Failure of stainless steel 304L air cooler tubes due to stress corrosion cracking caused by organic chlorides
By Ravindranath, K.; Alazemi, R.
Published in Engineering Failure Analysis
2019
Abstract
The paper presents the failure investigation of stainless steel (SS) 304L air cooler tubes in a petrochemical company. The company encountered repeated failures of the finned tubes at the outlet section of the air cooler in its carbon dioxide manufacturing unit. A comprehensive failure investigation including visual examination, optical and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), fluid analysis, chemical characterization of the tubes and cyclic polarization studies were carried out for the identification of the root cause of failure. The results obtained indicated that the failure of the air cooler tubes was due to chloride stress corrosion cracking (SCC). The source of chlorides that caused the cracking was the acidic chlorides formed as a result of the decomposition of organic chloride compounds present in the process gas. The presence of acidic chlorides and the optimum temperature existed at the outlet of the air cooler resulted in the pitting and the SCC of the tubes. Recommendations made to mitigate the failure of tubes include the introduction of a scrubbing system upstream of the air cooler and the upgradation of the metallurgy of the tube to high alloy SS or nickel-base alloy.