Emergency Stop Function

A.  Understanding ISO 13850:2015 - Emergency Stop Function

The ISO 13850:2015 standard provides clear and detailed specifications for the design, operation, and functionality of emergency stop systems in machinery. Its primary purpose is to ensure the safety of operators and to mitigate risks associated with the malfunction or unexpected behavior of machinery in industrial environments. In modern industries, where complex machinery operates at high speeds or under significant pressure, the ability to quickly and efficiently stop machinery during a potential emergency can make the difference between life and death, as well as between equipment preservation and total loss.

1. Key Characteristics of the Emergency Stop Function

The emergency stop function, often abbreviated as E-stop, is designed to be an easily accessible and human-operated control mechanism that immediately halts machinery or industrial processes when engaged. It goes beyond simple machine stoppage; it interrupts the flow of energy to the machine's critical components, effectively ceasing all hazardous movements or operations. This function is crucial in preventing dangerous accidents, ensuring operator safety, and minimizing damage to equipment.

ISO 13850:2015 defines emergency stop mechanisms as a last resort safety measure that complements other protective systems like guards, interlocks, and sensors. While these systems work to prevent hazardous situations, the emergency stop function is meant to act when all other protections fail, giving operators the power to immediately remove all risk.

2. Scope and Applicability of ISO 13850:2015

ISO 13850:2015 applies to all types of machinery and equipment across various industries, including but not limited to:

• Manufacturing and assembly lines.

• Construction machinery.

• Automated production systems.

• Chemical processing plants.

• Heavy machinery used in mining and material handling.

The standard’s requirements are essential for design engineers, safety professionals, and machinery manufacturers who are responsible for implementing reliable safety measures. The standard doesn’t only provide technical specifications but also offers guidance on how to achieve ergonomically friendly and functionally reliable emergency stop mechanisms.

3. The Legal and Safety Impact of ISO 13850:2015

In many regions around the world, compliance with ISO 13850:2015 is not just a recommendation it is often mandated by national safety authorities. The standard is included in the legal frameworks of countries that prioritize industrial safety and protect workers from machinery-related injuries. Failing to comply with this standard can result in severe consequences for manufacturers and facility operators, such as fines, legal liabilities, or even the shutting down of operations.

Moreover, the safety benefits of complying with the ISO 13850 standard are evident. Machinery equipped with an effective emergency stop mechanism can significantly reduce the number of accidents, thereby protecting human lives, lowering insurance costs, and reducing equipment downtime. For companies that handle high-risk operations, compliance with this standard is not just a legal obligation, but also a corporate responsibility to ensure the well-being of its workforce.

4. Design and Functional Principles of ISO 13850:2015

The design of emergency stop devices under ISO 13850:2015 requires careful consideration of both technical functionality and usability. Some of the design principles emphasized by the standard include:

• Immediate Action: The emergency stop function must work instantaneously. Once activated, it should bring the machinery to a complete halt as quickly as possible, preventing any ongoing hazardous activity from continuing. This immediate response is critical in mitigating the severity of an incident.

• Visibility and Accessibility: ISO 13850:2015 requires that emergency stop buttons or actuators be placed in positions that are easily accessible to the operator. The placement should be such that the operator does not have to move far from their normal operating position to activate it. The color coding (usually a red button with a yellow background) ensures that the emergency stop control is highly visible and distinguishable from other machine controls.

• Mechanical Latching: The standard mandates that emergency stop devices should incorporate a mechanical latching mechanism. This means that once the stop is initiated, it latches in the engaged position and requires a manual reset before the machine can be restarted. This feature prevents accidental or premature restart of the machine without a full inspection.

• Fail-Safe Operation: The system is designed to be fail-safe, meaning that it will continue to perform its stopping function even if there is a power loss or a system malfunction. In critical safety systems, it is essential that the emergency stop device still works independently of other controls, ensuring machinery halts regardless of other failures.

• Function Independent of the Control System: An important principle of ISO 13850:2015 is that the emergency stop function should be independent of the machine’s control logic or program. This means that regardless of the state of the machine’s control system, the emergency stop must function. In more complex systems, where programmable logic controllers (PLCs) are used, the emergency stop must bypass any software malfunction or failure.

