)
44-in. HDPE – Submarine Tailings Disposal (STD) Pipeline
Dexon Technology inspected a 44-in. HDPE submarine tailings disposal (STD) pipeline in Southeast Asia, with the line terminating at depths greater than 100 meters. Engineers designed a floatable tool, allowing recovery upon the completion of the inspection. Dexon has collaborated with this partner for 20 consecutive years.
Overview
Key challenge:
Inspect a 44-in. HDPE tailings pipeline that emptied out into the ocean, overcoming ultrasonic signal attenuation from material and ensuring reliable tool recovery offshore without a receiver.
Project Details
• Length: 3 km
• Diameter: 44-in.
• Type: HDPE submarine tailings disposal (STD) pipeline
• Inspection Medium: Water
• Threats Assessed: Erosion, gouging, & wall loss
• Location: Offshore (>100 m)
• Continent: Asia
• Tenology: UT-R Owl
)
A cut-out of an HDPE pipeline with sever erosion at the 6 o’clock position.
Challenges & Solutions
Challenge 1:
• Pipeline had no subsea receiver, creating major tool recovery challenges offshore
• Ocean currents and unpredictable surfacing behavior increased recovery uncertainty
Solution:
• Designed the inspection tool with positive buoyancy to allow retrieval at the ocean surface
• Conducted extensive pre-inspection buoyancy testing in controlled conditions prior to deployment
• Validated flotation and recovery behavior using large-scale tank testing at Dexon facilities
• Integrated GPS tracking equipment into the tool for accurate offshore tracking and recovery
• Positioned a support vessel onsite to recover the tool after surfacing
)
Dexon inspector alongside the UT-R Owls after recovery.
Challenge 2:
• High attenuation of ultrasonic signals in HDPE reduced inspection effectiveness
Solution:
• Developed proprietary ultrasonic transducer optimized for HDPE materials, enabling reliable ultrasonic inspection through HDPE wall thicknesses up to 100 mm
• Thoroughly tested design at Dexon’s 7-acre test yard with pull-through testing prior to deployment
Challenge 3:
• Operator required data repeatability and consistency across multiple tools for multiple runs over multiple years
Solution:
• Performed three separate inspection runs using three different tools under identical operating conditions to prove performance in real-world conditions
• Verified consistency and reliability of defect detection performance across multiple datasets
)
Image of internal HDPE pipeline during trial run.
)
3D visualization of the internal HDPE pipeline, confirming erosion in above photograph.
Conclusion
Dexon Technology successfully completed the inspection of the 44-in. HDPE submarine tailings disposal pipeline while overcoming complex offshore recovery and material challenges.
Through customized ultrasonic technology, offshore recovery engineering, and repeatability validation testing, Dexon delivered reliable integrity data for one of the region’s most challenging HDPE pipeline inspection applications—with the client returning to Dexon for over 20 years.