The electrification of subsea control and production systems is essential to achieve the low carbon emission and high productivity targets that the offshore industry is facing now. But how to electrify these controls without compromising safety? This paper provides a comparison of the design strategies using mechanical springs or electric batteries to implement safety functions in control systems, considering as a case study the development of the new subsea electric actuator for small-bore valves SVA R2 from Bosch Rexroth. Traditionally, to control process valves with safety functions, hydraulic actuators have been applied with field-proven springs to bring the valve to a specific position (open or closed, depending on the application) in case of a safety-related failure such as a loss of power supply. However, the first electric subsea actuators developed with fail-safe springs turned out to be too large, heavy, inefficient, and costly due to their complex electro-mechanic system for broad adoption by the subsea industry. Thus, new electric subsea actuators [2] were developed using electric batteries to reduce overall size, but this added new risks: now the safety control has to detect a dangerous situation by itself and actively drive the system to the safe position. But, at the OTC 2021, a new electric subsea actuator for small bore valves was presented which achieves Safety Integrity Level SIL 3 using field-proven springs as compact as a hydraulic actuator (OTC-31083-MS) [17]. Following the functional safety methodology acc. to the IEC 61508, IEC 61511 and ISO 13849, this work provides a comparison between a control architecture with mechanical springs and another with electric batteries, considering the whole product life cycle (design, manufacture, installation, commissioning, and operation). An evaluation of the failure modes and failure mechanisms of existing subsea equipment, from field data available in the OREDA@Cloud, gives a proper assessment of the risks associated with implementing the new functional safety architecture. Costs of engineering, production and operation are taken into account to find out the most technical and economically feasible solution. This case study is a reference for the design and qualification of new subsea electric actuators with functional safety requirements using mechanical springs or electric batteries. It provides technical guidelines and risk assessment for designers and users of subsea control systems such as machine builders, EPCI companies, operators, service providers or certification bodies. If electrification is a prerequisite for a low carbon future, safety is a prerequisite for the adoption of all-electric control systems. This paper shows how to electrify subsea production and process systems by using mechanical springs or electric batteries without compromising safety.

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In order to realize the benefits of the digitalization and automation of production and processing systems, users first need to increase the level of integration, controllability and monitoring capabilities of each component applied. Therefore, digital twins turn out to be a highly important asset not only for designing greenfield applications, but also for improving brownfield machines. Up to now, digital twins were barely implemented to their full potential throughout the design, integration, and operation phases of production and processing equipment. Based on the experiences gained during the development of a subsea valve actuator, this paper highlights the importance of the digital twin to speed up the engineering and qualification of an innovative mechatronic system, reducing not only the time to market, but also increasing quality and allowing a fast reaction to the experience of the users. As a perspective, the paper shows how an accurate digital twin is a key to successful integration of a new component into complex machines. This includes the entire product lifecycle, from the conceptual work of a system and its virtual commissioning up to remote cloud-based monitoring systems. This paper finishes with an overview of some of the challenges which need to be resolved by the cooperation among different players in order to allow a wide and deep application of Digital Twin in the energy sector industry.

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