• Resetting the System: Once activated, the emergency stop cannot be undone by simply pulling the button back. Instead, the system must be manually inspected, and a safe condition must be verified before the machine is allowed to restart. This ensures that potential hazards have been dealt with, and the machine is returned to a safe operational state.

5. Real-World Application of ISO 13850:2015

In industries such as automotive manufacturing, food processing, and heavy equipment production, ISO 13850:2015 is vital for maintaining operational safety. In these environments, machinery often operates at high speeds or under heavy loads, where any malfunction can lead to severe injuries or costly damage.

For example, in an automated assembly line, multiple robots and conveyor belts work in tandem, and an operator may need to quickly stop all machines in case of a fault. Here, an emergency stop button placed strategically at the operator’s workstation allows immediate halting of the entire system, preventing injury or machine damage. Compliance with ISO 13850:2015 ensures that such systems are reliable, ergonomically sound, and fail-safe.

In more dangerous fields like mining, where large drilling and crushing machines are used, any delay in halting operations during an emergency could result in catastrophic outcomes. Emergency stop buttons compliant with ISO 13850:2015 can be installed on machinery in areas where operators or maintenance personnel may be working, giving them the ability to immediately shut down heavy machinery in a critical situation.

6. Compatibility with Other Safety Standards

ISO 13850:2015 often works in conjunction with other safety standards, such as ISO 12100 (Safety of Machinery), which outlines the principles of risk assessment and risk reduction. Together, these standards create a comprehensive safety framework, ensuring that both risk prevention and emergency response measures are fully integrated into machinery design and operation.

Other relevant standards, such as ISO 62061 (Safety of Machinery – Functional Safety of Safety-Related Control Systems) and IEC 60204-1 (Safety of Electrical Equipment for Machines), complement ISO 13850:2015 by ensuring that machinery is designed to be intrinsically safe and that the electrical systems supporting the emergency stop functions are reliable.

7. ISO 13850:2015 and the Future of Industrial Safety

As industrial machinery continues to evolve, becoming more automated and powerful, the need for effective emergency stop mechanisms will become even more critical. ISO 13850:2015 provides the foundation for a safer work environment by establishing clear guidelines for emergency stop functions, ensuring that they are reliable, accessible, and efficient.

By adhering to this standard, manufacturers, engineers, and safety professionals can significantly reduce the risk of accidents, protect workers, and ensure the long-term reliability of their equipment. As technology advances, compliance with ISO 13850:2015 will remain a cornerstone of machinery safety, helping to maintain high standards in industrial safety and reducing risks for operators worldwide.

B. What is the Purpose of the Emergency Stop Function?

The emergency stop function is designed to provide operators with a quick and effective way to halt machinery during dangerous or potentially harmful situations. It is not a substitute for other protective measures but rather an additional layer of safety.

The main objectives of the emergency stop function include:

• Preventing injury or fatalities in cases where a machine malfunctions or behaves unexpectedly.

• Minimizing damage to machinery and equipment, which can result from continued operation during abnormal conditions.

• Reducing downtime and costs associated with repairs by stopping machinery before a catastrophic failure occurs.

• The ISO 13850:2015 standard ensures that emergency stop devices meet these objectives, providing the necessary specifications to guarantee they are effective in real-world applications.

The ISO 13850:2015 standard ensures that emergency stop devices meet these objectives, providing the necessary specifications to guarantee they are effective in real-world applications.

C. Key Requirements of ISO 13850:2015

ISO 13850:2015 outlines several crucial requirements that must be met to ensure the effectiveness and reliability of emergency stop devices. These requirements are split into categories that address design, functionality, and usability.

1. Device Accessibility

Emergency stop devices must be easily accessible to the operator, ensuring that they can be activated immediately when needed. The standard mandates that these devices be placed in strategic locations on the machinery, considering ergonomic factors and the machine’s operating environment.

2. Activation Simplicity

The standard emphasizes that the emergency stop mechanism should be simple to activate without requiring complex actions. Typically, the activation mechanism is a single-action button that immediately interrupts the machine's operation. The button should be large and clearly identifiable, often colored red, and surrounded by a yellow background to ensure visibility.

3.  Manual Resetting

Once the emergency stop has been triggered, the machinery should not resume normal operation until the emergency stop function has been manually reset. This requirement ensures that the machine does not inadvertently restart while still in a dangerous condition.

