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 […]
When people discuss ‘Risk’ there are a lot of different assumptions made about what that means. For me, the study of risk and risk assessment techniques started in 1995. As a technologist and controls designer, I had to somehow wrap my head around the whole concept in ways I’d never considered. If you’re trying to figure out risk […]
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, a clarification: Emergency stop categories DO NOT EXIST, but stop categories do. A stop category is a description of a control function – what the control does – and […]
This article explores the requirements for safety related control systems meeting ISO 13849 – 1 Category 2 requirements. “Gotcha!” points in the definition are highlighted to help designers avoid this common pitfalls.
This article expands on the first in the series “Interlock Architectures – Pt. 1: What do those categories really mean?”. Learn about the basic circuit architectures that underlie all safety interlock systems under ISO 13849 – 1, and CSA Z432 and ANSI RIA R15.06.
Did you know that interlocked gates require stopping performance testing?
Machinery needs to be able to stop in the time it takes a person to open the guard and reach the hazard. If the distance from the guard opening to the hazard is short enough that a person can reach the danger point before the hazard can be controlled, the guard is useless. The resulting situation may be worse
I get a lot of calls and emails asking about emergency stops. This is one of those deceptively simple concepts that has managed to get very complicated over time. Not every machine needs or can benefit from an emergency stop. In some cases, it may lead to an unreasonable expectation of safety from the user, which can lead to injury if they don’t understand the hazards involved. Some product-specific standards