John S.S 347 cold rolled helical coil (for fired heaters) - i have seen some European process and piping specifications call for a stabilization anneal after cold rolling to avoid later complications of SCC. If helical coil bending (cold rolled coil) is > 10% it may be worthwhile to consider PWHT to relieve sresses after beding process. Theoretically SS 347 coil may not PWHT or stabilization anneal so long as the cold work is restricted to less than 10%. Trust this answers your querry C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 20. India april 20,2005 E-mail: nishi@vsnl.com >Do 347 SS seamless tubes which will be cold rolled for a >helical coil in a fired heater need stabilization prior to >rolling? After rolling, do the tubes require PWHT to >relieve stresses created during the bending process?

>John >As Srinivasan says normally SS 347 tubes are delivered under >stabilized annealed condition after cold rolling. To avoid >cold bending your tubes and PWHT after cold bending if >possible you should use elbows instead of cold pipe bands >Luis Marques Luis, I think you didn't get the picture. There are few furnaces where the radiation coils are basically a single helical coil. We do have a similar heater - radiation coils having OD 168.3 mm, TCD of 3082 & 16 nos. turns. The material is SS 321 H. The inlet is from top (ex-convection) & outlet is from bottom. The shell, as obvious, cylindrical & firing is from bottom. Regarding the HT process employed during fabrication process - I have to dig a bit - consult the original passpor. Regards Chakra