VVP10 HART
HART
®
VALVE POSITIONER
INSTALLATION, OPERATION, CONFIGURATION AND MAINTENANCE MANUAL
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Position Histogram
Diagnosis that provides the user with a history of the positions traveled by the valve during its operating period. It
enables the visualization of a graph (via DTM or another configurator that offers graphs) with the percentages of time
in each of the 5% ranges of the valve travel.
The Histogram does not require any configuration and does not have any alarms, being a system behavior monitoring
diagnostic for user analysis and comparisons.
Figure 3.24 shows an example of a graph of the history of the positions traveled by a valve during its operation. Note
that the control was about 80% of the time between 40% and 60%, plus about 20% of the time with PV=0% - indicating
possible valve closure for maintenance, for example.
Figure 3.24 – Example of graph for valve position history.
The diagnostics has an Operation Time count, informing how long it has been active since the diagnostics was last
reset (reset). On restart, operating time and graph points are reset to zero.
Valve Signature Test (Full Stroke Test)
Test that verifies the performance of the system throughout its excursion, varying the Setpoint from 0% to 100% and
returning to 0%, in a period configured by the user through the
FST Stroke Time
parameter, performing Position,
Setpoint and Output Pressure readings (for models with pressure sensors) that can be archived.
This test is also known as Valve Signature because it maps the possible sticking points of the system at a given point,
recording the complete valve performance profile for future comparisons.
The default runtime per cycle setting is thirty seconds (30s) and can be changed to 60s, 90s, 120s or 180s. At the end
of the test, if performed successfully, the system Hysteresis value (difference between the opening and closing
performances of the system) is displayed, together with the point of occurrence. If the execution fails, the system total
stuckness alarm (
No Movement / Low Air Supply
) will be activated.
In the graph of figure 3.25 is an example of a curve of a single action system (spring return) after the Valve Signature.
Note that there is a point P1 that indicates an increase in pressure, in order to maintain the Position following the
Setpoint, followed by the normalization of the curve, forming a “bump”. This condition indicates punctual friction of the
system, since the linear pressure was not enough to move the valve in that position, causing oscillation in the opening
and closing curves (
Pressure x Position
).
Note in figure 3.26 that, even for models that do not have pressure sensors installed, the friction of the system can be
analyzed by the opening (blue) and closing (red) curves of the test at the same point P1 -
when the pressure sensors
are not available, the Valve Signature graph is plotted as Position x Setpoint.
Also, note that there is a gap between the upper and lower pressure curve, the system hysteresis (H). The higher its
value, the greater the difference between the opening and closing pressures for the same point in the system, which
is not desirable, suggesting maintenance. The beginning and end points of the curves indicate the valve seating, with
maximum and minimum pressures.
NOTE
The first point on the graph indicates the percentage of time the valve was fully closed (PV=0%), while the
last point indicates the percentage of time the valve was fully open (PV=100%) – considering the installation
to Open (AirTo Open).
