However let me be specific. we have a pipe of A335 P22 , (105 kg/cm/62 press & 500 deg^c temp.) but accidentaly was subjected to a temperature more than 600 deg. c for 4 hrs.
Visual inspection revealed a creep in the pipe. the diameter has increased by 20%. can we use this pipe back into service after hydro test?
ak1965;
Apparently your original post regarding the failure was inadvertently deleted. Anyway, here is what I would suggest if the OD has increased by more than 5% after careful cleaning and checked with calipers or a pipe tape; I would not recommend it be re-used.
In my past life when we monitored both hot reheat and main stem piping, we performed in-situ surface replication and dimensional checks for creep swell. Normally, 5-7% creep swell is a good indicator that you are reaching end of creep rupture life. Remember, this is seamless material just like boiler tubes, and when you measure OD changes of this magnitude, replacement should be scheduled. If necessary, you could possibly push this limit to 8% with comprehensive surface replicas, as I mentioned in your OP.
I too was surprised to see that the original mail has
become extinct suddenly. i searched but failed.
Any ways I appreciate your experience and we are also thinking on the same lines and arranging for in-situ replica followed by metallogrpahical examination of ruptured piece.
I shall get back to you with more inputs in due course of time.
For the P22 fatigue data, see Brinkman et al:"Elevated temperature fatigue behavior of 2 1/4Cr 1 Mo steel", J Press vess tech, trans ASME Nov 1975 pp252-257. This formed the basis of the fatigue curves in the ASME code case N-47.
ASME Section III, Division 1, Subsection NH, Class 1 Components in Elevated Temperature Service, Table I-14.6D shows the expected minimum stress-to-rupture values for 2.25Cr-1Mo material. The values are given in customary units as well as SI units.
