Emergency Stop & Emergency switch off

Emergency Stop”, “Emergency switch off” they both sound similar and sometimes lead to misunderstanding of the performed function. Nevertheless, they are one of the most important safety elements of machines and systems.

The operation performed after pressing the “Emergency stop” is “an emergency operation intended to stop a process, system, machine or a movement that has become hazardous.

And pressing the “Emergency switch off” triggers an operation of switching off the supply of electrical energy and aims to reduce risk of an electric shock or other hazard.

There are various solutions for the technical implementation of EMERGENCY STOP/SWITCH OFF command devices:

• E-Stop Mushroom Pushbutton: round, usually in red signal color on a yellow background, with or without lettering, also lockable.
• Rotary switch: also, mostly in red on yellow
• Emergency Stop Pull-Cords: operated by a pull cord, typically for conveyor belts or other more spacious systems, pull cord is in red color.
• Light barrier system: optoelectronic protective device with safety light barrier and sensors / evaluation device, typically as access control, e.g. for woodworking machines or high-bay warehouses

Switching off according to the norm EN 60204-1

In the area of standardization, the control functions “stop”, “emergency stop” and “emergency switch off” are also defined with regard to their specific requirements within EN 60204-1. Three basic categories are defined for stopping a machine drive in normal operation:

• Stop category 0: Uncontrolled shutdown of the machine through immediate interruption of the energy supply to the actuators.
• Stop category 1: Controlled shutdown while maintaining the energy supply in order to switch off. Interruption of the energy supply only after the machine has come to a standstill.
• Stop category 2: Controlled shutdown of the machine while maintaining the energy supply to the drive elements.