Dear wifi, Pl. note that every project generates from some basis and background. Any existing elemnt in any system obviously did w.r.t. some basic design engineering whatever old it should be. And before any retrofitting/ replacement from original the base level drawing/design documents has to be honoured and focussed. You may probably been directed to change from CS to SS , may be due to any repeated failure or surprise falilures. Pl. note that re-engineering does not mean overdesign or drastic change which could have associated impact on your other unchanged existing system. At the onset I would like to focus on condition of existing CS pipes and a detail failure (if any) investigation . This is not in principle recommended to change a CS system abrupt to SS system. Using SS 304 may not help you much as you are using cooling water and probably u are not fully aware about its chemistry and contaminants. So b4 taking any decision pl. make a small group who having basic material science/metallurgy-corrosion idea/knowledge and make a team effort to generate idea and proposal to your management. regards

In general for cooling water application SS pipes are not recommended due to high amount of chloride in the water and will cause pitting and premature failure.I know in some cases SS failed before carbon steel.My advise would be analyse the cooling water and find out the ingredients and select the suitable metallurgy.In any case GI coated CS pipe will serve better than CSand if there is no safety issue involved then you can very well choose non-metallic pipes. regards,