AMG SAD / SAF-HD quater-turn actuators are characterized by the essential design elements rack and pinion. In this case, the rotary movement is produced by the rectilinear movement of two pistons acting against each other. The toothed rods of the two pistons are engaged with the pinion, which transmits the rotary motion to the armature. The piston movement is effected by compressed air on the piston surfaces.
The transverse forces occurring during the movement of the pistons are absorbed by guide rods. This ensures a perfect axial guidance of the pistons, so that the piston seals function well and permanently.
The principle of rack / pinion results in a uniform torque course during the switching process due to the constant effective distances between the rack and pinion.
For AMG SAD-HD quater-turn actuators, the movement is generated with compressed air. When the outer chambers are ventilated, the switching shaft rotates clockwise (fitting closes). When the internal chamber is ventilated, the switching shaft rotates counterclockwise (valve opens).

AMG quater-turn actuators of type SAF-HD are moved with compressed air and spring force. For single-acting actuators, only the inner chamber is pressurized. The force generated thereby not only moves the fitting in one direction, but at the same time tensiones safety springs for the return. The spring force is able to move the valve into the safety position "CLOSE" or "OPEN" in the event of a failure.
AMG quater-turn actuators with hydraulic damping are used for the automation of ball valves, cock taps, butterfly valves and control valves, if these require a stable, temporal switching behavior during the closing or opening process.
By means of an integrated, hydraulic damping module, the regulation of the piston speed (switching time) of the double- and single-acting AMG SAD / SAF-HD quater-turn actuators is made possible.
The piston movement of the actuator is transmitted via a piston rod to a damping module, in which liquid flows from one chamber into the other. The opening and closing times can be adjusted independently of each other by means of a change in the cross-section via throttle check valves.