Control System Upgrade Part 1: Understanding When It’s Needed
Upgrading a control system is a complex process that requires careful analysis of the equipment to which it’s connected. While mechanical equipment upgrades can result in more tangible benefits (increased throughput, efficiency, etc.), the improvements resulting from a controls upgrade are more nuanced.
In general, a well-executed controls upgrade creates a safer, more reliable system with less downtime, better access to spare components, and the potential for savings on utilities. However, because the controller is the central hub of the system, the project needs to be approached in a thoughtful manner, with strong knowledge of the interfacing equipment, the protocols used for communication between them, and the programming methodologies used by both the old and new PLCs.
In this article, part of a two-part series, we’ll explore scenarios where a control system upgrade is necessary. Depending on the specific circumstances, one or several of these factors may be valid concerns driving the decision.
1. It’s Difficult to Obtain Replacement Parts
As a control system ages, it can become progressively more challenging to obtain the necessary spare parts needed to keep it in operation. If the older system was designed with custom parts, custom IC components, or relies on older communication protocols, any of these may become obsolete over time, making support for the system challenging.
Common parts that can be difficult to source for a legacy system include:
- Microprocessors
- Input and/or output cards
- Batteries
- Servos
- Variable frequency drives (VFDs)
2. There Are Compatibility Issues
A control system upgrade may be needed to support newer software platforms and/or equipment that isn’t backwards compatible.
Sometimes, a supporting reason for a controls upgrade is to have the ability to run newer software, such as Siemens TIA Portal, and access its benefits.
Older control systems like Simatic Manager Step 7 Classic do not necessarily have the hardware to support TIA Portal. Their processors may be insufficient, or, likewise, there may be insufficient memory within the computer. TIA Portal requires a means of high-speed communication, of which some older controllers may not be capable. In addition, older HMIs may not meet the requirements needed to run TIA Portal.
Additionally, supply chain problems that occurred alongside the COVID-19 pandemic, forced some controls manufacturers to switch sources for their integrated circuit components. For example, Siemens opted to redesign their TP1500 entire panel (inside and out). Therefore, a TP1500 purchased today as a spare part may not be directly compatible with older versions of the same model.
3. Downtime Issues Have Increased
As equipment gets older, the risk of failures increases. The environment in which the system is operating plays a substantial role in the system’s lifespan, with higher humidity and higher temperature environments presenting a larger strain on the operating components.
Some failure examples include:
VFD – Burning/Overheating Damage
A VFD is composed of power semiconductors in both its rectifier and inverter stages that perform the regular switching operations defining its function. Over time, these components deteriorate, become more resistive and less efficient, increasing energy dissipation as heat. Harsher electrical environments can also contribute to component wear and damage over time.
Relay Output Card Failures/Contact Wear Damage
A relay is a switching device at its core. Over time, the mechanical contacts of the device may become damaged, leading to poor, unreliable connections.
Intermittent component failures are an additional problem with older control systems, resulting in downtime.
4. There Are Cycle Time Gains
A newer control system will likely have a much faster overall processing speed. As a result, the time it takes to receive and interpret inputs, and then drive the resulting outputs, will be much less than that of a legacy device.
5. You Desire Brand Standardization
Streamlining to one particular brand of control system components, for example, Siemens, simplifies support and maintenance, staff training, resulting in less overall monetary investment.
6. The System Is a Security and Safety Risk
Today, two particular technology areas commonly driving the need to upgrade a control system include improved cybersecurity and safety optimization.
Cybersecurity
Depending on the system’s age, there may be limited means of meeting cybersecurity protection requirements. While an old system may have no network connectivity at all (and, therefore, no cybersecurity risk), some more recent systems may be connected to the OT network with limited means of addressing cybersecurity concerns. This limitation can leave more than just the particular device vulnerable to a cybersecurity attack; it effectively leaves an open door for a threat to find its way to several, or possibly all, networked devices.
Safety Standards
It’s important to note that safety standards within manufacturing have been continuously evolving in recent years. A system deemed “safe” as recently as 2005 would likely be deemed unacceptable by today’s standards. In the United States, it is the owner of the manufacturing facility who is responsible, and ultimately liable, for site safety.
As systems are upgraded, a safety risk assessment must be completed. While upgrading to meet today’s safety standards is not a strict legal requirement, failure to meet the standard leaves a manufacturer open to liability and fines should an incident occur. Ensuring equipment meets safety standards proves that a manufacturer has done their due diligence in creating a safe work environment, serving as some legal protection should someone be injured.
A control system upgrade may be required to meet today’s more stringent safety standards. Older control systems have very limited safety control capabilities, while newer systems have more integrated means of including robust safety features in a production line. This is an important requirement when completing a required safety risk assessment and selecting devices that are safe, will fail safe, or are configurable such that a single point of failure will not cause a human hazard or injury. This topic is discussed further in our recent eBook, Common Considerations Integrating Robotics in Manufacturing.
7. You Want to Switch to Servo
In the past, servo control systems were costly to purchase, integrate, and operate. Today, servo systems are far more competitive in price, and newer PLCs incorporate better means of connecting servo systems than their older counterparts. Newer PLCs also support the high-speed communication protocols needed for more precise control and performance, and feature built-in motion control and functionality.
Depending on the application, an upgrade from a hydraulic or pneumatic system to a servo system may improve energy efficiency and reduce overall electricity expenses. In addition, the possibility of costly air leaks (pneumatics) and installation of flow meters to monitor for them is removed. A move away from hydraulics also eliminates the possibility of leaking oil concerns and the potential for explosion in environments that include flammable substances.
