Design Considerations of Subsea HIPPS Architectures Evaluating Functional Safety and Reliability for HPHT Application

摘要

Objectives/Scope: Subsea high-integrity pressure protection systems (HIPPS) have become a standardrnfeature in numerous subsea fields around the globe. Subsea HIPPS’ reduced pipeline costs are proven tornshorten delivery times for pipelines by decreasing their pressure rating in green field projects or byrnincluding high-pressure wells into brownfield projects without modifying rating in existing pipelines.rnNew frontiers for HIPPS are created by high-pressure (7.5 to 20 kpi) and high-temperature (100° torn200°C) applications, as current pressure transmitters, valves and actuators reach their limits. Furthermore,rneach HIPPS challenges engineering to achieve a compromise between functional safety and reliability -rnespecially in demanding HPHT fields. These opposing characteristics within the protection systemsrncannot be treated separately but have to be evaluated as two closely related aspects of engineering.rnThis paper covers the balancing of these two engineering areas by using the numerical evaluation ofrnprobability of failure on demand (PFD) and failure rate (FR) figures. The evaluation is based on safetyrnintegrity level 3 (SIL 3) low-demand HIPPS, for which relevant subcomponents and system failurernbehaviours were simulated. Different HIPPS architectures were applied based on various process sensors,rnlogic solver and final element quantities and their arrangements. The objective of this paper is torninvestigate the potential improvement of HIPPS design with low PFD and high mean time to failurern(MTTF).rnMethods, Procedures, Process: Reliability methodologies are based on reliability block diagrams inrnaccordance to IEC 61508 and ISO 12489. Current state of the art safety equipment generic databases forrnsubsea equipment are used to reflect the sub-system’s section of HIPPS loops with regards to theirrnfunctional safety and reliability capabilities.rnResults, Observations, Conclusions: This paper indicates optimal and suboptimal architecturalrnconfigurations and their tradeoff regarding functional safety and reliability.