Guard Locking

Supplementary Release of Guard Locking

A risk assessment may require one or more methods of overriding the locking mechanism. Using one of these methods could result in a considerably longer stopping time than normal and this should be considered in the risk assessment.

Escape Release – a means of deliberately unlocking the guard locking from the inside of the safeguarded space if someone becomes trapped inside. It is only accessible from inside the safeguarded space and initiates and maintains a stop command.
Emergency Release – a means of deliberately unlocking the guard locking from outside the safeguarded space without auxiliary means (e.g. for rescue of persons or in the event of a fire). It must be well labelled for emergency use only and have a reset procedure that deters regular use.
Auxiliary Release – a means of deliberately unlocking the guard locking from outside the safeguarded space that is possible only with a special tool. It must be used in exceptional circumstances only, for example in a power outage if the guard locking is power to unlock.

Power to the Locking Mechanism

Power-to-Lock – the locking mechanism will release in a power failure; this could result in a hazardous situation if the run-down time exceeds the access time. Therefore, this solution is not recommended for situations protecting people.
Power-to-Unlock – the locking mechanism will not release in a power failure, so it is the preferred solution for situations protecting people. However, an auxiliary release should be considered if access may be required when there is no power to the control system e.g. for commissioning.

Additional Functionality

Proactive Inhibit Functions – the ability to release safety keys or use interlock blocking to protect personnel in whole body access situations
Control Functionality – e.g. buttons and lamps or connections to stack lights or hold-to-run devices
Access Control – limit who is able to carry out certain functions and log events to maximise productivity