Imagine if you could go to your treatment plant control system display and roll back and observe the events that took place in a given interval of time.

You can do just that with the Ovation playback recorder from Emerson, a software add-on to the company’s Ovation distributed control infrastructure. The system continuously records plant operating data at the same resolution as the live control system.

Functioning much like a household digital video recorder (DVR), it has standard functions such as play, pause, fast forward and rewind. Users can visually step through logic sequences with help from process graphics and signal diagrams. In this way, they can view historical data through the lens of what the operator would have seen under actual plant conditions.

Operators can use this holistic and repeatable view of plant events to speed troubleshooting, enhance training and support sound decision-making. They can review actions taken during an abnormal occurrence to identify what went wrong and determine what should have been done in response. They can then update procedures to better manage similar events in the future.

The recorder lets users quickly diagnose problems, limit equipment damage and reduce maintenance. Peter Gabor, business development manager for Emerson’s water automation solutions, and Shane O’Toole, Ovation product manager, talked about the offering in an interview with Treatment Plant Operator.

TPO: What led you to bring this offering to the market?

Gabor: The big thing that causes people to dig into data is a substantial event at a plant. On the water and wastewater side, that could be an unusual discharge or a permit violation. In those cases, it’s helpful to go back and see what the event looked like in real time through the lens of what the operators might have seen. Playback recorder provides the ability to do just that.

TPO: Without this capability, how would an operations team analyze an event?

O’Toole: Typically they would review trend data in charts, graphs and numerical tables.

Sorting through all that data to do a root-cause analysis takes a very long time. Larger customers sometimes subcontract to a consultant to do that analysis. It costs a lot. But if they can visually step through and watch exactly what happened, on graphics they’re familiar with, they can find the sources of problems a lot quicker. It’s easier when they can see it visually instead of stepping through values on a spreadsheet.

TPO: What do treatment plants need to have in place in order to use this tool?

O’Toole: They would need to have the standard Ovation control system infrastructure. If that is in place, all they need to add is a computer to connect to the network, a cable to make the connection.

TPO: If I were an operator, how would I interact with the playback recorder?

O’Toole: You would sit at the operator’s console and start the playback recorder application. You could hit play and watch on-screen signal diagrams, which are live running versions of control logic that show exactly what happened in the plant. That would give you the context to understand that process A was affected by process B or that thing A happened before thing B. 

TPO: Can you provide a scenario of when an operator at a water or wastewater treatment plant would put this capability to work?

Gabor: Suppose they have a permit violation. All of a sudden there’s a discharge and they hear news on the radio that there are problems. Where this really becomes valuable is when there’s a cascading effect with multiple issues causing the failure. Those are the hard ones to diagnose. When it’s over, the plant manager will ask, “Why did this happen? And how can we prevent it from happening in the future?”

TPO: What can operators actually observe on playback?

O’Toole: The playback recorder goes beyond the functionality of a household DVR in that operators can see things on playback that they may not have seen while looking at the screen at the time of the event. For instance, the operator might have been looking at screen A while doing day-to-day work, but the story of the event was actually unfolding on screen B or screen C. Playback lets them look at data that would have been on any of those screens at the time, because everything that happened was captured in the distributed control system.

TPO: Would they see the data all at once? Or would they view it one device at a time?

O’Toole: They can zero in on device A or device B. They can look at time period X, run through that scenario on screen A, then cue up screen B and run through that for same time period, then cue up screen C, and so on. They can go back and forward as much as needed to get the total picture of what went on during the event. It’s like a movie where you watch a scene from one character’s perspective, and then later you see the same scene through the eyes of a different character.

TPO: What do users actually see on the screen during playback?

O’Toole: They see exactly what they would have seen in real time, except there is a little icon in the toolbar at the top of the screen that tells them they’re reviewing historical data, along with buttons for play, fast forward, pause and rewind. The operator would see images of equipment, such as pumps, valves and tanks, and their levels.

TPO: Does this technology have uses beyond analyzing the root causes of events?

O’Toole: Root-cause analysis is not the only use case our customers have asked us about. In the water industry, we see turnover in organizations ramping up with retirements. Playback gives users the ability to capture, for example, a successful startup or a successful runtime with a piece of equipment that can be used for training purposes.

Gabor: In wastewater, for instance, it could be a scenario like switching over to a wet-weather event. That’s challenging, and there may be only one operator on staff who is really comfortable with it. There are a lot of moving parts and a lot of things to get ready, and they’re under duress. We can capture data on such an event so that up-and-coming operators and technicians can see and learn how someone did it successfully.

TPO: Is there a limit on the size of the slice of time that is captured by the recorder?

O’Toole: There is no hard-and-fast limit, but there is a restriction based on hard-drive space. The standard product includes an additional two terabytes of storage space. That provides on average about 28 days of data. That will scale up or down based on the amount of information the customer is pulling into the Ovation distributed control system. To retain events for long-term duration, such as for training, users can simply move those files to a different hard drive.