Archive | Process Measurement & Control

ISA Process Measurement & Control Division

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Use Signal Characterization in the DCS to Linearize the Installed Flow Characteristic of a Valve

Signal characterization to linearize valve installed flow characteristic has a bad reputation due to some practical implementation problems. These problems can be addressed today by doing the characterization in the distributed control system (DCS), but the stigma remains. With pneumatic positioners, signal characterization was done by the use of a cam. Standard cams were based […]

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How to Use Valve Position Control to Optimize Process Efficiency and Capacity

There are many opportunities for process optimization by valve position control (VPC). Table 1 summarizes common examples of the use of VPC for increasing process efficiency and capacity. Efficiency is increased by reducing energy and raw material costs for a given production rate. Capacity is increased by increasing feed rates for a given efficiency. Table […]

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How to Achieve Process Simulation Fidelity

The best way to classify process simulators is to look at the original intent of the simulator software when it was first released, who the software developers were, who configures the models, and how the models are used. Simulators originally designed for system acceptance testing (SAT), operator training systems (OTS), and process control improvement (PCI) […]

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How to Determine the Health of a Reference Electrode

The reference electrode should provide a fixed reference potential and a path of electrical continuity from the internal reference element via a porous surface or aperture between the reference electrolyte and the process called a liquid junction. Coating of the reference junction can cause slow equilibration. Process ions, such as cyanide, can cause precipitation of […]

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