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Old November 20th, 2020, 04:26 PM   #16
L D[AR2,P#0.0]
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As there are no safety outputs (i.e. hardware Q safety ouputs) there is no data for the safety program to compare. I suggest you drop the idea of using the safety program unless you are going to add some safety hardware.
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Old November 20th, 2020, 05:28 PM   #17
ltwatters
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Quote:
Originally Posted by L D[AR2,P#0.0] View Post
As there are no safety outputs (i.e. hardware Q safety ouputs) there is no data for the safety program to compare. I suggest you drop the idea of using the safety program unless you are going to add some safety hardware.
The integrated outputs, Q0.2 and Q0.3, are being used independently to energize pilot solenoid valves which supply pressure to pneumatic valves with monitoring contacts on safety inputs I1.3 and I2.3 operating in 1oo1. If an output goes high and a valve is opened, the PLC will know and be able to react to it. I think this holds my outputs to a higher standard than if I used safety outputs and only had them switch simultaneously.

I'm not accounting for the possibility that Q0.2 and Q0.3 have any means to fail simultaneously without any means of stopping them, which may or may not hurt the achievable safety rating depending upon whether or not the S7-1212 FC can switch off it's integrated outputs to any degree of SIL.

Mind you, I'm not going for a legitimate SIL rating. I was given a budget of $9,999 to build a "fail-safe" system in a hazardous location (Class 1 Div 1). I'm just trying to minimize the probability of failure with what we could afford, and I'm probably not going to listen to advice which suggests I don't put the start and stop buttons in the safety program because I don't have safety outputs.
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