超高压管道壁厚设计探讨

Discussion on wall thickness design of ultra-high pressure pipeline

超高压管道的壁厚设计与材料性能、设计工况以及计算方法等相关。对于公称压力大于PN420的超高压管道,国内尚未有相应的设计标准,目前均按国际标准进行设计。以美标为例,壁厚计算方法分常规管道和高压管道两种。有观点认为,当压力不超过70 MPa时,可以按常规管道计算,无需疲劳分析。就此,对承受内压的超高压管道壁厚设计、计算和取值进行了研究。以某装置某工况为例,按两种方法分别计算发现,按常规管道计算的壁厚略厚,其壁厚与D/6(D为管子外径)非常接近或超过D/6,疲劳分析也必不可少。因此,对于公称压力大于PN420的超高压管道,应按高压管道进行壁厚设计,并进行疲劳分析。内压直管的疲劳分析可采用有限元方法进行详细分析,亦可计算压应力进行评估,或者采用2倍压力试验进行验证。

The wall thickness design of ultra-high pressure pipeline is related to material properties,design conditions and calculation methods.For the ultra-high pressure pipeline with nominal pressure greater than PN420,there is no corresponding design standard in China.At present,it is designed according to international standards.Taking American Standard as an example,there are two wall thickness calculation methods:conventional pipeline and high-pressure pipeline.It is considered that the pipeline with pressure not exceeding 70 MPa can be calculated according to the conventional pipeline without fatigue analysis.Therefore,the design,wall thickness calculation and value of ultra-high pressure pipeline bearing internal pressure are discussed.Taking a working condition of a unit as an example,comparing the calculation results according to different methods,it is found that thickness by conventional pipeline calculation is very close to or more than D/6(D is the outer diameter of the pipe),and the fatigue analysis is also essential.Therefore,for the ultra-high pressure pipeline with nominal pressure greater than PN420,the wall thickness shall be designed according to the high pressure pipeline,and the fatigue analysis shall be carried out.The fatigue analysis of internal pressure straight pipe can be analyzed in detail by finite element method,evaluated by calculating the compressive stress,or verified by twice the internal design pressure.