guarding Archives | Machinery Safety 101

3 July, 2018

Trapped Key Interlocking

in Control Functions, Functional Safety, Hazardous Energy Control Procedures, Interlocks, Interlocks /

This is a trapped key interlock on the door of an electrical switchgear cabinet. To open the door the key must be inserted and turned to withdraw a bolt that holds the door closed. With the bolt withdrawn, the key is held in the lock. The upstream switching device is held open by another interlock using the same key; since the key can only be in one of the two locks, it prevents accidentally closing the upstream switch while the cabinet is open for maintenance. The interlock is attached to the door with one-way screws to discourage casual removal of the lock, which would defeat the system.

This entry is part 3 of 7 in the series Guards and Guarding

Many machine designers think of interlocks as exclusively electrical devices; a switch is attached to a movable mechanical guard, and the switch is connected to the control system. Trapped Key Interlocking is…

15 May, 2018

Five reasons you should attend our Free Safety Talks

by Doug Nix

in Events, Free Talks, Functional Safety, Hazardous Energy Control Procedures, Interlocks, Interlocks, ISO 13849, Lockout, News, Ontario, Pre-Start Health and Safety Reviews, Standards

Reason #1 – Free Safety Talks You can’t argue with Free Stuff! Last week we partnered with Schmersal Canada and Franklin Empire to put on three days of Free Safety…

29 May, 2015

Presence Sensing Devices – Reaching over sensing fields

by Doug Nix

in Canada, Guards and Guarding, Hierarchy of Controls, Ontario, Robotics

This entry is part 2 of 7 in the series Guards and Guarding

I recently heard about an application question related to a light curtain where a small gap existed at the top of the sensing field, between the last beam in the field and the…

27 January, 2014

CSA Z432 Safeguarding of Machinery – 3^rd Edition

by Doug Nix

in Canada, Control Functions, Control Reliability, Emergency Stop, Functional Safety, Guards and Guarding, Hazards, Hierarchy of Controls, Interlocks, Risk Assessment, Standards

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…

3 August, 2012

Get the Basics Right!

by Doug Nix

in Canada, CE Mark, Control Reliability, Functional Safety, General, Hazards, Hierarchy of Controls, International, ISO 13849, Risk Assessment, Robotics, Seminars, USA

For more than 15 years I’ve been teaching people about risk assessment, machinery safety and CE Marking of machinery in private, onsite classes and through presentations at safety conferences. Things are…

16 July, 2012

New HSE advice on CE marking assemblies of machinery

by Doug Nix

in CE Mark, EU European Union

This post was originally published on machinebuilding.net. Reprinted with permission. By Jon Severn, machinebuilding.net A degree of confusion surrounds the question of CE marking assemblies of machinery under the Machinery Directive 2006/42/EC.…

1 June, 2012

Interlocking Devices: The Good, The Bad and the Ugly

by Doug Nix

in Canada, CE Mark, Components, Control Functions, Control Reliability, EU European Union, EU Robotics, Guards and Guarding, Hierarchy of Controls, Interlocks, Interlocks, International, International Robotics, ISO 13849, North American Robotics, Ontario, Robotics, USA /

11 Comments

This entry is part 1 of 7 in the series Guards and Guarding

Note: A shorter version of this article was published in the May-2012 edition of Manufacturing Automation Magazine. When designing safeguarding systems for machines, one of the basic building blocks is the…

21 June, 2011

Hockey Teams and Risk Reduction or What Makes Roberto Luongo = PPE

by Doug Nix

in Canada, Control Functions, EU European Union, General, Guards and Guarding, Hazards, Hierarchy of Controls, International, Risk Assessment /

10 Comments

This entry is part 2 of 5 in the series Hierarchy of Controls

Special Co-Author, Tom Doyle Last week we saw the Boston Bruins earn the Stanley Cup. I was rooting for the green, blue and white, and the ruin of my voice on…

28 February, 2011

Understanding the Hierarchy of Controls

by Doug Nix

in Canada, CE Mark, Complementary Protective Measures, Control Functions, Control Reliability, Emergency Stop, EU European Union, Functional Safety, General, Guards and Guarding, Hazardous Energy Control Procedures, Hierarchy of Controls, Interlocks, Interlocks, Lockout, Ontario, Risk Assessment, Robotics, USA /

8 Comments

The Hierarchy of Controls illustrated as an inverted triangle with each level of the hierarchy written one above the other, starting with Inherently Sfe design, then Engineering Controls, then Information for Use, then Administrative Controls and finally descending to PPE at the bottom. An arrow with the text "Effectiveness" on it runs parallel to the triangle and points downward from Inherently safe design to PPE.

This entry is part 4 of 5 in the series 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…

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