2205 Duplex vs Carbon steel

[narmak32]

Hi Everyone,

We are choosing a tube bundle for one our alkylation unit Heat exchangers. We have Water(City water and smetimes Fire pound water) with some caustic carry-over in the shell side and the product in the shell side.I have been given two options by inspection department.
1- SA- 179 SEAMLEASS Carbon steel
2- 2205 Duplex welded

Water goes to the tune side and heat up to 120 F.

I would be happy to have any suggestion on this subject.

thanks

 

[EdStainless]

What is in there now?
How has it failed?

If you have decent water treatment then the CS should be fine on the water side. What about the product side?

= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[TomEun]

In addition to EdStainless’ questions, you may have to confirm the following details for the material selection.

- If it is for tube bundle replacement (not for new construction), what is the root cause (premature failure or retired-prolonged design life)? How long has it been operated? Were there any corrosion phenomena in tube side? Was there galvanic or crevice corrosion? Was the failure local/cracking or general corrosion? Was there erosion or wearing near the inlet or baffles?
- H/EX TEMA type? Horizontal or vertical?
- Chemical composition of the water : (chloride, TDS, Alkalinity, Calcium Hardness, pH, SRB, caustic, etc.)
- Operating temperature (normal, maximum, 120F & time, upset & time) on shell & tube sides respectively
- Water velocity in shell side
- What are the present materials of tube and tubesheet?
- Why do you consider only two materials (CS & DSS)? How about 304(L) SS, 316(L) SS, etc?
- Any chemical treatment in water side?
- Any other operating/maintenance history for this failure

 

[narmak32]

Edstainless

We do not have any treatment on the water side. on the product side, I should not see anything, however, i might have acid soluble oil in my product stream.

 

[strider6]

if it's a fresh water with not treatment carbon steel shall not be used cause it will corrode very fast in fully oxygenated water.
i'll consider to use a SS 316L if the chlorides are not to high in the process fluid and water side.

S.

http://www.corrosionist.com

 

[EdStainless]

IF he needs to go to a CRA, then 2205 would be a better choice than 316. It is stronger (thiner walls), has better pitting resistance, better CSCC resistance, better heat transfer, and the cost is almost the same today.

= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[rolledalloy]

Depending on the quantity, AL 2003 is a leaner duplex than 2205 that still offers the strength, pitting, and chloride SCC advantages that 2205 has over 316L. Allegheny Ludlum has worked with some tubing manufactures to supply strip for welded tubes. It should come in lower cost than 2205. In some cases lead time vs. 2205 could be an issue.

 

[robsalv]

Where service has corroded/holed out CS bundles of fixed tubesheet hX's, I often recommend A179 (usually like for like) or 2205 tubing materials to our Ops and maintenance group.

More specifically, I recommend a thicker gauge CS tube for a longer service life, OR if Ops wish to consider the lifecycle cost, then retube in 2205.

Why 2205 rather than 304/316etc? 2205's thermal expansion is similar enough to CS that it can be a direct swap over. We have even mixed the two materials throughout a bundle and haven't found galvanic issues.


Another reason why I might strongly suggest 2205 over 3xx stainless in certain instances is that 2205 is more resistant to erosion corrosion.


- - - - - - - - - - - - - - -
"Life! No one get's out of it alive."
"The trick is to grow up without growing old..."