Machinery Safety 101

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.

Question: Can a safety-related stop function, for example, be reset via a graphical object representing a reset button on an HMI? The short answer: No, with an exception. Read on if you’d like to know more. If you’re interested in knowing more about the manual reset function, see our previous post on the manual reset…

More E-Stop Questions

Here are some more questions I’ve been asked regarding emergency stop requirements. These ones came to me through the IEEE PSES EMC-PSTC Product Compliance Forum mailing list. Primary Sources There are three primary sources for the requirements for emergency stop devices: [1] Safety of machinery — Emergency stop — Principles for design, 3rd Edition. ISO…

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Can Emergency Stop be used as an “on/off” control?

Emergency Stop Button

Every couple of months I get an email asking me if there is any reason why e-stop functions can’t be used as the primary power control (on/off button) for machinery. Following a recent exchange, I thought I would share the reasons for why this is such a bad idea. The short answer The short answer…

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Introduction to Functional Safety Seminars

Man training a group of people, pointing to Functional Safety topics on the whiteboard

If you are interested in functional safety, and I know many readers are based on the statistics I see for my other functional safety-related posts, I think you will be interested in this. I am collaborating with the IEEE Product Safety Engineering Society’s Virtual Chapter to provide a series of three 35 minute seminars discussing…

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