Life Extension of a High Pressure Transmission Pipeline Using Structural Reliability Analysis

Abstract

Pipeline designers and operators recognize that the commercial viability of operating high-pressure gas pipelines decreases with time. This is because the structural integrity levels of the pipeline decrease, due to the action of deterioration processes such as corrosion and fatigue, until the level of mitigation required to ensure adequate safety levels becomes uneconomical. For this reason pipelines are assigned a nominal design life of typically 40 years. This paper describes the application of structural reliability analysis to a high-pressure natural gas pipeline having both onshore and offshore sections, in order to determine the extent to which the asset life could be increased beyond the design life without any significant reduction in reliability and hence safety levels. The approach adopted was to identify the credible failure modes that could affect each of the onshore and offshore sections and determine the probability of failure due to each failure mode taking account of the uncertainties in the parameters that affect each mode. Based on a detailed consideration of the results of the study it was concluded that the life of the asset considered here could be extended to 60 years without any significant reduction in safety levels. Moreover, it was concluded that if certain mitigating measures were to be implemented in the future then it would be possible to increase the asset life to significantly more than 60 years.

Análise de métodos para avaliar dutos com dano mossa e sulco

“…A 'interferência externa' destaca-se, frequentemente, como a causa dominante de falhas em dutos onshore [1][2][3][4][5][6], podendo gerar nos mesmos danos tipo mossa, sulco, mossa e sulco, ou perfurações. Como exemplo, pode-se observar na Figura 1 que a interferência externa é a principal causa inicial de incidentes (liberação de gás não intencional) em dutos onshore de transporte de gás na Europa, correspondendo a aproximadamente 50% de…”

“…Al. [3], Seevam et al [6], Jandu et al [7], API 579-1/ASME FFS-1 [8], Cosham e Hopkins [9], Cosham [11], Spiekhout et al [16], Jones e Hopkins [18], Bood et al [21], Roovers et al [22], Bai e Song [24], citam e/ou descrevem os métodos analíticos semi-empíricos abaixo relacionados, em ordem cronológica, que visam avaliar a adequação ao uso de duto com dano mossa e sulco. Detalhes gerais sobre cada um destes métodos encontram-se descritos, respectivamente, nos itens 3.1 ao 3.6.…”