Enhancing System Availability: Findings and Potentials Discovered During the Electrification of Large Subsea Valves

Abstract The electrification of large bore critical valves, such as Subsea Safety Isolation Valves (SSIV), Emergency Shutdown Valves (ESDV), the final elements of High Integrity Protection Systems (HIPPS), the Boarding Shut-Down Valves (BSDV) and, in general, all fail-safe valves is a crucial gap that needs to be filled to allow for a scaling of all-electric subsea production and processing sites. This paper presents the qualification results of a drive solution, designed to electrify hydraulic subsea actuators, used to control large bore valves, without compromising safety and reliability. Additionally, the paper provides an outlook on how intelligent software features enhance system availability. During the TRL 4 qualification in accordance with API 17D, a subsea drive unit, designed to power hydraulic actuators in a closed hydraulic loop, was integrated into existing Single Acting subsea hydraulic actuators, as presented in paper OTC-35045-MS. The valves selected for the qualification were a 5 1/8" 740bar Slab Gate Valve and a 10"-517bar Ball Valve. Embedded electronic components such as sensors and a drive controller were utilized to monitor valve behavior and allowed the development of advanced software features. The paper explains the physical test setup and the qualification for the drive unit in combination with several subsea hydraulic valve-actuator assemblies, detailing the requirements for the testing procedure. The main results show that the electrification of large hydraulic actuators can be achieved without compromising safety and reliability. In the process, some obstacles were identified that need to be closely monitored for successful integration. It was proven that the electrification of large hydraulic actuators, using closed-loop hydraulic technology leads to the possibility of increased step-out distances, while keeping the highest safety requirements, enabling instantaneous system response time, and simplifying subsea control infrastructure. Additionally, the paper shows how intelligent features, such as parameter estimation algorithms, can be included in the embedded control system to enhance monitoring and allow predictive maintenance of subsea production valves and their actuators. This and other advanced software features can enhance the overall system reliability and can have a positive impact on system availability. This paper shows results of the first-of-its- kind drive unit to electrify large subsea valves during TRL 4 qualification, including capability for intelligent control features to increase availability and reliability of overall subsea infrastructure. It demonstrates valuable knowledge gained during the conception, integration and qualification of such a system. Furthermore, it highlights the potential that the electrification of hydraulic actuators holds for the subsea industry, especially for stand-alone applications and in long step-out scenarios.