An Editor's Education on Process Applications

Besides learning about detailed best practices for calibrating pressure devices, Executive Editor Jim Montague was reminded of the underpinnings of not just pressure, but process applications in general.

Jim Montague
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I've covered and written about process control and automation for quite awhile, but it always seems like there remain many basic concepts that elude my limited ability to understand them. I can describe how they work, of course, but I'm short on knowing why. Luckily, several of these were cleared up on Feb. 19 when I attended the second of two 90-minute webinars hosted by the ISA and presented by Hunter Vegas, project engineering manager at Wunderlich-Malec, Ned Espy, technical director at Beamex and Roy Tomalino, professional services engineer at Beamex. I liked the second webinar so much that I asked ISA for the YouTube link to the first one held on Oct. 2, 2014, and…

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Timeless Resources

Beginner's Guide to Differential Pressure Level Transmitters

By David W. Spitzer

The importance of level measurement cannot be overstated. Incorrect or inappropriate measurements can cause  levels in vessels to be excessively higher or lower than their measured values. Low levels can cause pumping problems and damage the pump, while high levels can cause vessels to overflow and potentially create safety and environmental problems. Vessels operating at incorrect intermediate levels can result in poor operating conditions and affect the accounting of material. Learn more.

Controllers: Direct vs. Reverse-Acting Control

By Bela Liptak

Valve failure position is determined by safety considerations. If, in case of failure, you want your column to go on full reflux, your selection where the reflux control valve is fail-open, and net overhead control valve is fail-close, is right. Assuming that the valve actuators are spring-operated pneumatic ones, and assuming that you define "failure" as the loss of air supply, the spring will act to open a fail-open (FO) valve and to close a fail-closed (FC) valve, regardless what the controller actions are. Read more.

Voices: Ask The Experts

Linear or Equal Percentage Valves: When Should I Use Which?

Since the goal is to control loop stability, the choice that gives you the best chance of that is the one to make.

By Bela Liptak

Question: Is there some general rule on when we should use =% (equal percentage) and when linear control valves? I know that the determining factor is the inherent flow characteristic, the flow vs. lift at constant pressure drop, or something like that. I do not know what this means, because…

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Control Talk Blog

How MPC will Take Over More of the Role of PID Tips

The power of the PID largely remains untapped. I have recently documented the extensive capability of the PID but being a realist, I expect MPC is going to take over more and more of the role of the PID. Here we look at the reasons why there is a brighter future for MPC and if there is an opportunity to reverse the decline in PID expertise.

Control Talk Blog

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