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

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 […]

Asides

Interlocked gate testing

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Did you know that inter­locked gates require stop­ping per­form­ance test­ing?

Machinery needs to be able to stop in the time it takes a per­son to open the guard and reach the haz­ard. If the dis­tance from the guard open­ing to the haz­ard is short enough that a per­son can reach the danger point before the haz­ard can be con­trolled, the guard is use­less. The res­ult­ing situ­ation may be worse

Canada

Emergency Stop – What’s so confusing about that?

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Emergency Stop on machine console
This entry is part 1 of 16 in the series Emer­gency Stop

I get a lot of calls and emails ask­ing about emer­gency stops. This is one of those decept­ively simple con­cepts that has man­aged to get very com­plic­ated over time. Not every machine needs or can bene­fit from an emer­gency stop. In some cases, it may lead to an unreas­on­able expect­a­tion of safety from the user, which can lead to injury if they don’t under­stand the haz­ards involved. Some product-spe­cif­ic stand­ards