S series electric actuators with spring return are designed for fail-safe positioning of valves and dampers in the event of a supply voltage failure in addition to their normal function (stepless control, open/close control, position control). A mechanical spring set is used to move the controlled device to either the fully open or fully closed position without an external power source. In the open/close type, a mechanical buffer is used at the end of the spring stroke to reduce the dynamic effects of the spring return system. Manual override is optional for manual positioning of the controlled device.

• Controls: On / Off, stepless (optional), modulating (optional).
• Manual override (optional).
• ISO 5211 mounting flange.
• Built-in thermal protection.
• Springs are used to store kinetic energy to close a valve or damper each time to provide fail-safe operation in times of emergency without relying on batteries or other external power sources.