the correct valve and actuator for the
process and environmental application,
nor for the vendor’s quality assurance
program and unexpected changes that
occur in real-time situations.
Increasingly, industrial operations
are turning to “smart” Automatic Valve
Positioners (AVPs) with fully automated
diagnostic features. The automation
industry introduced the first such
devices more than 10 years ago. Since
then, intelligent valve controllers and
positioners have become widely accepted in the market. Powerful diagnostic
features are currently available on
equipment used throughout the control
Automated valve diagnostics provide
the reliability engineer with alerts when
a deviation from normal operation is
detected. Baseline tests for these diagnostics consist of data taken over an initial period with the device installed and
operating in normal process conditions.
Performance data are then continuously
monitored with the valve in operation in
Upon detecting a deviation, the valve
controller captures a data set encapsulating the alert and sends it to the diagnostic tool, which interprets the information
for the user and indicates the source of
the problem. The diagnostic automatically examines a host of parameters and
variables to identify performance issues
sometimes too subtle for even well-trained service engineers to distinguish.
ing valve package in order to obtain performance data. The automated valve
had to be forced out of its normal control region or operating condition in
order to determine its health status.
Such procedures frequently required
shutting down the process. Now this is
no longer required for capturing, storing
and managing “real-time” data.
Several industry acquaintances have
asked me if it’s possible to accurately
determine the cause and effect of valve
failure—and truly identify the compo-nent(s) that malfunctioned. There is no
possible way to answer this question in
the current article, but I do advise users
to identify the difference between behavior analysis and root cause analysis. In
other words, a safe objective is to predict failures in an effort to avoid unnecessary downtime.
CONTINUED ON PAGE 43
The Babbitt Safety
Wheel provides reliable
valve actuation 24
hours a day in refining,
processing and power
plants around the globe.
In the on/off batch-processing arena,
there is a need for more advanced
means of monitoring valve operation.
Unfortunately, users of quarter-turn
valves have never had access to the
same diagnostic solutions offered on
smart control valve positioners. In some
cases, users would install smart positioners in their applications. Now, discrete controllers with continuous 4-20
mA monitoring allow integrating the
appropriate solenoid for the application
with the advanced diagnostics.
Prior to launching on-board diagnostics, devices such as LVDTs and pressure
sensors had to be connected to the exist-
P.O. Box 51208,
New Bedford, MA 02745
Tel: 508-995-9534 Fax:508-995-2701
E-mail: email@example.com Web: www.babbittsteam.com