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User Instructions Logix 520MD - LGENIM0520-01 11/09
Logix 520MD Symptoms and Solutions
Failure Probable Cause Corrective action
No LED is blinking 1. Current source below 3,7 mA 1. Verify current source supplies at least 3,7 mA
2. Incorrect wiring polarity 2. Check wiring for correct polarity
Erratic communications 1. Current source bandwidth not 1. Maximum allowable current source rate of
limited to 25Hz change is 924 mA per second
2. Maximum cable length or cable 2. Check cable conductor size, length and
impedance exceeded capacitance. Refer to ‘Cable Requirements’ on
page 11.
3. HART modem connected to PC RS-232 3. Verify laptop battery is not low
port not receiving enough power
4. Interference with I.S. barrier 4. Must use HART compatible I.S. barrier
5. Current source stripping (filtering) 5. Use the HART filter (VHF) available from
HART signal Flowserve (FLS part-No. 10156843)
Alternatively a 250Ω and a 22 µF capacitor,
installed according to the following schematic
drawing can be used to establish communication
Unit does not respond 1. Unit is in digital command mode 1. Switch to analog command mode with ValveSight
to analog commands DTM software or handheld communicator.
2. Error occurred during calibration 2. Correct calibration error. Recalibrate
Valve position reading 1. Stem position sensor mounting 1. Reposition sensor
is not what is expected is off 180 degrees
2. Stroke not calibrated 2. Calibrate stroke
3. Tight shutoff MPC (Minimum 3. No action
position cutoff) is active
4. Custom characterization or soft 4. No action
stops active
Position is driven fully 1. Stroke not calibrated 1. Calibrate valve stroke
open or closed and will 2. Inner-loop hall sensor not connected 2. Verify hardware connections
not respond to command 3. Wrong air action entered in software 3. Check ATO (Air-to-open) and ATC (Air-to-Close)
settings. Recalibrate
4. Actuator tubing backward 4. Verify ATO/ATC actuator tubing
5. Electro-pneumatic converter 5. Replace electro-pneumatic converter
malfunctioning
6. Control parameter inner-loop offset 6. Adjust inner-loop and see if proper control
is too high/low resumes
Sticking or hunting 1. Contamination of the 1. Check air supply for proper filtering and meeting
operation of the positioner electro-pneumatic converter. ISA specifications ISA-7.0.01
2. Control tuning parameters not correct 2. Lower proportional gain settings
Control system
250Ω
22 µF
14 TROUBLE SHOOTING
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