1Ufa State Petroleum Technological University 2Joint Stock Company “Headquarters of the Ural-Siberian Trunk Pipeline” 3Institute of Energy Resource Transportation Problem EVALUATION OF STRENGTH OF OIL PIPELINES WITH DEFECTS TAKEN INTO CONSIDERATION

Damages of oil pipeline’s sections during the maintenance put it often out of operation or cause temporary stops, which as the result involves considerable financial costs. Therefore, the elaboration of efficient methods is an actual task for the estimation of possible consequences of damages and destructions of some sections and oil pipeline as a whole taking into account real defects. Such estimation requires a fulfillment of complex research works, both of destruction mechanisms and kinetics of growth of weary defects and cracks. Depending on the consequences, caused by a damage of the pipeline’s section, they are classified for “hazardous ” and “non-hazardous”. Damages can be divided conventionally into 3 classes: • The damages, related to an insufficient strength, for ex., due to an incorrect application of structural norms or accidental overloads; • The damages, related to macroscopically not localized accumulation of defects like corrosion sores or erosions; Among main methods of making prognosis of resource of the oil pipeline became methods based on the mechanics of destruction. A statistic nature of the distribution of heterogeneities in the details of machines brings to the fact that natural full-scale tests of the details with the usage of their results for a further estimation of the resource are first and foremost. The process of appearance of weary destruction is convenient to examine, dividing it into four stages, as it is shown in Fig.1. A traditional approach to making prognosis of weary strength in its simplest form is shown in Fig.2 and includes in itself static and cyclic tests of oil pipeline’s sections and its separate parts. The traditional method of safety estimation of the period of service of the oil pipeline’s sections confirmed its correctness for a number of years, preventing appearance of damages during the maintenance. Fig.1. Weary destruction stages 1- Stage of the crack’s origin; 2- Growth of short cracks; 3- A stable growth of long cracks; 4- A quick growth of cracks and ruptures h 1 2 3 4 de p