CE marking for retrofits: When a system modification requires a new conformity assessment

1. Introduction: Product safety and operator responsibility when retrofitting machines

The European CE marking is an essential tool for ensuring product safety in the European economic area. It confirms that a product complies with the applicable EU directives and harmonized standards. In the context of maintenance, repair and operation (MRO) of industrial plants, the correct application of the CE marking is critical, especially when integrating spare parts and retrofitting.

According to the Machinery Directive 2006/42/EC and other product-specific guidelines, responsibility for the CE marking lies primarily with the manufacturer. However, if a significant change is made to a machine that has already been placed on the market, the operator himself can become a manufacturer within the meaning of the law. This implies full producer responsibility, including the obligation to carry out a new conformity assessment and affix a new CE marking.

A thorough knowledge of these mechanisms is essential for maintenance managers, safety officers and plant operators to minimize liability risks, ensure operational safety and ensure the ongoing compliance status of their machinery fleets. This document highlights the technical and legal framework that must be taken into account when retrofitting and offers practical guidance for the DACH manufacturing industry.

2. Scope and scope: Who is affected and which systems are relevant?

The need for a new conformity assessment arises when a machine or part of a system is modified after its original commissioning in such a way that the original declaration of conformity loses its validity. This affects a wide range of machines and systems used in the DACH manufacturing sector, from machine tools to packaging systems to complex production lines.

2.1. Definition of “Material Change”

The key definition provides the interpretation of the significant change. A change is considered material if it:

• the intended use of the machine changes.
• creates new hazards or increases existing hazards.
• the safety function of protective devices is impaired or new protective measures are required that have not been adequately implemented.
• the performance data or the type of process is influenced in such a way that a reassessment of the risks in accordance with DIN EN ISO 12100 becomes necessary.

Examples of significant changes include replacing controllers with ones with modified safety functions (e.g. integrating a new safety switching device that is not identical to the previous model), increasing speeds or pressures beyond the original design limits, or adding new processing stations.

2.2. Affection of industries and actors

Practically all industrial sectors with significant machinery are affected: automobile manufacturing, mechanical engineering, food and pharmaceutical industries, chemistry, metal processing. The main actors are:

• Plant operators: They bear primary responsibility for the safe operation of their machines. If there are significant changes, you legally become the manufacturer.
• Maintenance personnel and maintenance managers: They must be able to recognize and evaluate the implications of modifications for CE conformity.
• Safety officers: Monitor compliance with occupational health and safety regulations and machine safety.
• Purchasing: Responsible for sourcing compliant spare parts and components.

3. Key Requirements: An Overview

If a significant change is detected, the operator must go through a full CE process. The most important steps and requirements are:

4. Impact on MRO processes

The need for a new CE marking has far-reaching consequences for daily processes in maintenance, procurement and documentation.

4.1. Maintenance and servicing

Maintenance personnel must be trained to recognize the difference between simple replacement (identity of function and form) and a potential significant change. Routine maintenance where components are replaced with identical or equivalent (in terms of the specification) replacement parts are not subject to the CE reassessment requirement. However, a modification that affects performance, safety, or control logic requires detailed analysis.

The maintenance manager's responsibility expands to include the initial evaluation of modification suggestions. This requires close cooperation with construction, occupational safety and purchasing.

4.2. Procurement and materials management

Purchasing must ensure that spare parts not only meet the requirements functionally, but also in terms of their certification. For critical components, especially those with a safety function, the CE conformity of the spare part itself and its suitability for the specific application must be proven. UNITEC-D ensures the delivery of certified and compliant components that support compliance with national and international standards.

4.3. Documentation management

Careful documentation of all changes is essential. This includes detailed descriptions of the modifications, the risk assessment carried out, the new declaration of conformity and the updated operating and maintenance instructions. Compliance with the documentation requirements according to VDI 4068 Sheet 1 and DIN EN 60204-1 is important here.

5. Component Requirements: Which spare parts must meet specific certifications?

Not every spare part requires its own CE marking. However, certain components, in particular safety components, must either be CE marked themselves or their suitability for the respective application must be proven as part of overall machine conformity.

