Legacy refineries weren’t built with upgrade pathways in mind. Most facilities are running multiple generations of control hardware simultaneously.
Different platforms across different units installed at different points in the facility’s history don’t just result in aging equipment. It creates a fragmented system where critical process data often never reaches the people who need it.
If your refinery is facing this dilemma and you’re not sure which steps to take in order to fix it, this guide is for you.
What “Obsolete” Actually Means in a Control System Context
Outdated hardware in a control system isn’t just about age. It shows up operationally in ways that pose real risks to refining and petrochemical facilities.
For example, vendor end-of-life declarations mean that replacement parts are no longer manufactured. When a card fails, the options are gray market parts, expensive cross-platform workarounds or an unplanned shutdown to redesign around unavailable hardware.
Legacy DCS platforms also frequently predate OPC-UA and modern Ethernet protocols, making them unable to feed data to historian systems, MES platforms or advanced process control layers. This means that operators are making decisions without real-time process visibility across the full unit.
Finally, older safety instrumented systems (SIS) may not meet current IEC 61511 functional safety standards, creating both regulatory exposure and a gap between a system’s designed safety function and its actual performance.
Understanding what an outdated system actually looks like is the starting point for any meaningful prioritization conversation.
The Signals Worth Taking Seriously
Not every aging system warrants immediate action, but certain patterns indicate that deferred maintenance has become a capital planning problem, including:
- Instrument technicians spending more time nursing failing transmitters than on preventive work
- Process upsets occurring, and the control room can’t reconstruct what happened
- Vendor support for a discontinued platform disappearing entirely
- Engineers no longer sourcing qualified personnel familiar with a legacy platform
Any one of these signals is worth investigating. More than one of these problems occurring simultaneously should be given high priority.
How to Prioritize When a Full Cutover Isn’t Realistic
Most facilities have accumulated a decade or more of deferred I&C investment and can’t address it in a single turnaround cycle. A practical prioritization framework considers three main factors.
Factor #1: Consequence-Of-Failure Ranking
Not all control systems carry equal risk. A failing level transmitter on a high-pressure vessel has a different consequences profile than one on a utility water line. Prioritization starts with identifying which systems (if they fail) affect safety, regulatory compliance or primary throughput in that order.
Factor #2: Platform Consolidation vs. Point Upgrades
Replacing individual instruments is sometimes the right call. However, if a facility is running multiple incompatible DCS platforms across different units, point upgrades may only delay rather than solve the underlying architecture problem, and a single instance of DCS modernization may not help.
Factor #3: Phased Execution to Protect Uptime
Sequencing work to align with existing turnaround windows and developing a detailed execution plan before any work begins is what keeps these projects from disrupting ongoing operations. Our recent PLC upgrade project involved loop checks, network modifications and PLC-to-PLC communications, all executed without disrupting ongoing operations.
The goal of this phase isn’t a procurement list. It’s to create a ranked action plan that your facility can execute incrementally without introducing new risk at each step.
What a Scoped Upgrade Engagement Includes
A well-scoped I&C modernization engagement covers execution planning and risk documentation, code reconfiguration, loop verification, network infrastructure updates, commissioning and checkout. Defining your scope upfront is what keeps these projects from expanding mid-execution.
At JEPCO, our instrumentation, automation and controls engineering capabilities span the full scope of this work—from initial assessment through commissioning—within the broader context of engineering services that can address related mechanical, process or structural issues identified during the upgrade process.
FAQs
How do refineries modernize legacy refinery control systems?
Effective modernization starts with a risk-ranked assessment of existing hardware, not a hardware procurement list. Facilities that skip the assessment phase tend to address symptoms rather than the underlying problems driving them.
What are the first steps in controls modernization in a refinery?
The first step in controls modernization in a refinery is to identify which systems are approaching or are past vendor end-of-life, which platforms can’t integrate with current process data infrastructure and which have functional safety gaps relative to current IEC 61511 standards. That gap analysis will drive your prioritization.
What risks come from outdated control systems?
The most immediate instrumentation obsolescence risks include parts being unavailable when hardware fails and functional safety gaps that may not be visible until an incident occurs. In the long run, the inability to integrate legacy refinery control systems with modern process data platforms limits a facility’s ability to optimize operations or meet evolving regulatory requirements.
Will Morrey
Electrical & Instrumentation Manager
Will Morrey is JEPCO’s electrical & instrumentation manager with a background in industrial I&C spanning oil and gas and mining environments.
