Materials Performance

MAR 2017

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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18 MARCH 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 3 MATERIAL MATTERS Common Pitfalls Encountered in Close-Interval Potential Surveys Close-interval potential surveys are useful in determining whether buried metallic pipelines have sufficient CP. Photo courtesy of Chapman Engineering. R ecurring themes have emerged in recent case studies of unsuccessful close-interval potential surveys (CIS), according to a pair of engineering execu- tives often contracted for such work. Mike Ames and Cal Chapman—vice presi- dent and president, respectively, at Chapman Engineering (Boerne, Texas)— are each certif ied as a NACE Interna- tional Cathodic Protection Specialist. In a presentation 1 at NACE's Central Area Conference 2016, Ames explained common CIS pitfalls encountered by his team in the f ield. "Learning if a pipeline is under good cathodic protection (CP) over its entire length is important," says Ames, who has years of prior experience working for pipeline operators. "CIS is able to show the degree of CP, averaged over 10 to 20 ft [3 to 6 m] of line at a time, and it may show interfering current from other structures. It can also help def ine areas of pipeline with poor coatings." According to Chapman, long known as a consultant, CIS often f inds such interference patterns if performed correctly. "You buy CIS to get good data and good value," Chapman says in a recent interview. "It's not just to f ile a report. Several steps are needed to assure that data are going to be valid, useful, and worth the money. They include using trained personnel, f inding and staying on the pipe's centerline, making good soil contact, applying 'clean' CP with synchro- nized and accurate interruption, and reviewing data for validity on a daily basis." In one unsuccessful case this decade, a company operating three parallel 37-mile (59.5-km) pipelines in a promi- nent U.S. shale region had CIS performed on all of the pipelines. Each pipe was sep- arated from the others by ~4 ft (1.2 m). The three pipelines were protected by two CP systems, and the lines were bonded to one another at multiple locations along the corridor. "What we have to do f irst is follow the THICKNESS MEASUREMENT OF PROTECTIVE COATINGS Coating Thickness Material Analysis Microhardness Material Testing (860)683-0781 www.fischer-technology.com info@fischer-technology.com Robust, fast and reliable For ships, bridges, off-shore plat- forms, pipelines and structures Measures in accordance with SSPC-PA2, IMO-PSPC and others From basic "readings only" to stats and detailed inspection plans Surface Profile Measurement Easy and affordable ▪ ▪ ▪ ▪ ▪ ▪ Accurate and precise measurement of coating thick- ness with the Fischer FMP Series

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