Plant Update: moving an industrial control network to Ethernet
Migrating the PLC network of an industrial site to Ethernet in two phases: design, build, testing and documentation, with a crew of casual workers, scheduled around production shutdowns.
Why it was needed
The site’s control system ran on Modbus Plus and PROFIBUS. The system was old and had many faults, so management decided to move to Ethernet. The old buses were only partly replaced: some units still communicate over them today (I don’t know these buses in depth, my field was the network).
The work ran in two planned phases. The first (2019-2020) was the larger one, the second (2021) the smaller.
My part
Design, build, testing and documentation of the Ethernet part. This included:
- the design and the coordination with the other trades
- installing, configuring and labelling every network device
- connecting the PLCs and the remote I/O cabinets to the central IT rack (52 cable runs at the end of phase two)
- fibre to the remote points (pump station, transformer house, tunnel, train and truck loading), with two independent paths to the pump station and the transformer
- Ethernet addressing of the Momentum I/O adapters: more than a hundred units under six PLCs
- testing and measurement: 61 measured links in June 2021, 173 in December, all passed
I worked with the PLCs up to the point where they were on the network. Their programs belong to the automation team.
How we worked
Cabinet survey with my own dimension markings, February 2021
I photographed the cabinets and drew the dimensions on the photos. The PLC7 on the picture was a temporary test PLC.
The hardest part was not the technical side but the organisation. I built it with casual workers, the work had to fit the production shutdowns, and the schedule had to hold. The crew always needed the material and tools at hand so nobody stood idle (this took serious planning ahead, and a lot of documents were made along the way).
Afterwards
Later a new plant section with two more PLCs was built on the site. An external integrator built it, my role was support, but I took part in the design. The original design had no fibre link between the new and the old plant; it was added at my request.
Today
The network still runs on this build in 2026. This year I turned the whole PLC network data (address plan, cabling, device list) into machine-readable form, and the topology drawing is generated from it. So the documentation is maintained data, not a 2021 spreadsheet.
This was one of my biggest jobs.