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발전소 및 화학플랜트용 고압 글로브밸브의 신뢰성 향상에 관한 연구
김지은(Jieun Kim),김정석(Jungseok Kim),임국주(Gukjoo Im),김종찬(Jongchan Kim),이진영(Jinyoung Lee),최준영(Junyoung Choi) 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6
Reliability standards for high-pressure globe valves for domestic power and chemical plants are currently not actualized. Therefore, it is necessary to secure the reliability of high-pressure valves for domestic plants in order to keep requirement with the international market. However, there are some problems to ensure reliability. First, the cause of the failure should be identified when using the existing valve. It is difficult to identify the cause of the failure because the database has not been established in the domestic market. Second, the reason for the lack of reliability evaluation devices and methods for each product has not been established. Therefore, this study has focused to solve these problems. The failure database in the field was analyzed to identify the failure status and cause. FMEA was conducted based on the analyzed data. It was found that the main cause of the failure was pressure and repeated operation. Accelerated life test method was developed based on actual conditions to ensure reliability of these causes. The Inverse power model for the various accelerated life test models was applied. In order to ensure 500,000 cycles of repeated operation at 180 bar pressure condi tions as actual conditions accelerated life test was conducted as repeated 40,000 cycles at 270 bar pressure. We found that there was no leakage and failure. For this purpose, a jig for repeated test was fabricated and a pressure sensor was attached to the front of each valve, and a monitoring system was installed to confirm the data. As a result of the test, it was sure to guarantee reliability by operating without leakage and failure until the end of 40,000 cycles. This study is based on a database of actual field failures and can be used to develop a reliability assurance test method.
복합재 대차프레임의 볼트 체결부 내구성 향상을 위한 인서트 영향에 관한 연구
김준환(JunHwan Kim),신광복(KwangBok Shin),김정석(JungSeok Kim) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.7
본 논문에서는 복합재 대차프레임 볼트 체결부의 내구성 향상 방안에 대한 연구를 다루고 있다. 이를 위해, 인서트와 나사산 유무에 따른 3가지 경우를 고려하여 볼트 체결부에 대한 시험 및 해석을 통해 인서트 형태 및 유무에 미치는 영향을 평가하였다. 제안된 볼트 체결부의 구조 성능은 ASTM D5961에 의거한 시험을 통해 비교 평가하였다. 시험결과, 나사산이 없는 인서트를 갖는 볼트 체결부가 가장 적합한 것으로 확인되었다. 또한, 볼트 체결부를 고려한 복합재 대차프레임에 대한 구조 안전성 평가를 JIS E 4207에 의거하여 유한요소해석을 통해 평가하였다. 복합재 구조물은 Tsai-Wu 파손기준식에 의해 파손평가를 적용하였고, 볼트 체결부와 같은 금속재 구조물은 Von-Mises 파손기준식에 의해 평가하였다. 이때, 볼트 체결부의 경우에는 상세한 구조해석 결과 검토를 위해 서브모델링 기법을 적용하였다. 구조해석결과, 나사산이 없는 인서트가 적용된 볼트 체결부의 경우에는 볼트 체결부 주위의 복합재 구조물에 발생하는 Tsai-Wu 파손지수가 다른 경우에 비해 약 50% 감소하는 경향을 보였는데, 이는 나사선이 없는 인서트 형상이 복합재 대차프레임 볼트 체결부의 내구성을 향상시킬 수 있을 것으로 판단된다. This paper describes the study on a method for improving the structural durability of bolted joints applied to a composite bogie frame. In this study, three bolted joints with and without inserts and screw threads were selected for determining the effect of the inserts, using experiment and analysis. The structural performances of the proposed bolted joints were compared and evaluated using the test method prescribed by the ASTM D5961 standard. The results revealed that the bolted joint having an insert shape without the screw thread offered improved durability for application to a composite bogie frame. Furthermore, the structural integrity of the frame comprising the bolted joints was evaluated using finite element analysis according to the JIS E 4207 standard. The Tasi-Wu and Von-Mises failure criteria were used for determining the failure of the composite structure and bolted joints, respectively. A sub-modeling technique was introduced for investigating the performance of the bolted joints in greater detail. The analysis results demonstrated that the Tasi-Wu failure index of the composite structure near the bolted joints was reduced by approximately one-half after applying an insert without the screw thread. This implies that the structural durability of the bolted joints of a composite bogie frame could be improved by using a metal insert without the screw thread.