Methods for the residual life assessment of corroded gas pipelines.

Abstract

Abstract. The article is devoted to processing the methods for the residual life assessment of pressurized gas pipelines affected by corrosion wear. The analysis of the operational viability of the facility was conducted using the analytical engineering-mechanical model ASME B31G Mod taking into account stochastic factors during defect progression. The results of these calculations were validated using programmatically implemented functions for diagnosing pipeline corrosion defects within the «pipenostics» function set for statistical analysis and data calculation. Applying a deterministic calculation method for corrosion rate in accordance with the API 570 standard, as well as the calculated results of the estimated failure pressure levels in accordance with the ASME B31G standard along with the associated industry document ASME B31.8, it becomes possible to obtain the failure limit value of the object based on the actual corrosion dimensions. By combining these methods, along with subsequent comprehensive calculations to predict the outcomes of the facility failure, it is possible to determine the residual life of a corroded gas pipeline. It is important to note that when applying the deterministic calculation method, most of the random physico-chemical degradation processes are disregarded, and the corrosion rate is assumed to be linear, while various external factors are not taken into account. To address this issue, a probabilistic-physical approach will be applied to assess the residual life of the facility, specifically the diffusion-monotonic DM-distribution model. Within this model, the variation coefficient of the mechanochemical wear process is used as an indicator of the random variable values dispersion while according to the study results, the inspection data on corrosion depth and its calculated limit value, are selected as the parameters for assessing the corroded defective area of the gas pipeline.