System and method for identifying data useful for valve diagnostics
Embodiments of systems and methods that can facilitate data collection for valve diagnostics. The systems can include a valve assembly with a valve and a sampling device that is configured to access a repository with a first buffer and a second buffer. During operation, the valve assembly is configured to read data representing operating variables for the valve into the first buffer. The valve assembly is also configure to determine a quality measure for a first sample set of data from the first buffer, the quality measure indicating the usefulness of the first sample set of data for predicting performance of the valve relative to a second sample set of data from the second buffer. In one embodiment, the valve assembly is further configured to read data from the first buffer into the second buffer in response to the quality measure indicating that the first sample set of data is relatively more useful than the second sample set of data.
1. A valve assembly, comprising:
a valve having a plug configured to move among a plurality of positions relative to a seat;
a valve positioner coupled with the valve, the valve positioner comprising a processor and a memory with executable instructions stored thereon and configured to be executed by the processor,
wherein the valve positioner is configured to access a repository coupled with the valve positioner, the repository comprising a first buffer and a second buffer, each for storing data, and
wherein the executable instructions comprise instructions for steps that, when executed by the processor, cause the valve positioner to:
continuously acquire datasets that quantify values for setpoint, position, and actuator pressure for the valve;
read the datasets into the first buffer;
determine a quality measure for a first sample set of the data from the first buffer by,
calculating a first value for a diagnostic statistic using the first sample set;
comparing the first value to a second value of the diagnostic statistic calculated from a second sample set of the data acquired chronologically before the first sample set, the first value and the second value of the diagnostic statistic quantifying performance of the valve as variance in one or more of the setpoint, position, and actuator pressure across all datasets;
using a relative position of the first value relative to the second value to assign the quality measure;
read the first sample set of data from the first buffer into the second buffer in response to the quality measure indicating that the first value is different from the second value which indicates that the first sample set of data shows observable movement of the plug on the valve;
calculate a performance indicator from the data in the second buffer, the performance indicator relating the observable movement to onset of problematic operation of the valve, and
generate an output with instructions to operate the valve in response to a signal from a host device, the instructions reflecting the performance indicator to cause the valve to operate to maintain stability of a process that uses the valve.
2. The valve assembly of claim 1 , wherein the diagnostic statistic comprises a weighted average of the performance metrics for the valve.
3. The valve assembly of claim 1 , wherein the executable instructions comprise instructions for receiving a signal and generating an output in response to the signal, wherein the output communicates data for use by a device remote from the valve that performs the diagnostic programs with the data.
4. The valve assembly of claim 3 , wherein the data comprises one or more of the first value and the second value.
5. The valve assembly of claim 3 , wherein the data comprises data from one or more of the first buffer and the second buffer.
6. The valve assembly of claim 1 , wherein the valve positioner incorporates the first buffer and the second buffer.