Determination of Corrosion Causes and Premature Failure of The Tubes of Air Cooler in ISOMAX Unit

In this study, causes of premature failure due to corrosion of air cooler tubes in ISOMAX unit of an oil refinery were investigated. Corrosion products and the scales formed on the surfaces of tubes were examined using x-ray diffraction and x-ray fluorescence spectroscopy. In addition, scanning electron microscopy and energy dispersive spectroscopy were employed to study the morphology of the voids and the effect of aggressive species on their growth. The results showed that two different mechanisms were responsible for failure of the tubes. Underdeposit corrosion due to formation of the scales on the interior surfaces supported by the presence of ammonium bisulfide salts and high amounts of oxygen played a significant role in pitting corrosion on one of the tubes. On the other hand, erosion-corrosion due to high fluid velocity was the major failure mechanism in the other two tubes.

Keywords:

Air Cooler , Isomax , Ammonium Bisulfide , Oxygen , کولرهوایی , آیزوماکس , آمونیوم بی سولفاید , اکسیژن