R. Rice, Control Station, Manchester, Connecticut
Most of us have used licensed software—whether a personal computer (PC) operating system, a word processor or something less mainstream—consistently. Furthermore, plenty of us have experience subscribing to an application or some other software on our mobile device, which, for some reason or another, we eventually abandon, relegating it to virtual or physical shelfware. The shelfware phenomenon can occur because the associated product is too unwieldy to learn or use, it does not do what is expected or needed, or the ongoing costs of its use are too great.
Concerns about software-turned-shelfware at a personal level are also relevant at the largest manufacturing and production companies but on a much grander scale. Consider a sizable refinery that procures a control loop monitoring software package for an automation upgrade project. While this software is a tool for getting the plant up and running, it can also deliver ongoing value by helping operations staff optimize production in the coming years, but only if the software is usable and applied correctly.
A comprehensive control loop performance monitoring (CLPM) solution goes well beyond basic loop tuning, as it provides a broader range of operational advantages and cost savings over the lifecycle of a production plant (FIG. 1). This article describes how CLPM technology provides the foundation for a dynamic partnership with a large U.S. refinery that has delivered quantifiable benefits and is projected to do so for years to come.
Establishing a loop optimization digital lifecycle. The example refinery had a production capacity of 200,000 bpd. The site processes heavy and domestic crude oils and includes a unit dedicated to producing low-sulfur fuels that reduce greenhouse gases (GHGs). Recently, it was necessary to undertake a capital project to upgrade a legacy distributed control system (DCS). The core functionality of the DCS involves clearly monitoring and efficiently controlling each of the process units. Additional software tools were deemed necessary to ensure that the refinery’s proportional integral derivative (PID) control loops were properly tuned at start up, enabling the DCS to fulfill its supervisory control function.
Refinery staff quickly realized that loop tuning was more than just a one-time event and that an investment in CLPM technology could facilitate ongoing process improvements. In addition to capitalizing on any “low-hanging fruit” found during commissioning, a CLPM solution could empower them to monitor and optimize production continuously.
Just as prudent organizations adopt a lifecycle approach to process designs, equipment maintenance and other business tasks, a digital lifecycle solution is often the best way for companies to ensure short- and long-term operational success with any software. The refinery team needed to determine the best path to start up the first unit and to assist with the ongoing operation and optimization of the refinery.
A three-step optimization approach. The author’s company offers CLPM software designed to be highly effective in analyzing PID control loop performance on a plant-wide basis. However, the software’s real differentiator is its ability to extend loop analytics to enterprise scale and provide manufacturers with fleet-wide analysis and benchmarking regardless of the number of unique operating states and conditions. Furthermore, a team of engineering resources with deep experience in process control and loop optimization is increasingly leveraged in partnership with end users.
To ensure the refinery would achieve maximum value from these capabilities, they embraced a three-step digital lifecycle approach: identify, implement and maintain (FIG. 2).
Step 1: Identify. A preliminary engineering study was the first step in quantifying potential performance and reliability gains, and it was also key to identifying possible risks. A team of CLPM experts interviewed the refinery’s process control staff and conducted workshop sessions designed to discover relevant operational activities, and associated business and technical key performance indicators (KPIs).
Project timing was coordinated so that the CLPM software was installed prior to the DCS upgrade and the restarting of the first unit. This provided an initial data source for assessing the performance of the unit’s most critical loops and for pinpointing specific PID controllers that required immediate attention. The CLPM technology, equipped with advanced forensic tools, included functions that allowed the team to distinguish between symptoms and root causes—recommendations for corrective actions designed to reduce variability guided the team’s next steps.
Step 2: Implement. Based on the initial plan, the project team executed steps to return each process loop to normal operation within the refinery’s designated limits. In this case, a CLPM engineer was present onsite and was available to consult with the refinery’s process control team. However, CLPM engineers are also familiar with fulfilling this role using remote methods, communicating their analysis and recommendations via email or phone. Principals at the refinery agreed to a combination of onsite and remote methods, allowing for a highly efficient approach to attacking the work and pursuing the site’s long-term performance goals.
Refinery staff who were familiar with the process, field equipment and automation platform were responsible for adjusting loop tuning parameters and for implementing other recommended changes (FIG. 3). Sometimes, the team’s suggestions were to evaluate or maintain physical equipment or recalibrate instrumentation in the field instead of trying to correct mechanical problems using software.
This digital lifecycle approach, where one party makes a recommendation and a second reviews the underlying details before implementing the corrective action, provides valuable checks and balances for the team’s collaboration. Another key to the identify-implement-maintain progression is having the team establish and follow a standard procedure for identifying and resolving performance and reliability issues.
The refinery’s raw petroleum coke (RPC) area provided an example of the implementation phase in action. Within the RPC area, the sulfur recovery unit (SRU) regulates steam pressure on the sulfur condensate line. Upon startup, the CLPM solution’s KPIs for assessing oscillations, variability and valve movement all showed behavior beyond the pressure loop’s acceptable ranges. Consistent with the CLPM’s recommendation for corrective action, a bump test was approved and performed by the team. Alternative tuning parameters were implemented, resulting in the immediate correction of loop behavior. Specifically, variability and valve movement were reduced by 95% (FIG. 4).
Step 3: Maintain. Process plants are dynamic by nature, but this constant change demands that continuous attention be paid to the performance of regulatory controllers on which the DCS or other supervisory system relies. A range of circumstances can result in negative loop control consequences:
Furthermore, because a loop appears to be performing adequately does not mean it delivers the highest quality output, most efficient operation, or most reliable or sustainable production. Undertaking process optimization by employing a continuous improvement program, utilizing best-in-class CLPM technology, and following effective and documented workflows are proven ways to realize effective and sustainable change.
Championing a collaborative plant performance solution. A lifecycle approach aligns with the continuous improvement mindset espoused by most manufacturers. Establishing workflows that leverage a facility’s available data and the increasingly effective analytics of tools like CLPM can support an identify-implement-maintain methodology. Partnering with third-party subject matter experts (SMEs) has also been shown to bolster a facility’s responsiveness and assist with achieving long-term performance goals.
Regarding CLPM software, certain capabilities are key to a plant- or an enterprise-wide digital lifecycle initiative. Beyond an architecture capable of supporting an enterprise deployment, the chosen CLPM solution should also incorporate:
The example refinery realized immediate success by leveraging CLPM software as part of a newly initiated digital lifecycle solution. With the startup completed, the refinery personnel and CLPM engineers continued to analyze available data, monitor trends and review events and alarms to gauge the facility’s overall effectiveness while determining the next steps. In fewer than 18 mos, the facility achieved a full return on the initial CLPM software investment.
In a typical process plant, there are always opportunities to optimize operations, advance safety and improve reliability. Partnering with an experienced CLPM software solution provider and employing an effective lifecycle workflow ensures that process plant staff are best positioned to capitalize on these opportunities. HP
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ROBERT RICE, PhD is the vice president of engineering at Control Station. As the company’s thought leader, he has published extensively on automatic process control, including multi-variable process control and model predictive control. Dr. Rice has received numerous awards for innovation and his contributions to the advancement of the process industry. He earned a BS degree in chemical engineering from Virginia Polytechnic Institute and State University and his MS and PhD from the University of Connecticut.