To limit global warming to 1.5 °C above pre-industrial levels, the Intergovernmental Panel on Climate Change (IPPC) recommends in its Special Report on Global Warming, among other things, the use of hydrogen and, in a number of cases, the capture, use and storage of CO₂ (CCUS). For the offshore plants needed to produce green hydrogen or for CCUS to be operated economically, the technology applied must become significantly more costeffective to purchase and operate than it has been up to date. To achieve this, Bosch Rexroth is expanding its portfolio of subsea actuators with additional variants and motion options to electrify and digitalize all safety-relevant movements at depths of up to 4,000 meters.
In the offshore storage of CO₂ as well as in the intermediate storage of green hydrogen, valves regulate the controlled flow of process gases and fluids. Up to now, these valves have mostly been operated by hydraulically driven actuators. This requires central hydraulic power units above water with kilometers of pipelines to the individual actuators on the seabed. Newly developed eSEA actuators supplied with 24 V low-voltage (DC) are an economical alternative to these capital- and energy-intensive conventional hydraulic systems. Their lower power consumption reduces operating costs. In addition, digital twins increase process reliability with condition monitoring.
Bosch Rexroth is now adding the eSEA Push actuator for linear movements and the eSEA Drive for applications with very high torques in excess of 35 kNm to its actuator for rotary movements (eSEA Torque), which has won several international technology awards. This means that all movements required for a safe and reliable valve control under water can be now controlled and executed purely electrically, with a standardized interface.
Safe without electric energy and with self-monitoring
All variants use the fail-safe principle, in which spring elements are actively clamped to keep the valve either open or closed. If the power supply fails, the clamping is released, and the valve automatically moves to the safe position in accordance with IEC 61508 and IEC 61511 without the need for expensive safety-relevant subsea batteries. Bosch Rexroth supplies the eSEA actuators with interface to external sensors and process valves as well as with digital twins of these assemblies. The control hardware is based on electronics from the automobile industry. The solution also comprises software, including machine learning applied for the embedded condition monitoring. On the basis of internal and external sensors and measured values, the condition of the overall system and impending wear can be detected before a failure occurs. If a sensor fails, the digital twin can take over and ensure continued operation.
Small energy requirement for low and high loads
The eSEA actuators significantly reduce the energy requirements of subsea systems. They also connect increasingly distant step-outs. In some cases, these are valves located more than one hundred kilometers from the coast, which also have to be controlled via actuators. eSEA Push modularly covers the performance range for valves up to five inches in diameter up to 745 kN. The eSEA Drive is designed for larger diameters and torque requirements of more than 35 kNm. This unit generates the high forces via a decentralized drive module suitable for deep-sea use with a closed hydraulic circuit and special protective measures to prevent hydraulic fluid contamination.
All eSEA actuators from Bosch Rexroth are designed for a safe and reliable operation over 25 years permanent subsea. Replacement is possible with subsea robots without impairing the function of the valves. The digital twins reduce the engineering and commissioning costs of the actuators for new systems.
They can also be retrofitted in existing installations.
