Flowserve Logix MD+ ValveSight - Manual (Page 32)

ValveSight™ Diagnostics DTM Manual for Logix MD+ Positioner with HART®
FCD- LGENSF0014-00
© Flowserve Corporation
32
Pilot Response
•
Definition: The pilot relay is sticking or slow to respond.
•
Implications: This affects the responsiveness, increases the chance of
limit cycling and excessive air consumption. The pilot relay is part of the
inner loop and consists of the driver module assembly with piezo (I-P
relay) which is coupled to the spool valve or poppet. The value of this
indicator corresponds with inner loop lag. Delayed response can be
caused by a partially clogged piezo or debris, oil, corrosion, or ice on
the spool, or low supply pressure.
•
Possible Solutions: Check response of the valve. If OK, adjust Pilot
Relay Response limits. Check supply pressure. Check the spool or
poppet for debris, oil, corrosion, ice on the spool. Clean or replace the
spool or poppet assembly. Replace the piezo or driver module
assembly. Maintain a clean, water-free air/gas supply.
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
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.
Driver Module
•
Definition: Driver module alarm.
•
Implications: 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.
Control Status
Command Frequency