Machinery Safety 101

More E‑Stop Questions

This entry is part 17 of 16 in the series Emer­gency Stop

Here are some more ques­tions I’ve been asked regard­ing emer­gency stop require­ments. These ones came to me through the IEEE PSES EMC-PSTC Product Com­pli­ance For­um mail­ing list. Primary Sources There are three primary sources for the require­ments for emer­gency stop devices: [1] Safety of machinery — Emer­gency stop — Prin­ciples for design, 3rd Edi­tion. ISO 13850. 2015. [2] Safety of…

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Can Emergency Stop be used as an “on/off” control?

Emergency Stop Button
This entry is part 16 of 16 in the series Emer­gency Stop

Every couple of months I get an email ask­ing me if there is any reas­on why e‑stop func­tions can­’t be used as the primary power con­trol (on/off but­ton) for machinery. Fol­low­ing a recent exchange, I thought I would share the reas­ons for why this is such a bad idea. The short answer The short answer is an unequi­voc­al NO. Don’t…

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Introduction to Functional Safety Seminars

Man training a group of people, pointing to Functional Safety topics on the whiteboard

If you are inter­ested in func­tion­al safety, and I know many read­ers are based on the stat­ist­ics I see for my oth­er func­tion­al safety-related posts, I think you will be inter­ested in this. I am col­lab­or­at­ing with the IEEE Product Safety Engin­eer­ing Soci­ety’s Vir­tu­al Chapter to provide a series of three 35 minute sem­inars dis­cuss­ing the fun­da­ment­als of func­tion­al safety. The…

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Emergency Stop Pull-Cords

This entry is part 15 of 16 in the series Emer­gency Stop

This art­icle was updated 2019-04-26, adding spe­cif­ic details related to IEC 60947 – 5‑5. When it comes to emer­gency stop devices there is no doubt that the red mush­­room-head push but­ton is the most com­mon – they seem to be every­where. The second most com­mon emer­gency stop device is the pull-cord, and like the light-cur­­tain in safe­guard­ing…

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 With the bolt withdrawn, the key is held in the lock.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

Q & A: Category 2 and Testing Intervals

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. In the short video below, Doug answers that ques­tion. If you have more ques­tions or felt some­thing was­n’t clear in the video, leave us a com­ment and…

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Five reasons you should attend our Free Safety Talks

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…

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Emergency Stop Failures

This entry is part 13 of 16 in the series Emer­gency Stop

I am always look­ing for inter­est­ing examples of machinery safety prob­lems to share on MS101. Recently I was scrolling Reddit/r/OSHA and found these three real-world examples. Broken Emer­gency Stop But­tons The first and most obvi­ous kinds of fail­ures are those res­ult­ing from either wear out or dam­age to emer­gency stop devices like e‑stop but­tons or pull…

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Safe Drive Control including Safe Torque Off (STO)

Graph illustrating STO Function
This entry is part 12 of 16 in the series Emer­gency Stop

Ed. Note: This art­icle was revised 25-Jul-17 to include inform­a­tion on safe stand­still. Safe Drive Con­trol includ­ing STO Motor drives are every­where. From DC vari­able speed drives and index­ing drives, through AC Vari­able Fre­quency drives, servo drives and step­per motor drives, the cap­ab­il­it­ies and the flex­ib­il­ity of these elec­tron­ic sys­tems has giv­en machine design­ers unpre­ced­en­ted…

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How to do a 13849 – 1 analysis: Complete Reference List

This entry is part 8 of 9 in the series How to do a 13849 – 1 ana­lys­is

Post updated 2019-07-24. Ed. As prom­ised in pre­vi­ous posts, here is the com­plete ref­er­ence list for the series “How to do a 13849 – 1 ana­lys­is”! If you have any addi­tion­al resources you think read­ers would find help­ful, please add them in the com­ments. Copy­right secured by Digi­prove © 2017 – 2018Acknow­ledge­ments: As cited.Some Rights ReservedOri­gin­al con­tent here is pub­lished under these license terms: X License Type:Non-com­mer­cial, Attri­bu­tion,…

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