Pipe bends form an integral part of any piping layout. Because of the ability to ovalize and warp during manufacturing, pipe bends offer higher flexibility and associated higher stresses with respect to straight pipes. In last few decades to construct an integrity assessment procedure on pipe bends, significant researches were carried out both an analytical and experimental approach. The results of examinations were included in terms of stress intensification factor (SIF) for piping analysis which differs for both in-plane and out plane bending moment. In the manufacturing process of inlet pipe bends, it is difficult to avoid thickening on the inner radius and thinning on the outer radius. The cross section of the bend becomes non circular…show more content… This additional flexibility is also accompanied by stresses and strains that are much higher than those present in a straight pipe of the same size and material, under the same loading conditions. Hence, for the purpose of designing a piping system, it is useful to have a reliable estimate of their load-carrying capacity of pipe bend, along with a deep understanding of their structural behavior, under different and combined loading conditions.
Systematic investigation in pipe bends was demonstrated that the curved pipe behaves differently under load than predicted by simple beam theory. The phenomenon of ovalization in pipe bend was observed and reported on the fact that it leads to greater flexibility than straight pipes that could be accounted for by simple beam theory. The induced stresses in pipe bend and its deformation are higher than those of a straight pipe of the same size and material (Bantlin 1910, Von Karman 1911). Analytical methods used for the analysis of the end effect in a pipe bend geometry with consideration for the action of internal pressure and bending moment. This method is based on the use of simplifying hypotheses and is reduced to the solution of a system of fourth-order differential equations along the axial coordinate with respect to unknown coefficients in the expansion for tangential…show more content… Inlet pigtail Pipe bends employed in a reformer are subjected to various degradation mechanisms, resulting in the failure of the pipe bend region. Failure of inlet pigtail pipe bend having catastrophic effect at extrados (Fig. 1) and this failure is identified at site. During plant operation, the piping system is exposed to thermal and mechanical loads due to internal pressure, axial tension, global bending moment, combined internal pressure and bending moment. These induced loads are transmitted to the curved region, causing high stress level when compared to a straight pipe . Further, during the forming process, the outer fibre of the pipe bends thin down when compared to the inner fibre, which leads to a phenomenon known as ovality and thinning