It is currently Mon Feb 19, 2018 2:57 am



Post new topic Reply to topic Go to page 1, 2  Next
Author Message
ekstra   ara
 Post subject: PPE While Gathering Arc Flash Data
PostPosted: Wed Mar 28, 2012 10:45 am 
Offline
Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 411
Location: Spartanburg, South Carolina
Getting trip unit settings for 480 V breakers in panelboards or MCCs often requires opening doors to read partially obstructed settings with small numbers. We find that it is usually impossible to read the settings while wearing a face shield. Before the arc hazard study is done, this could be done using the task tables (non-contact inspections outside the restricted approach boundary) with HRC 1 PPE, with safety glasses and hard hat only. After we have done the study, in many cases the IE is found to be above 4 cal/cm┬▓, so Cat 2 is required which includes a face shield.

If we had to go back and redo the study with the Cat 2 labels on the equipment, we would no longer have the ability to plead ignorance and use the task tables. How would we be able to do our work? Granted, in the cases where the IE turns out to be >4 cal/cm┬▓, the clearing time didn't meet the task table note requirements anyway, but we didn't know that before doing the analysis. If we had known it, we wouldn't have been able to gather the data required to do the analysis that shows that we can't gather the data to do the analysis.

How to solve this dilemma?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Mar 28, 2012 10:50 am 
Offline

Joined: Wed Jan 05, 2011 5:00 pm
Posts: 19
Only gather the data on deenergized equipment. :(


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Mar 28, 2012 11:14 am 
Offline
Sparks Level

Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
jghrist wrote:
Before the arc hazard study is done, this could be done using the task tables (non-contact inspections outside the restricted approach boundary) with HRC 1 PPE, with safety glasses and hard hat only. After we have done the study, in many cases the IE is found to be above 4 cal/cm┬▓, so Cat 2 is required which includes a face shield.

HRC 1 includes a faceshield, rated 4 cal/cm^2 or more (or a hood).


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Mar 28, 2012 11:36 am 
Offline
Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 411
Location: Spartanburg, South Carolina
Quote:
HRC 1 includes a faceshield, rated 4 cal/cm^2 or more (or a hood).

You're right. My bad. :mad: So how do you read trip unit settings with a face shield on? Not many plant managers will want to de-energize their equipment to get the data.

And even if you did de-energize the equipment, you would have to do a LOTO procedure with voltage measurements. This would make the time and expense of a study skyrocket.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Mar 28, 2012 11:53 am 
Offline
Sparks Level

Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
jghrist wrote:
So how do you read trip unit settings with a face shield on?

Photos.
Subcontractors and interns can be used in select jurisdictions only (not really).

Another question about fuses this time: if the fuses writing have been installed facing the back of the panel, how do you know the exact model (amp-wise) without de-energizing? Especially with bladed fuses.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Mar 28, 2012 12:10 pm 
Offline
Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 411
Location: Spartanburg, South Carolina
Photos could work. Be careful if you run into an arc flash detector, at least one without current supervision! :eek:

With three phase fuses, we've found that they are not all faced backward and you can usually see enough of the three fuses to piece together the necessary data.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Mar 29, 2012 3:28 am 
Offline
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 1877
Location: North Carolina
Read 70E carefully. Visual inspections do not involve interactions with the equipment and thus pose little to no arc flash hazard. Opening the doors themselves however is a different story. So you suit up, open all the doors you need, dress down, do the inspection, suit up again, close everything up. We do it all the time. "Dress down" usually means just stripping off the hood or face shield so it's no big deal.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Mar 29, 2012 5:44 am 
Offline
Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 411
Location: Spartanburg, South Carolina
If there is little or no risk, why do the task tables list "performing infrared thermography and other non-contact inspections outside the restricted approach boundary" as HRC 1 for both 480 V panelboards and MCCs? Opening hinged covers is HRC 0 for panelboards and HRC 1 for MCCs.

