Flowserve Logix MD+ ValveSight - Manual (Page 47)

ValveSight™ Diagnostics DTM Manual for Logix MD+ Positioner with HART®
FCD- LGENSF0014-00
© Flowserve Corporation
47
Tight Shut Off Mode
•
Definition: - (Also called MPC.) The Final Command is beyond the user
set limit for the tight shutoff feature and the positioner is applying full
actuator pressure to close (or open) the valve. This is a normal
condition for all valves when closed. The factory default setting triggers
this at command signals below 1%. This indication may also occur on 3
way valves at both ends of travel if the upper Tight Shut Off value has
been set.
•
Possible Solutions: If tight shutoff is not desired reset the tight shutoff
limits or adjust the command signal inside of the specified Tight Shut
Off values.
Pressure Control Lock
•
Definition: The pressures are held constant (locked), improving the
stability of the valve position. When the position of the valve gets very
close to the commanded position, the positioning algorithm will change
to pressure control. The point at which the pressure control is locked
depends on the Valve Stability switch on the positioner. When the
switch is set to “Lo Friction”, the locking point is self-adjusting to
optimize accuracy. When the switch is set to “Hi Friction” and the
deviation is smaller than +/- 1.0% (default), the pressure “locks”. The
High Friction window size can be changed to optimize the response for
valves and actuators with high friction levels. This setting slightly slows
the response and will normally stop limit cycling that can occur on high
friction valves.
•
Possible Solutions: If "Hi Friction" is set and this indicator never
comes on, the error band limits may need to be adjusted using the
Pressure Control page of the DTM or the Display Menu. Use the Valve
Stability Configuration Switch to toggle the Valve Stability from "Lo
Friction" to "Hi Friction" mode. A QUICK-CAL must be performed to
apply the switch settings. If a QUICK-CAL cannot be performed, use
the DTM to activate and set the "Hi Friction" window setting. .
CST Mode (Continuous Stroke Test Mode)
•
Definition: When there is no variation in the command input, this
feature is deliberately moving the valve as little as possible in order to
perform diagnostics and ensure the valve is functioning.
•
Possible Solutions: If more stability is required, turn off Continuous
Stroke Test mode, or configure the rate of travel, period, and allowable
movement using the Continuous Stroke page of the DTM.
Training Mode
•
Definition: The positioner is gathering data for a certain period of time.
This data can be used in the DTM to help set reasonable limits for
diagnostic warnings and alarms.
•
Possible Solutions: Training has no effect on control. Allow the
training to finish if the process conditions are typical. Or start the
training over if new process conditions have been applied. See the
Training Mode page in the DTM for configuration.