What happened to the series?

If you’ve been reading this blog for very long. you’ll know that I frequently write a series of posts on a topic, like this one on how to do an ISO 13849-1 analysis. A few months ago, the software I have been using for many years to organize those series posts stopped working properly and…

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Ontario OHSA turns 43

Headline, the Toronto Telegram, March 18, 1960. "It was a Hell-Hole."

The Ontario Occupational Health and Safety Act (OHSA) turns 43 today. For many workers, this important legislation came into force long before they were born, but some workers will remember the days before this important Act came into force. The Act came into force in 1979, but Ontario had a long history of labour-safety-related workplace…

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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…

Manual reset using an HMI

A Siemens HMI displaying control functions and data.

Update: Since this post was first published in 2021, things have changed a bit. There are now some safety-rated HMIs available from big controls companies like Siemens, so if you are considering this approach, consult with your controls vendor to see if their HMIs can meet the requirements of ISO 13849-1. Ed. – 2022-05-10 Question: Can…

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