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 With the bolt withdrawn, the key is held in the lock.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 […]

Events

Five reasons you should attend our Free Safety Talks

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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 Talks. We had full houses in all three loc­a­tions, Wind­sor, Lon­don and Cam­bridge, with nearly 60 people par­ti­cip­at­ing. We had two great presenters who helped […]

Functional Safety

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

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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 lock­out? Safety pro­fes­sion­als don’t always agree on this con­tro­ver­sial top­ic! Dur­ing the Free Safety Talks that we did with Schmersal Canada and Frank­lin Empire, this […]