Exxon Kizomba Satellites Phase 2 Project
When CPE looked into NDE processes for volumetric examination of welds in 60mm thick 6Mo stainless, traditional radiography and UT techniques were not suitable. CPE therefore needed to find a process which could accurately find any defects.
Major advances in NDE technology have lead to new techniques such as Phased Array UT (Paut) and Time of Flight Diffraction UT. CPE worked with RSA and NDE experts, Lateral Wave to prefect the process to the exact conditions.
In order to prove the process, CPE produced a representative weld with similar materials and dimensions, but with intentional defects at set locations. Defects included lack of side wall fusion, cracks, undercut and planar defects. The test piece was then examined with the new NDE techniques to verify that such defects would be clearly identified. The test piece was used to calibrate the UT processes.
The NDE process took several days to complete. As expected, defects were found in the test piece but no defects were found in any of the 16 vessels.
The vessels produced were for the Exxon Kizomba Satellites Phase 2 Project in Angola. They were manufactured from 6Mo stainless UNS31254 for a design pressure of 725 Bar G and tested at 1037 Bar G. The inspector representing Exxon was very complimentary regarding the standard of welding on these vessels.