Question:
A machine consists of several individual machines and each of these machines is fitted with a separate controller. There is also a higher level controller/control centre. When the emergency stop is operated, does the emergency stop command have to be reset on each individual machine or can the active emergency stop command be reset for the individual machines from the higher level control centre, in order to restart the plant?
Answer:
In accordance with DIN EN ISO 13850, the emergency stop may only be reset directly on the emergency stop device on which the command was initiated and by intentional human action.
Emergency stop pushbuttons may only be reset once the hazard that led to the initiation of the emergency stop function has been safely removed. If it is impossible to check this fully from the position of the emergency stop device, because the operating range of the emergency stop is not fully visible for example, then additional reset devices can be provided, such as a start button for example. This must be examined and assessed in the machine’s risk assessment. It's important to note that stopping in an emergency (emergency stop) is a complementary protective measure and not a primary means of risk reduction.
Also: resetting the operated emergency stop device must not automatically restart the machine, but only prepare for the machine to restart. It must be possible to start machinery only by voluntary actuation of a control device provided for the purpose. [Machinery Directive, 2006/42/EC, Annex I - 1.2.3]