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 Post subject: Equipment inspection/investigation
PostPosted: Thu Nov 18, 2010 10:40 am 
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What are your views regarding inspecting energized equipment? We had a discussion the other day and I was in the minority. We needed to verify some fuse information in a disconnect that served a non-emergency piece of equipment. The question is - can we open the energized disconnect and get this information and still be compliant with 70E? Thanks


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PostPosted: Thu Nov 18, 2010 10:45 am 
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100questions wrote:
What are your views regarding inspecting energized equipment? We had a discussion the other day and I was in the minority. We needed to verify some fuse information in a disconnect that served a non-emergency piece of equipment. The question is - can we open the energized disconnect and get this information and still be compliant with 70E? Thanks


Wearing the proper PPE you can.


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PostPosted: Thu Nov 18, 2010 11:44 am 
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Zog --- wouldn't this be putting you into an electrically "unsafe" working condition? You would be exposing energized parts and not be "testing & troubleshooting"

Thanks for any additional input.


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PostPosted: Thu Nov 18, 2010 4:13 pm 
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You may only work live if de-energizing is:

-Infeasible due to design and operational limitation
-de-energizing would result in additional hazards

Since de-energizing the disconnect to verify fuse info with power off is not infeasible and does not result in additional hazards, it shall be placed in electrical safe working condition, and then you may use a flashlight to find the fuse info. you need, thats if you want to be compliant with the standard ... but it might not be practical in industry, for instance when we collect information for an arc flash study we typically wear appropriate PPE and open panels, since we're not interacting with live parts and just observing it shouldn't be a problem


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PostPosted: Fri Nov 19, 2010 6:27 am 
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Mahan

Your interpretation is how I see it but as I stated many others disagree. It would make life a whole lot easier if we would change our rules in this area but until someone higher on the totem pole puts it in black and white I will probably continue with following the letter of the law "as I see it".


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PostPosted: Fri Nov 19, 2010 8:17 am 
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Even if you de-energize at the source you still need to wear the proper PPE to verify that the equipment is de-energized. Either way you are opening the disconnect wearing the proper arc flash & shock protection. I would think it's reasonable to check the fuse sizes without de-energizing. Now if you had to rotate a fuse within the holder to read the information I would tend to de-energize first.


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PostPosted: Fri Nov 19, 2010 8:32 am 
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Your are Interacting with the Switch

NFPA 70E defines an Arc Flash Hazard

Arc Flash Hazard. A dangerous condition associated with
the possible release of energy caused by an electric arc.
FPN No. 1: An arc flash hazard may exist when energized
electrical conductors or circuit parts are exposed or when
they are within equipment in a guarded or enclosed condition,
provided a person is interacting with the equipment in
such a manner that could cause an electric arc. Under normal
operating conditions, enclosed energized equipment
that has been properly installed and maintained is not likely
to pose an arc flash hazard.

Interacting is the key word. Opening a door of the disconnect switch is interacting.

_________________
Robert Fuhr, P.E.; P.Eng.
PowerStudies


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PostPosted: Fri Nov 19, 2010 11:55 am 
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100questions wrote:
Zog --- wouldn't this be putting you into an electrically "unsafe" working condition? You would be exposing energized parts and not be "testing & troubleshooting"

Thanks for any additional input.


Like I said, you still need to wear the PPE required by either your study or the tables. For using the tables 2 levels are required, the first for opening the door and the second for the visual inspection part. Both are listed tasks in the tables. But neither opening the door or doing the visual inspection meet the 70E definition of "Working (On energized conductors or circuit parts)" therefore you do not need to justify doing it energized or use an EEWP (This is specifically listed as an exception130.1(B)(3).

One could argue that opening a switch/breaker, opening the panel and testing for absence of voltage is actually a higher risk than just opening the panel and looking at the marking on a fuse without touching anything.


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PostPosted: Fri Nov 19, 2010 12:58 pm 
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I have seen the light-----

Everyone - thanks for the input. I see the exception in black and white.

ZOG - Thanks for pointing it out.


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PostPosted: Fri Nov 19, 2010 3:18 pm 
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Robertefuhr wrote:
Interacting is the key word. Opening a door of the disconnect switch is interacting.


No, it is not as simple as a "key word".

"Interacting...in such a manner that could cause an electric arc... "is the key phrase.

Simply interacting with equipment may not be sufficient to be a risk. Your interaction must be capable of causing an arcing fault.

This 'not causing an arc' rational is part of what lets us plug and un-plug equipment (a routine activity not even addressed by the task tables). It is also what allows us to have overhead uninsulated conductors feeding our facilities.

One could, and many do, argue that the routine operation of a properly applied and maintained switch or breaker is not "sufficient to cause and arc".


