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손상원인 규명을 통한 격리밸브 스템의 구조 신뢰성 향상
하각현(Gak-Hyeon Ha),박치용(Chi-Yong Park),정용찬(Yong-Chan Jung),유근배(Keun-Bae Yoo) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
This study is concerned to the root cause analysis of isolation valve stem, which was not functioned from power plant by valve failure after short normal operation. An improvement method of structural reliability was proposed through the root cause analysis about the failed stem of gate valve type. For carrying out the root cause analysis of failed components, material characteristics of as built metal was investigated, and failed metal was analysed metallurgically for understanding the chemical components. Heat treatment effect was investigated for verifying the sound material comparing with the required specification by heat treatment test. Also, investigation of failed surface suggested that stems were failed through crack initiation in non-metallic substitution due to stress concentration and crack propagation by bending fatigue load. This study has found that a critical failure cause was verified as non-heat treatment on martensitic stainless steel. Based on critical root cause of valve stem, structural reliability of valve may be improved in the power plant field.
원전기체이송계통에서의 샘플링 지점 및 입자통과율에 관한 연구
하각현(Gak-Hyeon Ha),이성노(Sung-No Lee) 한국유체기계학회 2008 유체기계 연구개발 발표회 논문집 Vol.2008 No.-
The revision of ANSI/HPS N13.l-1999 differs significantly from the ANSI/HPS N13.1-1969 in that it is now a performance-based standard rather than one based on prescriptive rules. There are two important aspects of performance addressed in the new approach. First, the concept of acquiring a representative sample is not based on rules for sample location and multi-point extraction, but rather on the premise that at any location where the contaminant concentration and fluid momentum can both be demonstrated to meet numerical criteria for acceptable mixing, a representative sample can be obtained by extraction from a single point in that profile. Second. numerical criteria are also used to provide the basis for a decision on whether a sampling system will deliver a representative sample to collector or detector. Essentially the concept of isokinetic sampling has been replaced by numerical criteria for the sampling performance of extraction nozzle and transport line designs.
하각현(Gak-Hyeon Ha),이성노(Sung-No Lee) 한국동력기계공학회 2007 한국동력기계공학회 학술대회 논문집 Vol.- No.-
The conventional control valves have been used at the locations occurring high differential pressure and high temperature which causes cavitation, flashing, severe vibration due to abrupt flow change, and sudden pressure drop. Previous studies concerning control valves focused to prevent damage of valve trim due to the internal leak and low flow rate. The newly designed helical trim of control valve has been installed at the location of high pressure change and high temperature in a power plant, and operated for evaluation. It is confirmed that the new control valve developed in this study generates flow characteristics in comparison with previous helical trim of control valves.
하각현(GAK-HYEON HA),정일석(ILL-SEOK JEONG),김상복(SANG-BOK KIM) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The revision of ANSI/HPS N13.1-1999 differs significantly from the ANSI/HPS N13.1-1969 in that it is now a performance-based standard rather than one based on prescriptive rules. There are two important aspects of performance addressed in the new approach. First, the concept of acquiring a representative sample is not based on rules for sample location and multi-point extraction, but rather on the premise that at any location where the contaminant concentration and fluid momentum can both be demonstrated to meet numerical criteria for acceptable mixing, a representative sample can be obtained by extraction from a single point in that profile. Second, numerical criteria are also used to provide the basis for a decision on whether a sampling system will deliver a representative sample to collector or detector. Essentially the concept of isokinetic sampling has been replaced by numerical criteria for the sampling performance of extraction nozzle and transport line designs.