Emergency Stop vs. Emergency Shutdown
ELECTRICAL & ELECTRONICS SAFETY SYSTEMS EXPLAINED
KRAUS & NAIMER
Emergency Stop vs. Emergency Shutdown
Key Differences, Standards, and Applications
In industrial safety engineering, emergency stop and emergency shutdown are essential safety functions. Although often used interchangeably, they perform different technical roles and address different types of hazards. Understanding this distinction is vital for compliant machine design, effective risk assessment, and safe operation.
Emergency Stop
An emergency stop is designed to halt hazardous machine movements or processes as quickly as possible to prevent or reduce imminent danger.
• The machine is brought to a safe, controlled stop
• The power supply remains on initially and maybe interrupted only after standstill
• Sudden loss of power is avoided to prevent secondary hazards
Emergency stops are primarily used to protect against mechanical hazards, such as rotating, moving, or crushing components.
Emergency Shutdown
An emergency shutdown is intended to eliminate electrical hazards by immediately disconnecting the power supply to a machine or system.
• Power is cut instantly
• The machine comes to an uncontrolled standstill
• This function is used when electrical risks represent the primary hazard
Emergency shutdown switch. Isolator in painted steel enclosure. IP66, 3-12 Pole, with or without aux.
Unlike emergency stops, emergency shutdowns prioritize immediate hazard elimination over controlled deceleration.
Legal Requirements and Standards( EU)
The Machinery Directive 2006 / 42 / EC requires machines to be equipped with at least one emergency stop device to protect against existing or imminent hazards.
Exceptions apply to:
• Hand held or hand guided machines
• Machines where an emergency stop would not reduce risk or could introduce additional hazards
Relevant standards, including DIN EN ISO 13850, specify that emergency operating devices must be clearly identifiable, unambiguous in function, and easily distinguishable from their surroundings.
Colour Coding and Identification
Standards emphasize rapid recognition of emergency operating devices.
• Red is specified for the actuating element
• Yellow is used as a contrasting background
This colour combination ensures reliable visibility, even in stressful situations or reduced visibility.
Typical Applications Emergency Stop – Controlled Motion Stop Emergency stops are used when dangerous movements must be halted without immediate power disconnection.
Example: Lathe in a workshop Tool jams during operation. The operator presses the emergency stop button. The spindle decelerates to a stop while power remains on, reducing mechanical risk.
Emergency Shutdown – Immediate Hazard Elimination Emergency shutdowns are applied when electrical hazards require instant power removal.
Example: Industrial robot cell An unauthorized person enters the danger zone. Activating the emergency shutdown immediately disconnects power, halting motion and also eliminating electrical risk.
Selecting the Correct Safety Function
The choice between emergency stop and emergency shutdown must be based on a thorough risk assessment, considering the nature of the hazard, the consequences of power loss, and applicable standards. Correct alignment of safety function and risk is essential for both operator protection and regulatory compliance.
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52 PECM Issue 80