Caustic Tank (21%) Temperature Hick-Up

[nejenrod]

I have a 22' diameter x 15'ht carbon steel (A36) tank. It operates at ambient (85oF) temperature under normal conditions. Built 2002 to API 650 standards with acceptable QA/QC records. Shell plate chemical composition: C=0.18, Mn=0.75, P=0.01,S=0.006, CU=0.02, Al=0.038. Current thickness measurements on the shell, roof & nozzle are at or near nominal thicknesses.

Over the weekend it was hit with 180oF for 48 hrs.

Our concern is do we have corrosion and or cracking potential.

 

[Duwe6]

Your probability for Caustic Stress Corr Cracking went up a minute amount. Very, very small amount.

On your 10-year 1st Internal, be sure to perform 100% MT on all welds below 6 to 8-ft up.

 

[nejenrod]

Duwe6 thanks for your comments. Did you base your decision from a time factor of exposure (48 hrs),temperature or % of caustic?

 

[Duwe6]

The answer is "E" -- all of the above. Mostly being a fairly low concentration and the very, very short duration.