Glyn Westlake, senior sales manager for Emerson’s Performance Services, explains how Emerson technologies and services help resolve process control issues, enabling energy companies to achieve efficiency savings.
For energy companies looking to improve environmental sustainability, decarbonise their production and move to a net zero operations, increasing energy efficiency has become an essential strategy. To help them, there are a broad range of solutions available to identify waste and reduce energy consumption, but one area where major energy efficiency improvements can be achieved for a low initial cost is optimising the performance of process control loops.
Improved process control is very cost effective, because the necessary infrastructure is already in place and the impact is immediate because control is the touch point to the process. From small production units to a large refinery, the effects of improved control can be significant. For example, more stable control can create step changes in product quality. Improved control also enables the process to be driven harder, increasing throughput and producing more product per unit energy. These factors also contribute to less wear and tear on the equipment, increasing availability and uptime. Typically, Emerson estimates that improved control can enable a 20% improvement in product quality variation, 2% increase in equipment availability, 5% increase in throughput and 5% reduction in energy consumption. For applications that consume a lot of energy, such as distillation columns, that can have significant effect on overall energy use and operational costs.
Underperforming control loops
By identifying underperforming loops and assessing the issues that cause them, this allows us to first stabilise the loop and then to optimise the operation. The immediate impact of this it to take the load off the operators who will be spending a lot of their time managing that process equipment. By stabilising the process, this will provide them with more time to focus on handling abnormal situations that lead to increases in availability. By optimising the process, this creates a step change in performance that leads to greater energy efficiency and lower emissions.
Control schemes are generally designed to keep the process stable and minimise variability, but in many cases this does not happen. Emerson estimates that in a typical process plant, around two thirds of control loops are under performing, with the main contributors to this under performance relate to issues with instrumentation and valves, such as poor installation and sizing, incorrect loop tuning and poor design, such as having instruments located too far away from the control point.
Poor tuning leads to greater process variability. In turn, this leads operators to run the plant away from the most efficient regions, which are typically close to operating constraints, such as quality limits, to allow for a greater margin of error. For example, in a feed heater this could mean a higher temperature setpoint and higher energy consumption. As a result, huge amounts of energy are wasted because of suboptimal control, particularly in high-energy-use units, such as distillation columns, boilers, reactors, dryers and evaporators.
Despite process variability caused by poor control loop tuning being a regular feature of process plants, many facilities do not have a formal, consistent approach to troubleshooting, and the root causes of issues can therefore go undetected for weeks, months or even years.
A major problem for many organisations trying to tackle control issues is that they lack the tools and resources to recognise that there is something that needs doing and then to make the necessary improvements. They have limited skilled resources, and those they do have are extremely busy – a situation made even worse as more experienced personnel retire. However, Emerson is helping by providing a range of services that can enable companies to achieve significantly better control performance at their facilities. Among these is the Guardian™ Loop Performance Dashboard. This is a free enhancement to Guardian Support, Emerson’s comprehensive service package designed to optimise control system reliability and performance.
The Guardian Loop Performance Dashboard measures the performance of every control loop. A control performance score is then provided that indicates how many control loops have limited control, high variability, uncertain inputs, or are not in the normal operating mode. A low score indicates that the current process control is jeopardising product quality, production and yield.
Where control loop performance issues are identified, Emerson’s DeltaV Loop Service adds the knowledge and experience of control performance experts to local facility teams, strengthening their ability to make improvements. This wholly remote service provides monthly reviews of control performance, identifying issues and making recommendations for corrective actions.
Loop performance is evaluated monthly without the requirement for additional software or detailed data to leave the local site. Problem areas are flagged for additional review to Emerson’s Control Performance Experts. Each month, following their analysis, the experts documents their recommendations within a report. The local facility personnel and Emerson expert then review the latest report by web-meeting, talking through recommendations and prioritising areas for the next month. This interaction is critical. It provides coaching for the customer teams and clarifies the process and operating objectives so that a control performance roadmap can be established and control loops that have the greatest impact on the bottom line can be prioritised. The DeltaV Loop Service will maximise the number of automatic, well-performing control loops, which will lead to greater product quality and throughput, fewer operator interventions on-site, and increased energy efficiency.
Where there are issues that require more than PID control, Emerson provides a range of flexible advanced control technologies, including our DeltaV PredictPro model predictive control application. DeltaV PredictPro automatically accounts for process interactions and difficult process dynamics, and easily handles issues such as excessive deadtime and loop interactions. Employing these advanced control techniques enables you to improve product quality by dramatically reducing key process variabilities, increase profitability by operating closer to process constraints and limits, and further increase energy efficiency.
www.Emerson.com/guardiansupport
Emerson Automation Solutions
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