Q & A: Can Safety PLCs be used for Lockout?

Questions about equipment lockout using safety PLCs are more frequent these days. Can Safety PLCs be used for lockout? Safety professionals don’t always agree on this controversial topic!

Can safety PLCs be used for lockout?

This hot question came up during the Free Safety Talks with Schmersal Canada and Franklin Empire, so I thought I’d cover it in a video. If you need specific help with an application like this, please contact Doug directly.

There is a lot to say, and in this video, I try to cover why Safety PLCs and Lockout don’t always mix well.


Ontario Regulation 851, Industrial Establishments

CSA Z432, Safeguarding of Machinery

CSA Z460, Control of hazardous energy — Lockout and other methods

ISO 13849-1, Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design

ISO 13849-2, Safety of machinery — Safety-related parts of control systems — Part 2: Validation

IEC 62061, Safety of machinery — Functional safety of safety-related electrical, electronic and programmable electronic control systems

IEC TR 62061-1:2010, Guidance on the application of ISO 13849-1 and IEC 62061 in the design of safety-related control systems for machinery

Questions? Leave a comment below or email Doug.

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3 thoughts on “Q & A: Can Safety PLCs be used for Lockout?

  1. Thanks Doug. Between talking with you last week and watching this video, I’ve learned a lot. Lol… Lost me on the math part, but, I understood the general concept of what you were trying to say. A very well done topic. Thank you!

    1. Hey Frank,

      Don’t worry – the calculations aren’t the heart of the story – the comparison between the reliability figures and the fact that CSA Z460 calls for lockout devices to be exclusively mechanical is the important part. Until there is sufficient real-world data on the application of hybrid devices with mechanical, electronic and software elements, we are not going to have enough information to know if these systems can be used in high-risk applications. Until then, a high level of mechanical reliability is required.

      Glad you found the video helpful. Let me know if you have any other questions!

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