Dear professionals, I am currently working on a demin water project and we are facing an SCC problem. I hope that your comments will be constructive to our evaluation of this engineering case. CASE: Cooling water exhibiting a Cl content of 150ppm is passed through a 304SS Heat-Exchanger operating at between 80%7E90 DegC. We can ascertain that Chloride-induced SSC is absent. If, however, we now increase the level of Cl to 179ppm, is there going to be a problem with SSC? How can we ascertain/prove/verify accordingly? It is not possible to change the Heat-Exchanger. Please advise. I will be very very grateful if anyone can cite me relevant publications or lab tests on this matter. I can be contacted at: jerri@mail.physics.org OR frigonale@gmx.net Thank you very much for your time. Kind regards, Jerri Ngow

Jerry De-min water with Chloride 179 ppm and SCC possibility for S.S 304 at 90 deg cent Possibility for S.S 304 for this choloride level and temp of operation may arise only if the deposit accumulates over a period of time and under conditions of low flow (stagnant conditions may also contribute). If S.S 304 tubes had been supplied in annealed condition then chances may be less. However, with S.S 304 pitting may start earlier than SCC for this choloride level. If the tube is procured as ERW then chances of SCC will be there where deposit accumulation is likely or when temp exceeeds more than design due to low flow or staganant flow conditions For the above indicated choloride levels and temp, residual stress left in the tubes should be high to develop SCC (other than deposits playing role for increasing concentration at local areas or tubes supplied in ERW condition). For ERW tubes chances will be high for SCC and also pitting to develop. More than the above choloride levels and temp, Residual stress in the tube will determine trend for SCC. For Annealed S.S 304 chances of pitting at local areas will be more than SCC trend. Pitting and SCC trend can be assessed by ET Inspection (Eddy Current inspection) of the inside of tubes. Trust this is of help to you C.V.Srinivasan Nishi Engineers Pvt Ltrd Chennai 20 India July 29 E-mail: nishi@vsnl.com >Jerri: > >Chloride SCC on the tube side of 304SS heat exchanger tubes >typically occurs due to build up of deposits, sediment, that >allows chlorides to concentrate. Low flow conditions can >also increase susceptibility to cracking. It's difficult to >say if 179 ppm chlorides will cause SCC or not, based on >your present 150 ppm, as we do not know how long the tubes >have been in service nor how you inspected the tubes for >SCC. Suffice to say that at 179 ppm chlorides at %7E90C, >chloride SCC is a potential risk, depending on deposits, >low-flow conditions, etc. > >Hope this helps! > > >David Hendrix >The Hendrix Group Inc.