CVA provides electrically actuated solution for automated sewage treatment control valves
Rotork’s CVA control valve actuator has provided a successful all-electric solution for the automation of the biological treatment process at a municipal sewage works in Sweden. The CVA was selected by Mälarenergi, the city-owned electric power and district heating provider for Vasterås, who also operate the sewage treatment plant.
The application involves the biological aeration process at the plant. Previously, two valves were installed in series on each air line, one electrically actuated and one manually operated. The electric actuator’s duty was to fully open or close the air line whilst the other valve was manually operated to regulate the flow of air into the aeration channel when the air line was open.
The CVA has replaced the old on-off electric actuator and now performs both duties with a single valve by automatically regulating its position from a 4 – 20mA control signal. This enables the aeration process to run with increased efficiency, with reduced air wastage and reduced manpower – the last factor being particularly welcome during the depths of the Scandinavian winter.
The CVA provides very precise electric control valve operation, with repeatability and resolution performance achieving less than 0.1% of full scale. The actuator also features a built-in super-capacitor, providing an advanced and programmable method of fail-to-position protection. Quick and easy commissioning and adjustment is achieved by wireless Bluetooth communication technology, whilst an integral data-logger stores an extensive record of operational and maintenance information, including valve torque profiles and dwell times.
Rotork’s agent in Sweden, Alnab Armatur AB, originally demonstrated the benefits of the CVA to Mälarenergi and has now received an order for six model CVQ-1200 actuators for fast-track delivery to the plant.