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Sustainability in Instrumentation and Process Control: The Benefits of a Holistic Approach

Posted on August 29th, 2016 by in Chemical Manufacturing Excellence


The existence of interrelationships between the domains of sustainability (processes, economics, politics and culture) is implied in our working definition of sustainability and alluded to in previous posts.  The existence of these interrelationships implies that superior sustainability can be achieved by considering all four domains holistically.  The advantage of a holistic approach is to be able to evaluate the effect(s) of a solution on the other domains and on overall sustainability.

For example, suppose that the tank levels in multiple tanks between serial processing operations are oscillating.  As a result, flow to each subsequent processing operation also oscillates and causes an economic penalty at higher production rates.  It is assumed that reducing the oscillations would make the plant operate more economically at higher throughput — thereby improving sustainability.  Interestingly, the solution to the problem is often determined by the skillset of the problem-solver and could range from looser controller tuning to installing larger tanks — neither of which would fully address the root cause.  Larger tanks would increase the amount of material in the plant (economic penalty) and make the plant more cumbersome (process penalty).  A previous post suggested upgrading to a cascade control loop in a plant where “cascade loops do not work — end of discussion” (political and cultural penalties).  Now what?

For the instrumentation and control professional, it would be prudent to ensure that all of the existing instruments and controls are functioning properly.  For example, are the flowmeters exhibiting hysteresis?  Are the control valves moving smoothly or sticking?  Would installing control valve positioners improve performance?  Are the controllers properly tuned?  Can the level controllers be configured to take no control action between reasonable limits allowing the level to fluctuate somewhat while stabilizing flows to the next processing operation most of the time?

Sometimes there is now one solution that checks all of the boxes.  However considering the problem holistically and examining the various sustainability domains simultaneously can go a long way to selecting the most sustainable solution and determining which battle (if any) needs to be fought.

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All opinions shared in this post are the author’s own.