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 With the bolt withdrawn, the key is held in the lock.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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16 May, 2018

Q & A: Category 2 and Testing Intervals

by Doug Nix
in Control Functions, Functional Safety, Interlocks, ISO 13849, Q & A /
6 Comments
Logical block diagram for ISO 13849-1 Category 2 architecture.
This entry is part 1 of 2 in the series Q&A

Dur­ing the Free Safety Talks that we did with Schmersal Canada and Frank­lin Empire, we had a “hot ques­tion” come up regard­ing Cat­egory 2 archi­tec­ture and the test­ing inter­val require­ment. The… 

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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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27 January, 2014

CSA Z432 Safeguarding of Machinery – 3rd 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… 

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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… 

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