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 Post subject: Wearing insulating gloves in the 50-300V range
PostPosted: Fri Jan 18, 2013 9:36 am 

Joined: Fri Nov 20, 2009 7:52 am
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Question in NFPA 70E-12
In paragraph 130.4(C), we can read : No qualified person shall approach or take any conductive object closer to exposed energized electrical conductors or circuit parts operating at 50V or more than the restricted approach boundary set forth in Tables 130.4(C)(a)(b) unless any of the following apply :
(a) The qualifed person is insulated or guarded from the energized electrical conductors or circuit parts operating at 50V or more. Insulating gloves or insulating gloves and sleeves are considered insulation only with regard to the energized parts upon which work is being performed. If there is need for an uninsulated part of the qualified person's boby to cross the prohibited approach boundary, a combination....

Yet, in Table 130.3(C)(a) column 4 for the 50-300V range, we can read Avoid contact as the restricted approach.

Since there is no value for the restricted approach for the 50-300V range, can we conclude that no insulating gloves are needed when working on energized parts between 50-300 V ?


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PostPosted: Mon Jan 21, 2013 8:15 am 
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I agree that "Avoid contact" is not a distance. I look forward to other's replies.


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PostPosted: Mon Jan 21, 2013 9:09 am 
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My approach has always been 50 to 300 volts you do not cross the restricted approach boundary until you make contact like with a voltmeter? I have always been unclear as to the meaning of "Insulating gloves or insulating gloves and sleeves are only considered insulation only with regard to the energized parts on which work is being performed."?


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PostPosted: Mon Jan 21, 2013 10:58 am 
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Jerry wrote:
My approach has always been 50 to 300 volts you do not cross the restricted approach boundary until you make contact like with a voltmeter? I have always been unclear as to the meaning of "Insulating gloves or insulating gloves and sleeves are only considered insulation only with regard to the energized parts on which work is being performed."?

It means that if you have other energized parts in the same vicinity to the energized parts on which work is being performed, your insulating gloves are not considered insulation because it may not be your hand which will touch those other energized parts.


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PostPosted: Mon Jan 21, 2013 11:16 am 

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We are debating this at my plant as well.
My take is that 130.7(C) (7) (a) states that “employees shall wear rubber insulating gloves with leather protectors where there is a danger of hand injury from electric shock”. Table 130.7(C) (15) (a) states work on energized conductors required gloves for less than 240V. Inside the restricted approach boundaries we have to consider inadvertent movement leading to contact with energized components. While there is no recommended distance with the restricted approach boundary, it would be hard to defend the stance that no gloves are required as inadvertent movement could lead to direct contact, which meets the “hand injury from electric shock” criteria.
If the panel has a finger safe design for anything greater then 50V, than there is no issue with inadvertent contact. Gloves would be required for voltage testing according to 130.7(C) (15) (a).


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PostPosted: Tue Jan 22, 2013 6:27 am 

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For our electrical safety SOP I made the restricted boundary be 1 inch (more restrictive than 70E) and left the prohibited boundary at "Avoid Contact". This then requires gloves for voltage measurements. I also put in an exemption of <= 120 volts with not more than 30 amp over current protection requires no gloves. This allows easier trouble-shooting of control circuits that are not in close proximity to 480 volts. This exemption is used at one of our national laboratories. My thought is that since the hands are VERY close, the gloves would give arc flash protection for the lower voltage circuits.


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PostPosted: Tue Jan 22, 2013 11:05 pm 

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BISAM wrote:
For our electrical safety SOP I made the restricted boundary be 1 inch (more restrictive than 70E) and left the prohibited boundary at "Avoid Contact". This then requires gloves for voltage measurements. I also put in an exemption of <= 120 volts with not more than 30 amp over current protection requires no gloves. This allows easier trouble-shooting of control circuits that are not in close proximity to 480 volts. This exemption is used at one of our national laboratories. My thought is that since the hands are VERY close, the gloves would give arc flash protection for the lower voltage circuits.


