Askar Soltani - Senior Corrosion Inspector , Phase 12 Gas Refinery, South pars Gas Complex
Koorosh Farzanfar - Head of Mechanical Inspection Department,
Reza Zarei - Head of Inspection Department,

Stress corrosion cracking in austenitic stainless steels is one the predominant failure root causes in oil and gas refineries. In this paper failure analysis of SS304L tubes in a shell and tube heatexchanger within one of the gas refineries in South Pars Gas Complex (SPGC) has been investigated. The medium inside the tubes was sour gas stream coming from gas separation sections of the gas refinery and shell side medium was pure steam in order to heat the gas duringwinter case to prevent hydrate formation in transferring the gas to related treating units.There is acontinuous injection of MEG (Mono Ethylene Glycol) into the gas stream before entering this gas heater. The gas heater failed in its first operational years. Many cracks observed on the tubessurface during visual inspection. Massive deposit formation observed after longitudinal cut of thefailed tubes. Samples were taken from deposits and also cracked area. XRD diffraction pattern of deposits revealed remarkable content of complex phases containing calcium and chromiumelements.SEM images of cracked area indicated highly branched Intergranular corrosion. Laboratory analysis of MEG revealed high contents of chloride and calcium. It appears that the stainless steels passive layer has been damaged due to high chloride content of injected MEG and because of higher thermodynamic affinity of chromium to combine with the calcium rather thanoxygen, deposit has been formed. Localized corrosion under deposit and presence of high tensile stress due to tubes internal pressure can lead to stress corrosion cracking.

CLSCC, MEG, SEM, XRD, Intergranular Corrosion