3 July, 2018

Trapped Key Interlocking

by Doug Nix
in Control Functions, Functional Safety, Hazardous Energy Control Procedures, Interlocks, Interlocks /
6 Comments
Mechanical locking portion of a trapped key interlock secured to the door of an electrical switchgear cabinet with one-way tamper-resistant screws.

Many machine designers think interlocks are exclusively electrical devices; a movable mechanical guard is fitted with an electrical interlocking device, and the interlocking device is connected to the control system. Trapped Key Interlocking is an equally effective way to interlock guards that is often more appropriate in severe environmental conditions or where the guard is…

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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
Typical plastic-bodied interlocking device

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 movable guard. Movable guards can be doors, panels, gates or other physical barriers that can be opened without using tools. Each of these…

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