Diversity in intelligent pigging solutions: Dacon

There is a constant thirst for new technology amongst our clientele, and we are constantly being asked to produce solutions for unpiggable pipelines, internally lined pipelines, and non-metallic pipelines,” says a Dacon spokesperson.

One such request came from PT Newmont Nusa Tenggara (PT NNT), the Indonesian subsidiary of mining giant Newmont.

“The company had been given permission to offload its treated tailings to a deep sea trench approximately 3.5 km offshore, but as the tailings pipeline would traverse protected fisheries, the Indonesian Government insisted they use non-metallic pipelines to reduce the operation’s environmental impact,” explains the Dacon spokesperson.

PT NNT opted to use with high-density polyethylene (HDPE) pipelines, but this meant there would be a high erosion rate from the abrasive tailings mixed with water. The Government stated that PT NNT should inspect these lines on a regular basis, and that once they reached a minimum threshold, they must be replaced. This directive prompted PT NNT to approach Dacon to develop a system capable of inspecting these pipelines.

“There were many challenges in developing such a system,” says the Dacon spokesperson. “Firstly the pipelines were 1,219 mm in diameter, with a nominal wall thickness of 110 mm. High density polyethylene (HDPE) has a very high attenuation of ultrasonic signals, and it is very hard to get a signal from the outside diameter of a normal thickness HDPE pipe, so this wall thickness was on the boundaries of possibility.

“Dacon developed a highly sensitive, low frequency system, which experienced less signal attenuation and was able to get reliable signals from the outside diameter of the pipe. Specialist software was also developed to apply complex algorithms to the data, to be able to visualise the erosion in the pipe, and give accurate remaining thickness measurements.”

HDPE pipelines fall outside of the normal codes and standards such as ASME B31.4 and B31G, but these standards were applied to calculate wear rates and remaining life of each pipeline, allowing PT NNT to accurately estimate when they would need a new pipeline.

“Each pipeline lasts generally between 1-2 years depending on the ore and production output,” says the Dacon spokesperson. “Working with Dacon, PT NNT was able to establish a system of when to install reserve lines, when to plan the next inspection, and when they must remove a line, seamlessly switching to a strategically installed reserve line to avoid interrupting production.”

The next challenge was that the pipeline is open to the sea at the end, with the exit of the pipe approximately 130 m below the surface. A system had to be devised to safely retrieve the pigs, so Dacon added pressure resistant buoyancy foam to the external bodies of the tools to allow them to float to the surface and be retrieved by a support vessel and divers.

The system has now been developed for smaller diameter HDPE pipe, and HDPE internally lined steel pipe where both the liner and the steel can be measured using advanced algorithms and analysis tools.

“All data is downloaded immediately and scanned for major defects, and a site report can be issued within a few hours highlighting any major anomalies in the pipeline, although full analysis takes longer and can normally be completed within two weeks of demobilisation,” says the Dacon spokesperson.

Whilst diversifying into HDPE inspections, Dacon also maintains its focus on the core steel pipeline business. Advances in technology, reliability, and resolution have seen Dacon become a trusted partner of some of the world’s largest pipeline operators.

For more information visit www.dacon-inspection.com

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