Retrofit: modernising a line without replacing its PLCs

In a plant, a working machine is worth a lot: it is paid off, its settings are mastered and its programs validated. Industrial equipment is designed to last 20 to 50 years. Modernisation therefore rarely means replacement: it means retrofit.

Add rather than replace

• An edge gateway reads PLC data (native protocol, Modbus, OPC UA) without modifying its program.
• Non-intrusive extra sensors: vibration, current, temperature, where the PLC measures nothing.
• Modern monitoring consuming this data, without taking over control.

Essential precautions

• Do not open a breach: every added connection fits within OT network segmentation.
• Preserve safety: machine safety functions stay hard-wired and independent.
• Document: diagrams, flows, versions, to stay in control over time.
• Plan for obsolescence: inventory end-of-life PLCs and parts to schedule necessary migrations.

What about the Machinery Regulation?

A substantial modification of an existing machine can bring it into the scope of the Machinery Regulation applicable from 20 January 2027. A retrofit limited to reading data does not have the same implications as changing control functions: assess case by case.

Our data integration service follows this logic: a one-line pilot, without touching the PLCs.

Information current as of 29 September 2026. Regulations and timelines change: this article is not legal advice.