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…
Read MoreIntroduction to Functional Safety Seminars

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.…
Read MoreEmergency Stop Pull-Cords

This article was updated 2020-06-13, adding links to the Rockwell Automation and Schmersal pull-cord data, and on 2019-04-26, adding specific details related to IEC 60947 – 5‑5 [7]. When it comes to…
Read MoreSafe Drive Control including Safe Torque Off (STO)

Ed. Note: This article was revised 25-Jul-17 to include information on safe standstill. Safe Drive Control including STO Motor drives are everywhere. From DC variable speed drives and indexing drives,…
Read MoreISO 13849 – 1 Analysis — Part 7: Safety-Related Software

Post updated 2019-07-24. Ed. Safety-Related Software Up to this point, I have been discussing the basic processes used for the design of safety-related parts of control systems. The underlying assumption is…
Read MoreISO 13849 – 1 Analysis — Part 2: Safety Requirement Specification
This article was updated 2019-07-24. Ed. Developing the Safety Requirement Specification The Safety Requirement Specification sounds pretty heavy, but actually, it is just a big name for a way to organize the…
Read MoreISO 13849 – 1 Analysis — Part 1: Start with Risk Assessment
This post was updated 2019-07-24 I often get questions from clients about how to get started on Functional Safety using ISO 13849. This article is the first in a series that will…
Read MoreWhy you should stop using the term ‘Deadman’
The Deadman Control Do you use the phrase ‘deadman’ or ‘deadman switch’ when talking about safety-related controls on your machinery? I often run into this when I’m working with clients who…
Read MoreUnderstanding the Hierarchy of Controls

(Eds. note: This article was originally written in 2011 and was updated in Nov. 2018.) The “Hierarchy of Controls” is one approach to risk reduction that has become entrenched in the…
Read MoreEmergency Stop Categories

I’ve noticed a lot of people looking for information on Emergency Stop categories recently; this article is aimed at those readers who want to understand this topic in more depth. First,…
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