Reliability assessment of free spanning subsea pipeline

Reliability of free spanning subsea pipeline has been estimated using theory of Probability of Failure (POF) and has been analyzed in accordance with a target safety level. The POF has been calculated using First-Order Reliability Method (FORM) and Monte-Carlo Sampling (MCS). The changes in POF with regard to six different ratios of span length to pipeline diameter and six clay types and also three sand classes are calculated. Finally, sensitivity analysis is carried out to determine the contribution of each parameter on POF. It is concluded that FORM analysis can be applied for large ratios of span length to pipeline diameter.