What are the differences between emergency stop and emergency switching-off pushbuttons?
The Schneider offer includes two types of pushbutton.
a) Emergency switching-off with mechanical latching
These have direct opening action.
The speed of opening of the NC contacts, and therefore the generation of the OFF command, is dependent on the speed with which the button is pressed.
The OFF command can (under some circumstances) be generated before the latching mechanism has operated, that is a momentary OFF command can be generated without the mechanism latching.
The Schneider offer comprises two types of pushbutton
Emergency break with mechanical latching
These are SLOW BREAK pushbuttons.
The stop command (opening of N/C contacts) and mechanical locking (latching of the pushbutton) are dependent on the operating speed.
The stop command can be separate from the latching.
Emergency stop with snap action locking and mechanical latching
These are SNAP ACTION LOCKING pushbuttons.
The stop command and the locking are independent of the operating speed.
The mechanical stored energy system makes the stop command and the latching inseparable.
What is the position of the standards on these two types of pushbutton?
The standards specify two different reactions to two electrical risks connected with two areas in which electrical energy is used.
The emergency stop operation is the action to be used when a dangerous process or movement may endanger equipment or people.
The device to be installed is part of the machine. A risk assessment is necessary to take account of all the risk aspects: dynamic, electrical, etc.
The machinery directive, 98/37/EC, together with standards EN/IEC 60204-1 and EN/ISO 13850, specifies the actions and equipment to be used to achieve this result.
The machinery directive clearly specifies the exclusive use of snap action emergency stops with mechanical latching.
The emergency breaking operation is to be used to cut off the source of electrical energy to all or part of an installation when it may cause an electric shock or any other damage to equipment or people.
This is an exclusively electrical hazard such that those that may exist in the "Building" trade.
International, European and French standards IEC60364-5-53 and NFC 15-100 specify the actions and equipment to be used to achieve this result.
It permits the use of two breaking devices:
=> Emergency break with mechanical latching
=> Emergency stop with snap action locking and mechanical latching
Emergency stops with snap action locking and mechanical latching must be marked with the logo: triangle within a circle on their labels.
The "Emergency stop" and "emergency break" part numbers are listed as such in the Schneider Electric Harmony XB4 and XB5 Pushbutton Controls catalogues.
Only the "mushroom head" concept is available for Harmony 9001 30 diameter range, and there is therefore no emergency stop or emergency break in the sense of the standards for this technology. XB4 or XB5 22 diameter pushbutton controls must be used.
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