STANLEY Inspection Completes a Full AUT Qualification to DNV-OS-F101
STANLEY Inspection recently completed a full AUT (Automated Ultrasonic Testing) qualification to DNV-OS-F101 and has received a compliance notification from Det Norske Veritas. DNV-OS-F101 is a comprehensive specification used in the construction of offshore pipelines and is the industry accepted methodology to verify AUT system and company performance. The DNV qualification starts with a review of the quality management system documentation, continues to specific inspection procedures, and concludes with measuring actual performance on welds with embedded defects. The qualification to DNV-OS-F101 ensures a consistent approach within the industry to qualifying AUT systems and validating AUT procedures.
The performance test is the most strenuous portion. Steps include:
- Purchase pipe
- Cut and bevel ends
- Measure ends and create alignment sheets
- Determine number welds and defects per weld (minimum of 122 required for program)
- Create welds (see additional information below regarding CRC welds)*
- Scan welds with AUT (scans done by two separate teams, each team scans forward and backwards - includes 2G and 5G tests along with temperature and offset band tests)
- Review weld scans and determine size and location of each defect
- Supplemental inspection with MUT (Manual Ultrasonic Testing) and Radiography
- Cut weld rings from main pipe
- IUT (Immersion Ultrasonic Testing) of weld rings
- Cross section analysis of individual defects to determine size
- Statistical analysis to determine POD (Probability of Detection)
All of the testing portions listed above have a DNV representative on-site for witnessing.
Over many similar qualification programs, CRC has developed and documented welding process techniques that allow very tight controls on seeded defects. These processes involve a variety of operations where the welding process is modified or halted, material is removed or modified, and the welding process continues. This enables the creation of very small – hard to detect defects. For this DNV qualification, 11 welds were created with the total number of intentionally created flaws exceeding 140.
IUT is an optional step in the process, but gathering the data proves that no defects were missed in the evaluation. Stanley Inspection completed this step as well.
A system is regarded qualified if it can be shown that the largest acceptable defect height has a Probability of Detection (PoD) of 90% at a 95% confidence level. Stanley Inspection easily met these requirements, and our certification allows us to pursue offshore work independently as well as with CRC-Evans Offshore.