Resetting a Safety Circuit

[beanpole_ecc]

@timbert

so if i'm reading that right, my situation could be satisfactory as far as the risk assessment is in line with what is wired. i didn't know about the falling edge specification, that's good knowledge to know.

now for a little gray area. What if the e-stop button is a three state push latched pull momentary button with the pull portion the reset button for the safety circuit? we have a couple of those on our OEM machines and i always thought that as a little fishy. haha. This is a good thread. Learning a lot.

 

[Timbert]

now for a little gray area. What if the e-stop button is a three state push latched pull momentary button with the pull portion the reset button for the safety circuit? we have a couple of those on our OEM machines and i always thought that as a little fishy.

I've never actually encountered those switches but I have heard of them.

My understanding is that these are acceptable (as with everything, following a proper hazard analysis) provided that the 'reset' position is distinct from the 'run' position (and of course the latched 'activated' position).

As with most things related to safety, a lot of this comes down to what are any hazards presented by this method.