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 13850. 2015. [2] Safety of…
Read MoreEmergency Stop Pull-Cords
This article was updated 2019-04-26, adding specific details related to IEC 60947 – 5‑5. When it comes to emergency stop devices there is no doubt that the red mushroom-head push button is the most common – they seem to be everywhere. The second most common emergency stop device is the pull-cord, and like the light-curtain in safeguarding…
Read MoreEmergency Stop Failures
I am always looking for interesting examples of machinery safety problems to share on MS101. Recently I was scrolling Reddit/r/OSHA and found these three real-world examples. Broken Emergency Stop Buttons The first and most obvious kinds of failures are those resulting from either wear out or damage to emergency stop devices like e‑stop buttons or pull…
Read MoreISO 13849 – 1 Analysis — Part 6: CCF — Common Cause Failures
Post updated 2019-07-24. Ed. What is a “Common Cause Failure”? There are two similar-sounding terms that people often get confused: Common Cause Failure (CCF) and Common Mode Failure. While these two types of failures sound similar, they are different. A Common Cause Failure is a failure in a system where two or more portions of the system fail at…
Read MoreTesting Emergency Stop Systems
I’ve had a number of questions from readers regarding testing of emergency stop systems, and particularly with the frequency of testing. I addressed the types of tests that might be needed in another article covering Checking Emergency Stop Systems. This article will focus on the frequency of testing rather than the types of tests. The Problem Emergency…
Read MoreCSA Z432 Safeguarding of Machinery – 3rd Edition
If you build machinery for the Canadian market, or if you modify equipment in Canadian workplaces, you will be familiar with CSA Z432, Safeguarding of Machinery. This standard has been around since 1992, with the last major revision published in 2004. CSA has reconvened the Technical Committee responsible for this important standard to revise the…
Read MoreEmergency stop devices: the risks of installer liability
On the MachineBuilding.net blog today, Alex D’Arcy, Sales Director at Hylec-APL provides some interesting insights into the liabilities associated with the installation of emergency stop devices on machinery. Hylec-APL provides technical products and solutions in the field of industrial machinery and emergency stop systems. Check out Alex’s article. If you need to know more about the…
Interlock Architectures – Pt. 5: Category 4 — Control Reliable
Ed. note: I’ve made a few updates to this article since it was first published in 2011, with the most recent today, 6‑Dec-18. – DN – The most reliable of the five system architectures, Category 4 is the only architecture that uses multiple-fault tolerant techniques to help ensure that component failures do not result in an unacceptable…
Read MoreInterlock Architectures – Pt. 4: Category 3 – Control Reliable
Category 3 system architecture is the first category that could be considered to have similarity to “Control Reliable” circuits or systems as defined in the North American standards. It is not the same as Control Reliable, but we’ll get to in a subsequent post. If you haven’t read the first three posts in this series, you may…
Read MoreUpdates to Popular Articles
We’ve recently updated a couple of our popular articles! Check them out! Busting Emergency Stop Myths Reader Question: Multiple E‑Stops and Resets