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| 6/6/2019 7:23 AM | |
Joined: 2/4/2015 Last visit: 6/18/2024 Posts: 64 Rating:
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Dear all, I want to know what is special in Fail safe CPUs. Even we can set the desired outputs during plc failure in standard plc. Kindly clarify Regards Surendhar M ------------------------------------------------------------------------------------------ |
Last edited by: Jen_Moderator at: 06/06/2019 11:52:13New subject after splitting |
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| 6/6/2019 12:34 PM | |
Joined: 3/5/2014 Last visit: 8/5/2022 Posts: 5521 Rating:
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hi Surendhar_M, this manual shows you what safety engineering is about: SIMATIC Industrial Software Safety Engineering in SIMATIC S7 regards, |
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FCK WAR! |
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| 6/6/2019 1:31 PM | |
Joined: 9/23/2005 Last visit: 9/19/2024 Posts: 4705 Rating:
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Some basics from other manufacturer: https://literature.rockwellautomation.com/idc/groups/literature/documents/wp/safety-wp002_-en-e.pdf |
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Regards, |
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| 6/13/2019 6:40 AM | |
Joined: 12/9/2010 Last visit: 10/8/2022 Posts: 623 Rating:
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Hi Surendhar_M, I don't think it is possible to set outputs in PLC failure. Fail safe PLC measures/detects hardware problems in input switches or transmitters & then takes corrective action depending upon user configuration. There is nothing happening after Fail safe CPU fails seriously. |
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| 6/14/2019 5:16 PM | |
Joined: 5/30/2013 Last visit: 9/19/2024 Posts: 50 Rating:
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First of all, the actual CPU supports profisafe, simply explained it is a telegram with some extra functionality, e.g. a incremented number for each telegram making sure it is not lost or duplicated, plus some other features. The CPU will compile the safety code into two different machine codes. The PLC will then run both versions of the program and then compare the result. Then you have safety IO, for example DI where you can treat two channels as one (1oo2) additionally you have a signal rather than 24V running through the loop(s) to differentiate between short to 24v and logical high. Basically it is measures making sure the PFHD (probability for a dangerous failure pr hour) stays low and within the requirements. |
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