Technology Can Help You Remain on Top of Dynamics that are In a State of Constant Change
As Practitioners we can all be a bit funny when it comes to energy conservation – generally mindful of energy consumption while at work but leaving items on and rooms lit even when they’re not in use while at home.
Maybe that’s just me and my kids! Regardless, there is some logic to this seemingly hypocritical behavior. First, the systems used in most manufacturing environments are industrial-size and they dwarf the energy draw of appliances typically found in homes. I’ve found that – like me – other practitioners tend to focus on minimising use of systems that consume the greatest amount of energy.
Some of those systems are huge and simply hard to be ignored. And second – well I’m not sure there is a second – maybe there’s a shared “don’t sweat the small stuff” mentality. Smaller systems can take the same amount of time and energy to fix even though they offer only a fraction of the savings. As I write I can hear you saying: But what if we all did it?
As a field services engineer I’ve worked at all sorts of production facilities. More often than not my focus has been on process control analysis and optimization. While I’ve worked around the world and in most every manufacturing sector, I’ve heard the same refrains from plant staff about tuning their PID controllers: We haven’t looked since the plant was commissioned. And – Ahem! – they’re running just fine!!!
It’s as though, the logic for managing a plant’s energy consumption should be applied to PID controllers: Just focus on what’s in plain sight. Here’s a thought: How many of your offices have been retrofitted with LED lights in the last few years? Weren’t the previous lights working just fine?
For many in manufacturing PID controllers are a “black box”. For starters, they’re virtually invisible. PIDs are contained within the Programmable Logic Controllers which more often than not are housed in a locked cabinet. Second – and in this case there actually is a second – an unfortunate percentage of PIDs are tuned using nothing more than basic parameters recommended in the vendor’s Quick Start Guide. In such situations no consideration is given to the individual PID’s unique use, whether it be to control a slow moving temperature process, a fast responding flow loop, or some other application.
Keep in mind: Tuning a loop to operate fast, because it can, is rarely a sound strategy. Lastly, many tuning methods can be both confusing and time-intensive. When the daily list of To Do’s is long it’s somewhat understandable when staff choose to tackle something else rather than wrangle with hidden controllers and their peculiar algorithms. There are plenty of other projects in plain sight, right?
The irony is that paying attention to a plant’s PID controllers and routinely correcting for performance issues can have a significant, positive impact. That reason alone is leading more and more process manufacturers to leverage plant-wide diagnostic tools that emphasize PID control loop performance. Consider these points:
- Dynamics change…and so should loop tunings
Trust me! Loops that were commissioned 6 years ago perform differently now. In fact they probably started responding differently to process dynamics within 6 months of commissioning.
While potentially hard for some to appreciate, it’s considered “best practice” to tune a plant’s PID control loops every 6 months or at a minimum look at their performance relative to the current process. That assures that each controller’s coefficients account for any vessel fouling or corrosion, differences in feedstock, seasonal changes that affect temperature and/or humidity levels within the plant environment.
Any baristas out there will tell you that even they change the grind process as their shift progresses in order to account for change. PID monitoring tools actively analyze changes in oscillations and other dynamic behavior to pinpoint control loops that require tuning. The good ones will even recommend new, accurate tuning coefficients from your plant’s existing data.
- Don’t get blindsided…anticipate mechanical failures
Most plants rely on hundreds of valves, dampers, and other mechanical devices to maintain control during production. While Stiction is the leading mechanical issue facing process engineers, few have the ability to identify and correct for Stiction before it impacts uptime.
There’s a wealth of information contained in a plant’s process data that can be used to proactively identify mechanical issues. Stiction monitoring and correction is one that gives instant performance improvement and it’s not hard to find in big data sets when using the right tools. If your valve is not doing what it is told to do, then how can your process possibly perform at optimal levels? Control loop monitoring solutions leverage KPIs such as Output Travel, Output Reversals, and – you guessed it – Stiction to determine when a mechanical issue is present.
- All aboard…the IIoT train is leaving the station
Manufacturers are adopting technology faster than ever, and they’re looking to their existing sources of plant data to create a sustainable competitive advantage. Lower cost sensors, faster processors, and powerful analytics are fueling both the Industrial Internet of Things (IIoT) and the push to do more with less.
Fact: Improved regulatory control performance contributes to less production waste and energy consumption, fewer quality defects, more throughput, and higher yield. Uncovering – let alone realizing – those benefits is challenging for most process manufacturers given the complexity of their automation environment and the growing responsibilities faced by engineering and maintenance teams. The reports, alerts and metrics included with most controller performance monitoring packages enable those teams to stay one step ahead of issues and downtime.
At the start I noted how we practitioners can be a funny lot when it comes to energy consumption. In the name of full disclosure I am wholly guilty of being an energy hog at home even though I frequently chastise plant managers for excessive guzzlers at their plant. As an evangelist of PID control I know that there is so much to be gained from the use of technology and from applying a system-wide approach to plant-wide optimization. And since there is no second point to that view, I have a few more lights to leave on at home! Yes – again – I hear you saying: But what if we all did it!