How to keep PID loops optimal

Posted by Julian Vidal on Aug 9, 2021 4:50:50 PM

Large processing facilities such as Refineries and Chemical plants spend money on technology to enhance process performance. Metrics are typically put in place to measure how well the technology is performing, and control engineers are required to report on these metrics regularly. There are thousands of PID loops on a typical refinery; what strategy should you use to identify poor performers and then rectify the issues?
How do you ensure that the reported metrics provide your management a full and clear picture of PID loop performance?

Monitoring PID loops is not the same as optimising PID loops

The functionality of technology is sometimes misunderstood, which leads to incorrect expectations. PID loop monitoring technology is an excellent tool to identify poor loop performance. This technology needs to be configured correctly before the results can be trusted. There is widespread misconception that PID monitoring software can also correct PID tuning problems automatically. Optimisation of PID loops is a different activity that requires process understanding, instrumentation knowledge and engineering judgement.

Typically, engineers will use PID tuning software to tune loops, particularly for interactive PID tuning problems that may be impossible to tune manually. What are the best practices that control engineers should use to maintain PID loops at their optimal performance?  

How to maintain PID loops at their optimal performance?

PID loop monitoring and PID loop tuning technologies are tools for control engineers to help them take a structured approach to identify and correct tuning problems. Technology should be combined with best practices and regular maintenance to keep PID loops in good working order.

Firstly, a methodology should be put in place to identify problematic PID loops. If you have PID monitoring technology, it should be setup correctly so there is confidence in the output and all stakeholders believe the results. Control engineers should confirm the list of poor performing PID loops with operators to fully validate whether the problem is associated with tuning or perhaps faulty instrumentation or process issues.

Tuning is the second step and can be done with PID tuning software, using a structured PID tuning approach.

The third ingredient of maintaining PID loops at optimal performance is a regular maintenance and reporting schedule. Regular 3-month checks will reduce problematic PID loops significantly. Simple reports can be generated monthly, showing a number of problematic loops, tuned loops, and outstanding issues. Organisations should give this activity high priority and should allow sufficient resources for this task, either internally or externally.


Optimal PID loops lead to improved process performance

Regular maintenance and performance reporting for PID loops creates awareness amongst all stakeholders such as operations, process and instrumentation departments in a structured way. This awareness creates focus to resolve outstanding issues such as instrument problems. The overall result of this maintenance and awareness effort is optimally tuned and well-performing PID loops that will improve process performance and possibly reduce wear on final control elements such as valves and actuators.

We are happy to advise you about how PID tuning, process knowledge and the right tools can help you accomplish optimized plant performance. Talk to an expert here. 




Topics: PID tuning