I suppose that the HRC 1 comes from the possibility of accidentally contacting exposed parts while doing the inspection. In reality, when doors are opened to expose trip settings, exposed parts are not in a place that can easily be contacted, so the real risk is low for a person qualified to identify and avoid the risk of contact.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Mar 30, 2012 3:29 am 
Offline
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 1877
Location: North Carolina
jghrist wrote:
If there is little or no risk, why do the task tables list "performing infrared thermography and other non-contact inspections outside the restricted approach boundary" as HRC 1 for both 480 V panelboards and MCCs? Opening hinged covers is HRC 0 for panelboards and HRC 1 for MCCs.


And we have come full circle again...70E Technical Committee, can you PLEASE insert FPN's explaining how you came to a conclusion of anything other than whatever the incident energy calculation says?

I can explain 0's. I can explain "fully rated". I flat out cannot explain the logic behind "reducing by 1, 2, or 3 risk categories" when there is no explanation of the logic and there does not appear to be any reduction in the severity of the arc flash, only reduction in the probability of occurrence. I would love for the Technical Committee to publish this because then I'd be applying it to my own risk assessments. Much of my metal enclosed 1 kV-38 kV equipment is HRC 3...if I reduce by even 1 category, the PPE gets significantly easier to deal with.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Sat Mar 31, 2012 10:37 am 
Offline

Joined: Wed Jun 24, 2009 8:47 am
Posts: 25
Location: Canfield, OH
This is no small issue. Wearing the sock hood and face shield holds in a lot of heat and tends to fog up the face shield as you are reading trip settings. I have to stick my face so close to the trip units this way I am at much more shock risk. I stopped wearing the sock hood even though the table has non-contact inspection as HRC 2 on 600V class switchgear.

Whenever you scroll through the settings on AC Pro or Ge MicroVersa Trip the cubicle door is open and I would argue that you are interacting with the equipment. Same thing for changing the battery on these units.

I also agree that the code does a good job of talking out of both sides of their mouth in 2012.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Sun Apr 01, 2012 4:17 am 
Offline
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 1877
Location: North Carolina
Whenever you scroll through the settings on AC Pro or Ge MicroVersa Trip the cubicle door is open and I would argue that you are interacting with the equipment. Same thing for changing the battery on these units.

OK, I'll concede the idea that an arc flash can happen. I'll even concede the idea that you can get struck by lightning in a cloudless sky, or that you can get wiped out by a meteor shower or a drunk driver.

Now, what is the likelihood of the scenario that you are describing happening? Is it greater than the risk while reading a meter while operating a meter stick? Is it greater than the risk of simply walking by while the equipment is in operation? Is it greater than the risk of an arc flash while operating the CB or fused switch with the doors closed and latched?

The risk assessment methodology in the annex is one of the most important sections in the whole document. It's too bad that nobody pays it any attention or respect. Thus the reason that it is useless in it's current form.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Sun Apr 01, 2012 7:55 am 
Offline

Joined: Wed Jun 24, 2009 8:47 am
Posts: 25
Location: Canfield, OH
Scrolling through the digital parameters makes me a little uneasy since I have had breakers trip will changing parameters (even when increasing a setpoint). The feeling when that happens is somewhat less than fun. Interacting with the digital trip units in any way is riskier than just reading the dials on other styles. There are also units where you have to remove a jumper to see the settings -delicate surgery in gloves depending on the breaker frame.

Since the annex is informative only it does get less respect. The code seems to prove the axiom that a camel is a horse designed by a committee.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 02, 2012 6:25 am 
Offline
Arc Level

Joined: Mon Jan 18, 2010 11:35 am
Posts: 445
Location: Wisconsin
FEC2 wrote:
Scrolling through the digital parameters makes me a little uneasy since I have had breakers trip will changing parameters (even when increasing a setpoint). The feeling when that happens is somewhat less than fun. Interacting with the digital trip units in any way is riskier than just reading the dials on other styles. There are also units where you have to remove a jumper to see the settings -delicate surgery in gloves depending on the breaker frame.

Since the annex is informative only it does get less respect. The code seems to prove the axiom that a camel is a horse designed by a committee.

Interacting in a manner to cause a trip is not the same as interacting in a manner that causes an arc flash.

