Machinery Safety 101
12 July, 2021

Understanding Safety Functions: the Safety-related stop function

by Doug Nix
in Complementary Protective Measures, Control Functions, Emergency Stop, Functional Safety, Interlocks, Interlocks, ISO 13849
A stop sign - A red octagon with a white border, and white block text reading STOP.
This entry is part of 3 in the series Under­stand­ing Safety Functions

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… 

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2 June, 2021

Manual reset using an HMI

by Doug Nix
in Complementary Protective Measures, Control Functions, Control Reliability, Emergency Stop, Functional Safety, Inherently Safe Design, ISO 13849 /
1 Comment
A Siemens HMI displaying control functions and data.
This entry is part 2 of 3 in the series Under­stand­ing Safety Functions

Ques­tion: Can a safety-related stop func­tion, for example, be reset via a graph­ic­al object rep­res­ent­ing a reset but­ton on an HMI? The short answer: No, with an excep­tion. Read on if you’d like… 

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8 May, 2021

What is risk assessment?

by Doug Nix
in Canada, EU European Union, Hierarchy of Controls, International, Risk Assessment, Standards, USA
This entry is part 11 of 10 in the series Risk Assess­ment

Risk assess­ment began as a dis­cip­line in the late 1960s, with some of the earli­est form­al papers pub­lished in the early 1970s. The early research­ers were part of the US military… 

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14 April, 2021

What exactly is PELV?

by Doug Nix
in Electrical Safety, Inherently Safe Design
Photo of the interior of an electrical control cabinet showing the components and wireways on the backplane.

What exactly is PELV? Elec­tric­al design­ers run into all kinds of spe­cial­ized ter­min­o­logy as part of their work. IEC is notori­ous for cre­at­ing spe­cial­ized terms that are not famil­i­ar to… 

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23 May, 2019

Force and injury — How hard is too hard? ISO/TR 21260 will help

by Doug Nix
in Hierarchy of Controls, Inherently Safe Design, Robotics, Standards /
5 Comments
ISO/TS 15066 body model
This entry is part 5 of 5 in the series Hier­archy of Controls

Force rep­res­ents the mech­an­ic­al energy that causes injury to the human body. ISO/TC 199 has been work­ing on answer­ing that ques­tion since 2012.

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