Process Control and the Internet/Intranet

Twenty-five years after their introduction, the Internet protocols are becoming accepted as the standard by companies such as Microsoft and most HMI / SCADA software vendors. They are now being used in process control applications in both internal (intranet) and external (internet) networks. The widespread acceptance of Internet technologies is driving down costs and making this mode of communication extremely accessible.

Until recently, connecting control systems with other information systems was possible, but not easy. Efforts to improve the situation have now seized on the model of the corporate intranet as a paradigm. That is, browser technology from the Internet running on a secure computer system within a company. Using pages and links, information can be directed anywhere within a manufacturing facility, or beyond. The use of Internet allows access to information that was previously isolated in a distributed control system or operator interface on the plant floor, and opens it up to business needs.

The change to common standards reduces the effort required to introduce and maintain connectivity between different areas of an organisation's information systems. It also enables the use of powerful tools that have been developed for the Internet to monitor and control plant processes. Standards being adapted to process control applications include TCP/IP, HTML, DCOM, CORBA, OLE, ActiveX, and Java. Technology that can operate using these standards includes:

• web browsers
• network PCs and Windows CE (that can run programs locally)
• thin clients (that can only run programs on a server and display the user interface locally)
• push technology (servers select information to be sent to clients)
• OLE for Process Control (OPC)

Most HMI / SCADA packages now provide a method for viewing process information remotely using an intranet or Internet connection. Some do this using a utility to export the graphical operator screens as HTML, which can then be accessed via any standard web server and client. Other packages provide network access using a proprietary client to view information made available by a proprietary server application. In the remote viewing screen, points are updated as the values in the SCADA database change, allowing remote users to monitor processes. It is also possible to change values remotely with some SCADA software, however very good security is required if this is permitted. Possible uses of the technology include:

• viewing plant operation in almost real time from any location, using any web browser
• receiving production reports automatically via E-mail
• viewing trends in the production process
• being notified of alarms as they occur
• access to equipment supplier's technical support, for debugging plant problems on-line, viewing technical drawings and other information
• having one on-line copy of all documentation, avoiding problems with different versions

At the same time, software vendors are standardising on a few object-based platforms, such as Java and ActiveX, which allow individual software packages to easily interact and share data. Running on the Internet/Intranet infrastructure, programs using these software platforms can exchange information with little or no customised integration.

The primary benefit of Internet/Intranet technologies in process control applications is the single window interface provided by web browsers. It provides a simpler operator interface, a more consistent, shorter learning curve, with more information in a familiar environment. The operator has one interface - the browser - and he can uncover layers of information within the browser.

Even with an established network infrastructure and the end of integration problems, there are a few roadblocks to using Internet technology for real-time control systems. One is speed. Anyone who has used the Web has been frustrated by slow graphics and long downloads. At present, Internet/intranet applications are not practical for very critical, real-time applications. Another potential problem is how to maintain security and restrict information and system functions to authorised personnel.

Although evidence of the actual application of this technology in the real world is limited thus far, many of the major HMI/SCADA vendors have released, or will soon be releasing, products to take advantage of Internet technologies. Some of the products available include:

• Intellution- FIX Web Server - for viewing SCADA screens in a Web browser.
• Intellution - FIX Broadcast Network - push configured information to clients (PointCast)
• Wonderware - Scout Outpost - for viewing SCADA screens using Scout VT. A Web browser version will be available soon.
• Wonderware - push configured information to clients (Internet Explorer channels).
• Citect - supports viewing information and reports exported to a Web server as HTML
• GenSym G2 - this is an Artificial Intelligence package that can view information in a Web browser. Supports CORBA and DCOM, Java, ActiveX.
• PCSoft WizBrowz - displays Wizcon screens in any web browser using Java, providing a view of up-to-date process, production, inventory, and commercial data.
• USDATA Batchlink - provides a view of the process and shows what batches are coming off the line in real time.
• BroadWin WebAccess - a completely web-based SCADA system.

Organisations that need to make process information, including trends and alarms, available to a wider audience within an enterprise should look at the benefits of using Internet standards. It is likely they will be the cheapest and easiest method to provide this access in the near future.

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