8. You Need Software Functionality Improvements
Upgrading to a newer control system allows you to operate your facility using the most up-to-date, integrated software systems, improving code efficiency, downtime recovery, and data connectivity (Industry 4.0). You can read Part Two of this blog series to learn more about software.
When to Replace Outdated Equipment Versus the Controller
There are times when it’s a better decision to fully replace outdated equipment rather than try to update the controller, including:
- The cost of the upgrade is 50% or more of a new unit: Upgrading controls is likely a lesser and short-term monetary investment compared to a full equipment replacement. On the other hand, the latter option comes with a longer lifespan for all system parts.
- The entire system is in poor condition: If the mechanical portion of the system is in generally good condition, a controls upgrade may be the best approach that balances project cost with benefit. On the other hand, if the physical portion of the system is in poor condition, investing in a full replacement could offer the best return on investment.
- You’re okay with waiting: It’s not uncommon for equipment to have a six-month lead time, a timeframe that may be longer than that of an upgrade. You may want to consider a replacement if lead time isn’t an issue, and a replacement seems like the better option based on the conditions listed above.
You’ve Decided to Upgrade—What’s Next?
If upgrading your control system is a better approach for you rather than a replacement, we recommend reading our next blog in this series, Control System Upgrade Part 2: Planning for the Upgrade, which discusses the preparatory steps required for a control system upgrade.
FAQs
What Are the Benefits of Upgrading Control Systems?
A control system upgrade improves safety, reduces unplanned downtime, and extends your operational lifespan by moving to a platform with active vendor support and available spare parts. Beyond reliability, modern systems provide better cybersecurity posture, faster processing speeds, improved software integration (including Industry 4.0 connectivity), and reduced energy costs. The compounding benefit is operational: a plant running on a supported, well-documented platform is easier to staff, easier to maintain, and more resilient to supply chain disruptions than one running on legacy hardware.
What Parts Are Often Hard to Replace in Older Systems?
The most commonly unavailable parts in aging systems are microprocessors, I/O cards (input and output), batteries, servos, and variable frequency drives (VFDs). Custom IC components and older communication protocol hardware are particularly difficult because they were never widely distributed and have no modern equivalent. When sourcing shifts from OEM to secondary markets — brokers and rebuilt components — lead times become unpredictable and quality guarantees disappear. That transition is typically the first clear signal that a platform is past its serviceable window.
How much does a control system upgrade cost?
Most control system upgrades range from $50,000 to $500,000+ depending on system complexity, scope, and the platform being migrated to. A targeted upgrade on a single line or subsystem is typically at the lower end; a plant-wide migration involving multiple PLCs, HMIs, and SCADA layers is at the higher end. The more useful comparison isn’t upgrade cost in isolation — it’s upgrade cost versus the accumulated cost of unplanned downtime, parts sourcing premiums, and the increasing labor required to maintain a degraded system. A qualified integrator can scope your specific situation and produce a meaningful estimate before you commit to a direction.
How long does a control system upgrade take?
Most projects run 3 to 12 months from initial assessment to commissioning. A focused upgrade on a single controller or subsystem can move faster; a full plant-wide migration takes longer, particularly when hardware lead times are a factor. The single biggest variable is how much work can be done offline — programming, testing, and staging — before the live cutover window. Projects that compress that window effectively minimize production impact. Timeline estimates improve significantly once a detailed scope is defined.
What causes control systems to fail more frequently as they age?
Failure frequency increases as components degrade, spare parts become scarcer, and the people who know the system retire or leave. On the hardware side, VFDs develop heat damage as power semiconductors become more resistive over time; relay output cards develop contact wear; processors slow. Environmental factors — high humidity, high temperature, vibration — accelerate all of these. Intermittent failures are particularly costly because they’re difficult to diagnose and often masked by workarounds that add fragility. When mean time between failures is shortening and mean time to repair is growing, that combination is a clear signal the system is in decline.
Is it better to replace equipment entirely or just upgrade the controls?
It depends on the condition of the mechanical and electrical systems connected to the controller. If the physical equipment is in good condition, a controls upgrade typically offers a better return — lower cost, shorter timeline, and you preserve the mechanical investment already made. Full replacement makes more sense when the upgrade cost approaches 50% or more of a new unit’s cost, when the broader system is in poor condition, or when a replacement would provide a meaningfully longer service life. Lead time is also a factor: equipment replacements often carry 6-month lead times, while an upgrade can move faster.
What safety and cybersecurity standards apply to control system upgrades?
The most commonly applicable standards are IEC 62443 (cybersecurity for industrial automation and control systems), IEC 61508 (functional safety of electrical safety-related systems), and ISO 27001 (IT/OT system convergence). Safety standards in manufacturing have evolved significantly — a system considered safe in 2005 may not meet current requirements. While upgrading to meet current standards isn’t always a strict legal requirement, failure to do so creates liability exposure if an incident occurs. A safety risk assessment should be completed as part of any upgrade scope to identify which hazards need to be mitigated and which standards apply to your environment.
How do I find a qualified control system integrator?
Look for CSIA certification — the Control System Integrators Association certifies firms through independent audits covering project management, business practices, and technical competence. Beyond certification, verify that the integrator holds direct platform credentials on the system you’re migrating to: Siemens Solution Partner, Rockwell Automation recognized integrator, Ignition Gold, or FANUC Authorized Integrator status, depending on your platform. Cross-industry experience matters — integrators who have worked across automotive, pharma, food and beverage, and semiconductor environments bring pattern recognition that single-vertical specialists don’t. Ask specifically about post-commissioning support: the transition period after cutover is when problems surface, and you want a partner who’s still accountable at that stage.
Related categories: Blog Control Systems Integration
