September 9, 2026

Overview
A Midwest United States dairy products manufacturer operating a GMP facility was running plant-wide control systems that had reached the end of their lifecycle. The legacy Allen-Bradley PLC5 and SLC platforms were no longer in full production, and replacement parts were only available through unreliable third-party brokers at a high cost. For a perishable, short-shelf-life product line, that exposure was serious. A controller or I/O failure with no redundancy behind it could mean days waiting on a part instead of hours, and downtime on dairy production costs twice over: lost output plus whatever product is in process at the moment of failure. The manufacturer issued a formal PLC and SCADA Modernization RFP covering the entire facility. Grantek won that RFP outright, and the relationship has continued ever since, with the client returning for each subsequent system rather than putting the work back out to bid. Twelve projects in, the partnership reflects the kind of trust that food and beverage manufacturers look for when modernizing control systems without disrupting production of a perishable good.

Challenges
Grantek and the client weighed two broad paths forward: a single plant-wide shutdown-and-replace, or a phased, system-by-system migration. A dairy plant running a short-shelf-life product cannot absorb an extended outage, so a full shutdown was effectively off the table from the start. The team also considered whether to rewire each panel from scratch or reuse the existing field wiring with conversion kits. The phased approach won out, both because it kept the plant running and because it let the client spread the investment across multiple budget years instead of taking it in one large hit. The migration unfolded over four years and touched HTST 1 and 2, blending, the milk distribution loop, hot water, CIP 1 and 2, raw CIP, the pump system, silo chiller, silos and silo HMI, the flow meter and shear pump, and the CIP-to-filler signal exchange, including two sealed HTST legal panels tied to the HTST 1 and 2 work.

The project surfaced real complications along the way. Much of the existing controls hardware had no supporting documentation, no SOO and no P&ID drawings, and a good deal of the PLC logic turned out to be years of maintenance patches that behaved differently once faster scan times were introduced. The legacy HMI and PLC communicated by reading and writing individual bits within a byte, which added complexity to the conversion. The sealed legal panels could only be upgraded after breaking the seal, which then required validation by a legal representative, a process the team had to learn as they went. Conversion hardware brought its own surprises: faulty cables needed to be replaced with direct wiring, and a Rockwell Automation I/O module had undocumented supply voltage limitations. Some of the oldest PLC5 controllers also could not communicate with the new ControlLogix platform over Ethernet. Each of these was solved individually, from field-verifying and updating drawings ahead of every cutover to building a temporary software bridge between old and new controllers during the transition, keeping the plant running as a mixed estate throughout.

Solutions
Grantek migrated the legacy Allen-Bradley SLC systems to CompactLogix 5380 controllers and I/O using Allen-Bradley conversion kits, allowing the new hardware to land on the client’s existing field wiring rather than requiring every panel to be rewired from the ground up. HMI platforms moved to PanelView Plus 7, and the HMI software itself was brought current so the HMI, PLC, database, and reporting systems all operate on a supported version. The new Rockwell Automation CompactLogix controllers, HMI, FLEX EtherNet/IP adapters, and valve banks were all connected over EtherNet/IP through the server room switches. Using 1492 wiring conversion kits meant large systems could be migrated within a weekend sanitization window instead of requiring a dedicated week-long outage, a critical factor for a facility that could not afford extended downtime.

Throughout the project, every migrated system had to keep communicating with systems not yet converted, which is exactly why the CIP-to-filler signal exchange was built as its own project. All work was carried out to the client’s electrical standards, safety practices, lockout-tagout procedures, and GMP requirements, with decommissioned panels handed over to plant maintenance for salvage evaluation.

The result is a facility migrated essentially end to end onto current Rockwell Automation controls, achieved without ever taking the plant down to do it. The obsolete-spares exposure that started the project is gone, maintenance now supports a single platform instead of a patchwork of aging systems, and replacement parts come from a distributor rather than a broker. The client has reported a significant reduction in downtime and now has the confidence to pursue further updates and improvements across their processes, something the old control platform made difficult. The approach has already proven portable, having run to completion at this facility with additional modernization work completed at another of the client’s sites as well.