Petrochemical process plant construction materials deteriorate when the plant is in service. In consequence, planned maintenance is undertaken to repair and replace equipment when it is predicted or detected that the facility has sustained damage. Typically, the operating environment does not normally vary very much. However, from time to time, process conditions may change rapidly and unexpectedly, due to contamination by water or other impurities, which can result in severe and widespread damage to the materials of construction. One such example concerned a process plant operated by our company. In this instance, damage to a process heat exchanger could result in moisture ingress that, in combination with an anhydrous hydrocarbon process stream that contained hydrogen chloride, produced a highly corrosive downstream environment, due to ionization of the HCl even though the bulk liquor stream was relatively non-conductive. The low conductivity of the bulk environment meant that conventional process and corrosion monitoring instrumentation was unsuitable to detect the onset of the fault condition or provide an indication of the likely corrosion rate. In consequence, it was desirable for corrosion combination of monitoring techniques to be developed that could detect changes in the service environment in real time in order to reduce the severity and duration of such attack. This paper describes the development of the monitoring approach, and in particular on the application of electrochemical noise analysis, which, in combination with certain process chemistry parameters, could be used to detect the onset of the fault condition and prompt timely remedial action in such complex and/or low conductivity hydrocarbon processing systems.
Keywords: petrochemical plant, corrosion, monitoring, low conductivity hydrocarbon streams, electrochemical noise