TECHNIQUE FOR DETERMINING OF THE CRITICAL A LONGITUDINAL COMPRESSIVE FORCE FOR UNDERWATER CROSSINGS OF PIPELINES

Abstract

For the engineer-pipeliner it is very important to keep a steady condition of the underwater pipeline in the course of installation and operation. The steady condition of the underwater pipeline is understood as such state at which it will be in rest in advance set (design) situation at the most adverse combination of the loadings seeking to bring it out of this situation. Such loads include Archimedes buoyancy force, horizontal and vertical components of the hydrodynamic flow impact, the elastic force of the pipeline and other. The greatest interest for the engineer-pipeliner is represented by the compressing longitudinal forces arising at change of temperature condition or pressure of the pumped-over product. Calculation of underwater crossing of the pipeline to stability from influence of longitudinal forces doesn't occur in the specifications and technical documentation, and there is only a check of stability of the pipeline against emersion. But the matter is that after a construction of underwater transition of the pipeline attach landfall wet section of the main pipeline owing to what the longitudinal effort which is defined by temperature difference, and during tests and after introduction of the pipeline to operation and change of pressure starts influencing it to it. Therefore carrying out check of the pipeline on stability from longitudinal forces is considered a necessary component at design of underwater crossing of the pipeline. The aim of this paper is to develop a methodology for determining the critical longitudinal compressive force directly to submerged crossings, which can cause deflection of the pipe axis in the form of arch ejection. In this paper the formula conclusion for definition of the critical longitudinal compressive force is in detail described, the example of calculation of the critical compressive force for the set conditions is given.