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Old October 9th, 2006, 06:31 PM   #1
plcnewbie
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LOTO question

I have what may seem like a dumb question to a lot of your guys but here goes.
We have a LOTO system in place and depending on what you are working on decides what you lock out. But, The cabinets with the switch on the doors puzzle me. I am wireing up a 480 drop off of one of them now and if I lock the door then I can not open it to work. If I open it then put the lock on the right place it does nothing for me since all one has to do is turn the knob with a pair of grips, and power is back on regardless of the lock being in place.

Anyone else have this situation and what do you do about it?
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Old October 9th, 2006, 06:55 PM   #2
geniusintraining
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Where is the cabinet power coming from? can you lock it out at the bucket feeding the cabinet?

Also the majority of the mains that I have seen, you can lock out at the main, not just on the outside of the cabinet....so what I have done, is open the cabinet and place the lock on the switch...not on the handle on the door
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Old October 9th, 2006, 07:06 PM   #3
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Some of the mains give you that option and some do not have it. I wonder why then they put the switches on the doors at all.Maybe we need to rethink some of the procedures on a few of our machines??
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Old October 9th, 2006, 07:14 PM   #4
geniusintraining
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Just looked the ones that don't, the LOTO procedure points to the main that is feeding the cabinet

And yes, I am also not a fan of the twist lock on the door style either
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Old October 9th, 2006, 09:47 PM   #5
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Our policy is to lock out the source breaker if work inside the cabinet needs to be done. Each cabinet gets it's own breaker in the source distribution panel.

Locking out the cabinet so a field device can be serviced can be done with the handle lockout point on the cabinet. But this is not a suitable lockout point for work inside the cabinet because of the issues you mentioned above.

The idea is that if working in the cabinet everything must be dead including the power feed.

On some of our machines, we've mounted a seperate lockable disconnect to the side of the cabinet, so the power feed can be locked out without having to run back to the source breaker.
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Old October 9th, 2006, 09:48 PM   #6
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We try to engineer around this. Some methods we use are:
1, Switch on the side of the cabinet, not on the door. Only works if there is room on the side, and no plans to ever mount another cabinet on that side
2, Mount the whole CB on the door. This way, when the door opens, the CB comes with it and can remain locked. The down side is that it is only feasible for small cabinets.
3, Separate door for the isolator, this is best for the larger sized feeds. You can work on everything except the CB/isolator. Down side is that this method is difficult to re-fit on a board, you generally have to buy a special board for this to work.
4, Tag out the open board. Once you have opened the board and switched off the power, put danger tags on the isolation handle and the isolator or CB. This is not as good as lock out, but it is leagle for situations where lock out is not practicable (in Western Australia).
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Old October 9th, 2006, 10:04 PM   #7
Jim Dungar
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There are some mechanisms that can be locked with the door open. Square D's 9421 line of breaker mechanisms is one style, I am not sure but I think the fusible ones from Ferraz are also.

NFPA 79 makes a statement suggesting(?) the lockout means to be independent of the door, so maybe they will become more common.
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