Machinery Safety 101
3 July, 2018

Trapped Key Interlocking

by Doug Nix
in Control Functions, Functional Safety, Hazardous Energy Control Procedures, Interlocks, Interlocks /
6 Comments
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 With the bolt withdrawn, the key is held in the lock.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… 

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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
Banner for the Free Safety Talks

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… 

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15 May, 2018

Q & A: Can Safety PLCs be used for Lockout?

by Doug Nix
in Functional Safety, Hazardous Energy Control Procedures, ISO 13849, Lockout, Ontario, Q & A /
3 Comments
Disconnect Switch with Lock and Tag
This entry is part 2 of 2 in the series Q&A

The ques­tion of lock­out and the use of safety PLCs as a means to meet the lock­out require­ments comes up more and more fre­quently these days. Can Safety PLCs be used for… 

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15 March, 2011

Updates to Popular Articles

by Doug Nix
in Canada, CE Mark, Control Functions, Emergency Stop, Hazardous Energy Control Procedures, Robotics, USA
This entry is part 8 of 16 in the series Emer­gency Stop

We’ve recently updated a couple of our pop­u­lar art­icles! Check them out! Bust­ing Emer­gency Stop Myths Read­er Ques­tion: Mul­tiple E‑Stops and Resets

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 /
4 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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