Flowserve SMB Series Electric Actuators - Manual (Page 33)

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SMB Series/SB Series Installation and Maintenance FCD LMENIM1401-04-AQ – 01/15
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The thrust developed by the actuator is absorbed by the heavy-duty Bearings (piece #75, 76, 77,
78) on the top and bottom of the main Drive Sleeve. As the actuator develops greater torque, when
seating the valve, the Worm (piece #53) slides axially along the splines of the Worm Shaft (piece #43)
and compresses the Belleville Springs (piece #56) in the torque spring pack.
The Belleville Springs are calibrated springs. For every increment of compression from a given size
unit, a certain pre-determined amount of torque is developed. The Worm mechanically actuates
the Torque Switch. When the Worm moves back a preset distance and develops the torque output
required, the Torque Switch opens and a pair of electrical contacts that are wired into the motor
control circuit interrupt the circuit and stop the motor.
The Geared Limit Switch (piece #105) is directly geared to the Worm Shaft and is in step at all times
with the movement of the actuator. The switch cannot slip because no belts or other friction devices
are used in its operation. Once the Geared Limit Switch (piece #105) is set to trip at its proper posi-
tion of valve travel, it will trip at the same point every time.
The Torque Switch (piece #104) is wired into the motor control circuit to stop the actuator in the full
closed position for any rising stem operation. The Geared Limit Switch (piece #105) is wired into
the motor control circuit to stop the operator at the full open position. For most 90° turn valves and
sluice gates, the Geared Limit Switch is wired into the motor control circuit to stop the actuator at
both the full open and full close position of the valve or gate. The Torque Switch is wired in series
with the Geared Limit Switch in both directions so that in the event of a mechanical overload, the
Torque Switch will open and cause the motor to stop.
Check the applicable wiring diagram to determine the correct wiring connections made for the torque
switch and geared limit switch.
5.2 Manual Operation
In the event of a power failure, the actuator can be operated by hand using the handwheel. The
actuator has an automatic handwheel declutching arrangement. For manual operation, the declutch
lever is pulled downward. This mechanically disconnects the electric motor from the handwheel
through the clutch assembly.
5.2.1 SMB-000 and SMB-00
The operation of the SMB-000 and SMB-00 are functionally the same. Due to a difference in piece
numbers between these actuators, the following description refers to the SMB-000 (Figures 7.1 to
7.3).
For the SMB-000 and the SMB-00, the Clutch Ring (piece #33) and the Clutch Keys (piece #23) are
moved upward until the Clutch Keys engage with the lugs on the bottom of the Handwheel (piece #5).
For the side-mounted Handwheel on the SMB-00, the Clutch Keys engage the lugs on the bottom of
the Bevel Gear (piece #100).
Trippers (piece #28, 29) hold the Clutch Keys in this position. The actuator will remain in hand opera-
tion indefinitely until the electric motor is energized and the Tripper Cams (piece #27) mounted on the