Control Functions

Trapped Key Interlocking

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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 With the bolt withdrawn, the key is held in the lock.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 a way to inter­lock guards that is equally effect­ive, and often more appro­pri­ate in severe envir­on­ment­al con­di­tions. Copy­right secured by Digi­prove © 2018Acknow­ledge­ments: As cited.Some Rights ReservedOri­gin­al con­tent here is pub­lished under […]

Guards and Guarding

How to Apply a Safety Edge to a Machine Guard – Part 3: Stopping Performance

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CNC machine with sliding doors and safety edges
This entry is part 7 of 7 in the series Guards and Guard­ing

In Part 2 of this art­icle, I looked at the pres­sure-sens­it­ive devices (safety edges) them­selves. This part explores the stop­ping per­form­ance require­ments that engin­eers and tech­no­lo­gists need to con­sider when apply­ing these devices. Copy­right secured by Digi­prove © 2018Acknow­ledge­ments: As cited in the text.Some Rights ReservedOri­gin­al con­tent here is pub­lished under these license terms: X License Type:Non-com­mer­cial, Attri­bu­tion, Share AlikeLi­cense Sum­mary:You may copy this con­tent, […]

Courses

RA101 – Introduction to Risk Assessment

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Graphic illustration of a factory line

Learn Machinery Risk Assess­ment any­time and any­where.  Intro­duc­tion to Risk Assess­ment is our 12-week machinery risk assess­ment course, based on ISO 12100:2010 and ISO/TR 14121 – 2:2012 stand­ards. Delivered online, this course fea­tures widely accep­ted meth­od­o­logy that can be used without modi­fic­a­tion in Canada, the EU, and the USA. Copy­right secured by Digi­prove © 2018Some Rights ReservedOri­gin­al con­tent here is pub­lished under these license […]