25% Caustic Soda Storage Tank

[mcb02]

I am in the process of contacting several Tank Manufacturing companies to provide Carbon Steel Tanks for our Wastewater Treatment Plant. The caustic is 25% with the maximum temperature leaving the Chemical Plant being 165 F. I have seen that with temperatures reaching 165 F, stress relieving welds may be necessary. My questions are, should the tank have stress relief welds? Also, would the tank need to have an internal lining to prevent any type of corrosion? Any information on this will be greatly appreciated.

Matt

 

[bimr]

Here is the information that you are looking for:

http://www.hghouston.com/naoh.html

http://www.oxy.com/oxychem/Products/caustic_soda/literature/caustic

[1].pdf

You might consider the use of a tank made from 304 SS designed to the API-650 Code as an alternative to carbon steel. The tank should have a 0.125" corrosion allowance as well.

"In steel systems, temperatures above 120°F will cause accelerated corrosion and iron contamination of the
caustic (above 120°F, cracking can occur if concentrated caustic is processed in steel equipment that thas not been stress relieved.) Where iron contamination or corrosion is unacceptable, epoxy lined steel, 316L and 304L stainless steels are recommended. 316L and 304L stainless is acceptable to 200°F. Consult with the epoxy supplier about the working temperature range of a particular
epoxy lining."

A 1/8-inch corrosion allowance should be included in the design.

 

[mcb02]

Thanks bimr. The links have been very helpful.

Matt

 

[LHA]

Have you considered FRP instead of metal? No corrosion at all, and I'm sure no thermal strain at 165F

Engineering is the practice of the art of science - Steve

 

[mcb02]

Iha,

Currently at our Site we have 3 FRP Tanks. However, during the recent Tank Integrity Testing, the inspectors noticed a severe amount of delamination in the Tanks. Our Treatment Plant should continue on for another 20+ years and I've heard Steel Tanks should definetely hold up for that time frame.

Matt