machine safety plugs

[joe0072]

My company wants me to install a pull plugs to disable the controll on machines at work,so the operators can pull the plug and workon their machines .The plugs have 2 terminals. They also want me to wire them into the E-stop circuit is this legal?

 

[jim dungar]

If the task the operators are performing requires an actual LOTO action, then simply opening the control circuit is not acceptable.

If their task requires them to simply "turn off" the machine, then unplugging the control circuit should be allowable.

 

[S'mise]

Yes, I've seen interlock switches like that used in the master control circuit circuit lots of places. As long as there is e-stop buttons used (in series) also.

 

[S'mise]

But that does not mean that they don't have to follow lock-out/tag policies.

 

[RHJohnson]

Just opening the control circuit is not acceptable. I would not recommend working on anything that has not had the main power opened.
Case in point: This was a terrible accident...probably 30 years ago...several men were lining a ball mill - long cylindrical tube with wear plates on the inside, and filled with ball mills.
Picture this - the ball mill is 50' long and 6' diameter, the ball mills are cast iron about the size of a soft ball when new, I'm not sure what size the wear plates are, but they are good sized and heavy.
3 men were in the ball mill working, the start stop station was opened and locked out. It was raining very hard outside, water ran down the wall and managed to enter an enclosure with the control circuit wiring, shorting it out and allowing the ball mill to start, the motor - 2300 vac and 200 hp started up - it actually ran for a couple minutes before someone saw what happened and managed to kill the power. True story - I worked for the same company. You have to make it safe....

 

[S'mise]

Is it leagal to install them? According to NFPA79, Yes it is. But OSHA requires further actions (lock-out) before working on the machinery.