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PostPosted: Fri Nov 19, 2010 4:33 pm 
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JBD wrote:
One could, and many do, argue that the routine operation of a properly applied and maintained switch or breaker is not "sufficient to cause and arc".


Outside of a safety related system at a nuclear power plant find me a breaker properly maintained.


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PostPosted: Sat Nov 20, 2010 10:55 am 
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JBD wrote:
No, it is not as simple as a "key word".

"Interacting...in such a manner that could cause an electric arc... "is the key phrase.

Simply interacting with equipment may not be sufficient to be a risk. Your interaction must be capable of causing an arcing fault.

This 'not causing an arc' rational is part of what lets us plug and un-plug equipment (a routine activity not even addressed by the task tables). It is also what allows us to have overhead uninsulated conductors feeding our facilities.

One could, and many do, argue that the routine operation of a properly applied and maintained switch or breaker is not "sufficient to cause and arc".


I respectfully disagree with your interpretation of interacting. Things break! As a field engineer and power study engineer, I have seen many loose connections, parts and pieces in equipment that have caused an arc flash accident. You never know if when you open that cover or operating that breaker, that a unsecured part can fall in the energized section and cause an Arc Flash. I do not open any covers or close any breakers without wearing my PPE. Metal Covers on electrical equipment will not protect you from arc flash. They simply blow open or blow off.
Always wear your AF and Shock PPE when interacting with electrical equipment!!!

_________________
Robert Fuhr, P.E.; P.Eng.
PowerStudies


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PostPosted: Sat Nov 20, 2010 11:01 am 
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Zog wrote:
Outside of a safety related system at a nuclear power plant find me a breaker properly maintained.


The proper maintenance for a thermal magnetic breaker is simply mechanical operation (times per year depends on the breaker) as long as it does not interrupt fault current near its AIC rating. So a breaker that is used as a bi-yearly 'isolating' disconnect and has never interrupted a current greater than its short time rating (i.e. <12X) would be 'properly maintained'.


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PostPosted: Sat Nov 20, 2010 11:24 am 
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Robertefuhr wrote:
I respectfully disagree with your interpretation of interacting. Things break! As a field engineer and power study engineer, I have seen many loose connections, parts and pieces in equipment that have caused an arc flash accident. You never know if when you open that cover or operating that breaker, that a unsecured part can fall in the energized section and cause an Arc Flash. I do not open any covers or close any breakers without wearing my PPE. Metal Covers on electrical equipment will not protect you from arc flash. They simply blow open or blow off.
Always wear your AF and Shock PPE when interacting with electrical equipment!!!


Things do break, and tested devices do fail, therefore we should consider that no protective device will ever function correctly.

Parts that are loose indicated improper maintenance.

I have not said, and do not mean to suggest, that metal equipment covers will protect you from an arc flash.
I have simply said that not all interaction will "cause an electric arc".

A maintenance person comes up to an operating motor and wants to change a belt on it. They stop the motor using the controller, now they want to operate, open, the properly maintained and applied LOTO disconnect, is this interaction likely to cause an electric arc? After they change only the belt, they again want to operate, close, the LOTO, is likely to cause an arc?

A building HVAC Motor Control Center is located 5ft away from a machine operator's work station, the AFB is labled/listed as 6ft. This operator never interacts with this MCC. However, the motor starters within the MCC regularly turn on-and off as required by a remote building automation controller. Is PPE required for the operator?


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PostPosted: Sat Nov 20, 2010 11:41 am 
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JBD wrote:
The proper maintenance for a thermal magnetic breaker is simply mechanical operation (times per year depends on the breaker) as long as it does not interrupt fault current near its AIC rating. So a breaker that is used as a bi-yearly 'isolating' disconnect and has never interrupted a current greater than its short time rating (i.e. <12X) would be 'properly maintained'.


Molded case, yes. I always think power breakers, just my mindset.


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PostPosted: Sat Nov 20, 2010 3:20 pm 
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Zog wrote:
Molded case, yes. I always think power breakers, just my mindset.


And yet, molded case breakers are the predominant type in non-utility industry. The majority of PPE and power system questions I deal with, on a daily basis, do not involve 'power breakers' or 'switchgear'.


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PostPosted: Sun Apr 10, 2011 2:14 pm 
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Lets say there is a 120v relay circuit or a PLC I/O rack located in an MCC bucket (no 480v). The MCC has a Cat#3 rating. What PPE would be necessary to open the door of this bucket?

I believe that each facility could address that question with a risk asessment mentality and come up with a documented risk level to be applied to the hazard. I would call that task an extremely low risk task and reduce the PPE necessary to perform it.

The same risk based mentality can be applied to thermograpic scans of a bucket as well as other tasks that are necessary in the course of maintanance, etc.


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