Complementary Protective Measures

Emergency Stop Pull-Cords

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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 […]

Control Functions

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

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

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. Book List Here are some books that I think you may find help­ful on this jour­ney: [0]     […]

Canada

ISO 13849 – 1 Analysis — Part 6: CCF — Common Cause Failures

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This entry is part 6 of 9 in the series How to do a 13849 – 1 ana­lys­is

What is a Com­mon Cause Fail­ure? There are two sim­il­ar-sound­ing terms that people often get con­fused: Com­mon Cause Fail­ure (CCF) and Com­mon Mode Fail­ure. While these two types of fail­ures sound sim­il­ar, they are dif­fer­ent. A Com­mon Cause Fail­ure is a fail­ure in a sys­tem where two or more por­tions of the sys­tem fail at the same time from a single […]

Canada

Testing Emergency Stop Systems

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This entry is part 11 of 16 in the series Emer­gency Stop

I’ve had a num­ber of ques­tions from read­ers regard­ing test­ing of emer­gency stop sys­tems, and par­tic­u­larly with the fre­quency of test­ing. I addressed the types of tests that might be needed in anoth­er art­icle cov­er­ing Check­ing Emer­gency Stop Sys­tems. This art­icle will focus on the fre­quency of test­ing rather than the types of tests. The Prob­lem Emer­gency […]

Control Functions

Interlock Architectures – Pt. 4: Category 3 – Control Reliable

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Category 3 Architecture Logic Block Diagram
This entry is part 4 of 8 in the series Cir­cuit Archi­tec­tures Explored

Cat­egory 3 sys­tem archi­tec­ture is the first cat­egory that could be con­sidered to have sim­il­ar­ity to “Con­trol Reli­able” cir­cuits or sys­tems as defined in the North Amer­ic­an stand­ards. It is not the same as Con­trol Reli­able, but we’ll get to in a sub­sequent post. If you haven’t read the first three posts in this series, you may […]

Canada

Reader Question: Multiple E‑Stops and Resets

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This entry is part 7 of 16 in the series Emer­gency Stop

I had an inter­est­ing ques­tion come in from a read­er today that is rel­ev­ant to many situ­ations: “When you have mul­tiple E‑Stop but­tons I have often got­ten into an argu­ment that says you can have a reset beside each one. I was taught that you were required to have a single point of reset. Who is cor­rect?” — Michael Barb, […]

Canada

Understanding Risk Assessment

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A group surrounding a computer discussing a problem.
This entry is part 10 of 9 in the series Risk Assess­ment

When people dis­cuss ‘Risk’ there are a lot of dif­fer­ent assump­tions made about what that means. For me, the study of risk and risk assess­ment tech­niques star­ted in 1995. As a tech­no­lo­gist and con­trols design­er, I had to some­how wrap my head around the whole concept in ways I’d nev­er con­sidered. If you’re try­ing to fig­ure out risk […]

Canada

Emergency Stop Categories

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Emergency Stop on machine console
This entry is part 4 of 16 in the series Emer­gency Stop

I’ve noticed a lot of people look­ing for inform­a­tion on Emer­gency Stop cat­egor­ies recently; this art­icle is aimed at those read­ers who want to under­stand this top­ic in more depth. First, a cla­ri­fic­a­tion: Emer­gency stop cat­egor­ies DO NOT EXIST, but stop cat­egor­ies do. A stop cat­egory is a descrip­tion of a con­trol func­tion – what the con­trol does – and […]