Remaining strength assessment of dented pipe based on depth and strain based criteria

Abstract

Abstract There are currently two methods which are used in feasibility operation of dented pipeline systems, namely depth based and strain based. In this research, both methods will be compared to determine conservatism degree of each method and as a guideline and considerations in the integrity assessment of pipeline system. The finite element method with including nonlinearities of material properties and dimension will be used as a tool in the analysis. Static indentation was held with using half ball indenter. Variations of applied load are 600 N, 1000 N, 1500 N, 2000 N, and 2500 N. The results of indentation are dent depth ratio (d/D) with value 1,93 %, 3,78 %, 5,53 %, 7,08 %, 10,63 %, and plastic strain with value 4,24 %, 5,87 %, 8,36 %, 11,43 %, and 12,93 %, respectively. Based on the Code, depth based criteria use d/D<6 % and strain (ɛ) < 6 % as an acceptance criteria. Based on this research, it can be concluded that strain based method is more conservative rather than depth based method. Then, five model of defected pipe will be simulated in the condition of operation pressure applied to the pipe. Operation pressure was varied with (P/Py) 0.2, 0.4, 0.6, 0.8, and 1. The results show that depth of dent will decrease with variation of strain value.