Failure Analysis and Reliability Assessment of the Spring-Loaded Safety Valves
金 大 仁
|關鍵字:||失效分析;可靠度;安全閥;Failure Analysis;Reliability;Safety Valve|
Generally speaking, high-pressure fluid is commonly and frequently employed in industrial systems, chemical equipment, boilers, pressure vessels and pipes. As a result that the anti-pressure design of the pressurization equipment still has its limitation, it is necessary to take prevention from over-pressurized accidents. The Spring-loaded Safety Valve (SLSV) is one of the indispensable devices, which is installed in pressure equipment to prevent from over fluid pressurization. Although SLSV relieves high fluid pressure as well as helps to exhaust and pop action, instead of being static, the operational factors, such as temperature, pressure, and load vary with environmental stress and frequency of movement. Moreover, affected by the nature of fluid and environmental stress, SLSV often comes into being fatigable, corroded, and exhausted, or it may even cause structural degradation and functional degenerate if it is continually used over a long period of time. Hence, it is difficult to precisely predict the safety of SLSV due to its fortuity, randomness or variability. SLSV is not allowed to fail since it plays one of the key roles to prevent high-pressure accidents. Therefore, the functions and reliabilities of the SLSV should be seriously concerned. The purpose of the study is to explore SLSV by discussing its failure analysis and reliability assessment. To study the function, structure and operational condition of SLSV, the characteristic variables and failure mechanism will be analyzed and the environmental stress and the cause-effect relationship of failure phenomena will be explored. In additions, those failure phenomena in respect of fatigue, corrosion, exhaustibility will be investigated from the perspectives of Physics and Chemistry. In this study, the reliability index (β-Method) based on Strength-Stress Interference Model will be used to predict and evaluate reliability quantitatively to meet safety demands. The simulation method will be applied to distinguish fatigue deterioration during operating processes. Failure Modes and Effects Analysis (FMEA) technique will be used to understand the failure model and effect of different parts of SLSV, which may shed a light for practical application or further researches.
|Appears in Collections:||Thesis|