Flowserve Logix MD+ ValveSight - Manual (Page 89)

ValveSight™ Diagnostics DTM Manual for Logix MD+ Positioner with HART®
FCD- LGENSF0014-00
© Flowserve Corporation
89
Piezo Voltage
The Piezo Voltage page shows detailed information about the circuit that drives the piezo
valve in the pilot relay. The piezo valve converts the voltage to a pressure that acts to move
the poppet or spool.
Status Area
The Active Indicator area shows the status of the most relevant active indicator. The color
of the "LED light" corresponds to the Active Indicator and the first color of the blink code
sequence on the positioner. Generally green indicates no immediate issues. Yellow
indicates a developing issue. Red indicates the ability to control may be compromised. A
detailed list of the indicators is given in the
Alarm Congfiguraion - Alarm Annunicator page.
The Command Source field indicates weather the positioner is being controlled by digital or
an analog (4-20 mA) command source.
Piezo Voltage
The Piezo Voltage shows the Piezo Voltage and the warning and alarm limits. The Current
Value field displays the measured piezo voltage. A outside the Warning limits will cause
the health bar on the dashboard to turn yellow. A voltage outside the Alarm limits will
cause the health bar on the dashboard to turn red. The limits are not adjustable.
Warnings and Alarms
Piezo Volts High
•
Definition: The voltage driving the piezo is above the warning limit.
•
Implications: 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.
•
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.
Piezo Volts Low
•
Definition: The voltage to the piezo is too low.
•
Implications: 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