In recent years electric valve actuators have grown in importance in modern power plants. Now they are recognized as major contributors to efficiency, economy and safety as well as facilitating the quick start-ups demanded by today’s working practices and the emission reductions dictated by environmental legislation.

Electric actuators may be required for an extensive range of duties encompassing isolation, regulation, modulation and failsafe operation of valves and dampers.

Developments in electric actuator design have improved the situation, particularly with the introduction of secure, “noninvasive” water and dust tight enclosures. Standardized electronic actuator controls and a wider range of torque outputs also helped the design engineers, whilst improved motor controls and the introduction of thyristors rather than traditional reversing starter controls have increased the “starts per hour” performance of the electric actuator.

This has enabled it to be used for many regulating and modulating duties.

Changing Actuation Requirements

In the past ten years these developments have dramatically accelerated with the introduction of high temperature modulating duty actuators. This is a major leap forward, enabling electric actuators to be installed in more environments where only hydraulic and pneumatic actuators used to be specified. This has been a welcome improvement, since hydraulic systems incorporating traditional power packs have become unpopular due to high maintenance costs and other operational issues.

Instrument air for pneumatic actuators is also expensive to produce and look after, with leakage, water ingress and vulnerability to freezing all threatening reliability and requiring special attention.