Context card
Retrofit and substantial modification under the Machinery Regulation
When does a retrofit make the operator the manufacturer of a machine?
The short answer
Only when the retrofit is a substantial modification: a change by physical or digital means that the original manufacturer did not foresee and that creates a new hazard or increases a risk so that new guards or protective devices changing the safety control system, or new measures for stability or strength, are needed. A new program on the safety controller can meet this test as much as a new guard. Then Article 18 of the Machinery Regulation treats whoever made it as the manufacturer. Most retrofits are not substantial, but each one needs the assessment that shows it.
For: Plant operators, integrators, safety engineers and technical writers working on retrofits
Key points
- The Machinery Regulation (EU) 2023/1230 defines substantial modification in Article 3(16) and applies from January 20, 2027.
- Article 3(16) covers modifications by physical or digital means: a software change, such as a new program on the safety controller, can be a substantial modification just like a mechanical one.
- Article 18: whoever makes a substantial modification is considered a manufacturer, with conformity assessment, technical file, declaration and CE marking.
- Annex III, 1.2.1(f): the control system must enable a tracing log of interventions and of the safety software versions uploaded after placing on the market, kept for five years for a competent authority's reasoned request.
- Repair and maintenance that do not affect compliance are not substantial modifications.
- In an assembly of machinery the obligations apply to the affected part, but line-wide stop controls (1.2.4.4) must still work for the whole line.
- Independently of product law, the operator updates its own risk assessment and documents for every retrofit.
The context
The test
A retrofit modernizes an existing machine. Whether it is a substantial modification follows from the risk assessment of the change:
- Does the change create a new hazard or increase an existing risk?
- If so, are new guards or protective devices needed that change the safety control system, or new measures for stability or mechanical strength?
- Was the change foreseen and planned by the original manufacturer?
Only a change that is not foreseen and needs such new measures is substantial. The legal consequences are explained in retrofit under the Machinery Regulation.
Physical and digital changes
Article 3(16) of the Machinery Regulation expressly covers modifications by physical or digital means. The test is the same for both: a new or changed program on the safety PLC, new parameters of a safety function or a remote software update can create a new hazard or increase a risk, and if new protective measures that change the safety control system are then needed, the change is substantial. A software change is not harmless because nothing is bolted on.
The regulation also makes software changes traceable. Under requirement 1.2.1(f) of Annex III the control system must enable a tracing log of the data generated in relation to an intervention and of the versions of safety software uploaded after the machine was placed on the market or put into service, kept for five years after each upload and used exclusively to demonstrate conformity at the reasoned request of a competent national authority. For a retrofit this means: the safety software versions belong in the tracing log of the control system where the machine provides one, and in the change documentation in any case, as part of configuration management.
Before and after January 20, 2027
Until the Machinery Regulation applies, the Machinery Directive 2006/42/EC applies; it does not define the term, and in Germany the BMAS interpretation paper on substantial modification is used.
Lines
In an assembly of machinery a new machine changes which equipment has to stop together. Requirement 1.2.4.4 is old, but its age does not make it less demanding.
The operator's side
Even a retrofit that is not substantial changes the operator's risk assessment under the BetrSichV and, where the technical file of the line no longer matches, its documentation. Calling a retrofit "like for like" does not replace the assessment.
Questions readers ask next
- Is replacing an obsolete PLC a substantial modification?
- Usually not, if the functions and the safety concept stay the same and no new hazard arises. It still needs a documented assessment and updated documentation.
- Can a software update alone be a substantial modification?
- Yes. Article 3(16) covers digital changes too. A new program on the safety controller is substantial if the manufacturer did not foresee it, it creates a new hazard or increases a risk, and new protective measures that change the safety control system are needed; otherwise it still needs an assessment and a recorded software version.
- Does a substantial modification need a notified body?
- Only if the modified machinery falls under a category for which the regulation requires one; otherwise the modifier carries out the conformity assessment as manufacturer.
Sources
- Regulation (EU) 2023/1230 on machinery and related products — Official Journal of the European Union, June 29, 2023
Review log and changes
Every context card is checked against its sources before it is published, and again whenever it changes; the date under the byline is the last review. Corrections (something was wrong) and additions (something was missing) are logged below with date and time (Berlin time). Typos, formatting and link fixes are not listed.
Reviewed
Corrections and additions
Every correction and addition to this card, with date and time (Berlin time).
Addition
Added the digital side: Article 3(16) covers modifications by physical or digital means, so a program change on the safety controller can also be a substantial modification, and under Annex III 1.2.1(f) the safety software versions belong in the tracing log.