Flowserve 420 IOM - Manual (Page 25)

User Instructions - Logix® 420 Series Digital Positioners FCD LGENIM0106-06 12/13
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25
Window - When the position of the valve gets within the
pressure control window, the positioning algorithm will
change to pressure control. This means the pressures will
be held constant (locked), improving the stability of the
valve position.
NOTE: The pressure control feature of the Logix 420
functions without the use of pressure sensors. In the DTM,
this feature is configured on the Valve Stability page.
10.3.8 Configuration (Soft Limits and Shutoff)
Soft Limits allows the user to limit the movement of the
valve. Shutoff allows the user to tightly shut the valve with
all available force.
High Soft Limit and Low Soft Limit - This feature is used to
simulate physical blocks on the valve that restrict
movement past a set point. Once the Soft Limit is set, the
positioner will not attempt to move the valve position (final
command) beyond the set point, regardless of the analog
or digital command input signal.
CAUTION: Changing the Soft Limits may limit the
movement of the valve. The valve may not shut or open
fully.
NOTE: Removing power to below 3.6 mA will still cause the
valve to move to the de-energized state regardless of the
Soft Limits.
Upper Position Shutoff and Lower Position Shutoff - This
feature, (also called Minimum Position Cutoff or MPC) is
used to tightly close or open the valve. It is used when a
tight seal is needed or when debris or friction may
otherwise interfere with complete closure. When the valve
is commanded past the Shutoff points, the pilot relay will
direct full supply pressure to the appropriate port, applying
all available force to close (or open) the valve. The Shutoff
points apply to the Final Command.
CAUTION: Changing the Shutoff limits may cause the
valve to fully open or fully close after the command passes
a set limit.
Though Shutoff and Soft Limit features should not be used
together, if both are set, the greater of the two settings will
take precedence at the closed end; and the lesser of the
two settings will take precedence at the open end.
10.3.9 Configuration (User Preferences)
The User Preferences menu allows the user to format how
information is displayed.
The following table shows the available options. By default
the positioner is set to show information in International
System (SI) units. To change all units to North American
(English), make the selection under All Units. Each
selection can also be changed individually.
Table 14: User Preference Options
Units/Format
International
System (SI)
(Default)
North
American
(English)
Other
Options
All Units SI North American -
Temperature degrees C degrees F -
Actuator Area cm2 in2 -
Date Format Day.Mon.Year Mon/Day/Year -
Number Comma Decimal Point -
LCD Orientation
– Use this selection to turn the turn the
display upside down (rotate 180 degrees). Use this feature
when the positioner is mounted upside down.
►Configuration
►Soft Limits & Shutoff
►High Soft Limit
►Low Soft Limit
►Upper Position Shutoff
►Lower Position Shutoff
►Configuration
►User Preferences
►All Units
►Temperature Units
►Actuator Area Units
►Date Format
►Number Format
►LCD Orientation