Many pipelines within water and wastewater treatment plants that were constructed within the last 50 years are nearing the end of their service lives. Owners have invested in condition assessments to help them make the difficult decision to repair or replace these pipelines. There are many types of condition assessment methods that can be used to determine the existing condition however, this paper will discuss a data-driven approach. Rehabilitation of the pipelines with protective coatings can also be challenging due to limited access and limited construction schedules. Important factors to consider when selecting protective coatings based on case histories are discussed.
Broadband electromagnetic testing is a non-destructive frequency-independent application of electromagnetic or eddy current systems that produces a thickness profile of a pipe. The BEM scan is not affected by background electromagnetic interference, and the test frequencies can be adjusted to the specific pipe material and site conditions. This technology allows for the assessment of ferrous metal pipe thickness. Metallurgic changes in the pipe composition, as formed by corrosion processes such as graphitization can be identified. The BEM assessment of a pipe can be performed externally or internally and does not require intimate contact with the metal surfaces. Removal of coatings, mortar, or insulation from pipe surfaces up to two inches is not required.
The BEM scan is performed using a handheld antenna tool within the excavation (Photo 1). The antenna is moved 360 degrees around the circumference of the pipe. Typically, a full-circumference scan of the pipe can be completed in two to four hours, making it possible to perform multiple scans within a day of field work. The handheld antenna is moved around the pipe taking successive readings, which are stored on a computer. An example of the BEM equipment set up is shown in Photo 1 and Photo 2.
