A-T Controls TRIAC® THD Series Heavy Duty Scotch Yoke Actuators

TRIAC THD heavy duty pneumatic actuators are designed for quarter turn operating devices including ball valves, butterfly valves, plug valves and dampers. The standard configuration is a symmetrical design yoke that delivers maximum torque at both ends of the 90° angle.

THD actuators are manufactured for extended high cycle life with alloy steel corrosion resistant and heat-treated springs, steel slide block, bronze slide bearings, and extra-large, strong piston. Their modular design allows for the actuators to be set up for different air pressures and for fail clockwise and fail counter-clockwise.

Key Specifications

  • Double acting or spring return
  • Torque: to 1,600,000 in-lbs
  • Travel adjustments ±8° for clockwise and counter-clockwise strokes
  • Ductile iron center body
  • Symmetric or canted yoke design
  • Visual position indicator
  • NAMUR accessory mounting


Subscribe to the Lesman Instrument Company YouTube channel.Lesman Instrument Company on YouTube

Video is a great way to learn about instruments and technology, and it's available whenever you need it. Watch step-by-step instructions on how to configure a transmitter, tune a controller, or troubleshoot a safety valve. We'll post videos we create, and those our manufacturer partners share with us, so you don't have to look in multiple places to find the video training you need.

Subscribe to Lesman's YouTube channel, and you'll get email notifications as soon as we add new training videos and webinars.