Storyboarding as the First Step in High-Performance HMI Migration

Jul 20, 2016 9:32:43 AM | Posted by Jim Ford

Storyboarding as the first step in high-performance HMI migrationThe first step in migrating to a high-performance human-machine interface (HP-HMI) should always be storyboarding, which offers a visual representation of the layout and hierarchy of the new high-performance graphics (HPGs). This helps operators become an active part of the migration planning process.

Human-machine interface (HMI) migration can be a painful process—especially for operators who have resisted the move from 1st or 2nd generation CRT-based graphics to the new world of gray-scale, ASM-compliant displays with little color and greater concentration of process and instrumentation. One of the prime benefits of migrating to high-performance HMI (HP-HMI) is a reduction in the total number of graphics by as much as 25 to 50%.

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DCS Migration Project Checklist

Jun 10, 2016 11:00:00 AM | Posted by Jim Ford

Checkmark.jpgPlanning for a major project, like installing a new main control platform, can never start too early. The long-term effectiveness of the new system depends on it.

If you feel like you’re seeing discussions related to DCS migrations everywhere you turn these days, you aren’t imagining it. Lots of people are talking about it because so many of those systems are getting very old, but surprisingly few companies have started replacement projects. The failure rates are only going to get worse and some of those companies without a plan may soon be in trouble.

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How Much Are You Paying For Your Legacy DCS?

Jun 6, 2016 11:00:00 AM | Posted by Jim Ford

Your old DCS could be costing more to maintain than to replace. It’s a shocking thought, but it’s often true when all costs are considered.

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Advanced regulatory versus model-predictive control

Mar 17, 2015 3:46:00 AM | Posted by Jim Ford

Some currently practicing control engineers may be regarding the features and capabilities of advanced regulatory control (ARC) as inferior to model-predictive control (MPC)—but are they really?

A contributor to a recent LinkedIn APC blog made the following statement about the difference between advanced regulatory control (ARC) and model-predictive control (MPC):
“In a general and very simple way, an advanced regulatory controller acts based on an error, while a predictive controller uses a model in order to predict what is going to happen and acts in consequence to avoid it.”

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Distillation columns: Product composition control – process identification models

Nov 13, 2013 10:36:25 AM | Posted by Jim Ford

This technique can help reconnect information and actions that are separated by time.

Distillation columns are among the most common unit operations for separation and purification in process industries. Control of the composition (purity) of one or more of the product streams is invariably critical for economic operation of the column. For precise composition control, on-stream process analyzers are often employed to measure composition of the critical product. For example, monitoring the amount of a key impurity that must be kept below a maximum specification limit in the product.

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Initial Settings For PID Controllers

Jan 15, 2013 4:03:00 AM | Posted by Jim Ford

Let’s say you’re the lead configuration engineer on the automation portion of a green-field plant installation project, and you need to give your start-up guys a head start with a set of default PID tuning constants. You want to hand it over in a way that the board operators can place some of their basic controls in auto mode with the expectation that the loops will control fairly close to their setpoints without significant oscillation.

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Tricks Of The Trade: Level Control

Jul 23, 2012 9:44:00 AM | Posted by Jim Ford

I often say, “Levels are devils to control.” Why? They’re integrating variables; that is, if the level in a vessel is constant, and the valve is opened or closed and then brought back to its original opening, the level will be at a different place in the vessel. Levels are non-self-regulating – they represent an imbalance between the flow of material into and out of a vessel. The tuning challenge is to find the best combination of gain (or proportional band) and integral time (or reset) that attempts to react to material flow imbalances and maintain the level reasonably close to a set point. For a variety of reasons, using derivative is not a good idea for level control. Gain alone or PI control handles PV trajectory changes quite well.

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From the Trenches: Distillation Columns – Internal Reflux Control

Jun 6, 2012 3:31:03 AM | Posted by Jim Ford

Distillation columns are one of the most often used unit operations for separation and purification in the process industries. They can also be some of the most complex to operate and control, because they involve two-phase, multi-stage, counter-current mass and heat transfer (each tray or segment of packing is a theoretical equilibrium stage). The greater the number of trays, the longer the time constants related to composition changes.

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