User Instructions - Logix® 520MD+ Series Digital Positioner
FCD LGENIM0105-00
© Flowserve Corporation
46
Field Trial Version – Printed October 28, 2011
and, in severe cases, can be an indication of the process
fluid leaking at the valve stem.
Possible Solutions: Check for packing leak. Tighten or
replace the valve packing.
YRGR
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FRICTION HIGH WARNING
Description: The valve and actuator friction has passed the
user set limit. High friction 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 friction is significantly
interfering with the valve control. If not, consider increasing
the friction warning limit. Consider the following to reduce
friction: 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.
YRYG
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STICTION WARNING
Description: The stiction, or break-away friction, is above the
warning limit. This value is typically higher than the friction
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.
YRYY
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BACKLASH WARNING
Description: The amount of detected backlash has passed
the user set warning limit. This may affect valve stability.
Possible Solutions: Check the stem and actuator for loose
components.
YRYR
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PNEUMATIC LEAK WARNING
Description: The positioner has detected a leak in the
actuation assembly. Leakage from the actuator can cause
decreased
responsiveness
and
excessive
air/gas
consumption.
Possible Solutions: Repair pneumatic leaks at the tubing
junctions and actuator seals. Check spool valve for
excessive wear.
YRRG
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LOW BATTERY WARNING
Description: The battery for the real time clock is low. The
battery is designed for a 15+ year life with the positioner
unpowered. The battery is not required for the positioner to
control properly, but is used only to maintain the time and
date upon loss of power. The time and date affect the time
stamps of alarms, warnings and other events. This warning
could be caused by rapidly power cycling the positioner.
Possible Solutions: The battery is not replaceable. Verify or
reset the time and date. Replace the main board if the
problem persists for several days.
YRRY
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PIEZO VOLTAGE HIGH WARNING
PIEZO VOLTAGE LOW WARNING
Description: If the voltage to the piezo is to high, this could
indicate an error with the relay or the main board. This may
result from an extended period of inactivity, but in this case
should not persist for more than 30 minutes when the valve is
controlling. The positioner may still be functioning, but have
reduced performance under some circumstances. If 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.
YRRR
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SPRING UNABLE TO FAIL SAFE WARNING
Description: Upon loss of air supply, the valve may not move
to the fail-safe position. The spring alone is not adequate to
overcome the friction and process load in the system. The
system is relying on pneumatic force to actuate in the
direction the spring is pushing. The failsafe spring may have
failed, or it was not sized properly for the application. Friction
or process load may have increased.
Possible Solutions: Repair or replace actuator spring. Check
for high friction. Reduce process load.
RGGG
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COMMAND INPUT BELOW ADC RANGE
COMMAND INPUT ABOVE ADC RANGE
COMMAND INPUT RANGE TOO SMALL
Description: During Command Loop Calibration, the signal
was out of the Analog to Digital Converter (ADC) range, or
difference between the signal at 0% and the signal at 100%
was too small. The system is designed to accept a
difference greater than 5 mA and between 10 and 4085 ADC.
Possible Solutions: Recalibrate making sure to use valid
command signal values.
RGGY
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POSITION RANGE TOO SMALL
POSITION SENSOR ABOVE ADC RANGE
POSITION SENSOR BELOW ADC RANGE
Description: During calibration, the range of motion of the
position feedback arm was too small for optimum
performance or the feedback sensor moved beyond its range
of operation.
Possible Solutions: Check for loose linkages. Adjust the
positioner mounting. Adjust the feedback pin back into range.
Summary of Contents for Logix 520MD+
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