Diagnose Instrument and Valve Issues

The best tuning in the world can't fix a valve problem! For good control, you need the entire control loop to perform. This includes the instrument, the controller, and the control valve. ExperTune's PID Loop Optimizer contains the tools you need to: Reduce Control Valve Wear Extend Valve Life Ensure Optimal PV Filtering Reduce Maintenance Costs With PID Loop Optimizer, the net result is improved control and better reliability.

Valve Stiction Wizard

A sticking valve caused by friction within the valve can seriously degrade control loop performance. This phenomenon is called valve stiction. The more your valve suffers from stiction, the more your loop will oscillate around the setpoint. An ExperTune wizard guides you through determining the amount of stiction in your control loop. Anything more than 0.5% stiction and correcting the situation may dramatically reduce cycling and improve loop performance. The wizard will come up with a stiction value even in loops where noise is excessive.

Flow Control 2001 Innovation Award winner for Valve Stiction Wizard

Valve Wear Analysis

ExperTune shows how to reduce control valve wear extending valve life and useful valve service time.

Only ExperTune calculates optimal PV filtering and optimal PID values to reduce the valve travel and reversals for less valve maintenance cost. Lets you replace and rebuild valves less often.

Improve and maximize valve life by comparing tuning and PV filtering. Try what-if.

ExperTune compares predictions of valve travel and valve reversals numerically and graphically in the presence of noise for both current and optimized values. Both the Reversal and Travel Indices are directly related to valve wear. The software analyzes optimized values to reduce the indices resulting in longer valve life. Often times the life of the valve can be increased without sacrificing loop performance or robustness.

• Valve Travel Index—a quantitative comparison of how far the valve will move—lets you compare tunings and filters to see the effect on valve wear. Total valve travel for each case also given.
• Valve reversal index—quantitative comparison of the number of times the valve will change direction—compare tunings and filters to see the effect on valve wear. Total valve reversals for each case also given.
• Use the PV filter to minimize valve wear. Choose between first order, second order, Butterworth or averaging filters. Try changing the filter and PID values yourself and see immediately the effect on valve wear and loop performance.
• Simulation with noise. Try what-if to see how changing tunings or filters effects controller output wear.
• For a quantitative check of performance and robustness, the software computes a Performance Increase and Robustness Index. Use the Performance Increase to see if loop responsiveness is compromised by reducing valve wear. Use the Robustness Index to see if the loop sensitivity (to the process changing) is compromised by reducing valve wear.
• For ISO9000 or if problems occur later, ExperTune creates a detailed report of current to new settings for comparison. The report sums up the Tuning parameters, filter, Valve wear analysis, Performance and Robustness indices, and process model. The report also includes comparison graphs including: Robustness plots, simulated loop response, noise response plots. ExperTune creates reports in Microsoft Word. The report's graphs and values are driven by user set bookmarks, and are completely user customizable.
• Any tuning parameter, PV filter size or type are easily tested and compared off-line in simulated time response plots of set point changes, load upsets, or response to noise. These in one window and the robustness plot in another. Change a parameter and the graphs instantly update with both the current and new response plotted in red and blue for easy comparison. Try what-if analysis to get the exact response you want before you download tuning parameters or apply a PV filter.

Manage Noise with a PV Filter

Only PID Loop Optimizer calculates the largest possible filter for your selected tuning category. The filter is as large as possible without degrading performance significantly.

• Choose from first order, second order, Butterworth, or averaging filters. Try changing the filter and PID values yourself and see immediately the effect on valve wear and loop performance.
• Use ExperTune's filter time or try what-if with your own current or new filter times. Simulation and robustness plots update instantly to reflect your filter type and size.
• Use the new PV filter to analyze the effect on valve wear analysis using the new noise simulation.
• See the entire family of PV filters for each tuning category in the PID grid.

Specify your filter address and PID Loop Optimizer automatically reads the current filter value from your controller. It is displayed next to the current PID values. After the software has found the best filter for your process, click Download and the new filter value is written directly to your controller.

Is a Large Instrument Filter Hiding Problems?

If your process variable is filtered, the filter may be masking or hiding problems in the loop. Additionally, a filter could make the process much harder to control.

You can direct PID Loop Optimizer to automatically unfilter your data. With "Unfilter PV" checked, optimal PID Tuning and filter calculations are based on the true data. Even though you collected filtered data, you can also see the plot of the raw data by checking unfilter.

Two unfiltering options are available allowing you to remove the effects of PV filtering no matter where the filter is in your control system. The options are:

1. Filter time is automatically read and compensated for by PID tuner. In this option the filter time is read from an address in your controller. The data is automatically unfiltered (if you select "Unfilter PV")
2. Or enter the filter time used by your transmitter or control system.

Either option lets you see the result of unfiltering in the time response plot—see the raw, unfiltered data.

PID Loop Optimizer Does Much, Much More

Far beyond basic loop tuning, the PID Loop Optimizer Software does much more, including:

• Fast & Easy PID Tuning
• Process Modeling & Advanced Tuning
• Tools for Specific Applications
• Reporting & Documentation Tools
• Eliminate Interactions Between Loops
• Advanced Control Tools

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