Monthly Archive: January 2007

Jan
29

Protecting Your Back – the Cautious Approach and Fast Getaway Scenario

While approaching an optimum something can sneak up that catches the loop off guard. Because of the deadly foe dead time, by the time the loop sees and reacts, it may be too late, particularly if it was blind sided. The classic example is compressor anti-surge control. When moving to a lower discharge pressure or …

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Jan
26

SP104 Initiative to Raise Industry Awareness of EDDL

With the introduction of digital field devices, manufactures of control systems and maintenance tools were faced with the challenge of how to access and display information in devices that were produced by different companies. Over the years, a number of approaches have been developed. However, the Electronic Device Description Language (EDDL) is the dominant technology …

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Jan
22

Block Structure of Fieldbus Devices

The physical standard and technical report produced by ISA SP50 were used as a starting point for much of the work done by the Fieldbus Foundation. In particular, the Fieldbus Foundation function block specification team adopted some basic concepts such as the definition of mode and status with minor changes from the definitions contained in …

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Jan
22

Stuff that Comes at You Too Fast

Last year we had disturbing thoughts on how fast upsets were particularly disruptive and anything you can do to slow them down makes the job of a loop much easier. In real processes, step disturbances are quite rare. However, there are some noticeable cases (e.g. on-off level control, interlocked and sequenced valves, and compressor surge …

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Jan
15

Use of Mode in Process Control

One of the foundation pieces of measurement and control as utilized by the process industry is the concept of mode. The mode of a measurement inputs to a control system may be used to indicate if the associated device is in or out-of-service. For a control or output function in a control system, the plant …

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Jan
15

Five Weeks in Five Minutes

Time is precious so here is your chance to learn in five minutes what took me five weeks of investigation. While most of these thoughts were banging around in my mind for last couple of decades, they might never have congealed if not for some triggering thoughts from my colleagues Terry Blevins and Willy Wojsznis …

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Jan
08

Innovation in the Pharmaceutical Industry

When DeltaV Predict (embedded model predictive control, MPC) was introduced in 2001, I developed some of the MPC lecture material and process simulations that are used in our advanced control education class, 7201. Also, I helped teach the first three of four classes. I always enjoy teaching in these types of classes since of the …

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Jan
08

When is a Batch a Batch?

I haven’t gotten any feedback on process feedback, which is really fortunate because it allows me to keep my new years resolution, so I will slog the blog along to the question that has been keeping people awake at night; “When is a batch a batch?” Some say all processes like life are batches because …

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Jan
01

PID Modifications for Unreliable Communications

As noted in my December 4th posting, the Hart Communication Foundation has adopted the IEEE 802.15.4 physical layer for wireless HART. One of the technical challenges is that the 2.4 GHz spectrum defined by IEEE 802.15.4 is also used by Wi-Fi and Bluetooth devices. Also, some electrical devices found in industry generate noise in this …

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Jan
01

Top Ten Broken New Years Resolutions

(10) Stop talking about process feedback. I promise to do this right after this blog. (9) Listen intently to my wife’s instructions. Why does my mind still jump to weighty matters like what is next for dinner? (8) Stop making cheap control valve jokes. Could the next final element reputation I hurt be my own? …

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