It is currently Wed Dec 13, 2017 7:58 am



Post new topic Reply to topic Go to page Previous  1, 2, 3
Author Message
ekstra   ara
 Post subject:
PostPosted: Thu Nov 05, 2009 5:28 pm 
Offline
Sparks Level

Joined: Thu Oct 18, 2007 7:10 pm
Posts: 250
Location: NW USA
TxEngr wrote:
I have been in contact with one of the members of the 70E Committee to help understand what their thinking was as to open door/closed door. His response helped me considerably in understanding why it is written the way it is. I’ll attempt to summarize his response here:

In the 2004 70E, the arc flash boundary applied only to exposed energized components. For the 2009 cycle, a number of proposals were made to change the limitation of exposed conductors. A lively debate ensued and the committee compromised to amend the definition of Arc Flash Hazard as found in Article 100. The key points are in the FPN No. 1 which added “…or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc.” It also added “Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.” The definition of Arc Flash Protection Boundary was changed and includes the phrase “When an arc flash hazard exists”.

It is his interpretation of the standard (and he is on the committee) that the determination of arc flash boundary applicability is left up to the user to determine “when an arc flash hazard exists”. In other words, there is no blanket rule that can be applied when there are no exposed energized components. The user must make a determination of the hazard.

His response was a great help to me in understanding this. It is very clear that when there is exposed energized conductors or circuit parts, an arc flash hazard exists and everything applies. Using his interpretation and the text of the code, if the enclosed equipment is being used under normal operating conditions and is properly installed and maintained, then it is not likely to pose a hazard. So what is normal? A circuit breaker in a panel has been designed to switch a load. It is my opinion that this is a normal operation and therefore does not pose an arc flash hazard. If no arc flash hazard exists, then PPE is not required. I may be interacting with the switch, but not in a manner outside of the design nor in a manner that should cause an arc. But if the switch is not moving properly and I have to use excessive force to move it, it is no longer a ‘normal’ operation. In that case, some PPE would be required. This thought process would then apply to any application. You evaluate the risk and hazard and make appropriate determinations.

The downside of this interpretation is that there is no clear singular set of rules that can be painted. Things have to be evaluated. Rules can be set for a given location or facility, but to make blanket statements about enclosed equipment operations really isn’t possible. A good solution might be to use the tables for closed door operations since they address the open door/closed door issue in the tables.

I apologize for the long post, but I felt the information provided by this committee member was important.


Thanks for the insight. The thoughts that go into these rules seems reasonable, yet so often the legalistic interpretation goes badly. I especially like the statement that things have to be evaluated, and that a circuit breaker switching a load is within it's design parameters. Perhaps you could suggest to your friend that some of this wording be included in the next write up. Your summary is helpful but the same content issued from an 'official committee' would even be more useful.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Nov 06, 2009 1:02 pm 
Offline
Sparks Level

Joined: Thu Jul 19, 2007 7:54 am
Posts: 201
Location: St. Louis, MO
Zog wrote:
Now here is the scary part, the defendant (Engineering firm) was found liable because the GF settings were not set to the minimum settings!!! The prosocution argued that the arc flash would have been limited if the setting were set to minimum.


Wow! There goes my goal of becoming a private consultant!
This kind of thinking just limits the available pool of resources by limiting it to those that are large enough to take on this kind of liability. It will do nothing to increase safety.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Dec 09, 2009 1:02 pm 
Offline
Sparks Level

Joined: Fri May 01, 2009 9:10 am
Posts: 73
Zog wrote:
OK, lets look at racking operations, HRC 4 for doors open or closed. But you are saying if you do the calculations instead of using the tables you would assume the door would contain the arc flash and not require PPE?? Is this what you are saying or am I reading this wrong?

Until the recent "arc rated" switchgear standard came along the was never any testing or designs doen for arc flash containment. The equipment was never designed to contain an arc flash, so it is silly to assume it would.


That is true for the MV metalclad equipment. How about the table for 600V Class MCC, SWBD or PNLBRD where Door Closed = Cat #0 and Open = Cat #1 which indicates the enclosure does provide some protection (at this voltage with this type of equipment).


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Dec 09, 2009 1:23 pm 
Offline
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
viper57 wrote:
That is true for the MV metalclad equipment. How about the table for 600V Class MCC, SWBD or PNLBRD where Door Closed = Cat #0 and Open = Cat #1 which indicates the enclosure does provide some protection (at this voltage with this type of equipment).


You are confusing the intent of the tables, they are risk based, not hazard based. The same equipment can have a HRC 4 LV (Switchgear racking operations) and a HRC 0 for operating the breaker with the door closed. The hazard is the same, both are for closed doors on the same equipment, the racking operation just has a higher risk.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Dec 10, 2009 6:39 am 
Offline
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
Here is a link to another thread for a new product, but the video is a good one to see for those people that think doors closed means no arc flash hazard.

http://www.arcflashforum.com/showthread.php?p=4187&posted=1#post4187


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Dec 14, 2009 1:08 pm 
Offline
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
Show them this

http://www.youtube.com/watch?v=exA0sHO-cZM


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Dec 25, 2009 12:44 am 
Offline
Sparks Level

Joined: Sat Nov 21, 2009 10:23 pm
Posts: 73
Location: Ohio
One issue that was not discussed is the ability of mangement to enforce a policy that the worker does not agree with. I have put hundreds of electricians into PPE, that is no easy task. We can talk all day about the technical aspects of arc flash, but, the biggest/hardest issue is getting the personnel into the PPE.

If I were to try and force those electricians into a zero-tolerance policy of using HRC#4 PPE when they were close to switchgear, I would lose a large percentage of those that are already using the PPE when working on exposed energized equipment. There may be perfect worlds somewhere, but, not in the electrical industry.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 48 posts ]  Go to page Previous  1, 2, 3

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2017 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883