某输油管线耐高温聚烯烃内衬塌陷原因分析

Collapse Analysis of the High Temperature Resistant Polyolefin Lining of Oil Pipeline

某输油管线用耐高温聚烯烃内衬服役3个月后出现局部塌陷变形,通过对塌陷变形后的内衬进行拉伸性能与维卡软化温度测试,结果表明塌陷变形后内衬的拉伸强度(19.4 MPa)、屈服强度(18.9 MPa)与维卡软化温度(122.2℃,A50法)均符合技术要求。通过对聚烯烃内衬渗透性测试以及力学有限元分析,明确了内衬塌陷原因为输油管线运行过程中,伴生气通过渗透作用进入内衬管与金属管夹层内,约83.5 d即达到运行压力(1.6 MPa);当单井管线泄压时,未完全恢复形变处的内衬优先发生塌陷,其塌陷需要的环空压力差(1.4 MPa)比完全恢复形变的内衬降低约46.2%。

A high-temperature polyolefin(HTPO)lining used in an oil pipeline collapsed after serving for three months.The tensile properties and vicat softening temperature were tested.The results show that the tensile strength,yield strength,and the vicat softening temperature(A50 method)of the collapsed lining could meet the technical requirements,the value are 19.4 MPa,18.9 MPa,122.2 ℃,respectively.Through the permeability test and the finite element analysis,it is clear that the reason of the lining collapsed is the associated gas entered the interlayer between the lining pipe and the metal pipe through penetrating,and the pressure of interlayer reaches the operating pressure which is 1.6 MPa after about 83.5 d.When the oil pipeline is depressurized,the lining where the deformation is not completely recovered collapsed preferentially,and the pressure of lining collapsed is 1.4 MPa,which is about 46.2%lower than the lining with recovered the deformation completely.