Machinery Safety 101

Interlocking Devices: The Good, The Bad and the Ugly

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

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Presence Sensing Devices – Reaching over sensing fields

This entry is part 2 of 7 in the series Guards and Guard­ing

I recently heard about an applic­a­tion ques­tion related to a light cur­tain where a small gap exis­ted at the top of the sens­ing field, between the last beam in the field and the sur­round­ing struc­ture of the machine. There was some con­cern raised about the gap, and wheth­er or not addi­tion­al guard­ing might be needed to close the gap.…

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Trapped Key Interlocking

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 With the bolt withdrawn, the key is held in the lock.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

Canada Adopts ISO 13857 – Safety Distances

This entry is part 4 of 7 in the series Guards and Guard­ing

Safety Dis­tances As part of the work on the 3rd Edi­tion of CSA Z432, Canada has decided to adopt ISO 13857 as CAN/CSA-ISO 13857. The stand­ard was adop­ted in 2015 without tech­nic­al devi­ations. Why ISO 13857? CSA Z432 has long had por­tions of the inform­a­tion in ISO 13857 in its annexes – Annex C has tables for reach­ing through open­ings and…

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How to Apply a Safety Edge to a Machine Guard – Part 1: Pressure-sensitive devices

CNC machine with sliding doors and safety edges
This entry is part 5 of 7 in the series Guards and Guard­ing

Safety Edges are often for­got­ten as safe­guard­ing devices. Most machinery engin­eers and design­ers are famil­i­ar with inter­lock­ing devices and light cur­tains, but once we step away from the famil­i­ar, our under­stand­ing of how to apply safe­guard­ing devices like a safety edge becomes a bit foggy.  Copy­right secured by Digi­prove © 2018Acknow­ledge­ments: SafeInd, IEC, ISO, Rock­well Auto­ma­tio more…Some Rights ReservedOri­gin­al con­tent here is pub­lished…

How to Apply a Safety Edge to a Machine Guard – Part 2: Design Considerations

CNC machine with sliding doors and safety edges
This entry is part 6 of 7 in the series Guards and Guard­ing

In Part 1 of this art­icle, I looked at the pres­sure-sens­it­ive devices (safety edges) them­selves. This part explores the design 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, cre­ate…

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

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,…

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