Introduction:

Dexon Technology's pipeline inspection department recently completed the inspection of a 44” gold tailing line in Southeast Asia. The endeavour marked the 18th consecutive year of collaboration between Dexon and a longstanding client in the region. The inspection presented a unique set of challenges due to the pipeline material composition and susceptibility to erosion. Mine tailings are a byproduct of the mining process and consist of ground rock present after the extraction of materials from ore. A common method of tailing storage is submarine tailings disposal or STD. The 3 km+ HDPE STD line under inspection, terminating at a depth of over 100m, demanded careful attention, particularly at the 6 o'clock orientation, where debris-induced erosion and gouging were identified as potential risks.

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The Challenge:

Receiver Absence on Sea Floor: The absence of a receiver on the sea floor, essential for dispersing tailings, presented a challenge in recovering inspection tools.
Tool Tracking Complications: Ocean currents, tool trajectory complexities, and unpredictable tool behaviour upon surfacing posed risks to tool recovery.
High Attenuation of UT Signal in HDPE: The inherent high attenuation of ultrasonic (UT) signals in High-Density Polyethylene (HDPE) reduced the effectiveness of the inspection. Attenuation refers to the reduction in signal strength as sound waves travel through a medium, impacting the collection of Time-of-Flight Diffraction (TOFD) UT data in Non-Destructive Testing (NDT).
Assessment of Data Repeatability: As part of Dexon’s ongoing Operational Excellence and Innovation Program a study was performed to assess the accuracy and repeatability of inspection data over multiple tools under the same inspection conditions. Dexon’s Operational Excellence and Innovation Program covers the continual assessment and development of inspection technology to meet future inspection requirements. Including tool design and fabrication and assessment of tool detection capabilities.

The Solution:

Tool Recovery Measures: To ensure tool recovery, the inspection tool was designed to be positively buoyant, facilitating retrieval by a support vessel waiting on the ocean surface. GPS tracking equipment was integrated into the tool design to assist in precise post-inspection tool tracking.
Pre-inspection Buoyancy Testing: Rigorous buoyancy testing was conducted on land prior to the inspection, ensuring the tool's capacity to float adequately. The tools were placed in a large tank while buoyancy was carefully measured to assess performance capabilities.
Overcoming High Attenuation of Ultrasound in HDPE: Dexon Technology's onsite Research and Development (R&D) facility plays a pivotal role in advancing technological inspection solutions. Understanding the intrinsic properties of ultrasound in HDPE, Dexon's R&D team was responsible for the development of proprietary ultrasonic (UT) transducers tailored to address these specific challenges. Achieving accurate inspection capabilities in HDPE of up to 100mm in wall thickness.
Triple Inspection, Data Repeatability Assessment: Recognizing the importance of the ongoing assessment of tool detection capabilities. The inspection was run three times with three different tools under the same conditions as part of a study performed under Dexon’s Operational Excellence and Innovation Program.

Assessing Data Repeatability:

Definition: Data repeatability refers to the ability to obtain consistent results when the same experiment or measurement is conducted multiple times under the same conditions by the same person or using the same equipment.
Key Points:

It focuses on the precision and consistency of measurements within the same experimental setup.
The goal is to assess the variation in results when the same procedure is repeated under identical conditions.

Dexon possesses more than 20 years of challenging or “unpiggable” pipeline inspection experience. Onsite R&D and pipeline inspection test yard facilities at Dexon’s headquarters allow for the customized design, fabrication and testing of ILI equipment before each inspection.

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