A typical longitudinal, linear, wide mouth, unbranched external crack noticed in one 9cr-1Mo H-Oil Furnace Tube . The crack has propagated approx. 70% WT from outside and not through. By careful partitioning of the crack face fractography done and surprisingly by EDX some high level of "Al" peaks are seen alongwith isolated population of creep voids. We are quite confused with the presence of "Al" peaks which could have been happened if there was any Aluminium paining etc. If anyone can share regarding possibility and any reference of Liquid Metal Embrittlement of P9 tube by "Al" it will be of help. Or any other discussion regards

Debasis Your furnace tube - P 9 - had seen external wide mouth cracks seen upto 70% - outer to inner wall thickness (from what is described). This could be probably due to impingement from flames or direct impingement from burner nozzle - fuel configuration not kept properly. Localized over-heating and short term stress-rupture due to over heating from flame impingement is a common phenomenon seen in such burner (burner nozzle angles not kept) impinged tubes ( whether related to steam-boiler water wall tube failures or in furnace tubes in refinery heaters). LME is a different phenomenon which external Al painting - if it had penetrated would have shown as intergranular cracks. For this heater coil should have seen around 650 deg cent at least. At 650 deg cent, P 9 would have shown other effects - viz., more creep related voids and cracks. The fact that you had seen only isolated creep voids - to me it appears - this may not be a cause. Point raised by Krish - on hammer test ( No one does sledge hammering but in some refineries still slight tapping only is done during hydro test period). Slight hammer tapping will not be a big stress raising area to cause stress rupture. No one does a sledge hammer test during hydro test. Still evidence of this would have been noted from metallography. Your description did not indicate the same. Fish mouth rupture in heater coil is mostly due to direct flame impingement. Please examine from this angle. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India April 11, 2008 E-mail: nishi@vsnl.com >A typical longitudinal, linear, wide mouth, unbranched >external crack noticed in one 9cr-1Mo H-Oil Furnace Tube . >The crack has propagated approx. 70% WT from outside and not >through. > >By careful partitioning of the crack face fractography done >and surprisingly by EDX some high level of "Al" peaks are >seen alongwith isolated population of creep voids. > >We are quite confused with the presence of "Al" peaks which >could have been happened if there was any Aluminium paining >etc. > >If anyone can share regarding possibility and any reference >of Liquid Metal Embrittlement of P9 tube by "Al" it will be >of help. Or any other discussion > >regards

Debasis Check if the cracks originated from the dented locations at either ends of the crack tip. Fractograph taken would have given some clues on this. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India April 13, 2008 E-mail: nishi@vsnl.com >Thank U Sir. > >I missed to point out that at both the extremities of the >crack tip there exist visible shallow dent. > >regards>Debasis >> >>Your furnace tube - P 9 - had seen external wide mouth >>cracks seen upto 70% - outer to inner wall thickness (from >>what is described). >> >>This could be probably due to impingement from flames or >>direct impingement from burner nozzle - fuel configuration >>not kept properly. >> >>Localized over-heating and short term stress-rupture due to >>over heating from flame impingement is a common phenomenon >>seen in such burner (burner nozzle angles not kept) >>impinged tubes ( whether related to steam-boiler water wall >>tube failures or in furnace tubes in refinery heaters). >> >>LME is a different phenomenon which external Al painting - >>if it had penetrated would have shown as intergranular >>cracks. For this heater coil should have seen around 650 deg >>cent at least. >> >>At 650 deg cent, P 9 would have shown other effects - viz., >>more creep related voids and cracks. The fact that you had >>seen only isolated creep voids - to me it appears - this may >>not be a cause. >> >>Point raised by Krish - on hammer test ( No one does sledge >>hammering but in some refineries still slight tapping only >>is done during hydro test period). Slight hammer tapping >>will not be a big stress raising area to cause stress >>rupture. No one does a sledge hammer test during hydro test. >> >>Still evidence of this would have been noted from >>metallography. Your description did not indicate the same. >> >>Fish mouth rupture in heater coil is mostly due to direct >>flame impingement. Please examine from this angle. >> >>Hope this helps >>C.V.Srinivasan Nishi Engineers Pvt Ltd India April 11, 2008 >>E-mail: nishi@vsnl.com >> >>>A typical longitudinal, linear, wide mouth, unbranched >>>external crack noticed in one 9cr-1Mo H-Oil Furnace Tube . >>>The crack has propagated approx. 70% WT from outside and not >>>through. >>> >>>By careful partitioning of the crack face fractography done >>>and surprisingly by EDX some high level of "Al" peaks are >>>seen alongwith isolated population of creep voids. >>> >>>We are quite confused with the presence of "Al" peaks which >>>could have been happened if there was any Aluminium paining >>>etc. >>> >>>If anyone can share regarding possibility and any reference >>>of Liquid Metal Embrittlement of P9 tube by "Al" it will be >>>of help. Or any other discussion >>> >>>regards