Machinery Safety 101

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

Disconnect Switch with Lock and Tag

The question of lockout and the use of safety PLCs as a means to meet the lockout requirements comes up more and more frequently these days. Can Safety PLCs be used for lockout? Safety professionals don’t always agree on this controversial topic! During the Free Safety Talks that we did with Schmersal Canada and Franklin Empire,…

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Safe Drive Control including Safe Torque Off (STO)

Graph illustrating STO Function

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

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 © 2017-2020Acknowledgements: As cited.Some Rights ReservedOriginal content here is published under these license terms: X License Type:Non-commercial,…

ISO 13849-1 Analysis — Part 8: Fault Exclusion

Post updated 2019-07-24. Ed. Fault Consideration & Fault Exclusion ISO 13849-1, Chapter 7 [1, 7] discusses the need for fault consideration and fault exclusion. Fault consideration is the process of examining the components and sub-systems used in the safety-related part of the control system (SRP/CS) and making a list of all the faults that could…

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ISO 13849-1 Analysis — Part 7: Safety-Related Software

General architecture model of software

Post updated 2019-07-24. Ed. Safety-Related Software Up to this point, I have been discussing the basic processes used for the design of safety-related parts of control systems. The underlying assumption is that these techniques apply to the design of hardware used for safety purposes. The remaining question focuses on the design and development of safety-related…

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