Challenges and Solution for Corrosion under Pipe Supports

Petrochemical facilities and refineries consist of many miles of above ground piping that transports product between processing and storage units. These pipes are either supported at ground level or in multi-story pipe racks on varying types and sizes of supporting structures. A common problem these structures create is corrosion and erosion at the junction between the pipe and the support, which reduces the remaining wall thickness of the pipe and compromises the integrity of the entire system. Corrosion Under Pipe Support (CUPS) also known as Touchpoint Corrosion is a widespread issue within the industry that has caused in-service leaks and ruptures. Crevice corrosion is the mechanism were by which CUPS are initiated in a pipeline. Water entrapment at metal to metal contact leads to crevice corrosion. Minimizing the area of contact between support and pipe is effective in reducing the CUPS. A solution for the quantitative measurement of CUPS is a major requirement of the industry. Visual Inspection can provide an indication of corrosion (product build-up) but it is significantly hampered by the lack of access to the critical areas. Line Lifting of a potentially corroded pipe from its support for direct examination is dangerous on live process lines. Hence it is necessary to use advanced NDT methods that can provide information on the severity of the CUPS without removal of the supports which would eliminate the need for a shutdown. CUPS is basically a hidden, inaccessible corrosion which cannot be quantified with simple NDT Techniques. GUL’s QSR-1 is a promising solution for the CUPS. Quantitative measurement of the corrosion is achievable with QSR-1. A study was done at our workshop with QSR-1 on a 10-inch pipe with artificial corrosion patches. Sizing capability for various defect orientation along the pipe circumference was also studied. The technology was used to inspect 20-inch cooling water header line for one of the prominent clients.