65
Logix
®
520MD+ and 510+ Digital Positioners FCD LGENIM0105-15-AQ – 05/16
flowserve.com
19 TROUBLESHOOTING
19.1 Troubleshooting Guide
Table 27: 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 7
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 9.3 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
2.
ISA specifications ISA-7.0.01.
3.
Lower proportional gain settings.
4.
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.
5.
Disassemble and clean spool valve
LCD backlight flickering or dim.
1.
The backlight uses any residual power not used by
other functions of the circuitry.
1.
Fluctuations in the LCD backlight are normal. No action
required.
Control System
HART
Comm
Device
22 μF
250Ω