Gloves

[wbdvt]

I couldn't tell you if the picture was a joke, but when talking arc flash protection we are talking protection from burns from the heat produced in the arc incident. That heat is measured in calories.

One calorie is the amount of heat needed to raise one gram of water 1 degree C.

Actually for arc flash it is incident energy not heat. The unit of measure is cal/cm2 (calories per square centimeter).

The definition of Incident Energy from NFPA 70E-2015: The amount of thermal energy impressed on a surface, a certain distance from the source, generated during an electrical arc event. Incident energy is typically expressed in calories per square centimeter.

Whereas the correct definition of heat refers to the transfer of energy between particles in a system and this is measured in calories. Temperature on the other hand is a measure of how much energy is in that item. So if one has a hot iron, that iron has a lot of energy in it (temperature) and touching it transfers that energy to your hand (heat).

So the 27 cal label on the gloves means that touching the glove will transfer 27 calories to your hand in the form of heat. I wouldn't want to touch that. :happysad:

 

[kwired]

Actually for arc flash it is incident energy not heat. The unit of measure is cal/cm2 (calories per square centimeter).

The definition of Incident Energy from NFPA 70E-2015: The amount of thermal energy impressed on a surface, a certain distance from the source, generated during an electrical arc event. Incident energy is typically expressed in calories per square centimeter.

Whereas the correct definition of heat refers to the transfer of energy between particles in a system and this is measured in calories. Temperature on the other hand is a measure of how much energy is in that item. So if one has a hot iron, that iron has a lot of energy in it (temperature) and touching it transfers that energy to your hand (heat).

So the 27 cal label on the gloves means that touching the glove will transfer 27 calories to your hand in the form of heat. I wouldn't want to touch that. :happysad:

I won't necessarily disagree with most of what you said, but there has to be more to that last sentence then what you mentioned. I would assume the gloves protect the user from 27 calories under certain conditions that are not declared on that label, one would need to see product specifications to fully understand exactly what that means or know any standards used in marking them much better then I do.

I would think a time factor has to be involved there, 27 calories in a few milliseconds is a lot of energy compared to 27 calories in 10 seconds.

 

[GoldDigger]

I would think a time factor has to be involved there, 27 calories in a few milliseconds is a lot of energy compared to 27 calories in 10 seconds.

Actually that misses the point. The *temperature* of the flash may be higher, but the amount of energy potentially transferred to is just as great and just as damaging.
A long time factor only mitigates the damage if you can get out of the way or conduct away the heat through your skin and body before a damaging temperature is reached.
It is rather like comparing a hundredth of a second of oxy-acetylene to 10 seconds of a candle flame. They both can do equal damage. (I may have the ratios wrong but the principle is right.)
One place where there is a distinct difference is in the blast effect and pressure shock wave.

 

[kwired]

Actually that misses the point. The *temperature* of the flash may be higher, but the amount of energy potentially transferred to is just as great and just as damaging.
A long time factor only mitigates the damage if you can get out of the way or conduct away the heat through your skin and body before a damaging temperature is reached.
It is rather like comparing a hundredth of a second of oxy-acetylene to 10 seconds of a candle flame. They both can do equal damage. (I may have the ratios wrong but the principle is right.)
One place where there is a distinct difference is in the blast effect and pressure shock wave.

I may not have worded it right but I think I was trying to make same point you are. 27 calories doesn't mean a lot by itself, 27 calories over a square centimeter means a little more, 27 calories over a square centimeter every tenth of a second means even more.

Just saying the gloves will protect you up to 27 calories don't mean a whole lot without more information.

 

[meternerd]

Sounds like some good Ole boys. Why would a person need to know if a stick is leaking while in use? I would much rather test the hot stick in a controlled environment.

In the real world, sticks are used by several different crews during less than optimal conditions (snow, dirt, apprentices loading and unloading the tools, etc). A visual inspection is not always sufficient, and testing means only that they were OK when they were tested, not after they've been used and stored in a truck bin. Leakage can be the precursor to failure, so hopefully a stick can be removed from service before an accident occurs. Just what the Good Ole Boys told me, though. Nowdays, most line work is done from a bucket, where the insulated bucket is additional insulation. But, just because it was fine out of a bucket, may not mean it'll be fine off of a pole. We need a few linemen to chime in.....then again, maybe not! Dang knuckle-draggers.... I meant, they don't use INSULATED GLOVES, by the way. Leathers are not voltage rated.

 

[MD84]

Thank you for that perspective. I have not had that exposure. The exposure I have is being issued live line tools and being personally responsible for its care. If the integrity of a tool was in question a field test was performed with a Hubbell/chance 120v wet/dry tester.

So you would recommend that if a hot stick is put into hard use situations and when you are not sure what the last guy did to it then it would be best to use it without gloves or other insulating measures? This way you can feel the current passing through your body. As long as you are not seriously injured you would know if the stick was failing by feeling the electric shock.

 

[iwire]

So you would recommend that if a hot stick is put into hard use situations and when you are not sure what the last guy did to it then it would be best to use it without gloves or other insulating measures? This way you can feel the current passing through your body. As long as you are not seriously injured you would know if the stick was failing by feeling the electric shock.

:thumbsup: