Krish If in-house expertise is lacking for a thorough study, suggest to engage a knowledgedable external consultant to study the process, process effluents, corrosion problems faced before remedial measures are planned or implemented. Discusssion forum can help to some extent only. This needs a study of the plant. Trust this helps you C.V.Srinivasan Nishi Engineers pvt ltd India Aug 7, 2006 E-mail: nishi@vsnl.com >Thanks to Shri.Debasis,MJ and Srinivisan. The designer has >chosen the CBD system to drian the content from hot process >pump,exchangers and columns with the intention that the >temperature may goes up to 350 Deg.C. That is the reason the >designer has not given external wrapping & coating system >which normally provided on underground pipeing system >operating up to 100 deg.C, > >The designer thought that with higher operating temperature >the external corrosion will not takes place.But in practical >we cant drain always the hot fluid in to the pipe and during >start-up and shutdown period the draining will be more. > >Now the corrosion takes place in external pipe without any >protective system which is the main reason for failure.What >are the remedial measure to tackle this problem? > >regards, >krish