Machinery Safety 101

Understanding Safety Functions: the start/restart function

Car engine start/stop button

After the safety-related stopping and the reset functions, the start/restart function is the next most common. Without a start/restart function, there is no way to make the machine do what it’s supposed to do. If you’re designing a machine control system, you need to understand this function.

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Understanding Safety Functions: the Safety-related stop function

A stop sign - A red octagon with a white border, and white block text reading STOP.

The most used safety function on machinery is the safety-related stop function. The requirements discussed in this post are not generally applicable to process-related stop functions unless the process and safety stop functions share the same control system hardware and software. Copyright secured by Digiprove © 2021Acknowledgements: ISOSome Rights ReservedOriginal content here is published under these license terms: X License Type:Non-commercial, Attribution, Share…

Understanding safety functions: Manual Reset

A reset button graphic

Following the risk assessment, risk reduction is the next step. Whenever the control system is called upon to reduce the risk, a safety function is needed. Safety functions are defined in safety requirement specifications. ISO 13849-1:2015 [1] offers descriptions of some of the more common safety functions. One of the most poorly understood is the…

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ISO/DIS 13849-1 Available for Public Review

Decision tree used to determine PL based on risk parameters.

Update 2020-10-11: The next three-day ISO/TC 199/WG8 meeting runs Tuesday-Thursday this week. Our committee members will be wading into the next 1 600 comments along with expert members from around the world. We’ll update you again as the changes get closer. Update 2020-09-29: Over 1 920 (!!) comments were received by the committee from the…

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Q & A: Category 2 and Testing Intervals

Logical block diagram for ISO 13849-1 Category 2 architecture.

During the Free Safety Talks that we did with Schmersal Canada and Franklin Empire, we had a “hot question” come up regarding Category 2 architecture and the testing interval requirement. The definition of Category 2 in 6.2.5 does not include any mention of a minimum testing rate, but 4.5.4 “Simplified procedure for estimating the quantifiable…

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