High pH (11-11.5) measured in Glycol units due to Monodiethanol amine (MDEA) carryover from sweetening units was a concern as it is generally considered that caustic cracking is possible at these conditions in equipment not subject to post weld heat treatment (PWHT). However, risk of amine stress corrosion cracking (SCC) in glycol rich system is not well studied or documented to define the limits. Monitoring of pH may not be the right integrity operating window (IOW) parameter as it may not reflect the actual risk of Amine SCC. Laboratory testing was performed to determine the susceptibility of welded carbon steel specimens (ASTM A106 Gr.B and ASTM A 516 Gr.70) to amine SCC under field conditions of glycol contactor at 190°C, in monoethylene glycol (MEG) mixture at pH 11. A blank test at pH 8 was conducted for comparison. The testing indicated that there is no perceptible detrimental impact of the presence of amine in glycol on non-post weld heat treated carbon steel.

Subject
Test methods, Water, Mixtures, Acidity, Mechanical failure, Amines, Elongation, Glycol, Carbon steel, Risk reduction, Caustic stress corrosion cracking, Alloys, Stress corrosion cracking
Keywords:
Amine SCC, Glycol, dehydration, carbon steel
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2021
Association for Materials Protection and Performance (AMPP)
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