Fisherr 480 Series Yokeless Piston Actuators
Fisher 480 Series actuators are yokeless piston
actuators that are used in either throttling or on-off
applications with ball valves, butterfly valves, louvers,
dampers, and rheostats. They require pneumatic
pressure loading from double-acting positioners
(Fisher 3570) or from on-off loading and unloading
Actuator Versatility–Actuator with or without
positioners and snubbers is available in an
assortment of sizes, stroking speeds, thrusts, and
travels to handle most control requirements.
Compact Design–Yokeless construction permits a
low-profile assembly by allowing close coupling to
the control device; either through a bracket or, with
some versions, by direct mounting on a bonnet
Wide Range Supply Pressure Capability–The
cylinder (and 3570 positioner if used) can operate
with supply pressures as low as 2.4 bar (35 psig) or
as high as 10.3 bar (150 psig).
Long Stroke–Actuators have maximum rated
travels of up to 206 mm (8.125 inches).
Positioner Versatility–Positioner/actuator action is
easily reversed in the field with no additional parts.
Positioner sensitivity, travel span, and travel starting
point are factory set and need to be reset only if
operating conditions have changed or if the
positioner has been reversed. See figure 1.
Fisher 480-15 Piston Actuator
Figure 3 shows how various size actuators respond
when the input supply pressure is cycled at small
amplitude (3 to 5 percent) and increasing frequency.
Assume the cycling supply pressure and the
movement of the actuator rod are represented by sine
waves. As the actuator rod is forced to move faster, its
motion begins to fall behind the input in both time
(shown as phase lag) and amplitude (shown as
normalized gain). Both of these parameters are
affected by the inertia of the actuator and,
consequently, changes are more pronounced in the
480 Series Actuators