【作者】 胡雄；

【导师】 何家胜；

【作者基本信息】 武汉工程大学 ， 化工过程机械， 2017， 硕士

【摘要】 法兰连接系统是一种结构简单、可靠性好的可拆卸密封结构,广泛应用于石油化工、航空航天及核能等工业领域。化工石油部统计数据指出压力容器和管道各类失效中法兰连接密封泄露占比达到48%,化工设备的介质具有高温高压和易燃易爆的特性,一旦发生泄露失效的安全事故,造成的损失将无法估量。合适的螺栓载荷及垫片压紧力是保证法兰连接密封的关键因素。法兰连接传统设计方法中推荐的垫片比压力y和垫片系数m自1943年提出之后未进行有效的试验验证及数据更新,在法兰连接实际工程安装中存在着无法精确施加螺栓预紧力的技术难题。本文以PN25/DN300带颈对焊管法兰连接为例建立了螺栓载荷及垫片压紧力检测试验装置,利用指针式扭矩扳手预紧及手动试压泵加压分别模拟了法兰连接的预紧和操作工况,实现了不同工况条件下对螺栓载荷及垫片压紧力的实时检测,得到了预紧扭矩与螺栓载荷及垫片比压力的对应关系,验证了传统法兰连接设计方法密封效果的可靠性,进而对垫片密封比压力y和垫片系数m的有效性进行了考查和讨论。以试验装置中的螺栓、法兰及垫片整体作为研究对象,考虑了各元件的非线性接触关系,使用实体单元、预紧单元和接触单元进行了有限元分析计算,实现了对法兰连接系统的预紧过程和操作过程的数值模拟,得到了不同工况条件载荷步下螺栓、法兰及垫片各节点的数值解,包括各元件应力应变云图、位移云图及接触压力云图等。通过有限元数值模拟还得到了预紧螺栓载荷与垫片接触压力的对应关系,测试结果与有限元分析结果有较好的一致性。基于螺栓载荷及垫片压紧力测试及有限元数值模拟,引入了无线测量技术的应用,验证了无线应变测量的可靠性和准确性,实现了对螺栓载荷及垫片压紧力的无线测量;探讨了法兰连接端面摩擦力对预紧扭矩传递的影响,发现利用端面轴承减小摩擦可以很好的减少能量的消耗并增加扭矩的传递作用,促使螺栓轴向载荷增加约150%;探讨了不均匀螺栓载荷对垫片接触压力的影响,得到了不同工况下垫片接触压力的分布规律,发现当一根螺栓发生断裂或未预紧的情况时,垫片密封接触面局部发生分离即发生泄漏失效。本文的测试试验及有限元分析研究为传统法兰连接的设计提供可靠的数据依据,对工程实际螺栓的预紧安装具有现实的指导意义,是保障法兰连接密封可靠性及化工设备长周期安全运行研究的重要组成部分。更多还原

【Abstract】 Flange connection system is a simple and reliable sealing structure,which can be widely used in petrochemical,aerospace and nuclear industries.Statistical data of petroleum and chemical industry department pointed out that the pressure vessel and pipe failure in the flange connection seal leakage accounted for 48%.The medium of chemical equipment has the characteristics of high temperature,high pressure,inflammable and explosive.Once the leakage accident occurs,the loss will not be estimated.The appropriate bolt load and gasket contact stress is the key factor to ensure the sealing of flange connection.Gasket specific pressure y and gasket coefficient m which recommended in the traditional flange connection design method has not been validated and updated since 1943.In the actual engineering installation of flange connection,there are some technical problems that pretightening force can not be accurately applied to the bolt.In this paper,the test device of the bolt load and the gasket contact stress is established by taking the PN25/DN300 flange joint with the neck as an example.The preload and operating conditions of the flange connection are simulated by the use of a pointer type torque wrench and a manual pressure test pump.Real-time detection of bolt load and gasket contact stress under different working conditions is realized.The correspondence between the tightening torque and the bolt load and the specific pressure of the gasket is obtained.The reliability of the sealing effect of the traditional flange connection design method is verified,and the effectiveness of gasket specific pressure y and gasket coefficient m is examined and discussed.Taking the bolt,flange and gasket as the research object and the nonlinear contact relation of each element is considered.The finite element analysis is carried out by using the solid element,the pre-tightening element and the contact element,and the numerical simulation of the preloading process and the operation process of the flange connection system is realized.The numerical solutions of the bolt,flange and gasket under different loading conditions are obtained,including the stress and strain nephogram,displacement nephogram and contact pressure nephogram.The corresponding relationship between the bolt pre-tightening load and the contact pressure is obtained by the finite element numerical simulation,and the test results are in good agreement with the finite element analysis results.Based on bolt load and gasket contact stress test and finite element numerical simulation,the application of wireless measurement technology is introduced to verify the reliability and accuracy of wireless strain measurement,and the wireless measurement of bolt load and gasket contact stress is realized.The influence of the friction force of the flange on the preload torque transmission is discussed.It is found that the use of end bearing to reduce friction can be a good way to reduce energy consumption and increase the torque transmission,and it causes the bolt axial load to increase by nearly 150%.The effect of uneven bolt load on the contact pressure of the gasket is discussed.The distribution of the contact pressure of the gasket under different working conditions is obtained.It is found that when a bolt is broken or not pre tightened,the sealing contact surface of the gasket is partially separated and the leakage failure occurs.The test and finite element analysis in this paper provide reliable data basis for the design of the traditional flange connection,and it has practical significance to the actual installation of bolt.更多还原