About Machinery Safety

International Standard Attitude toward Ensuring Safety
– Transition from Hazard-Detection System to Safety-Confirmation System –

The standardized ISO 12100 requires incorporating safety mechanism into a machine or equipment. Safety is defined by ISO as “the absence of unacceptable risks.” Thus, the approach to “machine safety” is changing from the conventional “hazard-detection system” to a “safety-confirmation system.” Safety measures at workplaces are undergoing a major shift from the traditional passive approach of relying on protective equipment and education and training for workers to the ones assuming that human error is inevitable and aiming to create machines that will not cause accidents even in the unlikely event by incorporating safety designs into machinery to prevent human error from leading to accidents.

Conventional approach: Finger pointing and call

• “With effort, we can prevent accidents from happening again.”
  Human error is the main cause of accidents, therefore, addressing human factor is more important than conducting technical measures.

• “Safety can be ensured by creating a management system, educating people, and strengthening regulations.”
• “Safety is basically free.” (It is difficult to acknowledge safety costs.)
  Respond to visible “concrete hazards” at the lowest possible cost.
• “Emphasis on frequency rate (number of accidents)”
• “Technology to eliminate identified hazards” (Hazard-Detection System)

A system in which energy conveys information about hazard and safety is indicated when the information is negated. In other words, a system that “does not allow machinery to operate or stops it only when a hazard is detected.”
This applies to systems that generate energy to prevent accident only after detecting hazard.
These systems cannot avoid accidents when energy cannot be generated.

Inherently Safe Design Measures

• “No matter how hard we try, accidents will always happen depending on our level of technology.”
  Preventing accidents is an issue of technology, therefore, conducting technological measures are more important than addressing human factors.
• “People inevitably make mistakes. Safety cannot be ensured without improving technology.”
• “Safety fundamentally comes at a cost.”
  Sources of hazards should be identified, risk assessment should be conducted, and costs should be paid according to the assessment.
• “Emphasis on intensity rate (serious accidents)”
• “Technology to verify safety logically” (Safety-confirmation system)

A system which outputs preliminarily prepared energy “only when safety is confirmed.”
It is a system that avoids accidents by stopping generating energy when safety cannot be confirmed. Such a system can certainly ensure safety when failures occur.
The machine will not operate unless safety is confirmed, because the system will not “execute operation” until it receives both “operation command” and “safety confirmation” signals.

Differences between safety-confirmation system and hazard-detection system

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