Lockout-Tagout (LOTO) is an essential component in controlling hazardous energy during work on machines, such as maintenance, inspection, and cleaning. Although the term “LOTO” itself is not explicitly referenced in all legislative frameworks, the underlying principles are embedded in European directives, international standards, and national regulations. For machine manufacturers, designers, and users, it is therefore necessary to understand LOTO as an integral part of machine safety, rather than merely an operational procedure.
This article provides a technical interpretation of the relevant legislation and standards, with emphasis on the European Machinery Directive 2006/42/EC, the international standard ISO 14118:2018, and U.S. OSHA regulations. It clarifies how these frameworks relate to each other and the implications they have for the design, use, and maintenance of machines.
Within the European Union, the Machinery Directive 2006/42/EC forms the basis for machine safety. This directive defines the essential health and safety requirements that machines must meet before being placed on the market. The focus is on risk reduction through safe design.
A central principle within the directive is that hazardous energy must be controllable. This means that all relevant energy sources, such as electrical, hydraulic, and pneumatic energy, must be capable of being effectively isolated. This isolation must be reliable and suitable for use in maintenance situations.
In addition, the directive requires that energy isolation points are clearly identifiable and accessible. In practice, this means that provisions such as main switches and shut-off valves must, where required based on the risk assessment, be suitable for locking. This forms the technical basis for the application of LOTO, where energy is physically blocked.
The directive also requires that unexpected start-up be prevented. Machines must not automatically restart after, for example, a power failure if this poses a risk. Restart must result from a deliberate action, such as a manual reset.
Furthermore, a systematic risk assessment is mandatory. All relevant hazards must be identified, including risks that occur during maintenance and interventions. Appropriate technical and organizational measures are determined based on this assessment.
Finally, manufacturers must provide clear instructions. These instructions must describe how energy can be safely isolated and which steps are required to perform work safely.
– Energy sources must be capable of complete and reliable isolation
– Energy isolation points must, where necessary, be suitable for locking
– Unexpected or automatic restart must be prevented
– Risk assessment is mandatory and includes maintenance situations
– User instructions must describe safe energy isolation
The Machinery Directive 2006/42/EC has formed the basis for machine safety in Europe for many years, but it will be replaced by a new legal framework. On 14 June 2023, the Machinery Regulation (EU) 2023/1230 was published, which will replace the directive as of 20 January 2027.
Unlike the current directive, this regulation is directly applicable in all Member States without the need for national transposition. This ensures a more uniform application of machine safety requirements within the European internal market.
The transition period is 42 months and runs until 19 January 2027. During this period, the Machinery Directive 2006/42/EC remains in force. From 20 January 2027, new machinery and partly completed machinery must comply with the new regulation, including the associated conformity assessment and CE marking.
The new Machinery Regulation has been developed to better align with technological developments. In particular, emerging risks related to digitalization, such as artificial intelligence, advanced robotics, and connected systems (IoT), are addressed more explicitly. The aim is to future-proof machine safety while ensuring consistent compliance within the EU.
For manufacturers, this means they must prepare in a timely manner for additional requirements, particularly in the areas of software, digital documentation, and risk assessment of autonomous functions.
While the Machinery Directive provides the legal basis, ISO 14118:2018 offers a technical elaboration on the prevention of unexpected start-up. This international standard, harmonized in Europe as EN ISO 14118:2018, provides concrete guidance for both designers and users.
The standard focuses on situations where persons are present in the hazard zone of a machine, for example during maintenance or troubleshooting. In such situations, the release of energy or movement of machine parts can lead to serious accidents. ISO 14118 defines unexpected start-up as the unintended activation or movement of a machine, for example due to energy restoration, external influences, or faults.
A core principle within the standard is the complete identification of all energy sources. This extends beyond electrical energy and includes mechanical, hydraulic, pneumatic, and thermal energy. In practice, this means that designers and safety professionals must have a comprehensive understanding of all possible forms of energy present in a machine, including stored or residual energy.
The standard then requires that this energy can be effectively isolated and that residual energy is dissipated or, if dissipation is not possible, safely controlled. This may include, for example, relieving hydraulic pressure, mechanically blocking moving parts, or discharging capacitors. Energy isolation therefore also includes the control of stored energy.
ISO 14118 further emphasizes that technical measures must be combined with organizational measures. Technical solutions may include lockable switches, mechanical blocking devices, or interlocks. Organizational measures include procedures, work permits, and personnel training. Within this context, Lockout-Tagout is regarded as an integrated approach in which both types of measures are combined.
An important aspect of the standard is the emphasis on competence. Workers must not only know how to isolate energy but also understand the risks present and how these risks may manifest. This requires targeted training and clear communication within the organization.
In contrast to the European approach, where the control of hazardous energy derives from functional safety requirements such as energy isolation and prevention of unexpected start-up, Lockout-Tagout is explicitly regulated by law in the United States. The Occupational Safety and Health Administration (OSHA) has established standard 29 CFR 1910.147, titled “The control of hazardous energy”.
This regulation specifically addresses activities such as maintenance and servicing, where employees are exposed to hazardous energy. OSHA requires employers to implement a formal energy control program in which procedures for isolation, locking, and verification are clearly defined.
A key characteristic of OSHA regulation is the distinction between lockout and tagout. Lockout refers to the physical locking of an energy isolation point, for example with a padlock. Tagout uses labels or warnings without physical restraint. OSHA states that lockout is preferred, as it provides a higher level of safety. Tagout is only permitted where lockout is technically not feasible, and provided that additional measures are taken to achieve an equivalent level of safety.
A critical element of the OSHA process is the verification of energy isolation. Before work begins, it must be confirmed that all energy has actually been isolated. This can be done, for example, by testing whether a machine can still be started.
In addition, OSHA requires employers to periodically evaluate their procedures. At least once per year, it must be verified whether the energy control program remains effective and is being correctly applied.
Training also plays a central role within OSHA. Only authorized employees may perform LOTO procedures, and they must be specifically trained for this purpose. Other employees must also be aware of the risks and the meaning of locks and tags.
– Mandatory energy control program with documented procedures
– Use of lockout (physical locking) as the preferred measure
– Verification of energy isolation before starting work
– Periodic evaluation of procedures
– Training and authorization of personnel
Although the Machinery Directive, ISO 14118, and OSHA regulations originate from different systems, they complement each other in substance. The Machinery Directive emphasizes safe design and compliance with essential requirements before a machine is placed on the market. ISO 14118 provides technical depth and concrete guidance for preventing unexpected start-up. OSHA focuses strongly on the operational aspect and sets explicit requirements for procedures and organization.
This combination makes it clear that effective control of hazardous energy cannot be achieved through a single type of measure. A safe machine begins with design but also requires appropriate technical provisions and well-defined procedures during the operational phase.
For machine manufacturers, this means that energy isolation must be integrated into the design from the outset. For users and employers, it means that these provisions must be correctly applied and supported by clear procedures and training.
Lockout-Tagout is not a standalone obligation, but a logical consequence of broader requirements within machine safety. Within the European context, LOTO derives from the Machinery Directive 2006/42/EC and is technically elaborated in standards such as ISO 14118. In the United States, LOTO is explicitly regulated through OSHA.
The core of all frameworks is the same: preventing the release of hazardous energy at times when people are working on machines. This requires an integrated approach in which design, technology, and organization converge.
By consistently applying these principles, organizations can not only comply with legislation and standards, but also significantly reduce the risk of serious accidents. LOTO therefore represents a critical element in achieving a safe working environment in industrial practice.
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