Logix
®
Digital Positioners FCD LGENIM0110-0 05/16
flowserve.com
42
28
TROUBLESHOOTING
28.1 Troubleshooting Guide
Table 20: Troubleshooting Guide
Failure
Probable Cause
Corrective action
No LED is blinking.
1. Current source too low.
2. Voltage of current source is too low.
3. Incorrect wiring polarity.
1. Verify current source supplies at least 3,8 mA.
2. Verify voltage source supplies at least 10VDC.
3. Check wiring for correct polarity.
Erratic communications.
1. Current source bandwidth not
limited to 25Hz.
2. Maximum cable length or cable
impedance exceeded.
3. HART modem connected to PC RS-
232 port not receiving enough power
4. Interference with I.S. barrier.
5. Current source stripping (filtering)
HART signal.
1. Maximum allowable current source rate of change is
924 mA per second.
2. Check cable size, length and capacitance. See
Section 20 ELECTRICAL CONNECTIONS.
3. Verify laptop battery is not low.
4. Must use HART compatible I.S. barrier.
5. Use a
250Ω resistor and a 22 µF capacitor to create
a HART filter according to the following schematic.
Unit does not respond
to analog commands.
1. The positioner is in digital
command mode.
2. An error occurred during
calibration.
1. Switch to analog command mode using the
procedure outlined in Section 22.3
Command Source Reset, use the
ValveSight
®
DTM, or use a handheld
communicator.
2. Check Status Codes. Correct calibration
error. Recalibrate.
Valve position reading
is not what is
expected.
1. Stem position sensor mounting
is off 180 degrees.
2. Stroke not calibrated
3. Tight shutoff MPC (Minimum
position cutoff) is active.
4. Custom characterization or soft
stops are active.
1. Reposition the sensor.
2. Perform a Stroke calibration (Quick-Cal).
3. Verify Tight Shutoff settings.
4. Verify custom characterization or soft-stop limits.
Position is driven fully
open or closed and will
not respond to command.
1. Stroke is not calibrated.
2. Inner-loop hall sensor is not
connected.
3. Wrong air action was entered in
software.
4. Actuator tubing is backward.
5. Electro-pneumatic
converter is malfunctioning.
6. Control parameter inner-loop
offset is too high/low.
1. Perform stroke calibration (Quick-Cal)
2. Verify hardware connections.
3. Check ATO (Air-to-open) and ATC (Air-to-Close)
settings. Recalibrate using Quick-Cal to apply
settings.
4. Verify ATO/ATC actuator tubing.
5. Replace electro-pneumatic converter.
6. Adjust inner-loop and see if proper control
resumes.
Sticking or hunting
operation of the positioner
1. Contamination of the electro-
pneumatic converter.
2. Control tuning parameters not
correct.
3. Packing friction is high.
4. Spool valve is corroded or dirty.
1. Check air supply for proper filtering and meeting
ISA specifications ISA-7.0.01.
2. Lower proportional gain settings.
3. Enable the stability DIP switch on the local
interface and recalibrate. If problem persists, adjust
pressure control window with handheld
communicator or ValveSight
®
and recalibrate.
4. Disassemble and clean spool valve.
22 µF
250Ω
Control System
HART
Comm
Device
→
To Logix
®
