Existing ultrasonic crack inspection services show acceptable detection and sizing accuracies for a variety of flaws. Nevertheless, there are still some crack types, e.g. embedded lack of fusion or hook cracks that are more difficult to address. The challenges are in terms of sizing, not detection for such flaws. Therefore, hydrostatic testing of pipelines is still an accepted methodology to detect critical flaws in a pipeline system. A release during this test removes a critical flaw from the system.
In 2014 Enbridge published a request for proposal to develop and provide a solution on a specific type of long seam cracks in a 26 inches pipeline. During the early phases of the project NDT Global analyzed in detail Enbridge's requirements, including the specific challenges, spool type, seam characteristics etc. and provided different proposals to Enbridge. In 2016 both parties signed a development contract to develop and build a 26" Next Generation Crack Detection Robot.
The project was separated in to different phases which can be summarized as:
1. Gap Analysis
2. Literature research & technology screening
3. Development of mechanic and electronic concepts
4. Prototyping and component testing
5. Development of entire robot, test and validation
6. API 1163 conform validation
7. Initial application in real pipeline with validation digs
The robot was utilized successfully. Processing, analysis and reporting was performed within pre-agreed time frames. Initial field findings show high correlation of ILI and real flaws and proof the stated accuracy of the new service.
The authors will present in detail some of the specific challenges of the pipeline system and limitations of available crack inspection technologies. Furthermore, solutions to address the shortcomings are presented including an in-depth comparison of ILI and destructive freeze breaks and cross sections.