Energized work

[cornbread]

Had a interesting discussion at our last electrical safety committee about energized work and energized work permits. We have a project where we need to add a MCC bucket to AB line up. We were debating on how to shut the MCC down and one of our seasoned electricians spoke up and indicated he would prefer to put the bucket in hot as going thru the shutdown would expose him to additional risk. He elaborated on the number of disconnects and breakers needed to be opened to accommodate this work and each action was an additional risk for the electrician performing the work. Our SOP for installing a bucket hot requires cat 4 gear & two electricians. In his opinion this was safest approach.

Curious how others feel about this? Is this a valid reason to work the MCC hot? Looking forward to reading your comments.

 

[wbdvt]

First I would start with the reasoning behind doing the work energized versus de-energized. Is the reasoning solid enough to withstand the scrutiny of an OSHA investigation and/or any legal litigation if something happened that caused serious injury? What if the MCC is severely damaged resulting in extensive downtime and cost? Can the business support either of those scenarios?

Secondly, does the manufacturer of the MCC have any statements in the manual for the MCC about installing a bucket on an energized bus?

Thirdly, I don't know how suiting up in a 40 cal suit can be safer than shutting the MCC down and LOTO. Maybe there is an extensive procedure to de-energize the MCC but is that not the safer approach. From the little that is in your post, is not the risk very high and the hazard great for installing the bucket in an energized MCC versus low risk, low hazard by doing it de-energized.

 

[brian john]

Well I am not familiar with ABB MCC's but I will say this, if I had to list the reasons for blow ups we have been called on for investigation and repairs where an electrician or maintenance man was the direct cause of the blow up, installing buckets in an MCC and installing Busway switches top the list.

Opening switches or circuit breakers IF PROPERLY MAINTAINED were very low on the list.

Your electrician IMO is wrong and could be dead wrong, foolish, naive and close to dumb.

 

[kwired]

one of our seasoned electricians spoke up and indicated he would prefer to put the bucket in hot as going thru the shutdown would expose him to additional risk. He elaborated on the number of disconnects and breakers needed to be opened to accommodate this work and each action was an additional risk for the electrician performing the work.

Sure there is risk in those additional tasks but doesn't installing the bucket while energized give you a greater chance of a high release of energy if something goes wrong? And on top of that a worker may be even closer to the point of origin of blast while installing the bucket then when operating a switch intended to open/close a circuit.

 

[Fulthrotl]

Well I am not familiar with ABB MCC's but I will say this, if I had to list the reasons for blow ups we have been called on for investigation and repairs where an electrician or maintenance man was the direct cause of the blow up, installing buckets in an MCC and installing Busway switches top the list.

yup. what he said, up there.... ^^^

turning off gear and turning it back on, ten times over,
is not risk accumulative like radiation exposure.

faulting a bus plug or a bucket insert isn't accumulative
either. i was at a convention center, doing a trade show,
when an electrician attempted to hang a disconnect on
a bus duct.... backwards. A phase and ground were reversed,
iirc. i do remember we heard it when it went off. it was pretty
hard to figure out how he got that asymmetrical bus tap to fit,
but by god, he did.

you could hear wires feeding the bus duct rattling in the pipes.
sounded like beating on the conduit with a hammer. impressive,
500 MCM copper beating up and down like that.

the electrician had shut off the bus to hang the bucket. it faulted
when he turned it back on. woulda been a different outcome if
he'd a been on the other end of this.

 

[petersonra]

I think he is just wrong.

There are old electricians.

There are bold electricians.

There are no old, bold electricians.

Now personally, I do not see how there is much risk if the main on the MCC is opened and someone installs or removes a new bucket 3 sections away with the main open.

 

[big john]

The way I see it: Breakers have the risk of mechanical failure.

Hot bucket swaps have the risk of mechanical failure plus the even greater risk of operator error.

There's no way that the least-hazardous of those tasks is the hot bucket swap.

I don't know why he's volunteering to do it, that's really poor judgment, in my opinion.

 

[Jraef]

Well I am not familiar with ABB MCC's but I will say this, if I had to list the reasons for blow ups we have been called on for investigation and repairs where an electrician or maintenance man was the direct cause of the blow up, installing buckets in an MCC and installing Busway switches top the list.

Opening switches or circuit breakers IF PROPERLY MAINTAINED were very low on the list.

Your electrician IMO is wrong and could be dead wrong, foolish, naive and close to dumb.

Bingo. Statistically, something like 90% of all arc flash incidents involving MCCs take place as the result of removing or installing buckets when hot. This is the reason A-B and Eaton have come out with units that can be disconnected from the bus (and reconnected) without opening the doors. The incidence of disconnects or breakers exploding is minuscule by comparison, and having that not be contained by the closed door is even more rare. His reasoning is statistically flawed.

If your A-B MCC was made after 2012, you can buy the buckets with the SecureConnect option and not need to shut down the MCC to install them. If they are older than that you can't use them, the slot opening in the bus bar barriers must be longer because the stabs operate in an arc instead of going straight in. They started using the longer slots in Nov. 2011.

 

[zog]

You could use a remote bucket extractor and do it hot while outside the AFB.

 

[mayanees]

Incident Energy level?

Incident Energy level?

It's probably impossible to rationalize that de-energizing is more dangerous than working it hot, which is the 70E criteria for hot work. But it would only get scrutinized if there was an incident.
I think the most important information to have on hand to assure that working it hot doesn't turn into an investigation is the incident energy (IE) level for an awareness of the hazard. If it's a 480V, 1600-amp MCC that's 30 feet from a 3000 kVA transformer then the IE level will be prohibitive and likely not even within the effective range of your Cat 4 suit.
But if it's an 8-calorie IE level and your guy's wearing a 40 cal suit, then even in the event of an arc flash the electrician walks away unscathed. And to go further down that path, is there an upstream breaker that can act as a maintenance switch for Instantaneous reduction and provide a reduced IE level during the bucket installation? That could take the IE level down to as low as a couple calories.
Again for emphasis though I rewrite - I don't think you'd be able to avoid OSHA fines if an incident occurred that they were called in to investigate because 70E prohibits energized work unless it's more dangerous to de-energize.

 

[cornbread]

Appreciate the feedback. I was taken aback when the discussion came up. Typically its the production folks that don't want to shut anything off .. surprised to hear the electrical guys lobbying for hot work.

You guys rock!