Kill switch

The emergency stop switch, also called emergency stop, is a switch to machines, vehicles and equipment or to rides such as roller coasters. It is used to quickly put these in case of danger or to avert a danger to a safe state. Depending on the application field, various strategies are pursued, in the simplest case, the release follows a power interruption.

Construction

Emergency stop switches have a red actuator on machines on a yellow background. The most common type are mushroom button, with large systems such as conveyors and pull cord switches ( Zugleinenschalter ) are common. In some cases, safety light barriers accomplish this task. For smaller machines also the main switch is used as an emergency stop switch. For hand machine emergency stop switch is not required, here can be drawn in an emergency the plug.

Function

The emergency stop switch must be locked after operation and, depending on the security level to be achieved, with a key, be restored by turning the emergency stop switch or the pull back to its original position. It must be designed so that the machine or system operator can operate it immediately in an emergency. For maintenance of the main switch of the machine must be switched off and secured against being switched on again.

Usually, along with emergency stop switches emergency stop relays are used which fulfill the necessary requirements of reliability, such as the machine may start by itself not again after unlocking. Emergency stop circuits, depending on the technical conditions in stop categories divided (EN ISO 13850:2008 clause 4.1.4 and EN 60204-1:2006 clause 9.2.2 ):

• Stop Category 0: energy supply to the drive elements is immediately disconnected (only possible if the sudden removal of power causes no hazard )
• Stop Category 1: controlled stop: Machine is placed in a safe state, then only the energy is finally isolated from the drive elements. This is useful if clamps, brakes need or similar energy.
• Stop Category 2: Machine is placed in a safe state, the energy but not separated. This category should only be used if technically there is no way to safely disconnect the power. For example, switching off the voltage at the magnet would with a crane with lifting magnet lead to crashing of the load ( only EN 60204-1:2006 clause 9.2.2 ).

Safety aspects

With regard to the hazards safety considerations and the possible impact the failure of a safety device must be carried out as the emergency stop circuit. The project uses such as the EN ISO 13849 or security levels according to DIN EN 61508 or the international standard IEC 61508. Here risk graph to quantify the hazards are created. This results in five safety categories. The higher the risks, the higher the demands on the reliability of the switch-off device.

Basically, the quiescent current principle is applied; ie in case of auxiliary energy, the safe state is achieved. Technical specifications are contained in DIN EN 13850 ( successor standard of DIN EN 418). In this case, there is no hard requirement for a caption.

In emergency is required to switch the system to protect the power supply against electric shock. Safety standards mention the emergency stop. For emergency stop, it is not required that the entire machine is de-energized. A drive must, upon detection of a hazardous situation by the operator can be stopped to protect against risks. For controlled deceleration of drive voltage is required. In most cases, such as a programmable logic controller ( PLC) or PC - connected equipment is not switched off. Also, brakes, cooling systems, exhaust systems and similar safety equipment are usually not turned off, if run out of them, no hazards.

Working on a system includes several components, each with an emergency stop together, each of these buttons must enclose the entire system out of service. For example, must be a laser processing machine from both the prescribed emergency switch off the laser as well as from that of the machine.

DIN VDE Standards relating to emergency stop devices

The following DIN standards are among the most important for electrical safety and explain the term emergency stop:

Other standards:

This standard replaced DIN VDE 0100-460 (VDE 0100 Part 460 ) :1994 -02. The term "Emergency Power Off" including "Emergency Stop " was changed to " actions in an emergency". In an informative annex ZA explains what is meant by "acting in an emergency".

In Europe, a concept is advised to standardize the use of terms that are associated with " emergencies ". These are summarized in the Appendix and is intended to facilitate user understanding of the concepts. There are the following four terms: Emergency stop (previously emergency stop), Starting in an emergency, off in an emergency (formerly Emergency stop ) and power on in case of emergency.

The DIN EN 418 ( Safety of machinery, emergency stop equipment, functional aspects, design principles) is defined by the DIN EN ISO 13850 ( Safety of machinery - Principles for design - emergency stop) have been replaced. Note the correction of the term emergency stop in emergency stop ( mistranslation of the English word emergency stop has been corrected ).

Criticism of terms

In general, the German language, the two functions of emergency stop and emergency stop are often subsumed under the term emergency stop what - has often led to confusion - even among experts.

At this circumstance, some translations are to blame who translated the English term emergency stop falsely with emergency stop. This is especially true for the EN418 ( Safety of machinery; EMERGENCY OFF equipment, functional aspects, design principles; German version EN 418:1992 ) and partly also for the old EC Machinery Directive 98/37/EC. In the new version of the Machinery Directive (2006/42/EC, 2009/127/EC and ) the term emergency stop was also replaced by emergency stop.

In the German version of EN 418:1992 has been translated from English with emergency erroneously the term emergency stop. The successor standard ISO 13850 has corrected this and speaks only of the term emergency stop. Emergency stop is the German translation of emergency switching off

Emergency stop switch for vehicles

For vehicles such as racing cars or commercial vehicles, the emergency stop switch ( battery switch ) interrupts depending on the requirement, the ignition and possibly also the fuel supply. In some cases, the vehicle is completely de-energized ( short-circuit and fire hazard in case of accident ). Modern cars are equipped with an automatic separation which is activated simultaneously with the triggering of the airbag and the main circuit separates from the battery. Other electrical systems such as hazard warning lights, car phone, among other things remain on a separate circuit for safety reasons still functional. With motorcycles, an emergency switch is usually mounted on the right-hand stalk switch. Modern motorcycles are additionally equipped with an automatic emergency stop switch ( Vehicle-down ), which is at an angle that suggests a fall triggered.