❌ ISO 13849-1:2023 – Do Not Use ❌

This is a first On Thursday, 2023-04-27, ISO published ISO 13849-1:2023, the 4th edition of the dominant functional safety standard for machinery. Usually, I would be the first to tell you that you should buy the standard as quickly as possible and start using it immediately. Today is not a normal day. As Command Module…

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Understanding safety functions: Safe speed and safe standstill

A red sign with white block letters reading "reduce speed."

In this post, I’ll discuss two safety-related parameters: safe speed and safe standstill. Speed control is a very common machine function. Conveyors, mixers, pumps, and many other applications rely on variable-speed drives. Some speed parameters are also safety-related because variations in speed can increase the risk to workers. See this post for more information on…

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CSA Z432 Public Review Open!

CSA Z432 Public Review is open. If you are a user, a builder of machinery, or an evaluator of machinery, this is your opportunity to see the draft of this important standard and to make comments to help the Technical Committee improve the standard on your behalf. Note: The start of the public review period…

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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.

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Manual reset using an HMI

A Siemens HMI displaying control functions and data.

Update: Things have changed a bit since this post was first published in 2021. 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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