VCIOM-05044
Page 20 of 75
DIgITal EPIC-2 TEChnICal Manual
InstallatIon and operatIng InstructIons
note with Full-Stroke Signatures they are
actually broken into two signatures, one
for opening direction and one for closing
direction which makes up one full-stroke
cycle. In addition, there are certain critical
points within these signature plots which are
very meaningful in determining if a valve/
actuator is performing properly. These critical
points or data are found by the device during
the capture of the signatures and save in a
database called Run-Time Data. There is
Run-Time Data for the Baseline Signature and
for the latest Maintenance Signature only. The
device in analyzing the Maintenance Signature
against the Baseline actually uses this data
derived from the signatures to determine if
there is degradation in performance. This way
the user does not need to actually analyze the
signature plots especially if unfamiliar. The
device looks at the Run-Time Data and makes
decisions and sets or clears alerts in an alert
File as notification to the user of any potential
problems. It is only up to the user to set
hysteresis settings in configuration as a guide
for the device to know what is out of tolerance.
Figure 17 shows an example of a PST signature
plot as they might appear displayed on a haRT
host using the haRT DD:
again, there are certain critical points within
these PST signature plots which are very
meaningful in determining if a valve/actuator
is performing properly. These critical points or
data are found by the device during the capture
of the signatures and saved in a PST database.
There is data for the Baseline PST Signature
and for the latest Maintenance PST Signature.
The device in analyzing the Maintenance
PST Signature against the Baseline actually
uses this data derived from the signatures
to determine if there is degradation in
performance. This way the user does not
need to actually analyze the signature plots
especially if unfamiliar. The device looks at the
data and makes decisions and sets or clears
alerts in an alert File as notification to the user
of any potential problems and also sets alarms
in the alarm File if there is a hard failure. It is
only up to the user to set hysteresis settings in
configuration as a guide for the device to know
what is out of tolerance.
FIguRE 17
PST signature
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