Actuators deliver improved control valve performance

Paul Boughton

From pipelines to wastewater treatment, Andrew Wade outlines the benefits of all-electric modulating actuators.

The all-electric Rotork CVA modulating actuator is designed to deliver very precise control valve operation, and delivers repeatability and resolution performance within 0.1 per cent of full scale.

The actuator also features quick and easy non-intrusive setting and commissioning using wireless Bluetooth communication technology, while an integral data-logger stores an extensive record of operational and maintenance related information, including valve torque profiles and dwell times.

Explosion-proof enclosure

A rugged, double-sealed IP68 watertight and explosion-proof enclosure enhances long-term maintenance-free reliability in the harshest of environments.

In an example of a typical application, the actuators are being installed during an upgrade programme on the pipeline network connecting Russia and Central Asia with Western Europe. Ukraine is an important part of this energy supply infrastructure which, in total, meets one third of Western Europe's demand for natural gas.

The Ukranian energy company Ukrgaz Energo has made it a priority to modernise the network in its country, which handles approximately 90 per cent of the gas supplied by Gazprom in Russia. In a recently completed project, Rotork CVA modulating electric valve actuators were installed on the compressor station at Bilche-Volytsa, replacing obsolete pneumatic equipment.

Dehumidification unit

ITO Ltd, Rotork's agent in Ukraine, supplied a package consisting of CVA (CVL linear output) actuators and new globe valves to improve diethylenglycol (DEG) control on the station's dehumidification unit.

Assembly, test and calibration of the actuators and valves was performed by ITO at their factory. The customer is very happy with the move to Rotork electric control valve actuation. In particular, the diagnostic capabilities, accuracy and reliability of the CVA 'have exceeded all expectations'.

In an example from another industry, CVA actuation technology has a been selected for a demanding duty involving continuous modulation at what is described as a 'new generation' wastewater treatment plant.

The plant is one of the largest in France as well as one of the most energy efficient. Designed for increased rainwater and effluent treatment capacity with improved treatment quality and reduced environmental impact, the plant incorporates a range of integrated energy saving and energy recovery processes.

These include solar water heating, heat pumps, heat recovery from final effluent and biogas production from sludge digestion processes.

Significant biogas production generates the daily equivalent of 27,000kWh, which is used as the energy source for a district heating scheme in the local area.

The biogas is produced in a process which uses a combination of solids filtration and biological aeration to remove pollutants including ammonia.

Regulating air supply

The Rotork CVA actuators are installed on butterfly valves to regulate the continuous supply of air to the process. Accurate air regulation enables the plant to run efficiently and reduces air wastage.

On previous installations pneumatic actuation was used for this application, but the more accurate positional performance available with the CVA has enabled the adoption of the electrical solution on this site and there are plans to use the same technology at more installations in the future.

Andrew Wade is with Rotork Controls Ltd, Bath, UK.