Aging control systems rarely fail all at once. They degrade slowly, through years of patched fixes and workarounds, until unplanned downtime becomes routine and the system becomes something nobody fully understands anymore. Zachary Neudorfer, an automation engineer on Premier's Automation team, describes the pattern well: equipment ends up on the wrong controllers, “temporary” programming and
electrical changes become permanent, which leads to years of incremental fixes rather than intentional design.

Modernizing before reaching that point is almost always the better decision.
Newer systems are easier to troubleshoot, spare parts are available, and the performance improvements that come with updated controls often recover more production capacity than the upgrade costs in downtime. The question is not usually whether to modernize. It is how.

Phased Modernization: Upgrading Around Production

Phased modernization breaks the upgrade into segments, each sized to fit within whatever downtime windows the operation can provide. For facilities where production schedules allow only a day of downtime per month, it is often the only viable path.

The approach requires careful planning up front. The engineering team needs current drawings and programs for the existing system, a clear understanding of how the equipment communicates, and a defined target state before any work begins. Knowing which components can be upgraded independently and which need to move together determines how the phases get structured. In some cases, certain drives or I/O have to be replaced alongside the PLC because the old network protocols simply cannot bridge to the new controller. That has to be identified before the first phase starts, not discovered during it.

There is a genuine troubleshooting advantage to phasing work this way. Upgrading one layer at a time makes it easier to isolate problems. If everything is replaced at once and something is not working, it is hard to know whether the issue is in the PLC code, the drive configuration, or somewhere else. Phasing the work simplifies that.

The tradeoff is real: phased projects require more total engineering time. When you upgrade the PLC in phase one, you program it to communicate with the existing drives. When you replace the drives in phase two, you rewrite those communications. Work gets done more than once. It is a more demanding process for everyone involved, but for facilities where extended downtime is not an option, it is the right one.

Full Replacement: The Case For Taking The Outage

When a facility can take an extended outage, full replacement is the cleaner path. The system gets designed as a whole, programmed once, and tested against its final configuration. There is no double work, no temporary code or communications to clean up later, and no risk of the system drifting into disorganization over a multi-year phased project.

The cost of aging equipment is real, but it tends to be distributed across months of small incidents rather than concentrated in a single visible event. Recurring failures, extended waits for obsolete parts, drives that are no longer performing reliably: that lost production time adds up. One planned week of downtime for a full replacement may return more capacity over the following years than the current situation allows. That argument does not always make it through to production leadership, but it is worth making clearly.

Making the call

The right approach depends on what the operation can realistically support. How much downtime is available, how large the system is, and how obsolete the current equipment is all factor into the decision. Large systems sometimes require phased execution not because of downtime constraints but because the scope of a full cutover would be unmanageable.

What both approaches have in common is this: neither works without a clear picture of where the system is going before work begins. A phased project without a defined end state tends to accumulate the same kind of disorganization it was meant to fix.

If your operation is managing aging controls and you are not sure which approach fits your situation, Premier's Automation team can help you work through it. Our engineers assess what you have, identify what needs to move, and put together a realistic plan built around your production constraints.

Start that conversation here: https://hubs.ly/Q04gDFVq0