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 Post subject: Questions for those who have the expertise and knowledge
PostPosted: Tue Jan 19, 2010 1:28 pm 
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I am fairly new to arcflash and have been given the responsbilities to ensure the testers at the end of each of our assembly lines are wearing the proper protective equipment. To maintain quality we 100% test every unit that is produced to verify sequence of operation and safety. For the test we attach alligator clips to stripped wires and then turn on a switch )the alligator clips do have protective sleeves around the connections.) The voltage ranges from 115V single phase to 575V three phase depending on the componets. The amps range from 30A to 80A. The tester then must reach into the cabinet and verify componets are working properly.

The issues we are having right now is that the V-Rated gloves which we are using do not provide enough dexterity for the tester to perform the test. The gloves get in the way of tight places or the tester is not able to grasp the terminals properly which leads to longer test times. My questions are as follows:

-At what voltage is the tester required to have the V-Rated gloves on?

-What are the best gloves out there that allow the operator/tester to move around easier and utilize their fingers?

- Do the leather protectors have to be worn? Can a substitution be made for the leather protectors (i.e. something tighter fitting that moves better with fingers.)?

- We also Hipot every unit with a voltage for 1.48KV - 2.58KV and a max of 2 amps. Do we have to have gloves on for this?

Any help will be much appreciated. Thanks

J


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PostPosted: Tue Jan 19, 2010 1:44 pm 
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First thing, welcome to the forum, you won't find a better place to learn about arc flash, some real gurus here.

Mikspeed wrote:
. My questions are as follows:

-At what voltage is the tester required to have the V-Rated gloves on?


>50V

Mikspeed wrote:
-What are the best gloves out there that allow the operator/tester to move around easier and utilize their fingers?


Class OO, but they are only rated for up to 500V so based on the info you provided you need class 0

Mikspeed wrote:
- Do the leather protectors have to be worn? Can a substitution be made for the leather protectors (i.e. something tighter fitting that moves better with fingers.)?


Yes and no, for higher rated gloves you "derate" them 1 class. OSHA says the following:

1910.137 (b)(2)(vii) Protector gloves shall be worn over insulating gloves, except as follows:

(b)(2)(vii)(A)Protector gloves need not be used with Class 0 gloves, under limited-use conditions, where small equipment and parts manipulation necessitate unusually high finger dexterity.


-
Mikspeed wrote:
We also Hipot every unit with a voltage for 1.48KV - 2.58KV and a max of 2 amps. Do we have to have gloves on for this?



Yes, I asked OSHA this once and recieved a letter of interpretation that gloves need to be worn while hipotting that are rated for the test voltages, I replied asking what to wear when using my 100kV hipot and never got a response to that one.


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PostPosted: Tue Jan 19, 2010 2:25 pm 
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You should look to modify your test cabinet in a manner that makes it easier to work. I can't say specifically because you didn't provide detail info, but, how about multiple plugs on the cabinet front that get energized via a contactor or manual safety switch. Have some lights on the plugs to indicate voltage. Then you could wire up your machine without gloves, plug it into a dead socket, and then energize the circuit. All live parts could be behind the dead front enclosure.

DC Highpotting should be done with gloves. The value of the gloves is an interesting question. I would probably say 1000V. The thing about a Hipot is that it generate sufficient current to really injure you.


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PostPosted: Tue Jan 19, 2010 5:25 pm 
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And I certainly would not want to have assembly line folks testing 600 volt equipment without protection, and some really good training.


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PostPosted: Wed Jan 20, 2010 10:00 am 
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Welcome to the forum Mikespeed.

As acobb says it would be important that the testers be qualified workers.
Qualified worker is in part:
1. Trained in proper PPE use
2. Uunderstand the hazards and loto
3. Trained on the task and work methods.
4. Worker is observed doing the task trained on and following procedures.

Hase10 makes a good point to modify your procedures if possible to make the testing someway safer by adding flashing lights and a remote circuit closure with maybe a light curtain to shutdown everything in the event someone enters the test area.

Of course if you’re performing diagnostic testing or troubleshooting it may not be possible to build in safety devices external the equipments protection boundary. Again this should be done by a qualified worker in the proper PPE.

The PPE is depending on the IE (incident energy) or fault current that may be released during a fault along with shock protection based on the voltages. By having low peak fuse protection upstream of the test connectors or the breakers trip level set to 0 the fault will be greatly reduced.


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PostPosted: Thu Jan 21, 2010 7:49 am 
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Thanks for the reply posts....

Thanks Haze, Zog, Acobb, and Cable Guy!

My first post was very general. I will try to be a more detailed in this one. We have 7 different assembly lines that run a varity of different voltage units. The testers have all completed the arcflash safety training and understand the dangers of electricity. The test station completes a function test of the unit and ensures there are no gas leaks on heaters (this means they must be within 12 inches of the clips to verify the unit is operating properly and check for the gas leaks).

Our voltages do range from 115V-575V however the primary voltages that we use on our 2 high production lines is 115V with less than 15A. I am assuming from previous statements Class 00 gloves are sufficient as long as the leather protectors are worn.

