A Strategic Approach for Upgrading Process Control Systems, Part 2

Basic migration approaches and the costs of change associated with them.

By Larry O’Brien and Dick Hill, ARC Advisory Group

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Migration could be the biggest single issue many process and batch automation system end users face today. ARC Advisory Group estimates that the combined value of the installed base of automation systems now reaching the end of their useful lives is approximately $65 billion. This represents a big opportunity for end users in the chemical process industries and their automation suppliers alike.

In Part 1 of this three-part series, we discussed the driving forces for system migration. Here, in Part 2, we discuss several different approaches and the respective benefits and challenges of each approach.

With turnarounds occurring every two years, it would be almost a decade before the entire migration project was completed. By then the first phase of the migration project would already be well out of date.

Control System Migration Alternatives

When upgrading an outdated system, end users face a difficult choice – should they replace the system wholesale, or in phases over time? The single total replacement option for migration or upgrade involves replacing the entire outdated infrastructure all at once, eliminating all existing control system equipment and installing new equipment. Phased migration, on the other hand, involves a gradual migration over a predefined period, using a phased approach. The former can be more costly in terms of initial cost layout for hardware, software, labor, downtime and training. It can also involve the greatest amount of risk because you cannot go back to the old system if the new system does not perform as anticipated.

Rip and Replace versus Phased Migration

Operational or commercial requirements often force owner-operators to consider either a wholesale “rip and replace” migration, characterized by a single project event where the legacy system is removed and the target system is installed, or a “phased” migration where different levels of the legacy system are replaced by levels of the target system in phases over time.

Protect your process control systems

Wholesale migration is straightforward and relatively simple to execute because it takes place in a single event. It will probably include a combination of primary alternatives, but is usually performed during a planned shutdown, with no need to accommodate intermediate components of the target system.

The hardware infrastructure, including wiring and I/O, can become embedded in the plant, making it very difficult and cost prohibitive to do a wholesale replacement of the system. Users also invest thousands of man-hours developing control code, graphics and documentation. Some form of intellectual property, whether it is a plant asset-management or information-management system, is also typically incorporated. Single total replacement makes it difficult to preserve this investment.

There are cases, however, where the user may want to consider a single total replacement approach. Primary factors driving this approach include availability of a time window during the regularly scheduled turnaround, the type of manufacturing process involved and the experience of the supplier and/or the system integrator partner involved in the project. When the circumstances are right, a single total replacement can be the fastest and possibly the least costly option because there is less downtime and less redundant labor compared to the aggregate cost of system evolution or migration in multiple phases. Another potential benefit of single total replacement is that it ensures a single, current generation of system and the associated reduced total cost of ownership (TCO).

Migration During Scheduled Turnarounds

If you plan to do your migration project during a scheduled turnaround, the space between shutdowns could turn out to be a serious issue. If you do a phased migration during scheduled shutdowns, but your plant only shuts down once every two years, your migration project will probably be obsolete once it is complete. Unless the migration can be accomplished with no downtime as a hot cutover (or at a time outside of the scheduled shutdown), the single total replacement approach could be justified.

Manufacturing Process Dictates Approach

The type of manufacturing process can also dictate the appropriate migration strategy. For example, many batch process manufacturers have facilities with multiple production trains and a common preparation area. These multiple processing lines can also have dedicated finishing areas for each train. In many cases, the trains are flexible enough so that multiple products can be made on any train and turnarounds on these kinds of processing lines can be very infrequent, along the lines of every two years or so.

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