Control Functions

Interlock Architectures – Pt. 1: What do those categories really mean?

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Basic Stop/Start Circuit
This entry is part 1 of 8 in the series Cir­cuit Archi­tec­tures Explored

In 1995 CEN pub­lished an import­ant stand­ard for machine build­ers – EN 954 – 1, Safety of Machinery – Safety Related Parts of Con­trol Sys­tems – Part 1: Gen­er­al Prin­ciples for Design. This stand­ard set the stage for defin­ing con­trol reli­ab­il­ity in machinery safe­guard­ing sys­tems, intro­du­cing the Reli­ab­il­ity cat­egor­ies that have become ubi­quit­ous. So what do these cat­egor­ies mean, and how are they applied under the latest machinery stand­ard, ISO 13849 – 1?

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