Trenchless installation of pipeline segments is an attractive option in construction areas including wetlands, congested areas, and road crossings. One of the operational risks of trenchless installation, however, is potential damage to external coatings when the pipe is pulled through the borehole as a result of the forces involved, and contact with soil, rocks, and other debris present in the borehole.
If the coating gets damaged, external corrosion of pipeline segments may occur. The risk of pipeline failure as a result of coating damage from trenchless installation is greater than that from in-trench installation for several reasons. These include (i) after pulling a pipeline into place through the borehole, it is difficult to determine the condition of the coating; (ii) a pipeline segment installed using methods such as HDD is not as readily accessible for future pipeline or coating repairs; and (iii) if the coating damage is not known, it is difficult to precisely estimate the level of cathodic protection (CP) current needed to protect the pipeline using a CP system.
Therefore, it is important to determine the coating damage on the pipeline segment with a high degree of certainty immediately after trenchless installation. Information on the coating damage will help determine how best to design a CP system that can protect the pipeline segment, or determine whether coating damage is too severe to be tolerated by the CP system, requiring repair of the damaged coating before placing the pipeline segment in-service. However, determining coating damage immediately after installation is challenging because existing techniques for coating evaluation require good contact between pipe and soil. This condition is not likely to exist immediately after trenchless installations. Therefore, improved techniques for coating evaluation are required.
The objectives of this project are as follows:
A project status update will be presented at the 2014 Pipeline Research Exchange Meeting in Atlanta, GA. Additionally, PRCI has funded a 2014 complementary research project aimed at establishing procedures and processes to ensure that the entire length of an HDD installed section of pipeline is receiving sufficient levels of cathodic protection to prevent corrosion.