Service Manual
MDE 252 Rev. 1 December 2021
Troubleshooting 27
Section 2: Troubleshooting
2.11 Excessive Torque for Valve Operation
1. Clean, lubricate and check the valve stem.
2. Valve packing too tight: loosen the gland bolt nuts.
3. Coupling type "A": tight t between bush and stem: increase the thread clearance
on the drive coupling.
4. Coupling types "B1", "B2", "B3" and "B4": ensure there are no axial forces on
the valve stem by leaving an adequate axial clearance between the stem and the
drive bush.
5. Check that all transmission shafts, universal joints or bulkhead passages have
sufcient lubrication and check that the transmission shafts are not bent.
6. Check that the internal valve trim or the reducer gears are well lubricated and
not damaged.
7. Check the alphanumeric display for diagnostic messages, and proceed with the
suitable corrective actions as described in this manual.
2.12 The Actuator Does Not Stop in Fully Open or
Fully Closed Position
1. Check that the actual open and close positions of the valve respectively
correspond to 100% and 0% on the actuator display.
2. Make sure that the torque and travel limits are correctly set (see Installation,
Operation and Maintenance Manual, VCIOM-08500).
2.13 The Numeric Position Display Indicates "---"
It is necessary to recalibrate the stroke limits (see Installation, Operation and Maintenance
Manual, VCIOM-08500).
2.10 The Valve Does Not Seat Correctly
1. If the valve is stopped by the torque limit in closing, increase the actuator output
torque limit.
2. If the valve is stopped by the position limit in closing, check that the valve reaches
its seat position, then readjust the setting of the position limit.
3. The internal trim of the valve may be damaged.
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