| The Liquid Medium Stop Ball Valve，which has been widely used, is one of theValve using ball as the shut component which have the advantage of fast action, good sealability, long duration, high stability. Certain progress has been made in Liquid MediumStop Ball Valve representative of Stop Ball Valve in industry, the reliability in lowtemperature is still the key problem.The material for sealing parts is versatile depends on the variety of the environmentand medium, which caused the difficulty in testing process of simulating the real usingstatus. This article parse the problem in the design and usage of the Valve, using theleaking accident as the top event，combined with malfunction in low temperature condition,analysis the different reasons for the leaking accident and confirmed that the main cause ofthe leading is the bottom event which contains the character of cold flow and theimproper ratio of sealing pressure in design. The improvements in design and protectivemeasure have been brought after the theory analysis and practical verification. Theimprovement goals and design proposal have been set by theory analysis and compare.It adopts the Finite Element simulating Analysis to process the complex boundaryconditions, the possible fatigue and damage have been analysed by simulating the pressure,temperature, moment, and numeric, calculating the thermal boundary and numericalconditions. The Finite Element orient computing model has been established by simplifythe3D model of the ball valve and grid division in which the core of valve, guide pillarand sealing cap have been redivided relatively dense process. The simulating calculationhas been made for turn on and off working status in different thermal boundary and thenumerical conditions. After the detailed data analysis in date of stress and deformationwith the confined boundary, the max stress and deformation have been derived in differentworking conditions, and the numerical requirement and thermal range have been obtained.The improvement in Liquid Medium Stop Ball Valve design have been made basedon the result of simulating and analysis, in which the redundancy design in sealing andcomposition part in disc spring have been added. The design parameter have been setbased on the analysis in valve body, core of valve, disc spring, sealing cap and sealscomponents. The data of strength grade, operating force, shearing force, pulling-out force,impact resistance capability and reliable testing times for the joints of the ball Valve havebeen calculated based on the empirical formula, which is the foundation for theSubsequent experiment. Concerned with the deformation problem caused by thermalcomplex, the variation tendency in volumn have been decided by calculation the gap widthin different parts and the volumn variation. The key index in valve design for sealingpressure, sealing parameter and moment of force have been obtained with selected suitable parameter and material.The experiments have been made combined the theory calculation and the practicalworking in Liquid Medium Stop Ball Valve to testify the design parameter andcomputation pattern, which include the High-temperature sealing detection, lowtemperature storage test, vibration test, Ground temperature cycle test, High and lowtemperature cycle test, alternating damp heat test, different medium heat cycle test and Xray detection. The integration performance test for different testing item combined with theproper boundary condition and predefined condition have been carried out. The results ofthe test meeting design requirement, indicated that the design is in correspondence with thetheory analysis and simulating results. The experiment result and the theory analysistestified each other especially in the testing of leakage and the working status of discspring. |
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