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S7-300 Distributed Safety programming

Created by: zombit at: 1/8/2013 4:48 AM (6 Replies)

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1/8/2013 4:48 AM	Rate (0)
zombit Posts: 16 Rating: (0)	Hello, this is my first post and my first project with siemens distributed safety, I have a very simple question: Do the safety F-applications blocks from the libraries need to be used in order to acheive safety category ratings? Or can standard logic be used in order to achieve the safety functionality? A simple emergency stop cat4 logic can easly be coded without the f-application block by using the direct safety inputs and safety outputs and some memory (F-DB) all within an F-LAD function. I have read through alot of the DS guides but I could not find answer. Thank you kindly, Dave
zombit Posts: 16 Rating: (0)
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1/8/2013 9:52 AM	Rate (0)
miami Platinum Member Joined: 8/31/2005 Last visit: 12/16/2025 Posts: 2198 Rating: (331)	Hello Dave, You don't have to use the blocks from the libary "distributed safety" and you can program all by yourself. But the provides blocks are tested and certificated. This will make it easier if you have to do the acceptence test of your machine.

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1/9/2013 5:23 AM	Rate (0)
zombit Posts: 16 Rating: (0)	thank you
zombit Posts: 16 Rating: (0)
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1/9/2013 12:20 PM	Rate (0)
Marko Bursic Posts: 1410 Rating: (154)	What is the purpose of F-system, than? I can also program e-stop function with normal PLC, but is not fail-safe. Programmable safety modules usualy have pre-programmedfeatures, you can choose from them, but you are not allowed to program yourself. The same rule is with F-system, if you don't use safety library then your system is an ordinary PLC, not fail safe, the customer would onlythink that it is.
Marko Bursic Posts: 1410 Rating: (154)
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This contribution was helpful to 1 thankful Users AutoGen_8836637

1/9/2013 1:09 PM	Rate (1)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 1/20/2026 Posts: 3054 Rating: (1062)	Marko Bursic ... if you don't use safety library then your system is an ordinary PLC, not fail safe I'm sorry Marko, but I need to disagree andthefollowing two threads which have more info on this: Simatic fails safe PLC what is the differnce between the functionality of a failsafe cpu and a normal cpu wich is programmed by failsafe method in LADDER for instance? In sums, miami is correct, you can use an F-CPU and program an E-Stop functionality without using the blocks from the safety library. In fact,even Siemens own AS-FE-I-007-V20-EN application example does NOT use FB215 "F_ESTOP_1"(which is useable for Stop category 0or 1)in it . @ zombit: Just like in the above example you would want to use FB216 "F_FDBACK" though to ease the programming of the contactor feedback monitoring (but then again, you can also choose to omit this FB and program the feedback monitoring yourself). Last but not least, plentymore very helpful Safety related Siemens examples can be found HERE. I hope this helps
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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This contribution was helpful to 4 thankful Users miami dchartier Marko Bursic thongbvt

1/10/2013 2:04 PM	Rate (0)
Marko Bursic Posts: 1410 Rating: (154)	Thanks fritz for your explanation, So in few words safety library is only a help library and is not mandatory. I couldn't understood why there is no SIL3/Cat4 e-stop function in that library or how to make it with use of other library elements, now I kno.
Marko Bursic Posts: 1410 Rating: (154)
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This contribution was helpful to 1 thankful Users fritz

1/14/2013 1:21 AM	Rate (0)
zombit Posts: 16 Rating: (0)	Thank you for the responeses, basically I should use the blocks when I can (for simplcity) but I am not required to do so as long as my logic behaves exactly the same as the requirements of the safety category. I have a uniqe case in my project where I am required to monitor the pulse counts from 4 safety proxs and 'trip' the system if the count difference between them has too much variation. (It is basically a lifiting platform with 4 screw lifts, one on each corner and the proxs are counting the screw threads.) From my understanding this will need some degree of custom logic to acheive. There are count up and count down functions I could use but there are no compare functions that I could find. Regardless some further logic is required to tie everything together. So I beleive I will just write my own logic within F-LAD to achieve this.
zombit Posts: 16 Rating: (0)
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