The Best Way to Automate a Hazardous Area

Four main methods are available for implementing automation in hazardous areas. Here's how to select the best one for your application.

Dan Hebert
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Automation and instrumentation components and systems must often be installed in process plant areas classified as hazardous according to IEC or NEC. These projects present challenges in terms of design, installation and maintenance. For all such installations, there are four main options as shown in the table: explosion-proof, intrinsically safe, non-incendive or purged. Each approach has its advantages and drawbacks, and many installations will be best served by a combination of two or more methods. Perhaps the newest development in hazardous-area installation is more widespread use of the non-incendive or non-sparking approach, which requires AEx nA-rated components.

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Timeless Resources

Beginner's Guide to Differential Pressure Level Transmitters

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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.

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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

Blowdown percentages to consider for pressure relief valves and interface level in oil separators

Our experts offer practical suggestions for solving these tricky problems.

By Bela Liptak

Q: Relief Valve Blowdown I want to know about blowdown percentage we should consider for pressure relief valves in liquid, gas, vapor services. Is there any reference which gives the percentage of blowdown for different services? Medhi Poormehdipoor.mehdi@gmail.com A: Blowdown (blowback) is the…

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Control Talk Blog

Good Tuning Rule of 5 Tips

Most of the control literature focuses on minimizing the integrated absolute error (IAE) for a step disturbance, often in a linear system. In the process industry, there are many other objectives and complications that require special attention. Here we quickly review when and how to achieve minimum IAE and see how a rule of 5 comes into play for applications with different challenges.

Control Talk Blog

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    Automation and instrumentation components and systems must often be installed in process plant areas classified as hazardous according to IEC or NEC. These projects present challenges in terms of design, installation and maintenance. For all such installations, there are four main options as shown…

    Full Story
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