PUMPS, VALVES & HYDRAULICS
Electric Valve Actuator Replaces Undersea Hydraulic Actuators
This new actuator enables remote valve control, lowers energy costs and saves the expense of installing miles of hydraulic lines.
Engineers at Bosch Rexroth have developed an electric valve actuator (SVA R2) that can replace the hydraulic cylinders commonly used to open and close valves used in undersea oil drilling and recovery. The electric actuator is as compact and safe as hydraulic cylinders. It can operate for up to 25 years at locations 13,125 ft beneath the surface of the ocean without needing to change batteries or install ancillary hydraulics, pumps and hoses.
Until the new valve was developed, petroleum engineers relied on hydraulics to control oil flow in undersea applications. This required piping hydraulic fluid thousands of feet to the bottom of the ocean and back, which consumes a significant amount of power. But hydraulic cylinders were the only devices that could provide the necessary failsafe features in underwater applications. Providing the same level of safety with electric actuators (i.e., being able to quickly and securely close the valve in case of power outages and emergencies) was too complicated and expensive. Plus, batteries for electric valves could not be guaranteed for the valve’s 25-year operational life.
The orange handle on top of the actuator gives ROVs a place to grab and hold the valve when it is installed horizontally. The
D-Handle in the back gives ROVs a place to hold the valve when installed vertically. These handles use standard interfaces, but they can be easily customized to meet any project-specific requirements.
The new actuator includes an electric drive, motion-control hardware and a spring-based failsafe feature housed in a pressure-compensated container that lets it operate at depths of up to 13,125 ft (4,000 m). The actuator uses reliable, industrial and automotive components with proven track records of durability.
The field-proven safety feature lets the actuator meet Safety Integrity Level 3 (SIL 3) standards (IEC 61508 and IEC 61511). It was designed with oil and gas production in mind, but it will also work in systems that pump and transport CO2, H2 and water, and can be powered by the same power supply the actuator’s sensors rely on.
Designing a failsafe subsystem that could close valves if power was
lost was a significant engineering challenge. Including a typical electro- mechanical failsafe would make the hydraulic actuator twice as large as it is. That’s why the design team went with a simpler spring- powered failsafe. The team specified a helicoidal spring strong enough to handle the task and small enough so that the new actuator is roughly the same size as hydraulic actuators.
The SVA-R2 has built-in sensors that monitor the valve’s operational torque and absolute position. Companies can add more sensors for measuring ambient pressure, humidity, vibrations, or other parameters. This data gets sent topside to technicians for use in predicting failures. All this lets the SVA-R2 act not only as an actuator, but also as a multi-sensor platform for automating subsea processes. Power and data are sent over a single cable, which simplifies the overall system.
The actuator was designed to be operated and monitored remotely by technicians on the surface, but the designers had to ensure the SVA-R2 could be installed and removed by an ROV. Accordingly, they made sure the new actuator would weigh less than 220 lb so that the ROV would not need special tools or cranes to handle it. And all the interfaces comply with API 17H so ROV operators know exactly how to use them. The standards also ensure typical ROV can install or remove the actuator using typical ROV torque tools.
September 2021
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