Abstract

Third-party contact with pipelines (typically caused by contact with a digging or drilling device) can result in mechanical damage to the pipe, in addition to coating damage that can initiate corrosion. Because this type of damage often goes unreported and can lead to eventual catastrophic failure of the pipe, a reliable, cost-effective method is needed for monitoring and reporting third-party contact events. The impressed alternating cycle current (IACC) pipeline monitoring method consists of impressing electrical signals on the pipe by generating a time-varying voltage between the pipe and the soil at periodic locations where pipeline access is available. The signal voltage between the pipe and ground is monitored continuously at receiving stations located some distance away. Third-party contact to the pipe that breaks through the coating changes the signal received at the receiving stations. In this project, the IACC monitoring method is being developed, tested, and demonstrated. Work performed to date includes (1) a technology assessment, (2) development of an IACC model to predict performance and assist with selection of signal operating parameters, (3) investigation of potential interactions with cathodic protection systems, and (4) experimental measurements on operating pipelines. Based on information recently found in published studies, it is believed that the operation of IACC on a pipeline will cause no interference with CP systems. Initial results on operating pipelines showed that IACC signals could be successfully propagated over a distance of 3.5 miles, and that simulated contact can be detected up to a distance of 1.4 miles, depending on the pipeline and soil conditions. Document type: Report