Emergency Stop Procedures

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Alvaro Rodriguez

We would like to find definitions or standards (if any) on Emergency Stop procedures, as opposed to Normal Stop. Specifically we would like to address: - Clear definition - Priorities on Emergency Stops (Machine or People) ? - When should be used ? Any literature on this subject? Thanks in advance Alvaro Rodriguez REDES ELECTRICAS [email protected] Bogota - Colombia
 
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For machines in the USA E-Stops must be no further than 6 feet apart and require a separate action to reset. Usual implementation is have all the buttons normally closed in series and drop out a relay that supplies machine power; this would frequently also vent any pneumatic lines. People protection is most important! If on power removal, something will move to possibly cause injury then keep the power on that item. An example would be an overhead crane holding things with an electromagnet. There often are not even fuses in the magnet circuit. Separate action to reset requires manually resetting the E-Stop button AND actuating a Start or Reset button.
 
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(continuation) Also the E-Stop function requires direct physical opening of electrical conductors. This means switch and/or relay contacts. Not PLC logic or solidstate relays. regards Tom Gallant
 
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George Moore

For USA E-Stop requirements you state that:

"For machines in the USA E-Stops must be no further than 6 feet apart and require a separate action to reset. Usual implementation is have all the buttons normally closed in series and drop out a relay that supplies machine power"

Can you provide OSHA, NFPA, or other reference #'s that back up this information. I have researched OSHA, etc. and can find nothing with this detail. OSHA describes 'non-automatic' reset.

Do you believe that a separate action to reset can be the same switch that initiated E-Stop? Or should there be a separate E-Stop Reset switch or contact pair that is used for this action exclusively?

I would appreciate your insight on these items.

Thanks,
George Moore
[email protected]
 
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