Blog series: The revison of EN ISO 13849: Part 0, the overview

For those of you who have followed my blog for a while you have probably read the blog post series on EN 13849 and the ongoing revision work. I have been going into quite a lot of detail in those posts but I have now come to a conclusion that it was slightly prematurely as the standard is not near its final content yet. By the end of April 2020 the DIS will be released and it is not until end of April 2021 that the final standard will be released. I.e. there will be ample time to study and prepare for the changes.

So, what I am doing now is writing this post which describes in general terms the changes in the revision of EN 13849 and at the release of the DIS I will post the entire blog series again, walking through the changes. So here we go.

Why the standard is revised


With the current progress of more and more intelligence in safety related products the need for more requirements on software is needed. In the project of revising the standard the requirements on software has been a large part and continues to be. At one point most of the software requirements from EN 62061 was included but is was later stricken and all initial requirements was taken back. Now it is discussed in detail what exactly should and should not be included, but we can state that changes to the current requirements will be implemented.

The choice of PLr

The actual level of PL is the guiding star of the entire standard and if one gets that wrong, the final product will either be too safe (well, too complex and expensive then) or too unsafe. There fore a lot of effort has been put into guiding the user of the standard to choose correctly.

The structure

The first few times we tried using EN 13849 to develop a control system from scratch we had a hard time to know exactly what was expected of us. What documents are we supposed to produce and in what order? This will really be given an uplift in the revision and even such a crucial document as the SRS (which was not even mentioned before) has now been given a lot of explanation and space in the standard.

The structure has changed so that we now get a more step by step approach meaning that chapters has been reorganized and combined or divided. Basically it is now a more easy read (can it ever be an easy read?).

The combination of EN 13849-1 and EN 13849-2

Statistics is a great thing and it can show us a lot. In the new revision, most likely the requirements of EN 13849-2 will be included into -1. Why? Because statistics showed that -2 was sold in far less numbers than -1 even though it is equally important to complete the requirements of the safety standard.


The new revision will be easier to use, mostly due to the fact that the structure and composition has changed a lot. When it comes to the requirements on software I hope that we get clearer and more precise requirements than what we currently have and we most likely will. The final revision will not change much from the DIS that is released in May, meaning that once I work through the following posts again I hopefully won’t need to change them much when the final revision is released.

Next step

In may I will finish the final 4 blog posts of the revision of the standard and until then I would be happy to answer any questions that may arise. Please feel free to contact me if you have any questions or maybe tips on what you want to read in these posts in the future.

Do you have problems with your functional safety project? Do you need a experienced functional safety manager or coach to help you handle your questions and troubles? Do not hesitate to reach out with a question or two or why not book a free coaching call with me?

You can email me directly at roberth.jonsson@zatisfy.se

The blog posts in the series:

  1. General, overview and methodology (chapters 1-4) (not released)

  2. Specification of safety functions and design considerations (chapters 5-6) not released

  3. Software, Verification, Ergonomics, Validation and Documentation (chapters 7-13) not released

  4. The Annexes (not released)

Roberth Jonsson

Consultant at Zatisfy AB in Umeå, Sweden. Roberth want companies to include CE marking naturally in their daily work. Roberth is taking part of the standardization of EN ISO 13949 by being a member of TK282 at SIS.

Read more about Roberth här.

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