In this study, non-destructive technologies that can be applied to evaluate the integrity of valve materials, safety against internal pressure caused by corrosion, and the blocking function of large-diameter water valves during operation without requiring specimen collection or manpower entering the inside of the valve were tested to assess the reliability of the technologies and their suitability for field application. The results showed that the condition of the graphite structure inside the valve body can be evaluated directly through the optical microscope in the field without specimen collection for large-diameter water butterfly valves, and the depth of corrosion inside the valve body can be determined by array ultrasound and the tensile strength can be measured by instrumented indentation test. The reliability of each of these non-destructive techniques is high, and they can be widely used to evaluate the condition of steel or cast iron pipes that are significantly smaller in thickness than valves. Evaluation of blocking function of the valves with mixed gas showed that it can be detected even when a very low flow rate of mixed gas passes through the disk along with the water flow. Finally, as a result of evaluating the field applicability of non-destructive technologies for three old butterfly valves installed in the US industrial water pipeline, it was found that it is possible to check the material and determine the suitability of large-diameter water valves without taking samples, and to determine the corrosion state and mechanical strength. In addition, it was possible to evaluate safety through the measurement results, and it is judged that the evaluation of the blocking function using mixed gas will help strengthen preventive response in the event of an accident.

1. 서 론
2. 연구방법
    2.1 안전성 평가
    2.2 차수기능 평가
    2.3 현장적용 대상 구간
3. 연구결과
    3.1 안전성 평가 결과
    3.2 차수기능 평가 결과
    3.3 현장 적용성 평가 결과
4. 결 론

• 이호민(한국수자원공사 K-water연구원) | Ho-Min Lee (K-water Research Institute, Korea Water Resources Corporation)
• 최현용(한국수자원공사 울산권지사) | Hyun-yong Choi (K-water Ulsan Local office, Korea Water Resources Corporation)
• 박수완(부산대학교 사회환경시스템공학과) | Suwan Park (Department of Civil & Environment Engineering, Pusan National University)
• 오태민(부산대학교 사회환경시스템공학과) | Tae-min Oh (Department of Civil & Environment Engineering, Pusan National University)
• 김채민(한국수자원공사 K-water연구원) | Chae-Min Kim (K-water Research Institute, Korea Water Resources Corporation)
• 배철호(한국수자원공사 K-water연구원) | Cheol-Ho Bae (K-water Research Institute, Korea Water Resources Corporation) Corresponding author