# Pull e-stops



## chrisfnl (Sep 13, 2010)

So here's an interesting safety issue...

Saw a number of mushroom head e-stops that had been rewired from push to pull to prevent accidental stops...

The first serious safety issue is that there was a mix of push and pull stops in the location, and they weren't even so much as labelled... If you pushed and it didn't stop, next you tried pulling.

The second serious issue was discovered during cold weather... Many of these e-stops were located outside, and the enclosures were prone to leakage and/or condensation.

As a result, the contact blocks were damp, and in cold weather, that dampness turned to ice... 

When the e-stop was pulled out, the ice in the contact held the contacts in place, as a result, the e-stop didn't work... 

Normally not an issue with any of the other push buttons on the control station, because pushing the button was enough to over come the ice, but because the e-stops were holding the contacts in, the only thing pushing against the ice was the contact block spring.

Rather terrifying situation (luckily discovered during a pm, not during an actual emergency)


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## emtnut (Mar 1, 2015)

Requirements are in the OHSA.
It HAS to be push/lock.
I'd suggest changing them back the way they were intended to be used:whistling2:


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## CADPoint (Jul 5, 2007)

Right, but this is Canada and up there it's HCSA


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## chrisfnl (Sep 13, 2010)

They had, for all practical purposes, an unlimited maintenance budget, why they couldn't just order guards, I have no idea.

I have no idea what hcsa is, but safety regulations may fall under provincial or federal regulations, depending on the nature of the worksite.


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## backstay (Feb 3, 2011)

Maybe post in the Canadian Section? In the power house all the E-stops were pull to stop.


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## chrisfnl (Sep 13, 2010)

It's not canadian legal that I know of, though there may be no specific regulation against it, it was someone's "bright idea".

Just something to be aware of if anyone else gets the same "bright idea"


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## dawgs (Dec 1, 2007)

I would find out the code. If you need to change them back, just get the guards to go around them. As far as the contacts icing up, you must be getting differential air within the conduit to make the moisture. Seal all conduits between buildings and at each penetration. If it continues, install larger enclosures with heaters in them. There's no price in safety.


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## chrisfnl (Sep 13, 2010)

They're not my problem any more, but just something to be aware of. 

Not an issue with condensation, installed outdoors, issue with environmental conditions. 

Rain, snow, and hurricane force winds are a "normal" day. 

Nema 4x is only water resistant at best in those conditions.


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## glen1971 (Oct 10, 2012)

Been on a few sites that are pull buttons.. They are labelled as such and it is covered in their on site orientation.. Avoided accidental contact and plant shut downs... 
Some engineers used to spec momentary contacts for them, but found that when the winds slammed doors closed, they'd be shutting down.. Those usually got changed...
Ran into a few that were regular light switches.. They may have been labelled when installed, but that faded or was missing over time.. A friend of mine thought he'd be helpful and "shut off the car plugs" with the switch at 4:25 one night... He found out right away what the switch did...


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