Electrify control of flow valves in subsea systems

Viable business models for the production of green hydrogen at sea or the storage of CO2 beneath the seabed (CCS) depend on cost-effective underwater technology. Therefore, Bosch Rexroth AG and Wittenstein motion control GmbH have jointly developed the electromechanical underwater actuator eSEA Spin for the continuous flow control of gases and liquids.

It operates at depths of up to 4,000 m using a 24 V power supply and therefore does not require the conventional hydraulic lines from the water surface to the seabed. This permanently reduces both the investment costs of the entire underwater system and the operating costs.

Joint development based on proven components

"The development of the eSEA Spin is not only a technological achievement, but also a testament to successful collaboration. By combining Wittenstein's expertise in gear technology with Bosch Rexroth's competence in automation and electronics, we are developing solutions that offer real added value for our customers. Together, we are shaping the future of all-electric actuators in underwater technology," summarizes Dr. Steffen Haack, CEO of Bosch Rexroth AG.

"Bosch Rexroth and Wittenstein both have proven and long-standing application experience in the field of underwater technology. Our gearboxes and electromechanical modules are designed for the required service life of more than 25 years under water – and have already proven themselves many times over this long period," emphasizes Dr. Bertram Hoffmann, CEO of Wittenstein SE.

Electric actuator replaces hydraulics

To date, valves in underwater systems have mostly been operated by unmanned, remotely operated underwater vehicles (ROVs) or hydraulically, requiring a complex hydraulic line from the water surface. The eSEA Spin is as compact as hydraulic modules and adjusts throttle valves rotaryly with a torque of up to 2,700 Nm. This corresponds to the torque of a 380 kW combustion engine for large tractors. However, the eSEA Spin only requires 480 watts of electrical power. This power is fed to two redundant 24 V motors, each with its own controller, which generate unlimited rotary motion for precise flow control via a planetary gear system.

Intelligent software maximizes availability

The robust control electronics are based on a control system from the automotive sector, which is manufactured in very large quantities and to a high quality. In addition, industrial sensors for condition monitoring continuously record operating data such as absolute position and torque. This enables precise flow control of the valve. "Bosch Rexroth has the software expertise and experience to filter the relevant information from this data, link it with the integrated digital twins of the components, and thus significantly improve the availability of the drive module over its entire service life," says Haack.

Standardized interfaces for mechanics and communication

The new actuator features the mechanical ROV Class 4 interface as well as the SiiS L2 interface for the electrical power supply and communication with higher-level systems on the offshore platform. The drive module is integrated within a few minutes.

Moving functions to the software reduces complexity and acquisition costs compared to actuators currently available on the market. The eSEA Spin integrates into the 24 V electrical infrastructure of underwater systems without additional effort and enables the valves to be operated even at greater distances, so-called "step-out" distances. Low energy consumption reduces operating costs over the entire service life.

The new actuator complements Bosch Rexroth's eSEA portfolio for linear and rotary movements that control underwater valves with different functions and requirements. A single 24 V power supply is sufficient throughout, potentially replacing the entire hydraulic system, including lines to the seabed. This electrification lowers the barriers to the commercial production of green hydrogen at sea or the storage of CO2 in subseabed storage facilities.