Download document () of 20
Send email
Download
You have exceeded the download limit
All machinery and equipment must be equipped with at least one emergency stop button or switch that can be accessed quickly. Emergency stop devices are used to immediately stop any dangerous movements or processes without creating further hazards, thereby making them one of the most important safety components of machinery and equipment.
Get our functional safety manual
In the technical code, a distinction is made between two safety concepts: the emergency stop and the emergency switching off. Both terms are often used interchangeably but this is incorrect as they provide different functions and different degrees of safety.
EN 60204 (entitled "Safety of machinery - Electrical equipment of machines") defines both terms as follows:
Emergency switching off (switching off in the event of an emergency)
An action intended to cut off the electrical power supply to an entire installation, or part of an installation, in the event of an emergency, where there is a risk of electric shock or another risk of electrical origin.
Therefore, an emergency switching off or power-off is understood as the switching off of the electrical power supply.
Emergency stop (stopping in the event of an emergency)
An action intended to stop a dangerous process or movement in the event of an emergency.
Therefore, an emergency stop is understood as the deliberate stopping of a movement.
Stop function (stopping during normal operation)
There is also the stop function but this is not a function that is triggered by an emergency stop device. Rather, a stop function is used to stop the drive during normal operation.
The machinery directive states that all machines must be fitted with one or more emergency stop switches or emergency stop buttons, which can be used to prevent actual or impending danger. But the term "emergency switching off" is not mentioned in the current machinery directive. In machinery directive 2006/42/EC, the terms emergency stop and emergency stop device are used throughout.
Details of the different "emergency stop functions" can be found in the EN ISO 12100, EN 60204-1 and EN ISO 13850 standards which have been harmonised in accordance with the machinery directive (2006/42/EC). EN 60204 defines three Stop categories as follows:
To determine the correct Stop category for an emergency stop, a risk assessment of the machine must be carried out. A risk assessment is also used to determine whether an emergency stop is required.
Get every important blog post or new information Eaton publishes for machine and system builders.
ISO 13850 defines the main principles of emergency stop devices and relevant functional aspects. In this case, the control command for the emergency stop is always triggered manually by an individual, specific action.
Emergency stop devices must ensure positive-opening operation. Various devices are available for this purpose, which shut down the respective hazards via a safety switchgear:
The operating elements of the devices must be coloured red, and if there is a background around the operating element, it must be coloured yellow. This colour scheme also applies to a supply disconnecting device (main switch) if it is to be used for stopping in the event of an emergency.
If a particular hazard related to the emergency stop button itself is detected during the risk analysis, e.g. the risk of moving parts in the environment hitting, colliding with or cutting the operating element, additional measures for detecting faults are essential. One solution is to use devices with contact monitoring through SMC (self-monitoring contact): In this case, if a contact element block or the cover of a surface-mounted housing is detached, the normally closed contact is opened in sequence with the normally open contact, thereby triggering the safety feature.
In line with the machinery directive, machines and equipment must be fitted with an emergency stop device to prevent or reduce hazards in the event of an emergency. There are various devices which can be used to implement this required emergency switching off or emergency stop function. The devices should be easily accessible, and they should be available at all operating stations and other places where an emergency stop may be required.
Contact our team or sign up to ask questions and stay up-to-date on news, product updates and industry trends.
Sign up for our newsletter for machine and panel builders. Stay connected for information about changing regulations and new technologies and services to facilitate your day-to-day working and help you grow your business faster.