I can see the benefits of your approach from a practical standpoint, but providing protection from shock with the 120V circuit is still seems like a gap. Do you use the restricted boundary for 480V as your rule of thumb for gloving up? Also, have you been through a 3rd party audit since adopting that policy?


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PostPosted: Wed Jan 23, 2013 12:06 pm 
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Great topic, been a debate for as long as I can recall.

My take has always been "avoid contact" was that rare chance in ESWP's to use some common sense and has many factors involved. The configuration fo the equipment, the body/hands positioning, the environment (Busy hallway or isolated room).

The way I always think of this for myself is "If someone bumps into me while I am doing [task] will I likely come in contact with energized parts?"

Testing voltage on a 120V receptacle? Not likely. Reaching deep into a control panel? Likely.


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PostPosted: Thu Jan 24, 2013 8:03 pm 
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I always defer to IEEE 516 which is what 70E refers to for shock. Gloves are not required for everything and are only one of 4 work methods. Insulated tools such as hot sticks or insulated screwdrivers or meter probes, working de-energizef, and bare-hands/live-line are other three. There is nothing in IEEE 516 requiring gloves in addition to tools, to say nothing of with bare hands.


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PostPosted: Fri Jan 25, 2013 5:30 am 
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PaulEngr wrote:
I always defer to IEEE 516 which is what 70E refers to for shock. Gloves are not required for everything and are only one of 4 work methods. Insulated tools such as hot sticks or insulated screwdrivers or meter probes, working de-energizef, and bare-hands/live-line are other three. There is nothing in IEEE 516 requiring gloves in addition to tools, to say nothing of with bare hands.

Hot sticks are tested annually, insulated screwdrivers are voltage rated if in good condition, and bare hands/live line work requires specialized training and equipment, e.g., insulated buckettruck, helicopter, etc.
Double 0 gloves have the required flexibility to perform work on LV circuits below 300v. i would not recommend them for work on 480V as the actual bus voltage may exceed the gloves rating of 500V. So I can see no reason not to wear them.


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PostPosted: Fri Jan 25, 2013 11:29 am 

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My copy of IEEE516 is old (2003) and is directed toward how to handle high voltage distribution power lines. All I can find in it with regard to below 300V is avoid contact similar to 70E. Section 6.5.5.2 does state "rubber gloves should be worn in a hazardous area and removed only after leaving the hazardous area". Does the 2009 version expand on this subject?


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PostPosted: Mon Jan 28, 2013 9:26 am 
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App NC wrote:
My copy of IEEE516 is old (2003) and is directed toward how to handle high voltage distribution power lines. All I can find in it with regard to below 300V is avoid contact similar to 70E. Section 6.5.5.2 does state "rubber gloves should be worn in a hazardous area and removed only after leaving the hazardous area". Does the 2009 version expand on this subject?


Also,
Quote:
130.7(C) (7) (a) states that “employees shall wear rubber insulating gloves with leather protectors where there is a danger of hand injury from electric shock”.


Then why pray tell does section 130.7(D) even exist?

First, taking 70E on. Shock protection is required when crossing the restricted approach boundary, 130.4(C). There are 3 work methods. They are covered in 130.4(C)(1), (2), and (3). (1) is clearly rubber glove method. (2) doesn't state it but allows insulated tools. (3) is clearly barehands method. Section 130.5 is arc flash protection and allows a tabular method of PPE determination in 130.5(B)(2), referencing 130.7(C)(15).

From here, we move to section 130.7. This section is all about tools and PPE. Section 130.7(C)(7) as stated above clearly requires rubber gloves when making CONTACT with energized conductors, aka "rubber glove method". But if there is no danger of hand injury from electric shock then 130.7(C)(7)(a) does not apply. Hence section 130.4 and 130.7(C)(7)(a) are in complete agreement.

