An Argument for Upgrading Obsolete but “Working” Systems

Introduction

The backbone of many important industrial control systems (ICSs) is made up of legacy platforms that have served as reliable workhorses for decades. These systems, like many other well-built electronic devices, are robust and have stood the test of time. However, this durability can make companies hesitant to invest substantial capital and time into upgrading them, and that hesitation can often result in significant losses that may exceed $50,000 for a single prolonged outage.

Parts Sourcing Difficulty and Reliability

One common complaint with legacy ICSs is the difficulty of sourcing appropriate spare parts. As the “out of support” dates of these systems move further into the past, fewer parts become available. At some point, parts for these older systems can become almost impossible to find, and those that are on the market must often be obtained secondhand via eBay or other resellers. While refurbished parts might be available, their quality can vary greatly. Over time, as sourcing becomes more difficult, spare-parts inventories grow in importance, yet the quality and reliability of those spares become increasingly dubious. They degrade over time, and some refurbishment companies have subpar quality control. As a result, spares become less reliable, which can lead to either the need for larger inventories or an increased level of risk.

For example, the swing arms on Allen Bradley PLC 5 I/O cards can dry rot over time and crumble when handled. Although they are small plastic pieces, they are essential to the PLC. When they break, what should be a quick five minute card replacement can turn into an hour long rewire job, especially if 120 V inputs must be reconnected and live work permits or lockouts are required. A failed PLC 5 I/O card may appear to be only a $200 replacement, but rewiring under lockout procedures can extend downtime and cost between $5,000 and $7,500 in lost production. An issue that begins as a minor fault can quickly become a costly outage.

Human Resources

Another significant challenge with legacy ICSs is finding qualified personnel to support them. For example, while it may be relatively easy to hire a controls engineer familiar with Honeywell Experion, it can be extremely difficult to locate someone with experience on Honeywell TDC2000. Identifying a competent engineer who is both experienced and within budget is often difficult. Senior experts for TDC2000 or similar platforms can command $150 to $200 per hour. On call support contracts often start at $75,000 per year. Moreover, attracting a new, lower-cost engineer to learn what they may view as a dying, obsolete system can be equally difficult. Early in their careers, many engineers prefer to focus on state-of-the-art products that will remain relevant throughout their working lives. While some may be willing, it can feel akin to asking someone to center their career on building horse-drawn buggies after the advent of the Model T.

If finding a full-time hire proves too difficult or impossible, it may become necessary to supplement the team with contract support, further increasing overall costs. Some platforms developed outside the United States, such as certain Siemens ICSs, may even require bringing in contractors from overseas to restore operations after a failure. If overseas contractors are needed, travel and emergency fees can easily exceed $20,000 for one event not including lost production during delays.

Conclusion

While it may be tempting to retain legacy systems because of their past reliability, these platforms can often become costly and significantly increase operational risk. As they age, spare parts grow harder to source, and engineers with the skills to support them become scarce. Once-reliable systems also gradually degrade as they are used beyond their intended life expectancy. Although the upfront expense of an upgrade can be difficult to justify and may range from $250,000 to $500,000 for a mid sized plant, the ongoing costs of maintenance, emergency parts, and downtime can exceed $100,000 each year. When outages occur, even a single day of halted production can result in more than $50,000 in lost revenue. For many facilities, the financial risk and operational strain of clinging to outdated systems far outweigh any short term savings. Modernization is the clear path to protecting profitability and ensuring long term success.