Hierarchy of Controls Archives | Machinery Safety 101

1 May, 2023

❌ ISO 13849-1:2023 – Do Not Use ❌

in Canada, CE Mark, EMC, Emergency Stop, EMO Emergency Off, EU European Union, Functional Safety, Interlocks, Interlocks, International, ISO 13849, Ontario, Pre-Start Health and Safety Reviews, Robotics, Safety-Critical Software, Standards /

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This is a first On Thursday, 2023-04-27, ISO published ISO 13849-1:2023, the 4th edition of the dominant functional safety standard for machinery. Usually, I would be the first to tell you that you should buy the standard as quickly as possible and start using it immediately. Today is not a normal day. As Command Module…

19 September, 2022

Understanding safety functions: Safe speed and safe standstill

by Doug Nix

in Canada, CE Mark, Control Functions, Functional Safety, Guards and Guarding, Hierarchy of Controls, International, ISO 13849, Robotics, USA

A red sign with white block letters reading "reduce speed."

In this post, I’ll discuss two safety-related parameters: safe speed and safe standstill. Speed control is a very common machine function. Conveyors, mixers, pumps, and many other applications rely on variable-speed drives. Some speed parameters are also safety-related because variations in speed can increase the risk to workers. See this post for more information on…

9 March, 2022

CSA Z432 Public Review Open!

by Doug Nix

in Canada, Control Functions, Functional Safety, Guards and Guarding, Hazards, Hierarchy of Controls, Information for Use, Risk Assessment, Standards

CSA Z432 Public Review is open. If you are a user, a builder of machinery, or an evaluator of machinery, this is your opportunity to see the draft of this important standard and to make comments to help the Technical Committee improve the standard on your behalf. Note: The start of the public review period…

8 February, 2022

Emergency Off (EMO) vs Emergency Stop

by Doug Nix

in Control Functions, Emergency Stop, EMO Emergency Off, Hierarchy of Controls, Standards /

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EMO Button, red with yellow surround. Credit: D. Nix

The concept of Emergency Off (EMO) used by the semiconductor manufacturing sector is similar in many ways to the emergency stop used in all other types of machinery, with some differences. This article covers the differences between these concepts. NOTE: This is a long post! TL;DR: EMO and emergency stop are very similar; however, some…

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.

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 safety stop functions share the same control system hardware and software.