Ingenuity Magazine Fall 2020

10 Pond | www.pondco.com Both solutions, inspection and corrections, are expensive. Excavation for coating repair is expensive and can be dangerous; often, the pipeline as-built drawings have margins of error or are incomplete, which could lead to excavation damage or catastrophic failure. Post-installation repairs may require removal of significant concrete and asphalt as well as deep excavations. For this case study, when looking from a financial standpoint, coating failure investigation of buried pipelines required workers to first dig down to the location of the defect, which range anywhere from 5 to 40+ feet deep. Accessing the pipe could be a challenge due to obstruction by roads and other blockages. Imagine a swamp crossing requiring cofferdam shoring. From a process management, financial and safety considerations standpoint, the only solution that meets all criteria is vendor inspection of purchased pipeline construction materials and best practices during installation. Digging these trenches and putting up (shoring) walls to prevent collapse is a tedious, costly endeavor (shown on pg. 8). Not only does the process run up to $500,000 per excavation, the egregious cost of performing these O&M remediations and the risk associated with them is a challenging model to follow. What if we could prevent these defects from arising in the first place? Qualified coating specialists are dual- trained to recognize mechanical defects are also equipped to recognize failure modes before they even make it to the project site. Once these defects are discovered, the failure is usually attributed to things such as poor surface preparation, substandard application or handling damage. Each of these issues could be identified prior to installation and these underlying concerns wouldn’t evolve into larger problems. Operators best value is to incorporate a trained coating specialist during the preconstruction phase. This investment decreases the likelihood that issues will warrant an extensive repair. CASE STUDY When the pipeline is installed and buried, corrosion control is maintained through CP systems. CP protects bare metal spots at coating failure from rusting by either connecting a metal that corrodes preferentially to the pipeline, thereby sacrificing itself, or through an impressed current system that provides outside current to drive the electrochemical corrosion reaction to perform the same function. As previously mentioned, one way to identify areas of coating failure is to use a method called a DCVG survey, which identifies voltage drops during an over-the-line survey. Voltage drops often correlate to areas of coating failure along the buried pipeline surface. Depending on the operator’s mechanical integrity plan, this may require confirmatory excavation that no cross-section wall loss is occurring at the location. In this situation, the pipeline was coated with fusion-bonded epoxy. FBE is a shop coating application in which dry, charged particles of epoxy powder are blown towards a preheated surface and melted and fused to the pipe. The performance of a coating system requires specified materials, applied Case study after case study can affirm that preventative inspection measures are more effective long-term than reactive corrections. If the product being transported is hazardous, the need to prevent corrosion failure is even greater. Figure 2 Figure 3