The Dutch main gas transmission system has been some 50 years in operation and in the transition to renewable and unconventional gases at least another 50 years of service are foreseen. Due to the transition to renewable and unconventional gases, gases with different compositions are expected to be injected into the Dutch main gas transmission system and it is likely to expect that the operating conditions will change compared to historical and current operating conditions. Without mitigation, these changing operating conditions and different gas composition in the ageing network can possibly result in different dominant pipeline threats than currently experienced. Therefore, the question arises what will be the relevant time dependent threats that could occur in the future and how can these be assessed and ranked.
This paper describes an explorative study on identifying and evaluating time-dependent threats in gas transmission pipelines and facilities caused by transporting renewable and unconventional gases, based on ASME B31.8S. The study bases on a systematic approach for assessing the failure probability and failure mode of threats. Based on an assessment of the existing gas transmission system, an outlook of the effect of changing gas compositions will be given. This approach can be used for determining mitigation measures to prevent future failures. Furthermore, it can be used to extend the life time of gas transmission pipelines at the lowest total cost of ownership.