高压复合管线法兰连接设计及疲劳寿命分析

Flange Connection Design and Fatigue Life Analysis of High-Pressure Composite Pipeline

针对油田高压注水地面管线腐蚀严重问题,以干线大口径复合管线为研究对象,设计了法兰连接复合管线连接处的6种内衬结构。依据抗凹陷强度准则,确定了管线内衬厚度。基于流固耦合理论,建立了复合管线不同连接结构的流固耦合有限元仿真分析模型,研究了高压注水条件下复合管线的应力分布。利用中间计算点插值拟合的方法,结合脉动频率与假设函数形态,得到了停机水锤下内衬最大应力的变化规律,基于Walker疲劳寿命模型,对复合管线启停机安全性进行了评估。研究结果表明:超高分子量聚乙烯具有较高的抗内压强度和耐疲劳性,更适合作为高压注水管道内衬材料;168 mm复合管线内衬的优选厚度为5 mm,245 mm复合管线内衬的优选厚度为7 mm,且所得复合管线径厚比S计算式通用;内衬翻边处理、限位环定位锁紧是大口径复合管线的合理连接方式;设计了水锤频繁冲击下具有较长疲劳寿命的连接方案。研究结果可为干线大口径高压复合管线的连接设计及工程应用提供参考。

To solve the serious corrosion problem of high-pressure water injection surface pipeline in the oil field,taking the large-diameter composite pipeline of the main line as the study object,six kinds of lining structures at the joint of flange connected composite pipeline were designed.According to the anti-sag strength criterion,the thickness of pipeline lining was designed.Based on the fluid-solid coupling theory,the fluid-solid coupling finite element simulation analysis models of different connection structures of composite pipelines were established to study the stress distribution of composite pipelines under the condition of high-pressure water injection.By using the interpolation fitting method of intermediate calculation points,combined with pulsation frequency and assumed function shape,the change rule of the maximum stress of the lining under the action of shutdown water hammer was obtained.Based on Walker fatigue life model,the startup and shutdown safety of composite pipeline was evaluated.The results show that UHMWPE(Ultrahigh molecular weight polyethylene)has high internal pressure strength and fatigue resistance,and is more suitable for the lining material of high-pressure water injection pipeline.The preferred thickness for 168 mm composite pipeline liner is 5 mm,the preferred thickness for 245 mm composite pipeline liner is 7 mm,and the calculation formula for the diameter-thickness ratio of the composite pipeline is universal.Flanging treatment of lining and positioning and locking of limit ring are reasonable connection modes of large-diameter composite pipeline.The connection scheme with long fatigue life under frequent impact of water hammer was designed.The research results provide a reference for the connection design and engineering application of large-diameter high-pressure composite pipelines in the main line.