Understanding Safety Functions: the start/restart function

Car engine start/stop button

After the safety-related stopping and the reset functions, the start/restart function is the next most common. Without a start/restart function, there is no way to make the machine do what it’s supposed to do. If you’re designing a machine control system, you need to understand this function.

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ISO 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.

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ISO 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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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 to design 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 software that…

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ISO 13849-1 Analysis — Part 6: CCF — Common Cause Failures

Post updated 2019-07-24. Ed. What is a “Common Cause Failure”? There are two similar-sounding terms that people often get confused: Common Cause Failure (CCF) and Common Mode Failure. While these two types of failures sound similar, they are different. A Common Cause Failure is a failure in a system where two or more portions of the…

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