5.1. Safety components

Components that explicitly serve safety and are listed in Annex V of the Machinery Directive must carry their own CE marking and provide a declaration of conformity. Examples of this are emergency stop command devices, light grids, non-contact protective devices, safety-related controls (e.g. according to DIN EN ISO 13849-1 for performance level) and pressure limiting devices. When replacing, it must be ensured that the new component has the same or a higher safety function and is correctly integrated into the existing safety system.

5.2. Electrical and electronic components

Electrical components such as motors, frequency converters or sensors often fall under the Low Voltage Directive 2014/35/EU and/or the EMC Directive 2014/30/EU. Your CE marking demonstrates compliance with these guidelines. When replacing, not only the electrical compatibility, but also the EMC compatibility in the entire system must be checked in order to avoid faults according to VDE 0100.

5.3. Pressure equipment and explosion protection components

Pressure-carrying components (e.g. valves, containers, pipelines) must meet the requirements of the Pressure Equipment Directive 2014/68/EU. Components used in potentially explosive areas fall under the ATEX Directive 2014/34/EU and require special proof of conformity for explosion protection.

UNITEC-D offers an extensive portfolio of certified industrial components that meet the strict requirements of DIN, VDE and ATEX and thus enable safe and compliant maintenance. The quality of the components is ensured by a robust supply chain and comprehensive testing procedures according to TUV standards.

6. Maintenance Manager Compliance Checklist

This checklist serves as a practical guide for evaluating retrofits and ensuring CE conformity:

1. Change analysis: Exactly define the scope of the planned modification.
2. Intended use: Check whether the change changes the original intended use of the machine.
3. Risk assessment according to ISO 12100: Carry out a comprehensive risk assessment for the modified machine. Consider new or increased threats.
4. Security functions: Evaluate the effects of the change on existing security functions (e.g. performance level according to DIN EN ISO 13849-1).
5. Applicable directives: Identify all relevant EU directives (e.g. Machinery Directive, EMC, Low Voltage, ATEX, Pressure Equipment).
6. Harmonized standards: Specify the harmonized standards to be applied (e.g. DIN EN 60204-1 for electrical equipment).
7. Compliance status: Determine whether the change represents a material change requiring a new CE assessment.
8. Internal competencies: Do you have the necessary internal resources and expertise for conformity assessment?
9. External support: If necessary, call in external experts (e.g. experts, accredited testing centers).
10. Technical documentation: Create or update all relevant technical documentation (drawings, circuit diagrams, parts lists, calculations).
11. Operating instructions: Adapt the operating instructions to the modifications.
12. Declaration of Conformity: Create a new EU declaration of conformity as the “manufacturer” of the modified machine.
13. CE marking: Remove the old one and apply a new CE marking if necessary.
14. Testing and Validation: Perform necessary testing and validation of security functions.
15. Staff training: Train the operating and maintenance personnel on the changes.
16. Supplier check: Make sure that all spare and new parts purchased have the necessary certificates and declarations of conformity.
17. Archiving: Archive the complete documentation over the entire life cycle of the machine, but at least 10 years.
18. Periodic Review: Schedule periodic CE compliance reviews, especially after further modifications.

7. Frequent non-conformities

In practice, auditors repeatedly find similar deficiencies in the CE conformity of retrofitted machines. Knowing these weak points helps to take preventive action.

• Missing or inadequate risk assessment: A modification is often made without systematically assessing the new or changed risks. However, a risk assessment according to DIN EN ISO 12100 is the basis of every conformity assessment.
• Inadequate technical documentation: The traceability of the changes and the proof of compliance with the security requirements are incomplete. Old documents are not updated and new ones are not created.
• “Gray area” definition: The difference between simple repair/replacement and significant modification is not interpreted correctly, leading to an underestimation of legal obligations.
• Use of non-conforming spare parts: Particularly in the case of safety-relevant components, spare parts are installed without sufficient proof of their conformity or suitability for the specific application.
• Defects in the electrical equipment: Failure to comply with DIN EN 60204-1 (Safety of Machines - Electrical Equipment of Machines) when making changes to the control or wiring.
• Neglect of EMC compatibility: New electrical or electronic components can disrupt the electromagnetic compatibility of the entire system, which can lead to operational disruptions and dangers (see EMC Directive 2014/30/EU).
• Missing or outdated operating instructions: The operating and maintenance personnel are not informed about the changes and their effects, which can lead to incorrect operation and accidents.

