分输减压阀温降与振动规律及其安全可靠性研究

发布时间：2018-05-12 03:14

本文选题：RMG530减压阀 + 节流温降　；参考：《中国石油大学(华东)》2015年硕士论文

【摘要】：RMG530减压阀是长输天然气分输站场的大型关键调压设备,天然气分输过程中由于节流效应造成减压阀处温度骤降,高压低温环境下,天然气水合物容易在阀内析出造成冰堵,同时冰块冲击阀体引起减压阀剧烈振动,振动易引起阀体疲劳失效。课题针对天然气分输过程中存在的节流温降、冰堵和振动等问题,结合秦皇岛天然气分输站的实际运行工况,利用有限元分析软件,建立RMG530减压阀阀内流体有限元模型,模拟不同工况环境下天然气的分输节流过程,分析天然气流速、压力与温度变化规律,比较入口压力、节流压降和环境温度等因素对减压阀节流温降过程的影响,并利用分输站场节流温降测试数据验证模拟结果的正确性;为分析低温下阀体材料的力学性能,以热轧与调质状态下天然气分输减压阀体用1.6220铸钢为研究对象,采用低温拉伸以及系列冲击试验方法对其力学性能随温度的变化规律进行了研究,观察不同温度下冲击试样断面的形貌,获得材料的韧脆转变温度;为分析RMG530减压阀静载作用下安全可靠性,考虑电缆加热对节流温降和阀体热应力的影响,分别进行了天然气流场分析,阀体有限元静力及热应力分析。基于计算分析结果,得出了阀内流场及热应力分布规律,分析阀体结构薄弱部位的安全性能。模拟冬季与夏季不同工况下减压阀的启停过程,获得阀体结构在运行过程中应力与变形情况,分析脉动循环应力对减压阀疲劳破坏的影响,依据修正获得的减压阀材料S-N曲线,计算减压阀静态疲劳寿命,并运用Weibull-Bayes方法对工况条件下分输减压阀的安全可靠性进行评估分析;最后,为了评估随机振动载荷下减压阀的安全可靠性,根据现场测得的随机振动载荷对减压阀进行振动响应分析,获得响应功率谱密度,最后依据修正获得的减压阀材料S-N曲线,应用有限元疲劳分析软件NCode,通过时域和频域方法对减压阀进行了随机振动疲劳分析,计算阀体关键部位的疲劳寿命。结果表明:节流分输过程阀内天然气流动复杂,呈强湍流特性;阀笼节流孔内流速激增,但压力、温度骤降,水合物析出在节流孔内完成;环境温度、入口压力和节流压降是影响节流温降过程的主要因素,考虑各因素建立的分输过程析出液态水合物判断公式能够准确预判调压阀冰堵的发生;现场实际注醇量与给出的计算注醇量吻合,采用给出的计算公式计算注醇量能够有效的防治分输站场冰堵;随着温度的降低,1.6220铸钢的屈服强度和抗拉强度显著提高,断面伸缩率和伸长率逐渐下降;调质处理明显改善材料的低温力学性能,调质状态材料的韧脆转变温度为-14.46℃,热轧状态材料的韧脆转变温度为2.76℃。减压阀结构设计较保守,天然气分输过程中阀体应力、位移响应幅值不大,不会引起共振。减压阀结构设计比较保守,振动载荷下最小寿命发生在进口管段到阀座的拐角处,时域疲劳计算最小寿命为41.79年,频域疲劳计算最小寿命为38.81年。本文的振动疲劳计算结果可为分输站场甲醇自控系统的开发和阀体结构的安全可靠性评估提供依据。
[Abstract]:RMG530 pressure relief valve is a large key pressure regulating equipment for long distance gas transmission station. Due to throttle effect in natural gas separation process, the temperature of the pressure relief valve is suddenly reduced. Under high pressure and low temperature environment, gas hydrate is easily precipitated in the valve and causes ice plugging. At the same time, the ice rock impact valve leads the pressure relief valve to vibrate, and the vibration easily causes the fatigue of the valve body. In view of the problems of throttle temperature drop, ice blocking and vibration in natural gas separation process, combined with the actual operating conditions of Qinhuangdao natural gas transmission station, the finite element model of the fluid in the RMG530 pressure relief valve is established by the finite element analysis software, and the natural gas flow and throttle process under different conditions are simulated and the natural gas flow is analyzed. The influence of the inlet pressure, the throttle pressure drop and the ambient temperature on the throttle temperature drop process of the pressure relief valve is compared, and the correctness of the simulation results is verified by the test data of the throttle temperature drop of the transmission station, and the mechanical energy of the body material under the low temperature is analyzed and the gas transmission and decompression under the hot rolling and tempering condition is analyzed. 1.6220 cast steel for valve body is used as the research object. The change law of mechanical properties with temperature is studied by low temperature tensile and series of impact tests. The morphology of the impact specimen section at different temperatures is observed and the toughening and brittle transition temperature of the material is obtained. To analyze the safety and reliability of the RMG530 pressure relief valve under static loading, the cable heating is considered. The natural gas flow field analysis, the finite element static and thermal stress analysis of the valve body are carried out on the influence of the throttle temperature drop and the thermal stress of the valve body respectively. Based on the calculation and analysis results, the flow field and the distribution of thermal stress in the valve are obtained, and the safety performance of the weak part of the valve body is analyzed. In order to obtain the stress and deformation of the body structure during the operation, the effect of the pulsating cycle stress on the fatigue failure of the pressure relief valve was analyzed. The static fatigue life of the pressure relief valve was calculated according to the modified S-N curve of the pressure relief valve material, and the safety and reliability of the pressure relief valve under operating conditions was evaluated and analyzed with the Weibull-Bayes method. In order to evaluate the safety and reliability of the pressure relief valve under random vibration load, the response analysis of the pressure relief valve is carried out according to the random vibration load measured in the field. The response power spectrum density is obtained. Finally, the finite element fatigue analysis software NCode is applied to the relief valve material S-N curve obtained. The pressure relief valve is used in time domain and frequency domain method. The fatigue life of the key parts of the valve body is calculated by the random vibration fatigue analysis. The results show that the flow of natural gas in the throttle valve is complicated and has strong turbulent characteristics; the flow velocity in the throttle hole of the valve cage increases sharply, but the pressure, the temperature drop suddenly, the hydrate precipitates in the throttle hole, and the ambient temperature, inlet pressure and throttle pressure drop are the influence throttle. The main factors of the temperature drop process, considering the separation process established by each factor, can accurately predict the ice plugging of the pressure regulating valve; the actual amount of alcohol injection in the field coincides with the calculated amount of alcohol given, and the calculated formula can effectively prevent and control the ice plugging in the transmission station. The yield strength and tensile strength of 1.6220 cast steel increased significantly, the expansion ratio and elongation of the section gradually decreased, and the tempering treatment obviously improved the mechanical properties of the material at low temperature. The toughening and brittle transition temperature of the material was -14.46 C, the ductile and brittle transition temperature of the hot rolled state material was 2.76 C. The structural design of the pressure relief valve was more conservative, and the natural gas was lost. The displacement response amplitude of the valve body is small, and the resonance is not caused. The structural design of the pressure relief valve is conservative. The minimum life of the vibration load occurs at the corner of the inlet pipe to the seat. The minimum life time of the fatigue calculation in the time domain is 41.79 years and the minimum life of the frequency domain fatigue calculation is 38.81 years. The results of the vibration fatigue calculation in this paper can be the transmission station. The basis is provided for the development of the field methanol automatic control system and the safety and reliability evaluation of the valve body structure.

【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE974

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