Process manufacturing plants are famous, some would say notorious, for their tendency to keep automation systems and associated networks up and running for decades. Some estimates suggest that easily half of the automation systems controlling North American plants have parts that are at least 20 years old — and 30-year-old systems aren't rare either.
Those systems don't look like they did when they were initially installed. Hard disk drives, monitors and keyboards that receive constant use simply don't survive over decades, and such old equipment isn't available anymore.
If you ask your local computer store for an IBM XT motherboard and 20MB hard drive, you'll get some puzzled looks. So unless your automation systems are brand-new, they are likely multigenerational due to obsolescence and devices wearing out. In some cases, old subsystems and components may be replaced to allow for the higher functionality of newer equipment, such as with the human machine interface (HMI) subsystem. Making that kind of upgrade will probably include adding new PCs, with operating systems capable of supporting functionality that wasn't available when the original HMI was installed.
With the long operating history of many automation systems, some may be experiencing problems due to system providers going out of business or being acquired by other companies. Think back to the 1980s or even 1990s, the landscape of companies providing control systems was much different than it is now. If one is working with an automation system from one of those more-or-less "extinct" companies, you are probably all too aware of this reality.
Getting an automation system that includes multigenerational and multivendor components to work together can be a challenge. But that approach may be the only option when there aren't any practical alternatives, and end-users must be prepared to deal with the inherent challenges.
At some point, an old automation system that has not been upgraded will become a serious threat to production. As printed circuit boards and network devices get older, individual components begin to fail and systems fault more often. These cause unscheduled shutdowns and outages that are especially disruptive when replacement parts aren't available. Some companies specialize in recycling parts for these old systems, and there's always eBay, but supplies tend to get tighter and tighter over time. Individual components, especially the chips, are often long out of production and cannot be replaced. The automation vendor may try to create some sort of functional replacement, but redesigning an old board with new components is expensive — which will be reflected in the price.
If you know a plant is going to be shut down or go through a major redesign for a specific period of time in the near future, one can limp along with the old system until that date. But that's not an appropriate long-term strategy, and eventually the system will have to go through some type of upgrade or migration. For purposes of this discussion, an upgrade is defined as adding newer elements, but largely sticking with the same automation system vendor and platform. A migration occurs when you make a major platform change, typically involving a different vendor, but sometimes sticking with the original manufacturer.
TWO PROJECT PATTERNS
Replacing some part of an automation system with something newer typically follows one of two patterns. The first pattern encompasses multigenerational systems. In these cases, the original company is typically still in business and has created upgrade strategies that allow users to add new parts to an old platform, gradually bringing up the whole system on a modular basis a bit at a time and without any major disruptions. This is not an easy accomplishment, and successful execution requires strategic planning.
A multigenerational platform is a good way to update your automation system, but it isn't possible in every case. Even if you remain with the original vendor, it is still important to be aware of the support dates for each piece of the automation system. Often, certain controllers or nodes lose support before others, so you need to incorporate this into the timing of the upgrades.
In the second pattern, new elements from a different vendor are "bolted on" to an existing automation system. This is difficult to pull off in the real world. Such a system can be buggy, and it won't have the greatest vendor support.
Personal experience working with many different types of automation platforms has proven these bolt-on solutions are rarely successful over the long term. Bolt-on solutions are really only temporary bandages, used either to add a few years to the older system or as a part of a larger phased migration plan that will change the bolt-on components to an integral part of an entirely new automation system.
BOLT-ON OR BOLT THE DOOR?
Bolt-on solutions may be necessary for discontinued legacy systems, but often we instead see them as the result of a vendor's aggressive cross-platform competitive attack. In our experience, one supplier trying to dislodge another often uses a bolt-on solution as a means to get in the plant and establish a position for getting deeper into the system. Unfortunately, we have seen too many situations where the effectiveness of these solutions was over-promised in the sales and marketing process.
So if a company is faced with making an upgrade but not ready for a rip-and-replace approach, following a cross-platform, multigenerational upgrade or migration to a new automation system may be the best path to take. There will be complications, but they can be managed if a comprehensive project plan is developed ahead of time.