外压作用对特殊螺纹接头内压密封性影响分析

对带金属密封结构的特殊螺纹接头来说,保证接头的密封可靠性是很重要的。根据井下管柱实际载荷工况,应用有限元方法研究了拉伸与内压载荷作用下的特殊螺纹接头同时受外压载荷时接触压力的变化,分析了此种工况下特殊螺纹接头的密封可靠性。分析结果表明,外压作用降低了特殊螺纹接头密封面接触压力。如果内、外螺纹的锥度、密封直径与螺纹中径的配合处于较差条件时,外压作用将导致特殊螺纹接头密封面上接触压力消失,使得密封面失去密封能力。研究结果表明,在评价特殊螺纹接头设计及工况适用性时,应考虑进行拉伸加内压加外压的复合载荷试验,增加评价结果的可靠性。

Analysis on the Effect of External Pressure Function on Internal Pressure Seal of Special Thread Connection

It is essential for the special thread connection with metal sealing structure to ensure the reliability of connection sealing.According to the actual loading condition of downhole pipe strings,finite element analysis method is applied to the research about the changes of contact pressure of special thread connections under the influence of stretching and internal pressure loading,as well as the effect of external pressure loading.Meanwhile,the sealing reliability of special thread connection under such working condition is analysed.The analysis shows that the effect of external pressure has reduced the contact pressure on the sealing surface of special thread connections.If there is poor condition in the match of internal and external thread dimensions,sealing diameter and thread middle diameter,external pressure function will result in the disappearance of contact pressure at the sealing surface of special thread connections,and will make the sealing surface lose sealability.Therefore,it is concluded from the above research that evaluation of design and fit-for-service of thread connections should take into account the combined load experiment of tension,internal and external pressure so as to increase the reliability of evaluation.