I know that they are saying that, but I have not heard any explanation of facts that would validate the claim. It is one thing to make an assertion and a somewhat different thing to be able to explain in detailwhy it is true. My feeling is that they have not covered all of the failure modes that I have seen. So if they would like to place a really detailed article in Design News about the actual mechanism of why their combined system is safer I would certainly be happy to read it.
You're not alone with this skepticism, William K. Certainly for years it was unheard of to combine both functions on the same network. But the safety folks are saying these combined networks are safer than the old single-duty safety networks.
I keep seeing the claims that somehow safety functions and control functions all using the same processor can offer complete separation and 100% reliability. Of course there are a few hardware parts that are common to both of them and it is a challenge to imagine that if excessive enclosure temperature causes one part of the processor to lock up that the other part will continue to function as it should. And a power supply failure would probably shut the whole package down, as well. So while automation has become simpler and less expensive it does not make sense to go to those extremes of combining everything, even if it does reduce the initial prices.
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