Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Protective devices and interlocks

Guard locking

Also known as: guard locking device

German: Zuhaltung

In machine safety, guard locking is a function that keeps a guard closed until hazardous conditions have ended or release is permitted. It is typically realized by a guard locking device combined with an interlocking device.

  • Machine safety
  • EU

In one sentence

Guard locking keeps a guard shut until hazardous motion or conditions have ended, and must be released only by a reliable signal such as standstill.

Example

On a lathe, the solenoid guard locking device on the chuck guard keeps the door closed until standstill monitoring confirms the spindle has stopped.

How it applies

  • Machine safety: Guard locking is needed when hazards persist after a stop command, such as run-down, hot surfaces or pressurized media, or when an unexpected opening would interrupt a process in an unsafe way. Compare stopping time with access time.
  • Design: ISO 14119 distinguishes locking principles, for example spring-applied and power-applied locking. Spring-applied locking stays locked on power loss and is generally preferred for personnel protection.
  • Functional safety: Both the locking and the release conditions are safety functions. The monitoring of the locked state must meet the required Performance Level or SIL.
  • Technical documentation: Describe release conditions, how to release the guard after power failure or for rescue, and the test of the locking function.

Guard locking vs. interlocking guard with guard locking

Guard locking is the function or device. The interlocking guard with guard locking is the complete guard arrangement that uses it.

By knowledge.aitechdoc.world · Published September 25, 2026 · Last reviewed

Source: ISO 14119, Safety of machinery — Interlocking devices associated with guards — Principles for design and selection

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Blog and are not part of any standard.

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