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Deference Between Fail safe & Standard Systems

Created by: Walid Elshazly at: 6/19/2013 12:40 PM (5 Replies)

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6/19/2013 12:40 PM	Rate (0)
Walid Elshazly Posts: 100 Rating: (0)	What is the Deference Between Fail safe & Standard Systems in depth ? Also , need some Documents to explain that , and how to select , as i know Fail Safe mostly be used in ESD systems
Walid Elshazly Posts: 100 Rating: (0)
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6/19/2013 1:15 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 9/16/2024 Posts: 12282 Rating: (2684)	Hello Walid; Basically Siemens Safety PLCs run a parallel Safety program in the F-CPU, on top of the "regular" program. It consists of F-blocks, controlling F-IO, and it is compiled separately from regular functions. S7-300F CPUs require a software package named Distributed Safety. S7-400F (or HF) CPUs require a special F-Safety programm, written in CFC. See the following discussions and manuals to get a feel of the extent of the safety application: Simatic s7 failsafe difference b/w failsafe(F),fault tolerant(H) and FH module Manuals on Distributed safety (with S7-300F CPUs) S7 Distributed Safety Getting Started SIMATIC Industrial Software S7 Distributed Safety - configuring and programming Manuals on S7-400HF (with S7-400H requires CFC programming) Product Information S7 F Systems V5.2 SP4 SIMATIC Industrial Software S7 F/FH Systems - Configuring and Programming Hope this helps, Daniel Chartier

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6/20/2013 11:41 AM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi Well what dchartier is correct. you will have to select the system according to the application. In general Standard system will execute the logic and given the ouput. In case of Fail safe system during failure your system is tasked with safe shut down of the system. fail safe devices such as a safety relays or safety PLCs, which in themselves are certified safe subsystems, should only ever fail to a safe state. That is if a system has number of failure and even then is able to maintain a safe state is a fail safe system. In normal system your failure of even one component may cause the failure of the entier system. If your system is used as ESD system then you must ask the customer about the Safety audit report and other documents as you will be requried with this during certification. You have to ask your customer about Hazard and Risk analysis documents as this will be required for your design of your system. Further more you will have to sit with the customer about the Software logics that need to be taken care of.
	Jazz
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6/22/2013 4:52 PM	Rate (0)
DS SURESH KUMAR Bronze Member Joined: 4/17/2012 Last visit: 8/30/2024 Posts: 474 Rating: (10)	thanks for the links dchartier Hello Walid; Basically Siemens Safety PLCs run a parallel Safety program in the F-CPU, on top of the "regular" program. It consists of F-blocks, controlling F-IO, and it is compiled separately from regular functions. S7-300F CPUs require a software package named Distributed Safety. S7-400F (or HF) CPUs require a special F-Safety programm, written in CFC. See the following discussions and manuals to get a feel of the extent of the safety application: Simatic s7 failsafe difference b/w failsafe(F),fault tolerant(H) and FH module Manuals on Distributed safety (with S7-300F CPUs) S7 Distributed Safety Getting Started SIMATIC Industrial Software S7 Distributed Safety - configuring and programming Manuals on S7-400HF (with S7-400H requires CFC programming) Product Information S7 F Systems V5.2 SP4 SIMATIC Industrial Software S7 F/FH Systems - Configuring and Programming Hope this helps, Daniel Chartier

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6/22/2013 6:19 PM	Rate (0)
Khaled_Ezzat Silver Member Joined: 9/7/2007 Last visit: 8/30/2023 Posts: 550 Rating: (61)	Hi Walid; All the previous posts bydchartierandTagoloverare perfect, but I have a small item to add. One of the main differences is the DIAGNOSTICS. in the Safety systems you will have a complete diagnostics starting from the CPU, communication between the CPU and remote I/O, the Interface Module, the I/O Module till the wire of the sensor/ transmitter/ valve, even so you can diagnose the field instruments. So you can all the time monitor what error happened where, when and the recommended action to take, all of this in a safe conditions (process wise) When you add redundancy to each component of the system you will increase the availability of the system.
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6/22/2013 8:55 PM	Rate (0)
Avinashkrishna Posts: 62 Rating: (4)	There are three different typoe of systems. 1. standalone system (something like one plc) 2. Fault tolerent system(where if the one system is fails another system will take care abt function) 3. Fail safe. 1. it is a system as per the tuv standard 2. where we have the emergency shutdown (like safe shutdown mean it should not harm any aspects. 3. voting concept(in this we can have the redunduncy in the instrument level.also voting sencer value like (1of 2,2 of 3,3 of 3) 4. Module Diag is more as compare to normal system 5.even we we have redundancy modules.
Avinashkrishna Posts: 62 Rating: (4)	Last edited by: Avinashkrishna at: 6/27/2013 11:55 AM
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