The need for Postweld Heat Treatment (PWHT) and the prevention of alkaline stress corrosion cracking of all welded carbon steel equipment.
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The equipment that handle potassium carbonate (except Catacarb solution or FLEXSORB HP solvent, each of which contains vanadium inhibitor) having a concentration greater than 2% (by weight) should also be postweld heat treated as well if any of the below is true:
If the potassium carbonate solution is generated in situ from potassium hydroxide, then the equipment should be postweld heat treated as well.
The following equipment for handling of Sodium Hydroxide (caustic solutions) should be postweld heat treated:
Additional information on the PWHT of equipment in Alkaline solutions.
All equipment that handle amine solutions, such as MEA, MDEA, DEA and FLEXSORB amines, with concentrations greater than 2% should be postweld heat treated except the following:
Coker and cracker fractionation and light ends equipment handling ammonium carbonate/bicarbonate mixtures (excluding piping) should be postweld heat treated regardless of metal temperature.
All equipment that may be exposed to alkaline solutions as a result of operational upsets should be postweld heat treated as well.