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Explanation of failsafe concept

Created by: mqueroco at: 8/4/2016 2:37 PM (5 Replies)

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8/4/2016 2:37 PM	Rate (0)
mqueroco Posts: 9 Rating: (0)	Hello, I've been trying to find some information about the failsafe concept and its applicactions, but I'm not able to find anything that can give me even a faintest description of what a failsafe CPU or module really is and what is the difference between a standard or a failsafe module. So far I've guessed that failsafe is used to say that the speciffic controller or module has been desgined in a way that provides higher durability, but first, I don't know if this is 100% true and if there are other additional improvements. For example, when I first heard of this, I thought it provided safety meassures as to how the system would behave in case of a problem (if the supply power went off, there could be a predefined state in which to set the outputs for example). I would be grateful if someone could give me a better insight on this topic. Thanks a lot in advance. Miguel
mqueroco Posts: 9 Rating: (0)
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8/4/2016 2:59 PM	Rate (1)
ChristophD Grandmaster Joined: 5/12/2006 Last visit: 11/14/2024 Posts: 22452 Rating: (3030)	Hi, here a actual topic (2days ago) with same question: https://support.industry.siemens.com/tf/ww/en/posts/153073/ Hope this help Regards Christoph

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8/4/2016 3:09 PM	Rate (1)
mopS04 Platinum Member Joined: 3/5/2014 Last visit: 8/5/2022 Posts: 5521 Rating: (1054)	hi, Failsafe is a certified system. When you use it right you have the guarantee that the signals will be captured processed and operated right and safe. When the system detects a manipulation, or a module won´t work right, the corresponding modules will be passivated. have you seen this discussion: Simatic fails safe PLC also this manual could be helpful: SIMATIC Industrial Software Safety Engineering in SIMATIC S7 If you need detailed information don´t hesitate to ask, hope this helps, regards,
	FCK WAR! Be nice!
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8/4/2016 3:18 PM	Rate (0)
mqueroco Posts: 9 Rating: (0)	Thanks for the references. I tried looking in the forum before posting this but I couldn't find anything useful. I'll have a look at all the documentation and answers and hopefully it should be enough to clarify everything. Yours, Miguel
mqueroco Posts: 9 Rating: (0)	Last edited by: AutoGen_5140795 at: 8/4/2016 3:19:21 PM
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8/5/2016 1:06 AM	Rate (0)
mqueroco Posts: 9 Rating: (0)	Hello again, I've been reading the posts you both linked and they have been of uttermost help. Nevertheless, I still have a question concerning the "safe state" into which the CPU is put in case of failure. Is it for example possible to predefine a default value for the state of a DO in case of failure -so that for example, some DOs change to an OFF state (or logical 0) whereas others can be set to an ON state (logical 1)- ? Or does this failsafe concept only involve the methods in which the processing and computation of the program is made in order to limit the impact of a possible failure not related to a power outage but of a communication failure for instance? I hope I made myself clear with the questions. Yours, Miguel
mqueroco Posts: 9 Rating: (0)
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8/5/2016 7:55 AM	Rate (1)
mopS04 Platinum Member Joined: 3/5/2014 Last visit: 8/5/2022 Posts: 5521 Rating: (1054)	hi mqueroco, you have to define what the fail-safe value is, and what the module has to do if there is a CPU-Stop Have a look to the assignable parameters of a F-DO-module in following manual, e.g. page 155. SIMATIC Automation System S7-300 ET 200M Distributed I/O Device Fail-safe signal modules hope this helps, regards,
	FCK WAR! Be nice!
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