Estimation of the load carrying capacity of the bellow compensator for gas pipelines in the mining production areas

Abstract

The paper deals with the estimation of the load carrying capacity of the bellow compensator DN100, made of stainless steel AISI 304, which is supposed to be used for providing the necessary level of deformability of main buried gas pipelines in the mining production areas. Experimental investigations of the compensator under cyclic loading by tension-compression with the simultaneous action of working internal pressure are carried out. According to the results of experimental research and numerical simulation, it is shown that such compensators can be used as structural elements of main buried gas pipelines in the mining production areas.Introduction. The problem of the buried pipeline failure as the result of geodynamic processes of the ground surface is very important. According to EGIG [1] 8 % of cases of lossof-piping integrity in the main buried gas pipelines (MBGP) in Europe are caused by their failure as the result of geodynamic processes in the Earth crust. Furthermore, the activity of coal mines also results in the ground surface displacement.The Coal mines influence on MBGP is an important problem on the territory of Ukraine as well since 22.1 km of MBGP [2] have been already located in the areas of their influence and this amount is constantly increasing due to the expansion of mining boundaries.The area of the ground surface where the deformation processes occur as the result of mining production forms so called "shift trough" (see Fig. 1: Нmining depth; mmining capacity; ηmmaximum ground subsidence).As the result of mining development in the shift trough the compression areas and areas of the ground surface tension are formed (see Fig. 1) transmitting their effect on pipeline. Since the axial forces are the main load factor then the horizontal substitution component (vertical is usually neglected) has sufficient effect on the pipeline stressed state.Analyzing the ground displacement kinetics during mining we determined [3] that for the worst case of lava mining (along MBGP) its most loaded areas are subjected to three consequent semicyclestensioncompression and again tension due to the relaxation processes in the ground. Depending on geological conditions, mutual location of the pipe with mining areas the MBGP section can reach the effect area of 15 minings and thus undergo 45 load semicycles.To ensure reliable operation of buried pipelines during lava mining a number of measures aimed at stress state [4 -6] reduction are used, such as:1. Carrying capacity (on the design stage) is increased by: