Here's a wireless alternative to expensive fiberglass cabling

WiFi network for chemical plant gas chromatographs saves big compared with fiberoptic cabling connections

CG1507 ABBwirelessSolution thumb

Problem The Axiall Corporation chemical plant in Westlake, La., a maker of chlorovinyl products, decided to upgrade several gas chromatographs within an analyzer building. The analyzers monitor chemical streams such as 1,1 ethlylene dichoride and 1,2 ethylene dichloride used primarily in the production of vinyl chlorides. Axiall is North America's second-largest producer of vinyl chloride monomer. Examples of stream components measured by the online gas chromatographs include methyl chloroform, ethylene, vinyls, butadiene, nitrogen, oxygen, carbon monoxide, and carbon dioxide. The online GC analyzer values are communicated to a central digital computer system (DCS) in…

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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

Should you use a Coriolis flowmeter as a backup system? Plus a search for information about diaphragm gas meters

A backup system may not be the best use of a Coriolis meter, and a century-old gas meter technology that still has some life in it.

By Bela Liptak

This column is moderated by Béla Lipták, automation and safety consultant, who is also the editor of the Instrument and Automation Engineers’ Handbook (IAEH). If you have an automation related question, send them to:  Q: Coriolis for orifice backup? I am working at RCSPL, a…

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Control Talk Blog

Why Batch Processes are Difficult

Batch process control can seem like another world compared to continuous process control. In batch operations, process conditions are constantly changing and control loops are going in and out of service. PID control may take a back seat to sequential scheduling of manipulated flows. Here we look at why batch processes are so different and challenging and what can we do wherever possible to apply the power of PID control and Model Predictive Control (MPC). The ultimate objective here is to take advantage of the lessons learned in both worlds and enable the process control engineer to move effectively between the two worlds.

Control Talk Blog

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