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MDA Technologies 3/2014

MDA Technologies 3/2014

The next Wave in Subsea

The next Wave in Subsea Motion Control Martin S. Jones With increasing frequency, oil and gas products are processed directly on the sea-bed. When it comes to transportation of the elements to the surface, use of electric solutions is beneficial. Hence, FMC Technologies employed Moog to supply electric actuation systems for its anti-surge valves. Martin S. Jones, Market Manager Niche and Emerging Markets Europe at Moog

Drive Technologies Moog actuator for turbine applications Traditionally subsea oil and gas reserves were brought to the surface for processing. This is an inherently inefficient process as the useful oil and gas components are a comparatively small proportion of the volume of material transported. With the advent of subsea processing the oil, gas, sand and water emerging from the well are separated at the sea-bed with only the useful oil and gas elements being transported to the surface. Regarding the transportation, electric actuation technology holds some key advantages in comparison to hydraulic solutions. FMC Technologies, specialist in sub-sea engineering, has chosen Moog to supply the electric actuation system, including control electronics, for its anti-surge valves used for subsea processing. Hydraulic or electric? Subsea processing requires the remote actuation of a number of process control valves controlling fluid switching and control of flow-rate and pressure. Traditionally these valves have been remotely actuated by means of a high pressure hydraulic system. Major drawbacks of hydraulic actuation are the complexity, inefficiency and cost of such power supply systems. Albeit being still in its infancy, electric actuation can be advantageous compared to hydraulic systems: reduced costs, higher efficiency and a reduction of the environmental impact. Specially developed actuator Moog was chosen to supply the complete electric actuation system, including control electronics, for the anti-surge valve for a Subsea Gas compressor. The prime mover of the actuator is a Moog duplex-redundant brushless motor utilizing twin rotors, twin position sensors and two independent sets of control electronics (The electronics are each mounted in a separate housing maintained at a pressure of 1 atmosphere). To convert the rotary motion of the motor to the high-force – 30 KN (6,760 lbf) – linear motion required the use of a precision “ball-screw actuator”. This long-life unit was specially developed for the application by Moog. A further design challenge was the dual functionality of the anti-surge valve. Firstly the actuator was required to modulate at high speed while maintaining high positional accuracy. The second requirement was to fully open the valve extremely quickly (ca. 2 s) to prevent compressor damage, in the event of a malfunction elsewhere in the control system. To address this, the actuator manufacturer turned to their patented “fail-safe” system. This arrangement uses a conventional failsafe spring override to power the anti-surge Valve to the “fully open” system in the event of a system problem. However, the novel part of the design is a “toggle” mechanism which holds the spring in its fully compressed position during normal operation. This toggle latched by a low-power electrical solenoid. In the event of a system failure the solenoid is deenergized, releasing the latch and the spring extends fully opening the valve. Because of this solution, the actuator can be designed with 50 % of the power output normally required. Comprehensive testing One of the key requirements for successful subsea equipment use is extreme reliability, as maintenance is very difficult and prohibitively expensive. To conduct a comprehensive test program, two prototype anti-surge valves were produced: one for life-testing at Moog and a second for hyperbaric testing at FMC. The test program consisted of functional testing of all operational scenarios (Factory Acceptance Testing), environmental stress screening, performance and power load testing, assembly environmental testing in accordance with ISO 13628-6 Level Q2, component environmental testing in accordance with ISO 13628-6 Level Q1, Electro Magnetic Compatibility (EMC) Testing, endurance testing (1 million operational cycles plus 5,000 failsafe operations) and hyperbaric testing at 220 bar (150 % of design pressure). All these tests have been successfully completed. The cooperation of FMC and Moog demonstrates that even the most critical processes on the seabed can be remotely controlled via electric actuation. Over the next decade a dramatic increase in subsea processing activity is predicted. This new electric actuation technology will play a major part in challenging new frontiers. Photographs: background fotolia www.moog.com Company name: Moog Established: 1951 Headquarters: East Aurora, New York, USA Turnover: .61 bn (2013) Employees: ca. 11,150 Products: motion control technology for aircrafts, turbines, racing and medical infusion applications About MDA Technologies 3/2014 39

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