Verification of wall thickness of these pipes is accomplished by first removing the insulation and then performing an ultrasound inspection or by taking x-rays through the insulation at an angle tangential to the edge of the pipe. The time required to obtain data with either method is measured in hours per meter. Furthermore, the ultrasound method requires that the insulation be replugged after inspection. The insulation surface also must be cleaned or the resulting data will not be accurate. Petroleum refining is an industry that is undergoing intense amounts of scrutiny in the United States from regulatory agencies and environmental groups. As a result, releases of pollutants caused by corrosion leaks are becoming a high-consequence event. The Clean Air Act of 1990 has forced refineries to implement a number of costly measures to reduce their impact on the environment, both in the types of products they produce and the manner in which they operate.
The total cost of corrosion control in refineries is estimated at $3.692 billion. Of this total, maintenance-related expenses are estimated at $1.767 billion annually, vessel turnaround expenses account for $1.425 billion annually, and fouling costs are approximately $0.500 billion annually. The costs associated with corrosion control in refineries include both processing and water handling. Corrosion-related issues regarding processing include the handling of organic acids (broadly referred to as napthenic acid corrosion) and sulfur species, particularly at elevated temperatures, as well as water carried over in processing vessels and pipelines. Water handling includes concerns with corrosives such as H2S, CO2, chlorides, and high levels of dissolved solids. (reference)
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