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Passport to Safety

A control system that uses a functional safety concept in effect gives you a ‘passport to safety’. That is because a system using functional safety meets international safety standards, making your system compliant with safety standards applicable in most nations. As a result, you have significantly increased global market opportunities to sell your product to new customers.



Functional Safety is the part of the overall safety implementation that depends on the correct functioning of the process or equipment in response to operational safety inputs. The name ‘functional safety’ is often associated only with programmable safety systems, but this is a misconception. It covers a range of devices, such as interlocks, light curtains, safety relays, safety PLCs, safety contactors and safety drives that are interconnected to form a safety system.

As an example of what is, and what is not functional safety, compare fixed hard guarding to electrically interlocked guarding. Although the fixed guard does perform a safety function — keeping people out and materials in — it is not considered ‘functional safety’ because there is no input to a system. The interlocked door, however, is an example of functional safety. When the guard is opened, the interlock serves as an ‘input’ to a system that assures a safe state is achieved.

Functional safety falls under the umbrella of the risk reduction process. The risk reduction process involves the following steps:

• Eliminate by design using inherently safe design concepts.


• Safeguarding and protective measures with hard guarding and safety devices.


• Complementary safety measures including personal protective equipment (PPE).


• Safe working practice achieved with procedures, training and supervision.

When you implement integrated safety by designing systems so that safety and environmental considerations are fundamental elements of doing work, you include functional safety measures as part of the safety system.

Hazard analysis and risk assessment
Performing a hazard analysis and risk assessment is the first step in the safety life cycle, and has five steps:

1. Risk assessment or hazard analysis.


2. Safety system requirements.


3. Safety system implementation.


4. Safety system validation.


5. Maintaining and improving the safety system.

Functional safety is part of the safety life cycle because it is involved in steps 2, 3 and 4.

When designing equipment and associated control systems, a hazard analysis will help determine whether functional safety is necessary to ensure adequate protection against each significant hazard. If so, then users can integrate functional safety into the machine design requirements, implementation and validation.

A hazard analysis identifies what has to be done to avoid hazardous events associated with the operation and maintenance of the machinery. In addition, a risk assessment gives the safety integrity required of the safety system for the risk to be acceptable.

Business Justification for safety investments
A white paper outlines the long-term financial benefits manufacturers can reap by integrating comprehensive machine safety programmes into their workplaces as a form of insurance against potential risks. The ‘Proving the Value of Safety’ white paper is linked from the safety Web site at: http://www.rockwellautomation.com/go/prsafety

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