pipe is 0.01" while the corresponding fittings (say A 234 or A 403) have M.T of 12.5%. How is this problem overcome.
Also there is a mismatch of mill tolerance (M.T) between pipe and fittings when we use pipes welded from rolled plates (like ASTM A 671 , A672 or A 358) as in these cases the M.T for pipe is 0.01" while the corresponding fittings (say A 234 or A 403) have M.T of 12.5%. How is this problem overcome.