Canadian Manufacturing

SPONSORED: Putting process optimization on the fast track

The majority of control loop performance monitoring (CLPM) solutions were first introduced at the start of the new millennium in direct response to industry’s need for improved awareness of issues affecting regulatory control

July 20, 2020  by Dennis Nash, President, Control Station Inc.

The following is sponsored content from Control Station

Just now an opportunity to optimize production came and went. An operator adjusted the Set Point (SP) of one of the facility’s countless PID control loops. The change was an activity of little consequence. It occurs countless times each day and usually fails to warrant a note in the shift’s log. Even though unnoticed the process responded to the operator’s modification, sending the Process Variable in pursuit of its newly assigned control target. The loop’s process data was steeped in important details – increased Stiction in the valve from excessive packing, slower heat transfer due to a new feedstock, and the temperature sensor’s increasingly noisy readings. On queue the plant’s data historian collected the data whether all of it or some compressed version of it. Like so many other SP changes that could be used to improve control loop performance, this data set was stored away without ever being evaluated. With industry’s need for process improvements and push toward profit, an important question to ask is: Why is that so?

The majority of control loop performance monitoring (CLPM) solutions were first introduced at the start of the new millennium in direct response to industry’s need for improved awareness of issues affecting regulatory control. In his study of control loop performance, David Ender of Techmation, Inc. found that most PID control loops within the average production facility were operating inefficiently. With 85% of loops operating inefficiently while in closed-loop and 65% of them cited as either poorly tuned or de-tuned to conceal other PID-related problems, the study underscored the need for improved regulatory control. CLPM solutions stepped in to help process manufacturers identify their bad actors. In addition to awareness of their problem areas, manufacturers needed insight into how to resolve them.

FROM ONE LOOP TO MANY LOOPS

CLPM solutions are a direct outgrowth of traditional process modeling and PID controller tuning technologies.  Rather than examining control loops one at a time, CLPM solutions evaluate each of the many loops located across one or more production facility. Using various key performance indices (KPIs), these solutions work to identify performance challenges associated with mechanical issues and architectural constraints. They also identify controller optimization opportunities, automatically identifying SP and Controller Output (CO) changes, and generating a model of the associated process’ dynamics. These functions are performed in near real-time and provide production staff with timely awareness of issues that may negatively affect production.

Until recently CLPM solutions were limited in their ability to model complex process dynamics and to recommend adjustments to PID controller tuning parameters. Like most commercial tuning software, early CLPM solutions failed to accurately model noisy, oscillatory process data. Their data capture and modeling functions were ineffective when applied to integrating processes. Such constraints put the value of CLPM solutions in question. So, what has changed?

OVERCOMING THE COMPLEXITY OF DATA

In 2013 select CLPM solutions gained meaningful ground with the incorporation of a proprietary Non-Steady State (NSS) Modeling Innovation™. The innovation enables accurate modeling of highly dynamic process data that is typical of industrial process manufacturing.

First introduced in 2008 the NSS Modeling Innovation was applied to traditional PID controller tuning software. The novel approach to modeling eliminated the need for a steady-state condition. Further, it supported both integrating and non-integrating processes. Noisy, transitional, and otherwise oscillatory data was no longer a deal breaker when individual regulatory control loops require tuning. Since its introduction, the innovation has been adopted by global OEMs including Rockwell Automation and Yokogawa.

More recently the innovation has been adapted for use with select CLPM solutions. Broadly deployed to process manufacturers located around the globe, it accurately models the troublesome dynamics that are commonplace in industrial applications. These CLPM solutions are capable of automatically capturing and modeling data from integrating and non-integrating processes. Beyond modeling, they provide users with recommendations for improving control.

INNOVATION THAT DELIVERS INSIGHT

More than accurate modeling is required to provide actionable benefits to process manufacturers. Even basic CLPM solutions utilize KPIs to identify loops with controller tuning issues. To be sure, they alert users to loops that are not operating in the proper or normal mode. Mode changes often result when operations staff lack confidence in a given loop’s ability to maintain safe, effective control – a proxy for sub-optimal controller tunings. Excessive levels of error or oscillation often indicate a need for retuning of the PID. Although each is a valuable source of insight, these basic metrics fall short of actionable information. Advanced capabilities have become a requirement.

Certain CLPM solutions go beyond diagnostics and offer recommendations for corrective action specifically related to controller tuning. These solutions compare each newly generated process model relative to the corresponding loop’s historical performance. The resulting analysis clarifies the effectiveness of existing controller tuning coefficients, offering graphical evidence that the controller is either performing satisfactorily or requires tuning.

In cases where tuning is required, these CLPM tools provide ready access to the process data that is needed to refine tuning parameters for optimal performance. The feature assures that the new coefficients are consistent with the PID loop’s unique control objective. Control loop diagnostic capabilities such as this streamline the process of issue identification, isolation, and correction on a plant-wide basis.

ENABLING REAL-TIME OPTIMIZATION

With 100s of PID control loops at the typical production facility the dual goals of first achieving and then maintaining profitable production presents a significant challenge to the average engineering and operations staff. It is clear that controller tuning is key to fulfilling that goal, but it is also worth noting that tuning is just one in a long line of tasks assigned to a plant’s production staff. Advancements to CLPM solutions address this challenge head on.

A small number of CLPM solutions like PlantESP™ simplify process optimization by providing actionable answers. While many acknowledge that their control loop performance issues are widespread, most are hard pressed to designate scarce resources to investigate and correct them. The time required to isolate the root-cause of issues affecting performance often outweigh the perceived gains. Those manufacturers operating CLPM solutions equipped with NSS modeling capabilities have no need to perform such time-intensive investigative research and root-cause analysis.

From actively monitoring loop performance and identifying SP changes to modeling the loop’s complex dynamics and comparing the results against historical performance, today’s CLPM solutions have streamlined real-time process optimization.

Contact Control Station to learn how CLPM is putting process optimization on the fast track.

Dennis Nash is the president of Control Station Inc., which solves difficult plant monitoring and controller challenges faced by process manufacturers with a broad portfolio of software-based solutions. Call (860) 248-2137 or e-mail dennis.nash@controlstation.com.


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