4. Fail-Safe Design

The ISO 13850:2015 standard mandates that emergency stop devices be designed to be fail-safe. In the event of a power failure or malfunction, the emergency stop device should default to the off position to prevent machinery from restarting unexpectedly.

5. Non-Reversible Action

Once the emergency stop has been engaged, it cannot be reversed by pulling or resetting the button until the underlying issue has been addressed. This irreversibility ensures that operators take deliberate action before restarting the machine.

6. Function Without Power

The emergency stop mechanism must be designed to function even if the machine loses electrical power. This is critical in situations where the power supply is cut, but the machine’s momentum or stored energy could still present a danger.

D. Importance of Compliance with ISO 13850:2015

1. Ensuring Worker Safety

Compliance with ISO 13850:2015 is essential to ensure the safety of workers who operate machinery. The standard establishes the minimum requirements to safeguard workers by ensuring that emergency stop devices are effective and reliable.

2. Reducing Risk of Machinery Damage

Adhering to the standard also helps to minimize the risk of machinery damage during emergencies. By ensuring that machinery can be quickly halted, the likelihood of catastrophic failures is reduced, thereby protecting both equipment and personnel.

3. Legal and Regulatory Compliance

Many regions and industries have incorporated ISO 13850:2015 into their safety regulations, making compliance with the standard a legal requirement. Failure to adhere to the standard can result in fines, penalties, or lawsuits, particularly if an accident occurs due to the lack of an effective emergency stop function.

E. Emergency Stop Function Engineering Design Considerations

1. Ergonomics and Human Factors

When designing an emergency stop system in compliance with ISO 13850:2015, it is important to consider human factors and ergonomics. The placement of emergency stop buttons should account for how operators interact with the machinery, ensuring that the devices are within reach in all scenarios. Additionally, the size, color, and shape of the button should facilitate quick recognition and use.

2. Formulas for Emergency Stop Mechanisms

The effectiveness of an emergency stop mechanism can be evaluated using various engineering formulas that take into account the kinetic energy, deceleration forces, and braking distances of the machinery. One essential formula is derived from Newton’s second law:

Where:

F = Force required to stop the machine.

m = Mass of the moving components.

a = Deceleration rate.

This formula helps engineers calculate the force needed to bring the machinery to a stop, which informs the design of the braking system and the emergency stop device.

3. Reaction Time and Stop Time

Another important factor in the design of emergency stop devices is the reaction time of the operator and the machine’s stop time. The total stop time is the sum of the reaction time (how quickly an operator can engage the emergency stop) and the machine stop time (how long it takes the machine to come to a full stop after activation). The following equation can be used to calculate the braking distance:

Where:

d = Braking distance.

v = Initial velocity.

a = Deceleration.

This equation helps engineers optimize the braking system and emergency stop function to ensure machinery stops within the shortest possible distance after activation.

F. Maintenance and Testing of Emergency Stop Devices

1. Routine Inspections

To ensure that emergency stop devices remain functional and reliable, regular maintenance and routine inspections are required. ISO 13850:2015 recommends periodic testing of the emergency stop function to verify that the device is in working order and free from damage or wear.

2. Functional Testing

Functional testing involves activating the emergency stop device and verifying that the machinery ceases operation immediately. After testing, the machine should require a manual reset before resuming normal operation. This test should be conducted in real-world conditions to simulate how the device will perform during an actual emergency.

3. Documentation and Record-Keeping

It is also important to maintain detailed records of all inspections and tests. This documentation serves as proof of compliance with ISO 13850:2015 and can be used during safety audits or in the event of an accident investigation.

G. Conclusion

The ISO 13850:2015 emergency stop function is a critical safety feature in the design and operation of industrial machinery. By ensuring that emergency stop devices are easily accessible, simple to use, and fail-safe, the standard helps to protect both workers and equipment from potential hazards. Proper implementation of the standard, combined with regular testing and engineering best practices, ensures that the emergency stop function remains an effective tool for risk mitigation in industrial settings.

Maintaining compliance with ISO 13850:2015 not only fulfills legal obligations but also enhances the overall safety culture within an organization, ensuring that machinery can be stopped immediately in emergencies, thereby saving lives and preventing property damage.

H. Reference

International Organization for Standardization. (2015). ISO 13850:2015 – Safety of Machinery – Emergency Stop Function – Principles for Design. Geneva, Switzerland: ISO.

Author: OHS Consultant

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