Prediction of strength of multi-support overground segment of main pipeline

Abstract

Abstract A problem of strength of a main pipeline in its zone of rectilinear overground passage through an obstacle is considered in the given case. In the given case. It is not the overground multi-support segment alone that is included in the calculation, the adjacent underground parts which are situated at a certain distance from the ground are also taken into account here. The pipeline is described by a beam model with piece-wise constant rigidity, i. e. each segment of the pipeline i of constant rigidity. This allows us to more accurately characterize different thicknesses of pipes of the overground segment of the main pipeline in its construction. There is also assumed that the overground segment of the pipeline is freely positioned and rests on the corresponding supporting elements. The latest can be mutually adjusted for the given altitude. This allows us to evaluate the strength in repairing lifting the pipe over supports. The supporting elements can also experience elastic deformations. Their case is the mechanical compliance of component parts of the supporting assembly and, especially that of the ground under the support. The entrance and the exit of the overground segment into the ground are also considered as supporting elements. Here, they can have vertical displacements and turns. They also take into account the weight of the ground over the pipeline. The calculation of a main oil pipeline with its overground segment resting on two supports has been carried out. There are taken real conditions of operational loading caused to be the following factors: internal pressure, temperature difference, and the weight of the product transported. It has been established that the maximal values of stresses are observed in support sections and between the supports. It is shown that the stresses caused by bending moment can amount to up to half the total value. The influence of altitudes upon the value caused by bending moment stresses in the pipeline is investigated. The change of stresses caused by mechanical compliance of elements of the supports and by adjusting vertical displacements of the supports during repair was studied.