Perpustakaan Digital ITB

Natural gas is a major energy source in Indonesia, with demand increasing annually. Based on the National Energy General Plan (RUEN), natural gas is targeted to meet up to 24% of the national energy mix. Indonesia has natural gas reserves of up to 62.39 TSCF, which can be utilized to meet increasing demand annually. Therefore, reliable facilities and infrastructure are needed to maximize the utilization of natural gas reserves. One key infrastructure that plays a crucial role is the pipeline system, which transports natural gas from one location to another for processing or direct distribution to consumers. This research aimed to analyze the safety of existing natural gas pipeline systems. The analyzed NSO pipeline system was suspected of free spanning. The analysis was carried out based on the criteria referred to by DNV RP-F105 and DNV OS-F101. Static and dynamic span calculations for the pipeline system were performed using Microsoft Office Excel software The results were obtained by applying the DNV RP-F105 free span assessment procedure. The pipeline was checked against the inline VIV, crossflow VIV, inline ULS, and crossflow ULS criteria. For each criterion the span length was iterated until the limiting acceptance condition was reached. The final allowable span was then selected as the smallest value among all criteria. The results show that the maximum allowable span length for the NSO submarine pipeline is 29 m, governed by the inline VIV screening criterion. This condition is influenced by the dominant current loading, indicated by a current flow ratio greater than 0.8. The static ULS assessment also shows that several span conditions produce equivalent Von Mises stresses exceeding the allowable stress criterion, indicating the need for span control or mitigation. Therefore, free span management is required to reduce the risk of VIV, excessive stress, and possible pipeline failure.