Here are some questions

1. Am I correct in saying that if they wear Class 0 gloves the leather protectors are not needed?

2. Can non FR gloves be worn ontop of the V-rated gloves (i.e. leather tipped gloves with stretch fit)?

3. What are some of the suppliers that you all use for your gloves (we currently are purchasing through Cintas)?

4. Have you heard of anybody supplying Size 7 gloves (Cintas can not supply these and I have some people small hands)?

5. How do you calculate incident energy (what is the formula)? Is there a table to reference the incident energy back to and determine the level of protection?

6. For Hipot... Wouldn't the incident energy be extremly low due to the low amps? Why does OSHA require the gloves?

7. When Cable Guy states "By having low peak fuse protection upstream of the test connectors or the breakers trip level set to 0 the fault will be greatly reduced.":

-What does low peak fuse protection mean? Is it having a lower rated amp fuse upstream?

-At what point can I get the incedent energy low enough to not require gloves/protection?

-What does it mean to have the breakers trip level set to 0?

Once again thanks for all the help.


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PostPosted: Thu Jan 21, 2010 8:24 am 
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1. Am I correct in saying that if they wear Class 0 gloves the leather protectors are not needed?

Don't think so for the repeated use. Topic has been discussed recently here.

2. Can non FR gloves be worn ontop of the V-rated gloves (i.e. leather tipped gloves with stretch fit)?

Same as above

3. What are some of the suppliers that you all use for your gloves (we currently are purchasing through Cintas)?

I have no info

4. Have you heard of anybody supplying Size 7 gloves (Cintas can not supply these and I have some people small hands)?

Same

5. How do you calculate incident energy (what is the formula)? Is there a table to reference the incident energy back to and determine the level of protection?

If you are in the US suggest IEEE 1584 and NFPA 70E....it's all there. If you don't have a grasp of the process yet, you are probably going to need much help with this.

6. For Hipot... Wouldn't the incident energy be extremly low due to the low amps? Why does OSHA require the gloves?

Gloves are for contact protection.

7. When Cable Guy states "By having low peak fuse protection upstream of the test connectors or the breakers trip level set to 0 the fault will be greatly reduced.":

-What does low peak fuse protection mean? Is it having a lower rated amp fuse upstream?

-At what point can I get the incedent energy low enough to not require gloves/protection?

-What does it mean to have the breakers trip level set to 0?

He probably means current limit type fuses and minimum settings on adjustable trip breakers, which you probably do not have, but will let him provide more info.

Hope it helps!


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PostPosted: Thu Jan 21, 2010 9:33 am 
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1. Am I correct in saying that if they wear Class 0 gloves the leather protectors are not needed?
Yes, this is true Class 0 can be used up to 1000V without protectors, Class 00 up to 250V, but, you have to replace or test the glove after each use if the leather protectors are not used. With the leather protectors its every 6 months.

2. Can non FR gloves be worn ontop of the V-rated gloves (i.e. leather tipped gloves with stretch fit)?
Electric gloves are not really Fire Rated. The leather is what afford the heat protection. The rubber is pretty tough but can melt, althought I doubt there would be sufficient long term heat in an arc to do it. The gloves are for contact protection from electric shock. There is times, like racking switchgear, in which the leather alone can be used without the rubbers just for thermal protection. But again, the leather does not have an IE rating.


3. What are some of the suppliers that you all use for your gloves (we currently are purchasing through Cintas)?
Call your local Graybar Electric Supply. W. H. Salisbury is a good name to know for all rubber products.

4. Have you heard of anybody supplying Size 7 gloves (Cintas can not supply these and I have some people small hands)?
Now you're just being lazy, I found this in a google search
http://www.kunzglove.com/products/lowvol.asp

5. How do you calculate incident energy (what is the formula)? Is there a table to reference the incident energy back to and determine the level of protection?
If you are asking a question like this, I really have to question what arc flash training has been provided. IEEE 1584 provides formulas, and NFPA 70E Art 130 provide the Task Matrix Table. This is rudimentary to an understanding of arc flash.



6. For Hipot... Wouldn't the incident energy be extremly low due to the low amps? Why does OSHA require the gloves?
The problem is 'how fast is the overcurrent device going to operate?' - there really isn't one. 40ma can kill you. The Hipot can put out that much, so an operator runs the risk of electrocution. If, you could find, or make, a hipot that would be limited to 5ma, then I would say you could make an internal policy that says arc flash is not necessary. You could probably do it with a fast acting 5ma fuse and holder, but you would have to have a policy in place that inspects the fuse size before each use. 5ma is what GFI devices are set to trip out in the house. If you are doing hipot, your measurement is typically in uA (microamps), do you ever get close to 5mA?

7. When Cable Guy states "By having low peak fuse protection upstream of the test connectors or the breakers trip level set to 0 the fault will be greatly reduced.":

-What does low peak fuse protection mean? Is it having a lower rated amp fuse upstream?
No, low peak fuses are more commonly called 'Current Limiting Fuses'. Its a two element fuse with one element designed to open the circuit on current inrush, ie, short circuit, and it can react within 1/4 of a cycle. So its 'so' fast, and the time element is so small, that the IE is also very small. But it never goes to 0.0, and thus won't eliminate PPE just reduce the magnitude of it.

