Make the most of control system migration

The right strategy may lead to significant improvements in plant performance

By Mark Rosenzweig, Editor-in-Chief

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The launch of the iPhone 3G in June once again demonstrates that electronics evolve fast.

Apple promotes the sleak device as “twice as fast, half the price,” compared to the original iPhone, which was introduced only about 18 months ago. Such a boast doesn’t even cause raised eyebrows nowadays. After all, we’ve grown to expect more speed and capability at lower cost from a host of products, from computers to digital cameras to global positioning systems.

While some people have no qualms about discarding a model that’s a year or two old in favor of the “latest and greatest,” chemical companies and other businesses certainly can’t operate that way. So, it’s not surprising that many plants continue to rely on older equipment and systems. Indeed, in these tough economic times for the industry, it’s even harder in many cases to justify capital spending for upgrades or replacements.

Consider distributed control systems (DCS). Such systems started to catch on in the industry in the 1970s. Everyone understands that the latest generation of DCS offer far greater capabilities and performance than systems introduced just a few years ago. Yet today many plants still rely on APACS, Infi90, Provox, TDC 2000 and other vintage systems. Indeed, ARC Advisory Group, Dedham, Mass., estimated last year that the value of the installed base of process automation systems reaching the end of their useful lives totals about $65 billion.

Vendors have withdrawn support for some of the old DCS, but plants still soldier on with them. After all, parts are available via eBay and from other indirect sources, and specialists familiar with the nuances of vintage systems and software are still around.

As John Dolenc of Emerson noted in an article in January’s Chemical ProcessingMake the Most of Automation Upgrades, “Using obsolescence for justification isn’t easy. While maintenance costs probably are rising and spare parts may be getting scarce and expensive, true maintenance savings normally aren’t large enough to justify the capital investment. Obsolescence is a viable approach only if you can show an increasing risk of control equipment failure shutting down a critical process. Establishing the risk factor becomes the challenge. It’s difficult to convince management that a system is about to fail when it has no history of failures.”

However, other drivers may provide a compelling business case for migration, says ARC. Its list includes: “limitations of the system preventing the user from taking advantage of an emerging business opportunity, or the old system cannot cost-effectively support the new generation of information and automation technologies that are available, such as open networks, plant asset management applications, and production management applications.”

Security concerns add another dimension to the discussion. There’s wide agreement that today’s open systems pose more cyber-vulnerabilities than earlier proprietary systems. So, some plants may cling to their vintage DCS in the hope of avoiding such risks. However, that provides a false sense of security, warns Todd Stauffer of Siemens. Legacy systems — open as well as proprietary ones — now are subject to stresses they weren’t designed for and this has security implications, he cautions. Regardless of whether a DCS is state-of-the-art or ancient, sites must adopt a security strategy relying on “defense in depth” (see article: Properly protect control systems).

Ultimately, unless a plant is destined for closure, it must consider migration to a new control system. As ARC says, the key question is “When to migrate?”

Once that’s decided, the site must grapple with some key issues in how to migrate — there’re many possible approaches, ranging from replacement of specific parts of the old DCS like the human/machine interface (HMI) or input/output modules to the installation of a complete new system. This demands careful evaluation. Which physical assets should be kept? What about the knowledge and information developed over the years that’s contained in the existing system — e.g., in control configurations, the HMI and historical data? What additional capabilities are needed, and how can they be most effectively employed? How can operations take fullest advantage of better control? Numerous other questions will arise.

Such implementation issues certainly can be daunting and likely contribute to the reluctance of some sites to face up to the need to migrate. Fortunately, DCS vendors clearly recognize the important role that they should play in easing the effort and helping plants succeed in the move.

Always view migration in context: it’s not just a way to enhance control but a key step for improving overall plant — and business — performance.

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