Digital Radiography Transition for Inspection of Welds and Castings
Project Participants: Newport News Shipbuilding
Project Start: November 2010
The current film-based radiographic inspection process uses expensive, non-reusable film and chemicals that contain materials (silver) that are potentially hazardous to the environment and wastes thousands of gallons of water every year. This film-based inspection process is also very cycle-time intensive, requiring manual handling of materials throughout the entire process. A previous Northrop Grumman Shipbuilding-Newport News (NGSB-NN) project successfully used commercially available computed radiography (CR) equipment to extend current technology and develop processes and standards to replace the film-based process in critical naval applications. NGSB-NN identified and acquired state-of-the-art CR capabilities, knowledge and supporting technical resources that are being tested in a practical shipyard environment to assess overall potential benefit.
This project will continue that effort by ascertaining inspection confidence with isotopes and high energy applications in addition to resolving technical and implementation issues leading to full implementation. It will define tasks for acquiring NAVSEA authorizations for further CR usage, plans to revise ASTM standards, a plan to liaison with CR equipment suppliers and users in an effort to improve the technology, and a plan to concurrently inspect and document results of approximately 300 production weld locations with low energy X-ray, Selenium-75 and Iridium-192 isotopes. It also includes a plan to evaluate, devise and document meaningful techniques with high energy X-ray used for CR inspections of variable thickness heavy wall castings. Pending development of successful high energy CR techniques for casting inspections, a future offering is planned for longer term concurrent film/CR evaluations and development of digital reference acceptance images via ASTM.
NGSB-NN will execute this project in two phases. Phase 1 will focus on eliminating or greatly reducing gray scale streaking artifacts while evaluating new technologies and acquiring Navy satisfaction with technical inspection processes and authorization of CR standards. Phase 2 will resolve any remaining issues with gray scale streaking artifacts and ensure that CR technical image quality is considered equivalent with class I and II film systems. It is estimated that this project will result in a cost savings of approximately $4.5M per CVN.