Carbon Steek Vs. Stainless Steel for Heat Exchanger Shell

[VenP]

I work in a pulp mill. I am upgrading an existing heat exchanger- vertical configuration) that handles Black Liquor in the tubes(304L) and water on shell side(Carbon Steel).

The cooler is in operation for 20 years and inspection reveal Micro Biological corrosion (MIC) at the bottom of the tubes. This has thinned both the shell and tube.

We have decided to go for 2205 tubes which have better resistance to MIC.

My question is: Would it be worthwhile to change the shell to SS, both in terms of life and cost?

 

[rustbuster]

MIC will attack stainless steels as well, I would think that biocides is what you need to be looking into, there are some very good treatment options.

 

[rmw]

You can make the steel shell of your new liquor HX a lot thicker for the price of stainless.

So, unless you think your water treatment is uncontrollable or likely to get worse, you know your rate of thinning and can compensate accordingly. SS is not a silver bullet. It has its own issues, especially with crappy water.

rmw

 

[rmw]

And why did you put a HX question in a pipeline forum? Just curious.

rmw

 

[VenP]

Thanks Guys. Input was useful. Regarding posting in pipeline forum, this is my maiden post and I guess I have not explored the forum for other options.

 

[MrBTU]

Yes, go with carbon steel shell and add appropriate corrosion allowance (1/8"?) and work on cooling water chemistry control.

 

[VenP]

What about 2205?