A valve actuator system includes a gearbox assembly including an output gear for coupling to a valve stem, an input gear operably coupled to the output gear to drive rotation of the output gear and an input shaft operably coupled to the input gear to drive rotation of the input gear, a torque-limiter coupling having a solid body defining a proximal end and a distal end, the proximal end including a recessed interior accepting the input shaft of the gearbox assembly, a retainer extending between the torque-limiter coupling and the input shaft to transmit torque therebetween, the retainer operable to disengage the torque-limiter coupling from the input shaft in response to a torque applied to the torque limiter-coupling exceeding a critical torque predetermined to prevent damage to the gearbox assembly, and an actuator operatively coupled to the proximal end of the torque-limiter coupling to provide torque to the torque-limiter coupling.

A valve actuator system includes a gearbox assembly including an output gear for coupling to a valve stem, an input gear operably coupled to the output gear to drive rotation of the output gear and an input shaft operably coupled to the input gear to drive rotation of the input gear, a torque-limiter coupling having a solid body defining a proximal end and a distal end, the proximal end including a recessed interior accepting the input shaft of the gearbox assembly, a retainer extending between the torque-limiter coupling and the input shaft to transmit torque therebetween, the retainer operable to disengage the torque-limiter coupling from the input shaft in response to a torque applied to the torque limiter-coupling exceeding a critical torque predetermined to prevent damage to the gearbox assembly, and an actuator operatively coupled to the proximal end of the torque-limiter coupling to provide torque to the torque-limiter coupling.

A disconnector system for disconnecting a drive shaft of a drive mechanism from rotating equipment, upon a failure of the drive mechanism or rotating equipment, includes a disconnector mechanism having a disconnector shaft disposed in a casing and moveable relative thereto, between a first position and a second position, and a cam surface on a distal end of the arm configured to engage a slidable coupler. The movement of the disconnector shaft can be triggered by an operation of a solenoid, or by a displacement of the solenoid responsive to a melting of a meltable element.