Revised standard ISO 14119 reduces risk of tampering with safety switches
Standard ISO 14119 focuses on the principles for designing and selecting interlocking mechanisms in machine guards. In short, this standard describes how safety switches should be applied to protective guards. An updated version has been available since October, in which not only the technological aspects have been sharpened, but also the role of human behaviour is taken into account more emphatically.
Human behaviour as a determining factor
What makes this revision special is the combination of technical regulations with insights about human behaviour. Where machines operate predictably, operators may sometimes try to circumvent safety measures. The challenge lies in designing systems that do not frustrate users unnecessarily, reducing the motivation to manipulate safeguards. Consider, for example, minimising waiting times when opening a protective door. Efficient unlocking contributes to both usability and security. Moreover, it is recommended that actuators be permanently fixed so that they cannot be easily removed or modified.
Choosing the right safety switch
ISO 14119 addresses the interlocking systems essential for machine safety and is applicable to all manufactured machinery. It is crucial that the interlock chosen matches the specific application. For example, a robust machine guard requires stronger components than a simple plastic switch. The materials must be able to withstand influences such as dust and high temperatures. Besides the right choice of components, correct installation and application are just as important. The interlock must work reliably mechanically and be controlled correctly electrically, depending on the risk level.
Obligation to check safety components
Like the Machinery Directive, ISO 14119 is based on risk assessment. This involves analysing potential hazards and the frequency of protected accesses. Based on this data, an appropriate interlocking system is selected that meets the required Performance Level. Performance testing remains a crucial part of this, and in the revised version, test procedures have been further refined. This checks whether doors still meet requirements and whether the correct signals are recorded. Components with Performance Level d or lower are subject to an annual verification requirement, while PLe-level measures must be verified monthly. As manual checks can be time-consuming, the standard introduces plausibility checks. This allows verification of compliance with time tolerances via the control system. In case of deviations, a notification appears on the HMI to alert maintenance personnel.
Industry Leading Practice
The revision of ISO 14119, released in October 2024, responds to the latest technological developments. Specifications for the four main types of safety sensors and switches have been updated to better reflect the current state of the art.
Here, the coded access key remains locked in the key switch that switches the safety circuit until the system is safely disconnected. Although this process takes longer than conventional electromechanical safety switches, it offers the advantage that no wiring is required and safety is increased without major modifications to the control system.
Safety Key A1
Safety Key B1
Isolation key A
Isolation key B
In addition, the standard introduces a method for calculating error masking when connecting multiple safety switches in series. This new calculation allows accurate determination of how many switches can be connected in series and the impact on the Performance Level.This enables users to make more informed choices when configuring their safety systems.