8. Sanctions and liability for non-compliance

Failure to comply with CE regulations and associated product safety laws can have serious consequences that go far beyond the purely technical area. For operators of industrial plants in the DACH region, the effects are potentially life-threatening.

8.1. Fines and criminal consequences

In Germany, violations of the Product Safety Act (ProdSG) and the Machinery Ordinance (9th ProdSV) can lead to severe fines. In the event of negligent bodily harm or death caused by non-compliant machines, there is also a risk of criminal consequences for the responsible persons (managing directors, technical managers, safety officers). Depending on the severity of the violation and the size of the company, the fines can be up to EUR 100,000 per individual case. Higher penalties are possible for repeated or particularly serious violations.

8.2. Civil liability and insurance coverage

In the event of accidents or material damage caused by a non-compliant machine, the operator as the “manufacturer” can be held fully liable under civil law. This includes claims for damages from third parties (e.g. injured employees, damaged products). The company's product liability insurance may refuse coverage in the event of gross negligence or intent with regard to CE conformity. This means that the company would have to bear the full costs of damages and legal proceedings itself, which can quickly run into the millions.

8.3. Operating ban and reputational damage

Regulatory authorities (e.g. trade inspection offices) are authorized to immediately prohibit the operation of machines that are classified as unsafe or non-compliant. This leads to production downtime and significant financial losses. In addition, reputational damage caused by media reports about accidents or official measures can permanently undermine customer trust and lead to long-term competitive disadvantages.

9. Conclusion: Proactive compliance for sustainable success

The CE marking for retrofits is not a bureaucratic hurdle, but an integral part of risk management and operational safety in the manufacturing industry. Proactively dealing with the requirements of the Machinery Directive and adjacent EU directives is essential to ensure the safety of personnel, the availability of the systems and the legal protection of the company. Through careful planning, a well-founded risk assessment and the use of certified components, operators can successfully master the challenges of conformity assessment for retrofits.

UNITEC-D is your reliable partner for high-quality, CE-compliant spare parts and components. Our products meet the relevant DIN, VDE and TUV standards and help ensure the conformity of your systems after every modification. Trust in certified quality for your MRO needs.

Discover our extensive range of industrial components that support compliance with your compliance requirements: UNITEC-D E-Catalog.

10. References and further information

• Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery and amending Directive 95/16/EC (recast).
• Directive 2014/30/EU of the European Parliament and of the Council of February 26, 2014 on the harmonization of the laws of the Member States relating to electromagnetic compatibility (EMC Directive).
• Directive 2014/35/EU of the European Parliament and of the Council of February 26, 2014 on the harmonization of the laws of the Member States relating to the making available on the market of electrical equipment for use within certain voltage limits (Low Voltage Directive).
• Directive 2014/68/EU of the European Parliament and of the Council of 15 May 2014 on the harmonization of the laws of the Member States relating to the making available on the market of pressure equipment (Pressure Equipment Directive).
• Directive 2014/34/EU of the European Parliament and of the Council of February 26, 2014 on the harmonization of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres (ATEX Directive).
• DIN EN ISO 12100:2010 - Safety of machines - General design principles - Risk assessment and risk reduction.
• DIN EN ISO 13849-1:2023 - Safety of machines - Safety-related parts of controls - Part 1: General design principles.
• DIN EN 60204-1:2018 - Safety of machines - Electrical equipment of machines - Part 1: General requirements.
• Product Safety Act (ProdSG) of November 8, 2011 (BGBl. I p. 2179), last amended by Article 1 of the law of July 27, 2021 (BGBl. I p. 3146).
• VDI 4068 Sheet 1 – Operational Maintenance – Documentation.
• Federal Institute for Occupational Safety and Health (BAuA) – publications on machine safety and CE marking.