Valve Magazine - Spring 2008

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 valve world.

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 the process.

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.

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Around The

Clock Valve

Safety

The Babbitt Safety

Wheel provides reliable

valve actuation 24

hours a day in refining,

processing and power

plants around the globe.

Latest Advancements

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.