Condition Assessment of Live PCCP Lines with Free-Swimming Electromagnetic Inspection System

Over the last 10 years, many large-scale water transmission projects which made extensive use of Pre-Stressed Concrete Cylinder Pipe (PCCP) have been constructed in China. PCCP correctly designed and manufactured is a skillfully engineered composite pipe that exploits concrete in compression and steel in tension to create an economical, efficient, and long-lasting product. However, if it is improperly installed or poorly made, PCCP may rupture due to corrosion and breakage of the high-strength prestressing wires that reinforce the pipe. Electromagnetic inspection has been successfully used in accurate condition assessment of PCCP in China. Since many pipelines cannot be taken out of service, manned EM inspection can only be used to inspect empty or depressurized pipeline. An innovative free-swimming EM inspection system has been developed recently. The principle, analysis method of this free-swimming system is introduced. Several field applications indicate that the system is capable of conducting EM inspection in live pipeline. EM surveys, whether undertaken in wet or dry pipeline, enable owners to estimate remaining pipe life and, if necessary, plan the timed removal of defective pipes which are likely to fail. The paper provides examples of surveys conducted in the Americas.