Integration – the next big hurdle
As automation systems become more mature, islands of information are starting to disappear. This article explains how to bring information from the PLC to desktop. This integration is important especially for the oil and gas industry where process plants are controlled remotely.
For over half a century, Moore’s Law has been a given. Digital electronic devices have also been strongly linked to the theorem, where a period of 18 months seems to be the time it takes to double their capabilities.
This has held true not only for personal computers, but also for control systems. The rate of capability in control systems didn’t keep pace with personal computers until these industrial systems began using more commercial off-the-shelf (COTS) parts. Today, control systems are moving to virtual server platforms and distributed control system (DCS) equipment rooms are looking more and more like their corporate data center counterparts.
One other characteristic DCS systems and corporate IT systems have in common is that nagging problem of "islands of information," where a tremendous amount of valuable information is closely held within a department, an individual, or a device.
While progress is being made in integrating the data coming from different devices into process control systems, there is still a significant amount of data that is isolated inside programmable logic controllers (PLCs).
Traditionally in process plants, PLCs were configured as stand-alone systems that were used as safety shutdown systems and for batch operations. These systems were not thought of very often, except when a unit would shut down or a batch process stopped. When that happened, the only way to troubleshoot or gather data from the unit was to congregate around it and try to do a root cause analysis in the field. Many times the root cause could not be determined since the "first in" alarm light would go off in the course of the shutdown.
The PLC was also a device rich in data that operations and engineering wanted to optimize a unit. Getting to that data was a problem.
Separate systems were built that could gather the data, which was a help, but they were still of limited value. What was needed was a system where data coming into and out of a PLC could be brought into a process control system where it could be viewed, analyzed, and historized by operators, technicians, and engineers.
PLC data started to come into process control systems via a serial connection, which was cumbersome. Each PLC company constructed the data "words" differently, so several drivers for the serial connection needed to be written for the different brands of PLCs.
Interfaces were later developed so that the process control systems could interpret the data from the PLC directly in the DCS. Different interfaces were needed depending on the brand of PLC, but the data integration process became much easier and widespread.
As easy as this process was, there were still obstacles to full data integration. While it was easier to bring the data into a control system, the data still had to be managed. Data had to be brought in and given assigned addresses in the DCS. Some control systems license by the point, so bringing in the data may have some unintended costs.
The points also have to be configured graphically on the operator screen. Most of the time the graphics given to the console operator in the control room bore no resemblance to what the outside operator saw in the field. This caused confusion when troubleshooting, when the outside operator or instrument technician tried to explain to the console operator what was being presented on the screen.
Most PLCs on the market now have addressed the problems associated with bringing information from PLCs in the field to the control room by embedding a graphics server into the device. PLCs now use a web server to replicate the HMI screens that the outside operator sees.
Taking advantage of this functionality is relatively straightforward. All that is needed is a computer with a Windows operating system running Microsoft’s Silverlight program, which was developed for web applications.
Once Silverlight is loaded on the machine, the computer is joined to the PLC via an Ethernet connection. The operator pulls up a web browser, enters the PLC’s IP address, and the device’s native web server presents the default operating screen on the browser. From there the console operator can navigate through the same screens that are on the actual PLC. This makes troubleshooting and communication much easier.
Older PLCs may also use this technology with a simple software upgrade, possibly for an additional cost, depending on the service agreement one has with the manufacturer.
There is a caveat with this technology. Most PLCs that use Silverlight to connect PLCs with the control room offer only a one-seat license, meaning only one person at a time can access the PLC. Future software upgrades may include multi-seat licenses so several people can access the PLC at the same time.
Many sites that have started to utilize this technology have connected their PLCs on their own network so that one computer can access all the PLCs in the plant. The network also serves as a data network that allows not only integration to the control system via OPC, but also direct access to the plant historian to archive the data.
Automation systems have come a long way in integrating the islands of information spread across the plant. This trend is bound to continue into the future. Data integration can only help improve decision making and make for more efficient and reliable process plants.
Steve Elwart is the director of Systems Engineering for Ergon Refining, Inc. in Vicksburg, Mississippi. He has spent 40 years in the oil industry, covering the areas of exploration & production, refining & marketing. He also works with DHS and DOE as a subject matter expert on cyber security and industrial control systems. Elwart also is the author of over 100 presentations and technical papers dealing with industrial control systems, international relations and cybersecurity.
Original content can be found at Control Engineering.