CHLORIDE STRESS CORROSION CRACKING IN BFW PREHEATER IN REFORMER UNIT

摘要

Hydrogen production in a heavy oil Upgrader is one of the most important unit processes, because it provides the hydrogen and steam required for heavy oil Upgrader process facilities. These units have large heat exchanger trains which are under severe conditions such as high CO2 content and high temperatures. Therefore, the equipment in this highest impacted service are designed with highly corrosion resistant materials such as UNS S30400 and UNS S316000. However, sometimes these materials are suitable for the severe conditions of the shell side but not for the condition on the tube side. This unsuitability, in this case, is primarily due to the boiler feed water, specifically the water's chlorine content. Even in low concentrations, chloride in the high temperature conditions in contact with austenitic material can cause a component to fail catastrophically. In addition design condition such as stress concentration devices and inappropriate commissioning procedures can make the austenitic steel tubes prone to fail too early. This paper shows the experience of failure of a heat exchanger due to chloride stress corrosion cracking (SCC)in the Upgrader facility.