Archive | Process Measurement & Control

ISA Process Measurement & Control Division


How to Select a pH Sensor for Harsh Process Environments

For today’s process plants, pH is an important parameter to measure in a host of demanding applications. A good example is flue gas desulfurization (FGD) control with systems using wet scrubbers in lime or limestone slurries. Proper pH can maximize sulfur oxide (SOx) removal and minimize the build-up of scale. Selection of the best sensor […]

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hot steel processing

What is an Optimal Control System for Batch Manufacturing?

If you’re working in batch manufacturing, you are painfully aware of the ever-increasing demand to produce more and more and – while you’re at it – cut costs. Well, hey, you weren’t doing much this week anyway, so you may as well increase production and lower operating costs, right? Reducing the total cost of ownership […]

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Pressure Meter

How to Select the Optimal Temperature Sensor

In industrial environments, high process temperatures, pressures, and vibration make it necessary to have a robust temperature sensor. Fast response time, accuracy, and stability are also needed. While several types of temperature sensors are available, such as thermistors, infrared pyrometers, fiber optic, and others, the two most commonly used in the process measurement industry are […]

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Chemical plant scientist

What are the Top 10 Mistakes Made Every Day in pH System Design?

Since we learn by example, here is a neutralizer tank that has the major mistakes I have seen in waste treatment system pH design and installation. Each mistake is the result of a fundamental lack of understanding of the heightened sensitivity of pH control systems to dead time, process and measurement noise, insufficient process attenuation […]

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Chemistry Lab Testing pH

What are the Essentials of pH in Industrial Applications?

The pH electrode offers by far the greatest sensitivity and rangeability of any measurement. To make the most of this capability requires an incredible precision of mixing, reagent manipulation, and nonlinear control. pH measurement and control can be an extreme sport. At the neutral point, the concentration of hydrogen and hydroxyl ions is by definition […]

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industrial laser with sparks flying around

How to Use Plant-Wide Feedforward for More Flexible and Efficient Production

The pressure to reduce inventories, coupled with changing market demands and fluctuations in raw material and energy prices, requires a process plant to be able to respond quickly to maintain optimum operation. To most efficiently support changes in production rate or product grade, flows must change in unison throughout the plant. Feedback loops cannot do […]

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Factory control room

What are the Benefits of Identifying Deadtime and Ramp Rate

In Tip #70, we learned that deadtime was the key to loop performance. The Control Talk blog The ABCs of Controller Tuning describes how tuning settings can be reduced to a simple function of deadtime. The InTech article PID Tuning Rules and the article’s online appendices describe the fundamental relationships between deadtime, performance, and tuning. […]

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Chemical factory

How to Smooth the Transition Between Batch and Continuous Operations

Processes often include a mixture of batch and continuous operations. For liquid products made in a batch operation, most of the time the batch flow is off because the drain valve is closed during the batch. When done, the batch is drained quickly. This discontinuous batch flow cannot directly feed continuous operations downstream. For traditional […]

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Modern refinery with blue sky

How to Use an Adjustable Flow Ratio and Feedforward Summer to Optimize Flow Measurement

If you look at a process flow diagram, you quickly realize that the flows are designed to move up and down in unison. The ratios of the flows are maintained. If you double production rate, you can double the process flows as a first approximation. The utility flows for heating and boilup will probably double […]

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