A power station in New Hampshire which burns both natural gas and low sulphur fuel oil has installed a Rotork CVA electric control valve actuator to help reduce maintenance costs and improve accuracy. The changing load on the units demands virtually continuous modulation to maintain the correct flow and a 6in Class 150 ball valve controls the flow from a storage tank to fuel oil pumps. It was decided to replace the existing pneumatic I/P positioner and spring diaphragm pneumatic actuator with the CVA electric actuator because it provides precise control valve operation with repeatability and resolution performance at less than 0.1% of full scale. In addition to the convenience of all electric control and operation, the CVA uses wireless Bluetooth communication technology for swift and user-friendly actuator set-up, auto calibration and adjustment. Further benefits include comprehensive performance data-logging, a double-sealed IP68 watertight enclosure for environmental protection and programmable fail-to-position options using integral super-capacitors. On-site technicians carried out extensive tests on the fail-to-position feature and verified correct performance in both loss-of-power and loss-of-signal situations. The CVA data-logger stores operational data such as valve torque profiles, events and statistics that can be downloaded for detailed analysis using Rotork Enlight software. By anticipating potential problems, preventative maintenance can be planned without interruption to the operation of the plant.