What gets me is how many people totally ignore 110.3(F) which clearly requires a risk assessment when working in the arc flash boundary.
Annex F is offered only as an example.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 02, 2012 7:13 am 
Offline

Joined: Mon Apr 02, 2012 6:54 am
Posts: 7
Its called barriers, plexiglass, we have used it for years. We simple open the door install the plexiglass, we bolt it in place. remove our face shields and take the readings. We also use a magnifying glass with a light on it. Normally you need manufacture material as references for the settings. Long time or short time settings. We have used plexiglass for other barriers while working on energized parts of course rubbering up.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 02, 2012 7:31 am 
Offline
Sparks Level
User avatar

Joined: Tue Oct 26, 2010 5:00 pm
Posts: 115
Location: Maple Valley, WA.
We have found that using a lighted magnifying glass works very well even with an AF Face Shield on. You can vary the distance and it acts like a zoom lense. There are many styles, just make sure that it has a plastic case.

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


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 02, 2012 9:49 am 
Offline

Joined: Mon Apr 18, 2011 1:43 pm
Posts: 10
Location: Denver, CO
What kind of plexiglass do you use? I would be concerned that you might be introducing more potential material into an Arc Flash should you have one. Is there a blast rating you can look for?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 02, 2012 10:28 am 
Offline
Sparks Level
User avatar

Joined: Sun Jan 04, 2009 5:00 pm
Posts: 264
Location: Louisville, KY
There is no official "blast rating" on plexiglass but you could use ASTM F2676 (for arc blast blankets) to test the design or another standard like for arc resistant switchgear. ASTM F2676 uses a 15, 25 or 40kA blast in a vault but could be modified to include a full enclosure. I happen to think plexiglass would NOT work well. The AB Chance safety shield by Gary Guard is made of polycarbonate (totally different response than plexiglass) and their shield for meter pullers is made of the same. I'd try to test some on switchgear bolted on and see what happened. Polycarbonate would likely do fairly well. I did a test one time for a utility on aluminum, plexiglass and polycarbonate and the polycarbonate did as well as the AL in an ejected electrica arc.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 02, 2012 10:58 am 
Offline

Joined: Mon Apr 02, 2012 6:54 am
Posts: 7
every thermoplastic is flammable and if a catastrophic incident takes place Plexiglass would melt and burn just like any other plastic including your face shield and cabling. However, the strength properties from an initial blast by diverting it outweighs the other but has to be secured or bolted down, Sorry about that, I've used it for covers on panels with reach rods to reset equipment or quick inspection without opening or exposing the hazard and installation of equipment on DC systems only exposing the connection area. So... some of the plexiglass will have holes cut to insert tools to make adjustments. So is it perfect "NO" but I do recommend the UV glass clear and follow the hole cutting procedures or have it professional cut and reinforced it where the bolts go though. I've seen some ingenious applications using plexiglass and would take it over most blast shields used today.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Apr 02, 2012 12:02 pm 
Offline
Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 411
Location: Spartanburg, South Carolina
JBD wrote:
Interacting in a manner to cause a trip is not the same as interacting in a manner that causes an arc flash.

What gets me is how many people totally ignore 110.3(F) which clearly requires a risk assessment when working in the arc flash boundary.
Annex F is offered only as an example.

A risk assessment may be required, but how many companies are willing to pay for it in addition to the substantial cost of an arc hazard analysis? A risk assessment would require a lot of effort and meetings with operating personnel to define tasks and evaluate risks. The skill set for preparing a good risk assessment is different from that of doing an arc hazard analysis.

This is not something that could be included in the estimated effort for an arc hazard analysis unless it was clearly spelled out in the request for proposals.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed May 23, 2012 12:51 pm 
Offline
User avatar

Joined: Wed May 23, 2012 11:59 am
Posts: 19
Location: Massachusetts
Opening covers on Switchboards and Switchgears requires Cat 4, I'm sure many of you have done it...
How about doing it an a hot pump station on a summer day!!! Maybe I'm crazy, but I feel that wearing Cat 2 will make this task safer as I have less of a chance of fainting into an open gear while reading the settings or unbolting the cover.
Using tables is great, but we still can't confirm clearing time ahead of the data collection in most cases.
What do you wear?


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 23 posts ]  Go to page 1, 2  Next

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 1 guest


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