Monthly Archive: December 2009

Dec
15

Exceptional Opportunities in Process Control – VSD Dynamics and Rangeability

The figures in the attached VariableSpeedDriveRangeability.pdf and the following discussion is an excerpt from the ISA book The Essentials of Modern Measurements and Final Elements – A Guide to Design, Configuration, Installation, and Maintenance. The 4 main practical reasons that variable speed drives (VSD) drives are not used as extensively as one might think for …

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Dec
08

Exceptional Opportunities in Process Control – Control Valve Rangeability

There are a lot of ways of looking at rangeability. Nearly all of them lead to the wrong conclusion as to what type of valve is best for process control. Some of the absolute worse valves for control (e.g. on-off piping valves) have the highest stated rangeability. Valve rangeability is particularly important for pH control, …

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Dec
01

Exceptional Opportunities in Process Control – Control Valve Dynamics

In the process industry, what a control loop eventually manipulates in nearly all applications is a flow via a final control element such as a control valve, damper, or variable speed prime mover (pump, fan, or compressor). Dampers and variable speed prime movers are commonly found in utility systems. Peristaltic pumps are used in labs …

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