Article

Dutch utility inspects rising main and reduces risk

It’s a major event when you’ve been asked to perform a first in terms of a pipeline inspection.

For starters, you must feel confident in the inspection technology you recommend. Second, you hope that all your planning for deployment and unexpected contingencies has been anticipated. And finally, with so many eyes focused on the outcome, you hope the first inspection of its kind goes off without a hitch.

That was the case in May 2017, when the Dutch utility Brabantse Delta retained Pure Technologies (Pure) to perform a SmartBall® inspection on a critical untreated wastewater pipeline near the city of Zevenbergen, located in the North Brabant province.

For Pure Technologies, this project marked the first SmartBall acoustic inspection of a rising [force] main in the Netherlands.

Brabantse Delta operates AWP-1, a pre-stressed concrete cylinder pipe (PCCP) pipeline that transfers industrial wastewater from the Moerdiijk pump station to the Hoven pump station. The 800mm (32-inch) pipeline traverses a lot of farmland near the city, which made accessing buried manholes somewhat of a challenge, as many of these were located on private land, making excavation difficult.

Gas pockets are of concern on wastewater lines

The pipeline has not experienced regular failures, but Brabantse Delta was looking for solutions to establish a baseline condition and manage the risk of this critical asset. The primary purpose of the SmartBall inspection was to identify and locate leaks and pockets of trapped gas along the approximately 8.3 km (5.1 mile) pipeline.

We were pleased the overall execution and excited that the SmartBall tool was able to collect inspection data while the force main remained in operation.” Ing. R van Wanrooij, Adviser Civil Engineering, Brabantse Delta

Gas pockets are of significant concern in force mains, as concentrations of hydrogen sulfide gas within wastewater may be subsequently converted to sulfuric acid by bacteria in the slime layer on the pipe wall.  This may cause corrosion and eventual breakdown of the pipe’s exposed surface.

The SmartBall tool was chosen as an inspection platform for its sensitivity to small leaks and gas pockets and for its ability to inspect long distances in a single deployment. Minimal pipeline modifications are required for insertion and extraction.

SmartBall tool tracked at known points along the pipeline alignment

The free-swimming, acoustic-based SmartBall® tool is inserted into the pipeline flow, and after traversing the inspection length, the tool is captured and extracted at a point downstream.

During inspection, the SmartBall tool’s location is tracked at known points along the length of the pipeline to correlate the inspection data with specific locations. As the SmartBall tool approaches a leak, the acoustic signal will increase and crescendo at the point when the tool passes the leak.

Unlike traditional listening tools like correlators, which have limited success on large diameter pipes, the free-flowing SmartBall technology provides a high degree of accuracy, since as the ball rolls inside the pipe, it can inspect every inch of the main to detect leaks and gas pockets.

Prior to the execution of the project, Pure Technologies reviewed the site and all pipeline drawings. The only real inspection challenge was taking into account the limited number of SmartBall receiver tracking units, as some of the buried manholes were located on private farms.

Inspection results

The inspection went smoothly, and all data successfully collected. From insertion to extraction, the SmartBall inspection took under 5 hours, with no unexpected events thanks to cooperative planning and full support of the Brabantse Delta team.

Preliminary data indicated no leaks and zero (0) acoustic events associated with pockets of trapped gas. Entrained air was present throughout the pipeline, but no events of significance were detected. Entrained air is a migratory event, meaning its location is dynamic and changes over time with the operational flow. These events are expected to move throughout the pipeline, and locations are specific to the time of the inspection.

Overall, Brabantse Delta was pleased with the execution, and excited to know there was an inspection tool that gave them a better understanding on the overall condition of the AWP-1 pipeline. The project demonstrates how Brabantse Delta uses actionable data to effectively manage risk, while continuing to provide the community with a safe and reliable delivery of untreated wastewater.