Thursday, July 4, 2019

Re: [MW:29773] Usage of SS304 tubes ot SS316L tubes in cooling water exchangers

Hello,

I am not familiar with this particular design and Hydrogen process piping is not this simple but as a general role, 304 has less ferrite in its microstructure (comparing to 316 which has 5-10% ferrite). This might have been the criteria to choose 304 over 316. Hydrogen embrittlement affects ferritic microstructures while austenite is immune to this failure mechanism. 

Regards
Ramin  Kondori
Sr. QA/QC & Welding Engineer
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On Fri, Jun 28, 2019 at 3:57 PM Praveen, Integrity engineer , Refinery <prav.mn@gmail.com> wrote:
Recently I observed that in one of the cooling water exchanger (tube in tube) which has Hydrogen at 230DegC on the outer tube and cooling water on the inner tube. The tube metallurgy was SS304. 
Where as in another unit, a cooling water exchanger with SS 316L tubes had lean amine on shell side. 

On what basis is 316L tubes chosen over 304  tubes when a cooling water exchanger is designed?

 - I have two things in mind as far as corrosion is concerned, one being ClSCC and another being PTASCC. 

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