Interlocking Devices in Light of ISO 14119

In industry, machinery safety standards play a key role in protecting operators and maintenance personnel. EN ISO 14119, harmonized with the Machinery Directive 2006/42/EC, is an important part of this framework. This article explains how and when to use interlocking devices with guard locking, and why stopping time matters in a safety context.

Interlocking device: what is it?

An interlocking device is a mechanical or electromechanical device connected to a machine guard that prevents access to the machine’s hazardous area until safety conditions are met. Its primary purpose is to protect operators and maintenance personnel from unintended or dangerous contact with moving machine parts. Interlocking devices are designed to minimize the possibility of tampering and to ensure compliance with safety standards such as ISO 14119.

Interlocking devices play a key role in minimizing risks associated with the automation of production processes.

What is ISO 14119?

ISO 14119 defines requirements for interlocking devices associated with guards, intended to prevent access to hazardous areas of machines. Its purpose is to minimize the risks associated with access to such areas while the machine is operating.

• Purpose of the standard: To ensure that interlocking devices are designed and installed in a way that keeps machine users safe.
• Scope of the standard: The standard covers all interlocking devices associated with guards used on industrial machines.

Key aspects of ISO 14119

This standard defines key terms and requirements for the design and installation of interlocking devices. These include:

• Types of interlocking devices:
  • Type 1: Mechanical interlocking devices that do not require an external power supply to operate. Examples include mechanical locks.
  • Type 2: Electromechanical interlocking devices that operate using an external power supply. Examples include electromagnetic locks.
• Design requirements: Interlocking devices must be designed to minimize the possibility of tampering. They should be located in hard-to-reach places or protected against manipulation; guidance on interlocking devices with guard locking according to ISO 14119 is particularly relevant here.
• Installation: Interlocking devices must be installed in a way that ensures reliability and effectiveness. They should be inspected and maintained regularly.

Interlocking devices: selection and design

When selecting interlocking devices, the following should be taken into account:

• Type of machine and its hazardous areas: The selection of interlocking devices should be matched to the specific machine and the types of hazards that may occur. Hazard identification according to ISO 12100 and cooperation with a design office and engineering outsourcing can help in choosing the right solutions.
• Type of interlocking devices: Type 1 for simple applications where the risk of tampering is low, and Type 2 for more advanced systems where a higher level of safety is required.
• Minimizing tampering: Interlocking devices should be designed and installed so they cannot be easily bypassed. This may include special security screws or concealed mechanisms.

When should interlocking devices with guard locking be used, and when should they not?

Guard locking is necessary when:

• The machine has a long stopping time: When a machine cannot stop immediately after the guard is opened, guard locking ensures that the guard remains closed until the machine has come to a complete stop.
• Risk of entering the hazardous area: If there is a possibility that the operator could enter the hazardous area before the machine has fully stopped, guard locking is essential to prevent accidents.

Guard locking is not required when:

• The machine stops immediately: For machines that stop immediately when the guard is opened, guard locking is not necessary.
• No risk of entering the hazardous area: If there is no risk that the operator could enter the hazardous area before the machine has come to a complete stop, guard locking is not required.

Interlocking devices: Reaching a safe speed and stopping time

The importance of stopping time in a safety context lies in determining how long it takes for the machine to stop after the interlocking device has been actuated.

• Stopping time measurement: Determining the time from actuation of the interlocking device until the machine comes to a complete stop. This measurement is critical for risk assessment according to ISO 12100 and for selecting appropriate interlocking devices.
• Risk assessment: Taking possible fault scenarios into account and selecting the appropriate interlocking devices. Depending on the stopping time, different types of interlocking devices may be required.

ISO 14119 and the Machinery Directive

The ISO 14119 standard is harmonized with the Machinery Directive 2006/42/EC, which means that meeting its requirements is equivalent to ensuring compliance with the Directive.

• Compliance documentation: Companies must document compliance with the standard as part of the conformity assessment process under the Machinery Directive. Technical documentation should include all necessary information on the selection, installation, and maintenance of interlocking devices, as well as issues relevant to CE certification of machinery.
• Audit and inspection: Regular reviews and audits can help maintain compliance. A safety audit carried out as early as the design stage can minimize the risk of non-compliance; in broader regulatory terms, it is also worth following the Machinery Directive 2006/42/EC and the new Machinery Regulation.

Practical guidance for companies applying the standard

To apply ISO 14119 effectively, companies should:

• Assess risk: Carry out a risk assessment related to access to hazardous areas of machinery. Risk analysis according to EN ISO 12100 is essential for a proper assessment.
• Select appropriate devices: Interlocking devices should be selected in accordance with the requirements of the standard. The devices should be suited to the specific machinery and the type of hazards involved.
• Regular inspections: Carry out regular inspections and maintenance of interlocking devices. These inspections should be documented and performed in accordance with the manufacturer’s recommendations.
• Cooperation with a design office: A design office can help with decisions on the type of guards and locks that will work best in specific applications.
• Strength calculations (FEA): A design office can also perform strength calculations to ensure that guards and locks meet the requirements of the standard.
• Project management: Effective project management should include a safety audit carried out by an external company to minimize the risk of non-compliance with the Machinery Directive.
• Engineering outsourcing: It is worth using the support of experienced engineers to ensure that interlocking devices are properly designed and installed.

ISO 14119 plays a key role in ensuring machinery safety and the safety of technical equipment. Its application is essential for minimizing the risk of accidents and ensuring regulatory compliance. In the future, safety standards will continue to evolve in response to new technologies and industrial challenges. In many cases, this also includes adapting machines to minimum requirements where existing equipment must be brought into line with current safety expectations.

Production automation and interlocking devices

Production automation significantly improves the efficiency and throughput of industrial processes, but it also introduces new hazards associated with machine operation. A high degree of production process automation can create situations in which operators and technicians are exposed to moving machine parts. Interlocking devices play a key role in minimizing these risks. They ensure that access to hazardous areas is possible only when the machine has stopped and is in a safe state. In the context of production automation, it is particularly important that interlocking devices are integrated with machine control systems such as SCADA and PLC programming to ensure full compliance and operational safety. Using the services of an industrial automation integrator and carrying out safety audits already at the design stage can significantly reduce risk and ensure compliance with the requirements of standards and directives such as the Machinery Directive 2006/42/EC. This is especially relevant in demanding sectors such as the automotive industry.

Regular inspection and maintenance of interlocking devices are essential to ensure their reliability and compliance with standards.

Interlocking devices and ATEX standards

When interlocking devices are used in hazardous areas with an explosion risk, it is important that they also meet the requirements of ATEX standards. The ATEX Directive and the related ATEX harmonized standards apply to equipment and protective systems intended for use in potentially explosive atmospheres. Interlocking devices used in such areas must be properly certified and meet stringent requirements to prevent sparking and other ignition sources.

• Selection of interlocking devices: In ATEX zones, interlocking devices with the appropriate ATEX certification must be used.
• Installation requirements: Interlocking devices must be installed in a way that minimizes the risk of explosion, taking into account the specific requirements of hazardous areas with an explosion risk.
• Maintenance and inspections: Regular inspection and maintenance of interlocking devices in ATEX zones are crucial to ensuring their reliability and safety.

ISO 14119 is a cornerstone of machine safety, helping companies protect operators and technicians. Complying with its requirements and implementing interlocking devices in practice significantly increases the level of safety in industry.