EN ISO 14119:2025 supersedes EN ISO 14119:2013 and establishes design and selection principles for interlocking devices associated with machine guards, independent of the energy source [S2][S4].
The scope covers position-monitoring devices with or without guard locking, and EN ISO 14119:2025 adds provisions for coded devices [S2][S4].
What ISO 14119 controls at the machine
ISO 14119 addresses interlocking devices associated with guards and seeks to minimize defeat in a reasonably foreseeable manner [S1]. The 2025 European edition retains the core subject, “Safety of machinery, Interlocking devices associated with guards, Principles for design and selection,” while extending the device classification to coded devices [S2][S4].
An interlocking device is not synonymous with a guard-locking mechanism. A conventional interlocking device monitors whether the guard is open or closed, while a device with guard locking also physically retains the guard in a safe position [S3]. Position monitoring can be performed by electromechanical safety switches or non-contact safety sensors [S3].
EN ISO 14119:2025 is classified under ICS 13.110 for machine safety and is intended for use by machinery designers, plant engineers, safety integrators, and maintenance teams [S4]. It does not remove the need for risk assessment, inherent safety, or an appropriately designed safety circuit; those remain separate design steps in the selection workflow [S3].
Choose the interlock from the guard and hazard
A defensible selection starts with the machine’s hazardous energy, the guard’s movement, the required safety function, and the foreseeable method of defeating the device [S3]. The product type follows those decisions rather than the number of guard positions or a generic preference for coded hardware [S2][S7].
Guard locking is a different selection decision from position detection. A position switch identifies whether the guard is closed, whereas guard locking prevents opening until the hazardous conditions have been controlled [S3][S7]. Guard-locking devices therefore require a defined release condition tied to the machine’s safety function, not merely a suitable switch bore and actuator geometry [S3][S6].
Compare coding, locking, and defeat resistance
The main options can be compared by the hazard they address, the degree of bypass resistance, and the control function they support. Coding raises difficulty against substitution, while guard locking addresses unintended guard opening; neither replaces the risk assessment or the safety circuit [S3][S5].
The comparison is intentional: coding and locking solve different failure mechanisms. ISO 14119 covers defeat-minimizing measures, while its integration into the control system remains part of the safety-function design [S1][S6].
Design defeat controls around incentives and misuse
Guard and protection devices should not be easy to bypass or render non-operational [S5]. ISO 14119 therefore calls for reasonable foresight: the design must address tampering, substitution, bypass, and misuse rather than assume that every operator will leave the interlock untouched [S1][S3].
The selection workflow in the Schmersal guide places risk assessment first, followed by inherent safety, technical protective measures, determination of the safety function, safety-circuit design, guard design, locking-principle selection, defeat-incentive rating, and product selection [S3]. This sequence matters because a coded actuator does not repair an incorrectly defined safety function or a weak safety circuit [S3][S6].
Controls can be evaluated at several layers: the location and mounting of the actuator, the device’s coding, the physical access required to tamper, the plausibility of defeating the circuit, and the control-system response to an open guard [S1][S3]. The applicable machine risk assessment determines whether these controls are sufficient and whether guard locking is necessary [S1][S7].
Apply the 2025 edition without losing machine-specific risk work
EN ISO 14119:2025 was published in March 2025 and supersedes EN ISO 14119:2013 [S4].
For new specifications, the document reference should identify EN ISO 14119:2025 and the applicable national adoption, while technical documentation should record the selected device type, coding arrangement, locking principle, mounting, and defeat-control rationale [S2][S3]. The ISO catalogue still identifies ISO 14119:2013 as the published ISO edition, while the 2025 European standard identifies ISO 14119:2024 in its title text [S1][S4].
That relationship does not make the interlock a complete risk assessment, nor does it establish that one device type suits every machine category [S3][S4].
Track the selection evidence at handover
The handover file should contain the risk assessment, guard drawing, actuator and switch part identification, coded or uncoded status, guard-locking release logic, safety-circuit diagram, and the rationale for defeat prevention [S1][S3]. For a coded system, the parts list must preserve the matched coding combination; an interchangeable-looking actuator should not be presented as functionally equivalent [S5].
Two signals deserve engineering review: guard openings that remain unexplained or repeated bypass attempts, and a safety-circuit change that removes the monitoring function or bypasses the release condition [S1][S6]. These are traceable design and operational signals, not substitutes for the machine-specific risk assessment.