Corrosion Failure Reason and Anticorrosion Recommendations of Broken Collecting-tube in Exit Tube of an Air Cooler in a 5 Mt/a Refinery

By means of macro-inspection, scanning electron microscopy and EDX, a corrosion failure analysis of broken collecting-tube in exit tube of the A-102/8 air cooler in a 5Mt/a refinery for Lanzhou petrochemical company was carried out. The results show that the reason of corrosion failure was severe acidic water corrosion and erosion-corrosion. The inconsequential design of the air cooler′s feeding tube brought out the deflection and uneven distribution of the feedstock flow, leading to enough gaseous fluid moving into later A-102/5~8 air coolers. The gaseous fluid contained much H2S, which was condensed and dissolved into the water of later air coolers and thus generated severe acidic water, but later air coolers were distributed with little water and corrosion inhibitor, whose dilution function and inhibition function were weakened, so the corrosion failure was engendered by severe acidic water corrosion and erosion-corrosion. Some improvement suggestions were pointed out.