Bigpond If your existing outlet pigtail Incoloy Alloy 800 H - 1.5" NB x 6.35 mm thick - is readily weldable there is no need to do any further treatment after welding repairs. If the outlet pigtail tube had seen appreciable creep - which would be visible by surface creep fissures and also the outlet pigtail tube would have seen a higher OD at the creep affected areas (due to higher operating temp in excess of design temperature) and as a result of over firing the reformer tubes the out let pigtail would also be subjected to higher than design temperature. If the creep fissures are visible at the pigtail tube surface (inspite of just 7 year usage but operated at higher than design temperature conditions) then you may have to do prior solution annealing to bring back the creep damaged and permanent metallurgical transformed outlet pigtail Incoloy Alloy 800 H to the original solution annealed conditions. Normally a 7 year used outlet pigtail - Incoloy Alloy 800 H - if operated within design conditions of exit temperature of reformer furnace, the tube should be readily weldable and can be easily repair welded without the need of solution annealing prior to repair. For any repair welding to be successful. solution annealing has to be done prior to weld repair and not after weld repair. Please note that a prior solution annealing only has to be done. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India Jan 09, 2009 E-mail: nishi@vsnl.com >We are replacing primary reformer tubes and its outlet pipe >which is made in inconnel 800 HT is welded to existing 800 >HT pigtail. I would like to know is it required to solution >annealed the weld after repair and why. The existing inconel >800 HT pigtail is in service for more than 7 years and >normally subjected to 700 to 750 Deg C. >The pigtails are 1.5" X 6.35 mm thk pipes. > >regards

Bigpond Usually with surface fissures - an indirect indication that the pigtail would have seen much higher than design temp conditions - repair by solution annealing may not give good results. Simple reason: a surface fissured pig tail tube would have much higher OD diametral expansion and thickness loss. upto 5-8% creep - tubes can be replaced with planned one year to two years. During shut down monitor tube OD and also surface fissures and do in-situ metallography to assess further deterioration. 5-10 % creep - watch and monitor till next shut down of plant or reformer furnace for replacement by keeping ready new out let pigtail tube. Same as for 5% creep effect. 10-12% creep - again watch and monitor and replace at the earliest -say within 700-1000 hrs. Replace at the first available shut down of the plant or reformer furnace. > 12% creep - some plants had run with close to 14% or 18% without failure and explosion or big fire hazard. You have to take a calculated risk if that be your creep% for running without new replacement. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India Jan 12, 2009 E-mail: nishi@vsnl.com >>Bigpond >> >>If your existing outlet pigtail Incoloy Alloy 800 H - 1.5" >>NB x 6.35 mm thick - is readily weldable there is no need to >>do any further treatment after welding repairs. >> >>If the outlet pigtail tube had seen appreciable creep - >>which would be visible by surface creep fissures and also >>the outlet pigtail tube would have seen a higher OD at the >>creep affected areas (due to higher operating temp in excess >>of design temperature) and as a result of over firing the >>reformer tubes the out let pigtail would also be subjected >>to higher than design temperature. >> >>If the creep fissures are visible at the pigtail tube >>surface (inspite of just 7 year usage but operated at higher >>than design temperature conditions) then you may have to do >>prior solution annealing to bring back the creep damaged and >>permanent metallurgical transformed outlet pigtail Incoloy >>Alloy 800 H to the original solution annealed conditions. >> >>Normally a 7 year used outlet pigtail - Incoloy Alloy 800 H >>- if operated within design conditions of exit temperature >>of reformer furnace, the tube should be readily weldable and >>can be easily repair welded without the need of solution >>annealing prior to repair. >> >>For any repair welding to be successful. solution annealing >>has to be done prior to weld repair and not after weld >>repair. Please note that a prior solution annealing only has >>to be done. >> >>Hope this helps >> >>C.V.Srinivasan Nishi Engineers Pvt Ltd India Jan 09, 2009 >>E-mail: nishi@vsnl.com >> >>>We are replacing primary reformer tubes and its outlet pipe >>>which is made in inconnel 800 HT is welded to existing 800 >>>HT pigtail. I would like to know is it required to solution >>>annealed the weld after repair and why. The existing inconel >>>800 HT pigtail is in service for more than 7 years and >>>normally subjected to 700 to 750 Deg C. >>>The pigtails are 1.5" X 6.35 mm thk pipes. >>> >>>regards > >Many Thanks Srinivasan, this was really helpful. Just one >more on the same subject, > >Can the visible creep fissure on the used pigtails can be >repaired by prior solution annealing? What shall be the >criterion for replacing the pigtails with new ones? I am >asking this because we did have temperature excursions due >to high dP acorss the catalyst. >regards