Dear Kochappan Life assessment of Outlet Manifold Headers (Primary Reformer Outlet Headers in Ammonia Plants) is a complicated one. I have not read the book referred by Debasis Mitra . Assessment of tertiary creep related damages in reformer outlet headers is a difficult and complicated one. Other than conventional N.D.T + In-situ Metallography computational stress and mathematical modeling can also be done by (FEA model approach) taking into account the combined residual and thermal stresses, operating history, history of failures, history of start ups and shut-downs the reformer furnace had seen over years, temperature profile of the header. Outlet Header assemblies - especially the "T" joint computational stress analysis (i.e., the combined residual and thermal stress, effect of thermal cycling on cast header assemblies) is more complicated than simple utlet pigtail weldolet socket welds and their computational stress analysis. Besides most outlet header assemblies are cast Fe-C-Ni alloys with additions of stabilizing elements and their metallurgical transformation factors have to be also considered. By and large, in-situ metallorgaphy and N.D.T will give enough information on the metallurgical transformation that had occurred over the years - say 50,000 hrs upwards. I am not sure if any practical paper has been published on computational stress analysis and the metallurigal transformation on outlet header assemblies. to predict the life cycle for these components of reformer furnace assemblies. You may look in Ammonia Plant Safety symposium papers. studies on microstructure and metallurgy - - a collection of research work by Battelle Memorial Institute Columbus Laboratores Ohio - if you have access to these private research sponsored work by designers, process licensees, users etc. DNV / TUV (U.S.A) had done some studies but not sure if ready access to these research papers will be available or not sure if full details of the research work would be available. Battelle / DNV/TUV reports may not be directly accessible or fully published - other than for those organizations who had sponsored the project funding. Also, you have to recognize these studies may not have been done based on practical case studies or failures of a particular plant header assembly. These could be part of discarded assemblies or life cycle computation or extention of residual life estiamtion taking several hypothetical assumptions in the evaluation. Hypothetical assumptions - whether these will be accurate or would have missed into account some other factors = one has to make a guess. To my mind, even such predictive residual life cycle analysis by DNV/TUV or Battelle papers may at best serve as a guide including the computational mathematical modeling. Inferences drawn will also be approximation only and may not be highly accurate to answer your specific question . In simple wrods, any user would be interested to know if the header is to be discarded or replaced in the next 12-36 months time. Simple in-situ metallography and operational history and failure diagnosis will give enough guideline to a user. A mathemtical computational model (stress analysis and FEA modeling) may also aid the user . There is no ready made solution to such complicated metallurgical transformation + geometry related header assemblies . You may not find any practical paper on this from any international publications or books published on this. Trust this is of help to you C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai India July 09, 2005 E-mail: nishi@vsnl.com >Thank you, Mr. Marquez, for the reference. >However, it does not answer my basic query, ie, life >assessment of Outlet Manifold Headers of Ammonia Plants. >As you know, the failure modes and causes of failures of >Headers are completely different form those of Heater Tubes. >Regards, >Kochappan.