SMB/SB Installation and Maintenance Manual 140-11000 • July 2003 9-1
Flow Control Division
Limitorque Actuation Systems
9
Troubleshooting
Symptom Corrective Action
Geared limit switch fails to stop valve travel. a. Verify that the control wiring and motor reversing contactor
wiring are correct.
b. Check the geared limit switch setting. See Section 4.4,
Setting Limit Switch.
c. Remove the limit switch gear box cover and inspect for
damaged or broken gear teeth. See Sections 7 and 8,
SMB Disassembly and Reassembly and SB Disassembly
and Reassembly.
Unable to motor-operate the actuator. a. Check the motor power and motor control circuits for
supply and continuity.
b. Verify that the supply voltage is in accordance with motor and
controller nameplate rating. If OK, check the motor
amperage load.
c. If a stalled motor is indicated, turn the power OFF and
operate the actuator by handwheel.
Excessive handwheel effort. a. Inspect the valve stem for proper lubrication or damage.
b. Check the valve packing gland. It may be too tight.
Loosen the valve packing gland.
c. Inspect the valve for proper lubrication.
d. Check the stem nut for tightness on the valve stem.
Loosen the stem nut on the valve stem.
e. Inspect the valve for faulty or damaged parts.
Reversing starter contacts fail to close. Check the line circuit breaker or fuses in the disconnect
switch (if installed) for possible interruption of incoming
line voltage. The holding coil may be open-circuited and, if so,
should be replaced.
Pushbutton contacts not making proper Adjust the contacts for correct movement and proper
contact when depressed. contact pressure.
Overload relays are open. Reset the relays. Continued tripping of the overload relays
usually indicates trouble with the motor or improper
sizing of the overload heater. See the electric motor
nameplate for full load current.
Reversing starter contact movement a. Check for worn or damaged mechanical parts.
is restricted. b. Clean, adjust, and align all parts for free movement.
c. Replace any defective parts. When replacing the contacts,
the complete set of moving and stationary contacts
should be changed along with springs to assure proper
contact pressure.
Pushbutton contacts stick. a. Trace out the connection of pushbutton contacts with the
wiring diagram for actual installation.
b. Adjust the contacts for free movement and normal contact
pressure.
c. Check the wiring for “sneak in” or grounded circuits and
defective insulation.
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