Then we get to 130.7(C)(15). There are a number of references to a requirement for rubber gloves and/or insulated tools in this section. However, remember that this section is invoked by 130.5, NOT 130.4. This is restated in 130.7(C)(15) itself: "Where selected inlieu of the incident energy analysis of 130.5(B)(1), Table 130.7(C)(15)(a) and Table 130.7(C)(15)(b) shall be used to determine the hazard/risk category, and requirements for use of rubber insulating gloves and insulated and insulating hand tools for a task." Clearly the "shock protection" in the tables arises out of the alternative arc flash analysis, NOT from the shock hazard analysis. Does this make sense? Yes. The next sentence states, "The assumed maximum short-circuit current capacities and maximum fault clearing times for various tasks are listed...". In other words, the shock protection PPE are simply further assumptions used by the 70E Technical Committee in defining the task table. They are not requirements except when using the tables in lieu of an incident energy analysis.

Section 130.7(D) covers requirements for insulated tools. If insulated gloves were the required shock protection method, then 130.7(D) wouldn't exist.

So in conclusion, 70E does not "require" rubber gloves except for the obvious case of when no other shock protection work method is being used and direct contact with live conductors is going to occur. If there is no danger of injury from electric shock, then 130.7(C)(7)(a) does not apply. You can only get there if taking 130.7(C)(7)(a) out of context. Doing so by the way also makes 130.4(C)(3) kind of meaningless since barehand method by definition means "the (rubber) gloves come off".

IEEE 516-2009 is drastically changed from 516-2003. It was a major rewrite and not just because the MAD changes that are pretty well known (above about 25 kV, the minimum allowable distances changed in IEEE 516 and were also updated in the OSHA 1910.269 and NESC over the past few years). In the 2009 edition, section 7 is still called "work methods" but doesn't come out and specify a work method as such. It contains a list of specific work rules for each method but doesn't specify a method. In Section 4.10 outlines various allowable insulation systems and in doing so actually specifies work methods! When working from a grounded potential, the principal insulation systems are rubber gloves, and "live line tools" (insulated tools in industrial electrician terminology). If working while "floating" (insulated from ground) or if using two different insulation systems such as using rubber gloves and insulated tools, the second insulation system is called "secondary insulation". When using two different insulation systems, "both mediums should be able to withstand the line-to-ground voltage since the division of the voltage gradient across the series combination is not determined. Use of rubber gloves as secondary insulation is not recommended where system voltage dictates an electrical stress beyond the capacity of the rubber gloves." For example, if working above 46 kV, the voltage stress across the gloves may be beyond the glove rating. So at 69 kV and higher, hot sticks must be used alone and not with gloves.

In conclusion, IEEE 516-2009 allows rubber gloves only, insulated tools only, or both. So there is no guidance here.

Finally as a matter of theoretical discussion, air has a dielectric constant of around 3,000 V/mm. So for 300 V, we need only 0.1 mm of some sort of relatively nonconductive spacer to eliminate a shock hazard. Dry, leather gloves have a resistance of around 100 k-ohms and certainly fit the bill. 300 V / 100 K = 0.03 mA, so hardly even a perceptible shock. However wet leather gloves are essentially conductors and useless. Further, the standard ASTM test for gloves requires immersion in water so leather gloves fail whereas rubber gloves will work correctly even if immersed in water.

Insulated tools, and by this I'm referring to the <1 kV variety, have specifications and standards. Meters have the Category rating system and insulated tools are similarly rated. There is no "annual testing" as with hot sticks and gloves for good reason. Gloves may be subject to very small pinhole failures that are hard to spot, and hot sticks are subject to creep/partial discharges that are not always visually apparent. At <2,000 volts, partial discharge essentially doesn't exist, and pinholes are highly unlikely with insulated tools so a simple visual inspection suffices over more sophisticated testing.

