User Instructions - Logix® 520MD+ Series Digital Positioner
FCD LGENIM0105-00
© Flowserve Corporation
49
Field Trial Version – Printed October 28, 2011
value. Stiction can cause loop oscillations, poor position
control, jerky motion, or valve sticking. It can be caused by
build-up from the process on the stem, trim or seat , by a
failing bearing or guides in the valve and actuator, galling of
the trim or stem, excessively tightened packing, linkages, or
other valve or actuator mechanical issues.
Possible Solutions: Determine if the stiction is significantly
interfering with the valve control. If not, consider increasing
the stiction warning limit. Consider the following to reduce
stiction: Stroke the valve to clear off build-up. Clear any
external mechanical obstruction, loosen the packing, clean
the stem, repair or replace the actuator. Highly localized
friction or very jerky travel can indicate internal galling.
Repair or replace internal valve components.
RRYY
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BACKLASH ALARM
Description: The amount of detected backlash has passed
the user set alarm limit. This may affect valve stability.
Possible Solutions: Check the stem and actuator for loose
components.
RRYR
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DRIVER MODULE ALARM
Description: The pilot relay can't open, the pilot relay can't
shut, or the Hall sensor circuit has failed.
Possible Solutions: Check the internal wiring connections.
Replace the pilot relay.
RRRY
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PIEZO VOLTAGE HIGH ALARM
Description: The voltage driving the piezo is above the alarm
limit. This could indicate an error with the relay or the main
board. The positioner may still be functioning, but have
reduced performance under some circumstances.
PIEZO VOLTAGE LOW ALARM
Description: The voltage to the piezo is too low. The piezo
may be damaged. This may prevent the proper failure
position upon loss of signal/power. This condition may occur
briefly on an air-to-close valve that is held for long periods of
time in the closed position, or an air-to-open valve held in the
open position.
Possible Solutions: Ensure the supply pressure is not low. If
alarm persists for more than 30 minutes, the Piezo assembly
is damaged. Replace the pilot relay.
RRRR
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POSITION DEVIATION ALARM
Description: The difference between the command and the
actual position has been greater than the user-set limit for
longer than a user-set time.
Possible Solutions: Review active alarms and warnings to
find root causes of this alarm. The deviation settings can be
changed in the Valve Health page of the DTM.
Summary of Contents for Logix 520MD+
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