Calculation results adequacy of the reliability current level of gas pipelines linear sections is determined by the actual laws of distribution of the parameters that are significant for calculating reliability indicators based on the probabilistic models. The practice of performing such calculations for the trunk pipelines shows that the laws of distribution of excess internal pressure and temperature difference are specific and individual for each section of the linear part. One of the parameters influencing significantly random spectrum of stresses arising in the pipe wall due to external loads is the pipe wall thickness. Despite the random nature of this parameter, in the probabilistic models, on which the current industry regulatory documents are based, that determine the approach to assessment of the reliability of the linear part sections of the main gas pipelines, the pipe wall thickness is considered a deterministic value.
The results of studies of actual regularities of distribution of the pipe wall thickness are presented. The effect of this parameter random nature on the reliability indicators quantitative values is assessed. It is established that when assessing the strength reliability of the main gas pipeline linear sections, it is an unreasonable assumption to consider the thickness of the pipe wall as a deterministic value without taking into account the actual regularities of its distribution. It leads to the incorrect results when calculating reliability indicators. The probability of failure in this case is underestimated in relation to those values that are obtained considering the actual regularities and limits of change in the pipe wall thickness. Hence the probability of errors occurs when planning of the maintenance and repair of the linear part sections of the main gas pipeline.
The obtained results can become the basis for improving the methods of calculating reliability indicators, which will allow to consider the random nature of the pipe wall thickness as a significant indicator. This contributes to a more accurate risk assessment during operation of potentially hazardous extended objects such as the main gas pipelines.