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Emergency-Stop Systems

An efficient Emergency-Stop device is much more than a well-visible red button on a yellow background switching off the power supply to the machine.

It is the target to prevent any damage to persons, machine and material in case of emergency. This task is quite challenging due to two factors:

  • Due to increasing requirements towards products, also the production plants become more and more complex from the technological point of view, thus an increasing number of interacting features must be considered.
  • A large number of national and European standards, laws and directives define safety rules. In addition, they are continuously updated.

We would like to present to you important criteria applicable to Emergency-Stop solutions. Let us start with the most obvious requirement: the ease of use:

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Jürgen Kalb, Team Leader Machine Safety / Electrical Engineering
Jürgen Kalb
Team Leader Machine Safety / Electrical Engineering
+49 (661) 103-810
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Stop is not the same as stop:
Stop categories according to EN 60 204-1

Under normal circumstances, safety switchgear is used together with Emergency-Stop switches preventing the automatic restart of machines after unlocking. Emergency-Stop Systems are divided up into stop categories depending on the technical conditions:

  • Immediate stop through immediate switching-off of the energy supply.
  • Electromechanical components are switched off.
  • Electronic devices are allowed.

This is only possible, if the sudden switching-off of energy will not result in new hazards.

  • The energy supply will continue, until the drive has been decelerated electrically to a standstill.
  • Electromechanical and electronic devices are allowed.

This option makes sense, if brakes and similar components need energy.

  • Controlled shutdown of the machine into a safe condition
  • The energy supply is maintained during a standstill of the machine.

Example for application: When using a crane with a lifting magnet, the switching-off of the power supply would result in a falling down of the load.

FAK foot and palm switch
An Emergency-Stop System must be clearly arranged and clear, so that it can be reliably operated even in case of panic This requirement is met, for example, by the FAK foot and palm switch shown above.

Redundant safeguarding, because your staff members only have one life

The higher the level of hazards, the higher the requirements with respect to the failure safety of the switching-off device. First of all, a risk analysis of a production plant will be carried out; the following factors are considered:

  • seriousness of injury
  • frequency and/or length of stay
  • possibilities to avoid hazards

This factors are linked as follows:

Risk analysis according to ISO 13849
Risk analysis according to ISO 13849

Risk analysis according to ISO 13849 (substitutes EN 954-1)

A PL-value of "a" thus requires a low contribution to a risk reduction, a PL-value of "e" will require a high contribution.

The risk will be reduced through the following measures:

  • design measures
  • protective devices
  • user information

The risk analysis is part of a comprehensive risk assessment.

ISO 13849-1 does not only govern the safety of electrically operated plants, but also applies to hydraulic, pneumatic and other areas.

Safety through redundancy at the Performance Level PL "d" means, for example:

  • In case of a single error, the switching-off function will be maintained.
  • This error will become visible, for example, because the plant cannot be started up again afterwards.
  • The components available twice will be individually monitored.

This has only been a short summary of the criteria to be taken into account when planning a suitable Emergency-Stop System.

We would be pleased to advise you how to prevent or reduce a hazard in emergency situations in a best possible manner.

Jürgen Kalb,
Team Leader Machine Safety / Electrical Engineering
Jürgen Kalb
Team Leader Machine Safety / Electrical Engineering

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