EFFECT OF ELEMENTAL SULFUR DEPOSITS IN REFINERY HEAT EXCHANGERS-A CASE STUDY

摘要

Heat exchangers are process equipment in which heat is continuously transferred between hot and cold fluids, or vice versa, directly or indirectly through a heat transfer surface that separates the two fluids. Heat exchangers consist primarily of bundles of pipes, tubes, or plate coils. Elemental sulfur corrosion in oil and gas production systems, refinery heat exchanger tubes, and fin-fan coolers is an insidious form of attack that initiates pitting corrosion by creating small anodic with large cathodic areas where the passive/protective film formed on the metal surface is often broken.[1,2,3,4,5] The resulting fouling reduces the heat transfer efficiency of the heat exchangers.[6] There are multiple initiators that can cause under deposit corrosion (UDC) in process equipment in addition to sulfur, which is the focus of this article.[7] This article presents a failure case related to cold preheat exchangers from a Middle East refinery. Leaks were noticed at the top portion of the tube, as well as severe pits and yellow color formation on the tubes (Figure 1). The heat exchanger tube material was carbon steel. The refinery heat exchanger tubes failed prematurely/ unexpectedly after five years in service. Inspection data collected using magnetic flux leakage (MFL) revealed that 27 (>10%) of the tubes out of 247 experienced accelerated wall thickness loss.