Annex E

Last edit: 28/06/2023

Explanation of emergency operation functions

We all have in mind the Emergency Stop pushbutton or rope: nearly all machinery have at least one! As soon as that button is pushed, the machine stops or goes to a safe state. However, there are situations whereby a safe state can be reached only by activating a movement.

Moreover, there are two types of Emergency operations:

  1. The first related only to Electrical Hazards
  2. The second related to all other Hazards.

In order to eliminate an “electrical hazard”, components suitable for both interruption and isolation are needed: possible components are Disconnectors, circuit breakers or a plug/socket combinations.  

In order to eliminate a “mechanical hazard” components suitable for energy interruption are enough. A typical component is the Contactor, or a Magnetic or Solid state Motor Controller (in north American language).

That means, there are four types of emergency operation functions:

  • Emergency stop: an emergency operation intended to stop a process or a movement that has become hazardous.
  • Emergency start: an emergency operation intended to start a process or a movement to remove or to avoid a hazardous situation.
  • Emergency switching off: an emergency operation intended to switch off the supply of electrical energy to all or a part of an installation, where a risk of electric shock or another risk of electrical origin is involved.
  • Emergency switching on: an emergency operation intended to switch on the supply of electrical energy to a part of an installation that is intended to be used for emergency situations.