In addition insulated tools have a guard or grip that is specifically positioned to prevent hands from slipping down into danger. This makes them a combination of both insulation and guarding/isolation for shock protection. This guard is specifically required by the standards but is almost overlooked as it is such a simple safety feature.

The following then is my opinion and my opinion only:
1. The standards don't specify a specific work method, only how to execute it safely under 750 V. 70E only specifies work methods if you don't do the engineering analysis and fall into one of several categories in the tables in 130.7(C)(15). IEEE 516-2009 edition specifically precludes rubber glove method from being used above 46 kV.
2. As a matter of good engineering principles, PPE reduces the hazard itself but does not reduce the likelihood. Because of this, as a matter of good engineering principles, it is always preferred to use a method of reducing the likelihood of a hazard to an acceptable level rather than using PPE whenever possible. This principle mandates that insulated tool method should be used whenever possible, either alone, or in conjunction with, rubber gloves.
3. Use of rubber gloves is not without it's own set of hazards. First and foremost, manual dexterity, no matter how thin the glove, is still impeded. The likelihood of a shock hazard is INCREASED for all tasks requiring fine manual dexterity. This specifically includes using meters and hand tools. In addition, rubber gloves increase the likelihood of additional mishaps and/or hazards in warm or cool environmental conditions. Hot, sweaty, slippery hands are not conducive to manual dexterity no matter whether using glove powder or not, and frost bitten and/or stiff joints are not conducive to good performance in cold conditions. For these reasons tasks which require lots of manual dexterity need to be done without the gloves. For those tasks where manual dexterity is not as critical such as switching tasks or examining cable, rubber gloves are likely to be preferred over trying to do the same tasks with tools.

Thus I would argue for using gloves OR insulated tools and the selection is task dependent for voltages under 750 V. Use the best tool for the job. Don't get hung up on one or the other because both have their place.

I'm sure that this approach is probably considered blasphemy in most circles. Linemen like the old adage of wearing gloves "cradle to cradle", some utilities have mandated stick-only work (made a lot of folks very upset in Alaska over this), and some safety professionals have adopted a stance of the idea that PPE is the cure-all for everything electrical and insist on arc flash and shock PPE automatically while ignoring basic safety principles of using PPE as a last resort. But good engineering practices argue for a different approach from either of these. Fortunately that approach is common sense.


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PostPosted: Mon Jan 28, 2013 8:25 pm 

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PaulEngr,
Thanks for the detailed run through. There are plenty of guys I trust to work without gloves at this voltage range with only insulated tools. But, there are a few that need a written a policy that includes Zog's bump into the person working in the panel rule of thumb.

130.7(C)(7)(a) It is hard to defend “no danger” in my control panels as there is still the potential of inadvertent contact of energized components. This could be overcome with design finger safe design changes over time. In the mean time my local written policy needs to prevent the once in a decade shock situation from occurring.


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PostPosted: Mon Feb 04, 2013 9:05 am 

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I see that the topic of wearing rubber insulating gloves at these lower voltages is not just a challenge here, North of the border. As a front line electrician, I follow the rule of doing a JHA. Yes both Z462 and FPA 70E do provide us with some good guidance on shock and shock protection, however situations out here are never the same. We have the guidance of the restricted and prohibited boundaries and also the possibility of inadvertent movement with in a panel, whether it be a control panel or combination loadcentre.

Last year I was called out to a residence at 10:30 at night. The homeowner claimed that all of a sudden there was no power in a portion of the home. As it turned out it was a loose neutral connection in the panel. Upon seeing the panel in the basement, it was a complete mess from the outside. The wiring going into the panel was disgusting. In removing the cover from the panel I choose to wear my gloves as I did not know what to expect from behind. Normally one would not wear gloves to remove a cover, however as part of the JHA and this particular situation I felt that it was for my own safety.

This may not be the answer one is looking for here, however there is allot to be said about JHA and ourselves having some input into the choice of PPE in oppose to relying on tables
Thank you

Len Cicero


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