Ananda Sarkar You have not explained whether A 106 Gr B pipe (4" Sch 40) with C.A 1.5 mm is exposed occasionally to 440 deg cent or continuously. Your pressure condition is not high (16 KSC @ 440 Deg Cent) assuming the pipe is continuously exposed to this temp - in two years time is not to be too worried at this stage. 16 KSC is not an abnormal pressure to develop creep and graphitization trends in just two years service. If ASTM A 106 Gr B had been supplied as a killed steel (which is the normal supply material for most industrial uses) - then to a large extent even silicon killed steel (de-oxygenated steel) will negate the trend of graphitization. Besides this silicon used as de-oxygenation, A 106 Gr B have small alloy additions of Cr, Mn, V, Ni. These will certainly give improved resistance to both creep and graphitization trends in A 106 Gr B. Creep in Super steam heated pipe service is a phenomenon that is to be considered if the pipe had been exposed > 50,000 hrs or so at 450 deg cent. Also the trend from graphitization may be a problem if the pipe had been exposed continuously > 50,000 hrs at 450 deg cent at this service design pressure. Small alloying additions of Cr,V, Mn will improve the resistance from creep and graphitization in A 106 Gr B even if it were exposed relatively or continuously in the last two years at close to 450 deg cent. Currently, i feel that you may be over-worried about the usage of this material (A 106 GR B for super heated steam service at 450 deg cent) at service temperature conditions of 450 deg cent. All i can say: Graphitization and creep are both slow proceeses which will not affect this material in just two years time. You have still a long way to go from these deteriorating metallurgical transformation conditions for this material (A 106 Gr B) Trust this is of help to you. C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 20 India August 24, 2004 E-mail: nishi@vsnl.com >Hi > >I am facing a real problem, ours is a petrochemical plant. >For the last 2 years a A106Gr.B pipeline in steam service is >exposed to 440deg.C, 16kg/sq.cm steam. Pipe dimensions O.D >4", thk 6.02 mm , corrosion allowance 1.5 mm. Is it feasible >to use the pipeline under same conditions for another 1 year >( till next shutdown ) or it has to be replaced soon ?? Any >time period available ? I found in the ASTM handbook that >A106 Gr.B CS is usable upto 426deg.C then creep and >graphitization problems may begun. Please advice .... > > > >Inspection Engineer >HPL, India >Ananda.Sarkar@hpl.co.in

You may want to keep the situation in check and balance by monitoring. It may help.