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Checking and Cracking Ñ Failure Before Service process, as the pipe sections were placed on the right-of-way, several sections were then welded together prior to burial and additional connections were welded. And some of these sections sat on the right-of-way for extended periods of time, even up to 18 months in some locations! Prior to service, this installed lining system exhibited failure. Unchecked Checking In many cases, the observed checking failure can turn into the initial phase of cracking. In other words, if the conditions that caused the checking continue, then the checking may turn into cracking. Whether the checking remains or progresses, it should be considered a failure when it's observed within a newly installed lining system that has not yet seen exposure to its intended service environment. So, if the coated pipe hasn't yet been installed, checking should not already occur on the coating. Cracking, on the other hand, is typically the result of stresses within the coating or lining film. The relief of those stresses can result in checking and cracking. In the instance of the newly buried pipeline, the observed failures became evident after hydrostat testing of various sections had been completed. The cracking of the lining system was easily observed. When the pipe was subjected to water during testing, the cracking of the lining showed that the carbon steel substrate was exposed; it began to rust, and, therefore, the rust stains made the cracks readily visible. See page 94 for a close-up of the cracking. Stress Factors As with any coatings problem, there was obvious concern as to the cause and extent of the observed lining failure within the pipeline system. After the failures were observed, it was decided that a complete failure investigation was to be initiated to make those determinations. Pipeline Project: A coating failure investigation was completed to determine what was causing the checking and cracking on the pipeline system. Cracking within a coating or lining is the result of stress relief, so the goal was to find out what was stressing the pipeline to cause this cracking failure. As previously noted, cracking within a coating or lining is the result of stress relief, so the goal was to fnd out what was stressing the pipeline to cause this cracking failure. Potential factors that may create stress on a pipeline include but are not limited to problems relating to: • Coating/lining formulation • Surface preparation (cleanliness and anchor profile) • Coating/lining mixing and application • Curing of the installed coating/lining • Temperatures (service environment) experienced after installation of the coating/lining • Duration of the temperatures experienced During the coating failure investigation, these various aspects were explored in parallel, and visual COATINGSPRO JANUARY 2014 93