-At what point can I get the incedent energy low enough to not require gloves/protection?
You can't really. You are mixing two concepts, thermal protection and electrocution protections. Incident Energy only deals with the thermal protection. You always have to protect against the electrocution protection whenever you are working within the approach boundary. If you could limit current to 5ma, then you might make an arguement as to why you don't need protection, but even at 480V, 5ma isn't going to run any machinery. What you really need to do is to shield or insulate your test equipment in a way that it isn't exposed.

-What does it mean to have the breakers trip level set to 0? I don't know what he meant by this, but probably was saying to have the breakers set to trip fast enough that the incident energy is less than 1.2cals/cmsq so that the PPE requirement is then Level 0. But again, this is the thermal energy and it would let you work in lightweight PPE.

Once again thanks for all the help.
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PostPosted: Thu Jan 21, 2010 1:22 pm 
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MIKESPEED,
Quote:
7. When Cable Guy states "By having low peak fuse protection upstream of the test connectors or the breakers trip level set to 0 the fault will be greatly reduced.":

-What does low peak fuse protection mean?


First, I see you’re confused with the two types of hazards. Don't worry that is a common problem when we look at electrical safety, everyone hears arc flash however, that is only part of the protection program.

1. Shock (electrocution) Hazard - PPE includes e.g. Gloves, insulating material, etc.
2. Thermal (Arc Flash) Hazard - PPE includes e.g. Leather covers, FR clothing, face shields, etc.

Fuse 101
LOW PEAK FUSES is another term for current-limiting or very fast blow.
The current-limiting Low-Peak fuse minimizes incident energy. Why, basically because of the quick action. [url="http://www.cooperbussmann.com/2/Low-PeakFuseUpgrade.html"]http://www.cooperbussmann.com/2/Low-PeakFuseUpgrade.html[/url] To help understand the link is just one manufacture of this type of fuse.

Quote:
Is it having a lower rated amp fuse upstream?

Nope, you install the fuse ratings AMPS size according to the equipment and associated devices. Saying that, you can de-rate fuse size if your equipment is found to use less current then figured. Example - A panel fused for 100A and the max load is found to be 25A the fuse value may be reduced to something like ~40A. In this case the arc flash fault current or IE will not change that much by de-rating. However, in larger systems the de-rating of fuses may actually reduce the potential of the hazard.


Arcing time is a complicated issue. Basically, using such LP type fuses and a short circuit occurs, the quick reaction of the fuse seeing the current raise will open the fuse which reduces the heat produced at the point of the arc. Longer fuse reaction time + Large available fault current = Large flash potential that is a thermal problem.

The thermal (heat) is produced by the arc flash. Flame resistant (FR) clothing will burn but, not sustains burning. The sustained burning of material not FR rated will cause sever burns. Most times the worker is momentarily blinded or rendered disabled after the blast. The worker not wearing FR clothing may burn for long periods of time. Fuses have different characteristics according to use. LP or current limiting type of fuses currently offers the best advantage in many situations for industry with <600v (low voltage) protection due to the quick reaction time.

Haze10 is correct; the hazard will not disappear but reduced. According to the fuses replaced can mean the difference between (HRC-Hazard Rick Category) HRC3 and reduced to HRC2 PPE or from a HRC1 to a HRC0 etc, etc,.

Circuit Breaker Trip Settings to 0
I should have said minimal trip settings. Sorry for the confusion. Many LV breakers have trip settings that allow you to adjust the percentage of short circuit current over the rating of the breakers standard trip rating. By setting the trip settings to minimum is basically the same as using a current limiting (LP) type fuse. It's a time issue. Say you have a 50A breaker with trip settings at 200% (max trip setting) the fault current will have to reach this value before tripping. This means longer time again means higher arc thermal hazards. Example - If you were working on something hot you may want to set the trip setting of the breaker to occur at 1,000 amps of short circuit current and not 20,000 amps.

This is a brief note so I would suggest you Google for advanced knowledge how reducing fault time of a short circuit fault reduces thermal energy.

Again the fuse and breaker trip settings are not for shock protection. Shock protection has its own boundary limits table according to the voltages. This requires protective measures of wearing insulating material.

Arc Flash or Blast has its table of defined boundaries according to the thermal energy released during a short circuit. The methods I explained for fuses and CB’s are used to help limit or lower that hazard.

The rated electrical gloves require leather covers for arc flash protection. The rubber is a insulator and can melt the leather covers serves two purposes.
1. Prevents burns and gloves melting.
2. Helps to prevent sharp edges or tearing of the insulating material during use.

If there is no interaction with electrical conductors outside the boundary area and arc flash is a possibility then you can wear the covers and not the rubber insulating gloves.

Look for the shock tables in NFPA 70E according to the voltages you have.

Hugh Hogland of ehazard.com may be able to help you with the glove sizes. Several companies HazCat and such may help.

Hope this helps. I feel I wrote a book.
Thanks,


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