kolyur
Lifetime Supporting Member + Moderator
I'd like to hear opinions about using safety I/O with pluggable connections. I'm referring to the IP67-style fieldbus modules with a number of M8 or M12 plugs that accept redundant signals from safety rated door switches, light curtains, etc. These are becoming available from a number of manufacturers, the 1732DS-IB8 is just one example.
The quick-disconnect aspect is certainly convenient from a wiring standpoint, but isn't it susceptible to tampering? The plugs are all keyed alike so there's no way to ensure that two cables aren't swapped--whether maliciously or accidentally. Yes this can certainly happen with normal pluggable I/O too but the result isn't a severed finger, just a little extra challenge for the troubleshooter. This would lead me to think that every input device wired to a single safety module would need to have the same function (such as four door switches that all trigger the same safety zone). But even with that precaution, swapping cables could cause incorrect indication on an HMI which may not be a direct violation but could certainly lead to confusion.
For those of you who have used these devices, how did you handle these issues? Safe application seems very limited. What am I missing?
The quick-disconnect aspect is certainly convenient from a wiring standpoint, but isn't it susceptible to tampering? The plugs are all keyed alike so there's no way to ensure that two cables aren't swapped--whether maliciously or accidentally. Yes this can certainly happen with normal pluggable I/O too but the result isn't a severed finger, just a little extra challenge for the troubleshooter. This would lead me to think that every input device wired to a single safety module would need to have the same function (such as four door switches that all trigger the same safety zone). But even with that precaution, swapping cables could cause incorrect indication on an HMI which may not be a direct violation but could certainly lead to confusion.
For those of you who have used these devices, how did you handle these issues? Safe application seems very limited. What am I missing?