Why do you need performance supervision?

Installing PSS can help. Not only can it help you optimize the process, but it can quickly pinpoint problems that are just waiting to occur, including potential alarm cascades and maintenance headaches.

Process optimization isn’t way out there. It isn’t necessarily a set of arcane mathematical constructs. Most process optimization issues consist in finding loops that aren’t working properly, pumps with bad seals, or worn motors and shaft couplings. These are simple tasks, but they’re also time sinks. And, again, where are you going to find more time?

Fortunately, PSS can do this automatically for you. It’s watched the entire plant, crunched numbers, and found “hot spots” that need your attention. A custom report is delivered into your hands. You spend little or no time finding the problems, so you can focus on making improvements.

Need Good Answers?
Another consequence of fewer plant-floor people and lower skill levels is that it’s become difficult to get useful answers. “My institutional knowledge walks out of the plant every day at 4 p.m.,” says one process plant manager. An instrumentation engineer at a Lyondell plant recently told CONTROL that he expects his standard technicians to know much more than they used to, and that pay scales and training are lagging behind what they need to know to do their jobs. If you’re in maintenance, you probably have many stories of being asked to replace a perfectly good piece of equipment based on faulty information.

Wouldn’t it be better to follow a problem to its root cause before you spend time on repairs? In maintenance, time also is money, but the cost of replacing a 12-in. control valve when it doesn’t need to be replaced is real money wasted. One of performance supervision’s key benefits is that it helps you drive to these root causes, before committing all that money and time. By using visual, drill-down analysis and ad-hoc reports, you can quickly get through voluminous data and find some real answers. These also can help you justify using PSS to cost accountants that run your business.

Similarly, as Google has transformed the individual’s ability to find information on the Internet, the concept of performance supervision can help transform process optimization.

For example, Figure 2 below shows the results of drill-down analysis and user-defined reports. Several control loops are cycling at the same frequency. The supervision system has looked over the entire plant, saving days of analysis. The data shows, without any doubts, which parts of the process are associated with this problem, and which ones are not. In fact, PSSs often will correctly identify related problems in seemingly unrelated areas.

FIGURE 2: LOOKING FOR TROUBLE

Based on several control loops cycling at the same frequency, the results of this drill-down analysis and user-defined report save days of analysis, and show which parts of the process are associated with a particular problem, and can correctly identify related problems in seemingly unrelated areas. (Click image to enlarge)

This is possible because PSS can automatically calculate process models. This allows users to pinpoint the exact timing of process changes, and track them to specific equipment changes, batches, or operator actions. This feature has been used to identify improperly-sized replacement parts. So, when a part was replaced, it was indicated when the process model changed.

“The performance supervision system identified over-sized valves as those with the highest process gain,” says Chris McAnarney, also of Columbian Chemical. “One valve had a process gain of 11. It was like trying to fill a shot glass with a fire hose! Fixing these problems reduced process variation, and helped to build the operator’s confidence that we could help make the plant perform better.”

Need Measurable Results?
High-level performance measures, such as cost, up-time and quality, have been tracked and historically documented for years, and have produced known benefits for plant optimization. Can those short-term performance measures do the same? Using a PSS, you can track and “historize” short-term performance measures that also fuel higher-level performance. For example, there’s a strong correlation between process oscillation and energy loss. If you measure, track, and drive down oscillation, you’ll reduce energy costs too. PSS will detect, track, prioritize, and report oscillations. In some cases, it will even identify the cause as valve stiction, load disturbance, or tuning.

Figure 3 below shows how focus on short-term performance measures can help move a plant to more stable operation. An intervention to improve the process occurred roughly half-way through this chart. The figure shows improvements in measures such as oscillation detection, percent of time in normal mode, and variability. Because the trends are normalized, it’s easy to interpret results.

FIGURE 3: SHORT-TERM GAINS

Focus on short-term performance measures can help drive a plant to more stable operation. An intervanetion to improve the process occurred roughly half-way through this chart, which shows improvement in measures such as oscillation detection, percent of time in normal mode, and variability. (Click image to enlarge)

Does this translate to bottom-line savings? Bet on it. Users are finding savings in energy, increased production rate, and reduced start-up time. PSS is aware of the relative economic value of different control loops, and can help guide you to those systems that deserve the most attention. Users of PSSs often report returns on investment in three months or less.

Call to Action
So, what should you do first? What about CMMS systems, asset-management systems, machinery-health-monitoring systems, and all the other ways vendors claim to improve plant performance? They all work well at what they’re designed to do, but it’s difficult to do much more than throw money at the problem if you’re operating blind.

Installing PSS can give you the information you need to tell you where, for example, it will pay most to install a machinery-health-monitoring system, or in what part of the plant an asset-management system will quickly pay for itself in improved performance, or where a CMMS system can best be used to reduce downtime.

The promise of open connectivity has finally been delivered, but many plants have yet to tap into it. After spending millions of dollars to put DCS systems in place, we are awash in a sea of data.
Fortunately, PSS does more than monitoring. It’s also analyzing, prioritizing, and recommending. It helps unlock the secrets hidden in your DCS. If you need more time, better answers, and measurable results, you need to think about a PSS.