Update: Things have changed a bit since this post was first published in 2021. There are now some safety-rated HMIs available from big controls companies like Siemens, so if you are considering this approach, consult with your controls vendor to see if their HMIs can meet the requirements of ISO 13849-1. Ed. – 2022-05-10 Question: Can…
Read MoreUsing Form C relays in safety circuits
I recently had a discussion with a colleague who wanted to know if it was OK for a design to include a form C relay in an e-stop circuit. You might recall that e-stop functions are required to meet at least PLc/SIL1 requirements [1], [2]. It’s important to remember that PLc/SIL1 can be met using…
Read MoreSafe Drive Control including Safe Torque Off (STO)
Safe Drive Control, including STO Motor drives are everywhere, some with Safe Torque Off (STO) capabilities and many without. 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 have given machine designers unprecedented capabilities when compared…
Read MoreISO 13849-1 Analysis — The 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.
Read MoreISO 13849-1 Analysis — Part 8: Fault Exclusion
Post updated 2019-07-24. Ed. Fault Consideration & Fault Exclusion ISO 13849-1, Clause 7 [1, 7] discusses the need for fault consideration and fault exclusion. Fault consideration is examining the components and sub-systems used in the safety-related part of the control system (SRP/CS) and making a list of all possible faults. This is a non-trivial exercise!
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