VA-9070 Series Electric Rotary Actuators for Two-Position and Modulating Service Technical Bulletin 3
VA-9070 Series Electric Rotary Actuators for
Two-Position and Modulating Service Technical
Bulletin
Introduction
The VA-9070 Series (Bray® Series 70) are quarter-turn, electric rotary actuators
with manual override, designed for use on most Johnson Controls® VF Series
Butterfly Valves sized for up to 18,000 lb·in (2034 N·m) of torque.
VA-9070 Series electric actuators cannot be used on the VF4000 Series and
VF5000 Series Butterfly Valves. Operating speeds vary between 6 and 60 seconds.
Internal and External Components
The VA-9070 Series actuator is divided into two internal sections: the power center
below the switch plate and the control center above the switch plate. The power
center contains the capacitor and gear motor, with its spur gear train. The power
center drives a final non-backdriveable worm gear output. The power center also
houses an override mechanism for manual operation. The control center has
several user-accessible components: the camshaft assembly, limit switches,
terminal strips, torque switches, heater, and servo.
On the outside of the actuator housing are adjustable mechanical travel stops, a
large position indicator, the manual override handwheel, and dual conduit entry
ports. The external coating is a polyester powder coat, providing resistance to
Ultraviolet (UV) radiation exposure and chemical exposure.
Electrical Operation
The motor in the VA-9070 Series actuator is a permanent induction split capacitor
design (single phase AC power). Travel limit switches are mechanical Form C
Single-Pole, Double-Throw (SPDT) switches with two independent circuits. These
SPDT switches are rated at 10 amperes (75 to 80% power factor), 1/2 hp 125 VAC,
and 3/4 hp 250 VAC.
If the torque capacity of the actuator is exceeded to the point where the motor stalls
and overheats, a thermal protector switch built into the motor windings
automatically disconnects the motor power. Once the motor cools sufficiently, the
thermal switch resets.
Mechanical Operation
Mechanically, the ratio of the gear motor determines the speed of the actuator. The
gear motor uses high-efficiency spur gears with different ratios for the different
speeds. Initial gear reduction through the spur gears transfers to the worm shaft.
The final gear reduction and output happens through a non-backdriveable worm
gear set. An indicator-camshaft linked to the output shaft determines positioning.
The manual override drives the worm shaft when engaged.
