Prescreening Using Inline Leak Detection
To begin assessing their critical pipelines, Interagua and Pure Technologies partnered in 2011. The scope of the project covered Interagua’s most critical pipelines that run through the north of the city. These mains are made of both steel and Prestressed Concrete Cylinder Pipe (PCCP) in diameters of 2000-mm, 1800-mm, 1500-mm, 1250-mm and 1050-mm. Considering that the 2000-mm steel main is only 20 years old and has a cathodic protection, the project focused on the other pipe diameters.
In total, roughly 66 kilometers of pipeline was surveyed for leaks and air pockets, and a significant portion of this was also assessed for structural deterioration. The main objective of inspecting the pipelines was to identify the actual condition of the pipes, including the specific amount and location of distress. From the results, a rehabilitation, replacement and maintenance plan could be created to ensure long-term service reliability. The inspections also provided Interagua with actionable information about pipe condition that could not be attained through conventional engineering studies.
In order to locate leaks and air pockets on all 66 kilometers of the transmission mains, Interagua used SmartBall® technology, an acoustic free-flowing leak detection tool that operates while a pipeline remains in service. The primary goal of the survey was to identify critical leaks that could be prioritized for repair by Interagua.
Locating and repairing leaks helps to reduce non-revenue water (NRW) and preserve a scarce resource. However, repairing leaks early also increases pipeline reliability, since leaks are often a preliminary indication of a failure location, particularly in metallic pipe materials. Failures in metallic pipe are often preceded by a period of leakage, so identification of leaks on metallic pipelines has the added benefit of ensuring structural reliability and preventing costly pipe failures.
Through the use of inline leak detection, Interagua identified 44 total leaks and four air pockets in the 66 kilometers of inspection. Of these leaks, 16 were identified as small, 17 as medium-sized and 11 as large leaks. Of the identified leaks, 14 were located on the 1250-mm sections of steel pipe.
Identifying Structural Deterioration through Condition Assessment
To identify structural deterioration on its PCCP mains, Interagua used the PipeDiver® platform, a free-flowing electromagnetic (EM) condition assessment tool. The tool finds structural defects by identifying and locating wire breaks in PCCP; the presence of broken wires is the main indication that PCCP will eventually fail.
The tool is able to effectively determine the baseline condition of PCCP while the pipeline remains in service. The ability to inspect live pipelines was a major factor for Interagua, as many of their critical PCCP mains could not be taken out of service for maintenance or inspection.
In total, Interagua completed almost 10 kilometers of EM inspection on its 1500-mm and 1800-mm PCCP mains that run north of the city. The inspection identified 90 pipe sections with some level of distress out of a possible 1429 pipe sections; after thorough engineering analysis, it was determined that only nine pipe sections should be replaced.
Through the use of EM condition assessment, Interagua was able to determine that only 6 percent of its PCCP inventory had distress, while less than one percent required immediate action. This approach saved a huge amount of capital budget by avoiding unnecessary replacement and also restored pipeline reliability.
For its 1250-mm steel pipeline inventory, Intergua also completed robotic CCTV inspection and Broadband Electromagnetic (BEM) inspection to identify areas of concern. Inline CCTV provides information about internal pipe conditions, while BEM technology can determine the remaining wall thickness of steel pipe through outer coatings of up to 50-mm.
In total, 21 kilometers of steel pipe was assessed, including 5 kilometers of BEM inspection. The results showed that Interagua’s steel pipe inventory was in good overall condition and had sufficient remaining wall thickness. Through the use of inline leak detection, CCTV and BEM inspection, Interagua identified the baseline condition of its critical steel pipes, which helped in the development of a future maintenance and repair plan.
Interagua’s large-diameter pipeline management program was very successful and determined that the vast majority of its large-diameter assets did not need to be replaced. The approach of assessing the pipelines to locate specific, isolated problems prevented the costly replacement of pipe with significant remaining useful life.
In addition to successful results, the project has been instrumental in the development of a reliable condition assessment method for mortar-lined steel pipelines; based on the initial results, Interagua will continue to assess its steel pipelines using the most advanced condition assessment technologies available, including free-flowing condition assessment of steel pipelines, which was unavailable at the inception of the project.
By investing capital resources into a condition assessment program, Interagua has successfully extended the useful life of its system and restored asset value by repairing isolated pipe sections and determining that the majority of pipelines have no distress and have significant remaining useful life.