Flowserve Logix MD+ ValveSight - Manual (Page 37)

ValveSight™ Diagnostics DTM Manual for Logix MD+ Positioner with HART®
FCD- LGENSF0014-00
© Flowserve Corporation
37
Supply Pressure High
•
Definition: The supply pressure is above the user set warning limit.
•
Implications: Supply pressure that exceeds the maximum rating on the
actuator can become a potential hazard.
•
Possible Solutions: Regulate the supply pressure at the positioner
below the maximum limit recommended for your actuator. Recalibrate
pressure sensors. Check the pressure sensor board
connections. Replace pressure sensor board if necessary.
Supply Pressure Low
•
Definition: The supply pressure is below the user set warning or alarm
limit.
•
Implications: Low supply pressure can cause poor valve response or
positioner failure. The minimum recommended supply pressure for
proper operation is 1.3 bar (19 PSI).
•
Possible Solutions: Regulate the supply pressure at the positioner
above 1.3 bar (19 PSI). Ensure system air/gas supply is
adequate. Repair kinked or restricted supply tubing. Check for
pneumatic leaks in the actuator and actuator tubing. Recalibrate
pressure sensors. Check the pressure sensor board connections and
replace pressure sensor board if necessary.
Actuation Ratio
•
Definition: The force required to control the system is close to the
maximum available force.
•
Implications: Actuation Ratio is based on the ratio of available force to
the required force to fully actuate. Control may be lost if this ratio
reaches 100%. It is affected by the process load, friction, spring force,
and available supply pressure.
•
Possible Solutions: Increase the supply pressure. Reduce the
friction. Check the actuator spring. Resize the actuator. Adjust user
set limits.
Spring Fail
•
Definition: Upon loss of air supply, the valve may not move to the fail-
safe position.
•
Implications: 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