Torque-limiter coupling for valve actuator

A method, comprising:

• locating a gearbox assembly including an output gear coupled to a valve stem of a valve, wherein the gearbox assembly includes 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;
• securing a torque-limiter coupling to the input shaft of the gearbox assembly such that the torque-limiter coupling freely rotates about the input shaft;
• installing a retainer to extend 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
• detachably coupling an actuator onto the torque-limiter coupling with one or more fasteners such that the actuator is operatively coupled to the input shaft to transmit torque thereto.

A torque-limiter coupling comprising:

• a cylindrical body, the body including:
• a proximal end including a recessed interior for accepting an input shaft of a gearbox assembly therein and a coupling hole defined laterally through the proximal end and recessed interior;
• a distal end defining a threaded recess for detachably coupling with an actuator and a key slot for receiving a key of the actuator;
• and
• a transitional section with tapered or rounded geometry extending between a larger cross-sectional area diameter of the proximal end and a smaller cross-sectional diameter of the distal end;
• and
• a retainer receivable within the coupling hole to operatively couple the torque-limiter coupling to the input shaft of the gearbox assembly, 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 predetermined shear limit.