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catnhat
02-15-2007, 08:07 PM
Does everyone calculate voltage as phase to phase for live line maintenance? At my utility, we have a 25kv gloving program with class 3 rubber. While riding to a job, I witnessed a contract crew gloving our 46 kv with class 3 equipment (including one company truck). Our safety rep says they are qualified and that their company calculates voltage phase to ground. As I read the OSHA regs, all voltage is referenced as phase to phase. Any input would be appreciated.

old lineman
02-15-2007, 09:25 PM
ASTM is very precise about this but I'll try to recall as near as I can. Forgot what I had for breakfast.
Class #00 up to 500 volts phase to phase, typically 440 volts secondary
Class # 0 up to 1,000 volts phase to phase, typically 600 volts secondary
Class # 1 up to 10,000 volts, typically 4,160 volts primary phase to phase
Class # 2 up to 20,000 volts, typically 14,400 volts primary phase to phase
Class # 3 up to 30,000 volts, typically 25,000 volts primary phase to phase
Class # 4 up to 36,000 volts, typically 34,500 volts primary phase to phase
You should note that all categories of class of rubber is higher than the phase to phase nominal voltage of the system. In other words there is a margin of safety.
In addition all of these voltages are from wye connected circuits. Which can be retained under the maximum voltage level of the class of rubber being used.
Delta connected circuits on the other hand experience switching surges that could/would exceed the class of rubber used for similar wye connected circuits.
Therefore, the next highest class of rubber should be used on a Delta circuit.
Eg. 25,000 volts Delta would require Class # 4 rubber gloves and coverup.
The contactor that you are referring to is absolutely in error because the maximum voltage that rubber gloves are designed to work on are 36,000 volts phase to phase wye.
ALL measurements are taken from the nominal phase to phase voltage, with no exceptions.
The old Lineman

wudwlkr
02-16-2007, 09:00 AM
Rule 441A3b of the National Electrical Safety Code 2007 edition states:

When the Rubber Glove Work Method is employed, rubber insulating gloves, insulated for the maximum use voltage listed in Table 441-6, shall be worn whenever employees are within the reach or extended reach of the minimum approach distances listed in Table 441-1...

Table 441-6, titled "Maximum use voltage for rubber insulating equipment" lists Class 4 rated equipment may be used to a maximum use voltage of 36,000 volts. This is the highest rating. Footnote 1 to this table then explains, "The maximum use voltage is the ac voltage (rms) rating of the protective equipment that designates the maximum nominal design voltage of the energized system that may be safely worked. The nominal design voltage is equal to the phase-to-phase voltage on multiple circuits.

catnhat
02-16-2007, 02:45 PM
Thanks for the input. I'm gonna bring this up at our monthly safety meeting and wanted to make sure I was reading the regs correctly

US & CA Tramp
02-17-2007, 09:57 AM
Make sure you read and understand the "foot notes" in the OSHA regs in the Construction Standard 1926 subpart V. There are some very specific circumstances where you can use the phase to ground voltage. I personnally agree that Rubber glove work on anyting over 36KV phase to phase is wrong!! Unfortunetly OSHA regulations are a minimum and until they are updated this company may be within the law. This has been a subject of debate for several years so be prepared to have a battle with management on this. I believe this issue is worth the fight so have the documents ready to back up your stance. Also you may want to ask how many fatalities, severe accidents, and burned off arms and legs this company has had while rubber gloving 44KV??

blackley
02-19-2007, 06:38 AM
The phase to ground voltage rating for rubber gloves is only applicable when no exposure to phase to phase voltage exist.

Although some may select PPE based on phase to ground voltages it not the original intention to allow such. The phase to ground clause was originally allowed for work with NO multi phase exposure.

However I have found no standards (ASTM, ANSI, OSHA, & IEEE) that limit the maximum voltage that can be worked with rubber gloves and I have personally researched more than a 1000 different standards in an attempt to find any restrictions on this matter.

I suspect that the intrinsic insulation value of rubber and how strong the fingers are will be limiting factor.

old lineman
02-19-2007, 07:55 PM
The phase to ground voltage rating for rubber gloves is only applicable when no exposure to phase to phase voltage exist.

Although some may select PPE based on phase to ground voltages it not the original intention to allow such. The phase to ground clause was originally allowed for work with NO multi phase exposure.

However I have found no standards (ASTM, ANSI, OSHA, & IEEE) that limit the maximum voltage that can be worked with rubber gloves and I have personally researched more than a 1000 different standards in an attempt to find any restrictions on this matter.

I suspect that the intrinsic insulation value of rubber and how strong the fingers are will be limiting factor.



That's a lot of time consuming research. The limit is 36,000 volts with class 4 rubber gloves no matter what way you cut it. Written or not.
Check with the rubber products manufacturers.
The question probably should be whether they are prepared to stand behind their rubber gloves if an accident occurred while wearing class 4 rubber gloves while rubber gloving 46 kv.
I cannot imagine they wouldn't phoo,phoo that idea.
It's puzzling that some union locals limit the voltages the linemen can rubber glove is under 20 kv. and then we have others going crazy and pushing the envelope.
This discussion has gone over the top. Some people see no limits.
Until disaster strikes. Give your head a shake.
Who dies the company excecutive who decides to do it or the lineman who is forced to?
The Old Lineman