Investigation of the influence of corrosion defects on the durability of main oil pipelines

Abstract

For the sake of ensuring the energy security of Ukraine, the trouble-free operation of the oil transportation system becomes of strategic importance. The problem is exacerbated in connection with the long service life of individual objects of the system, which leads to degradation of the properties of the pipe material due to corrosive and erosion processes, which is enhanced by the effect of time-varying loads. Today, in world practice, various methods are used to strengthen defective sections of pipelines: installation of steel, plastic and fiberglass couplings, winding of an elastic composite tape, the use of reinforcing composite couplings, etc. To study the effect of microcracks, corrosion and erosion defects on the Druzhba oil pipeline of OJSC Ukrtransnafta with an installed bandage, full-scale tests of a defective section of a pipe (material - 17GS steel) reinforced with bandages made of a similar material using a UI1 / 200 GK installation were carried out. As a result of research, the pressure of its destruction was determined. During the tests, strain gauging was used to determine pipe deformations. Comparison of the values of stresses obtained experimentally and analytically confirmed that the use of bands on defective sections of the pipeline is an effective means for extending their service life. For a more accurate and detailed analysis of the reliability and durability of oil pipelines, a study of the defective parts (break point) cut from the pipeline was carried out. As a result of the studies carried out on the models - "cutouts", corrosion defects with a depth of up to 5 mm were registered, which is about 55% of the loss of metal, however, the pipe was not destroyed by these defects, but by a defect of the "crack" type. To obtain the profile of the defect from the model - "cutout", scanning was carried out using a sensor fixed on a mobile tripod connected to a computer via an ADC. At the next stage of research, the assessment of the residual resource was carried out using the analysis of full-scale kinetic curves of damage to hazardous sections of the oil pipeline through experimental studies of models - "cutouts". A fatigue curve has been constructed, which can later be used to predict the fatigue life of such elements.