Materials Performance

DEC 2014

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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corrosion, pitting, and metal loss as well as the corrosion products present; and routine inspection results. Data analysis should demonstrate that microorganisms and their activities, as opposed to abiotic mecha- nisms, are responsible for providing the predominant influence over the corrosion mechanism present in the pipeline. Monitoring the corrosiveness of pipeline contents is frequently done using coupons inserted into the pipeline at locations where corrosion is a poten- tial threat. When possible, corrosion monitoring data and microbiological test data should be collected from the same locations. Corrosion products may be taken from the metal surface, a lining, or from a pit underneath a deposit that has been removed. When corrosion monitor- ing and microbiological monitoring are performed at different locations on a pipeline, the relationship between the two test locations should be identified (e.g., upstream, downstream, similar operating conditions, etc.). Inspection techniques commonly used to detect and monitor corrosion-related damage generally include visual inspec- tion, ultrasonic testing (UT), radiographic testing (RT), and magnetic flux methods. The results can be used to establish the orientation, distribution, density, size, shape, and extent of internal corrosion damage. Inline inspection (ILI) may provide information about the location and severity of internal corrosion relative to operating parameters, design, elevation, and other considerations; and ILI data may be used to identify sample locations for microbiological and chemical testing of pipeline fluids. As with most data related to MIC assessment, longer-term operating parameter trends are preferred over one or a few data points as these provide more meaningful information. Simply reducing the numbers of viable microorganisms in a pipeline system won't necessarily control internal corrosion and MIC in the pipeline system. A mitigation strategy typically addresses both the micro- biological and corrosion threats where MIC is present. Knowing the identity and charac- teristics of the microorganisms present and how they interact with the pipeline system promotes an understanding of their impact on the corrosion that is being experienced, which is important when developing a mitigation strategy. A successful mitiga- tion treatment can only be designed when the problem has been properly diagnosed. General information about methods for controlling MIC by design, operation, and specific measures, such as maintenance pigging and biocide treatment, can be found in NACE standard SP0106. 4 Editor's note: NACE standard TM0212- 2012 applies to the internal surfaces of pipelines, and describes types of microorgan- isms, mechanisms by which MIC occurs, methods for sampling and testing for the presence of microorganisms, research results, and interpretation of test results. It describes methodologies by which the appropriate tools and techniques may be selected and practically applied. The methods presented in this standard represent the general consensus of industry experts in pipeline corrosion and industrial microbiology at the time this standard was published. This standard test method was prepared by TG 254, "Microbiologically Influenced Corrosion on Internal Surfaces of Pipelines: Detection, Testing, and Evaluation—Standard Test Method." TG 254 is administered by Specific Technology Group (STG) 35, "Pipelines, Tanks, and Well Casings." This standard is issued by NACE under the auspices of STG 35. References 1 NACE TM0212-2012, "Detection, Testing, and Evaluation of Microbiologically Influenced Corrosion on Internal Surfaces of Pipelines" (Houston, TX: NACE International, 2012). 2 R. Eckert, T.L. Skovhus, "Using Molecular Microbiological Methods to Investigate MIC in the Oil and Gas Industry," MP 50, 8 (2011). 3 NACE TM0194-2014, "Field Monitoring of Bacterial Growth in Oil and Gas Systems" (Houston, TX: NACE, 2014). 4 NACE SP0106-2006, "Control of Internal Corrosion in Steel Pipelines and Piping Systems" (Houston, TX: NACE, 2006). MATERIALS PERFORMANCE DECEMBER 2014 NACE INTERNATIONAL: VOL. 53, NO. 12 31 Diagnosing Microbiologically Influenced Corrosion in a Pipeline

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