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 Post subject: Battery Manufacture and ARC Flash Safety
PostPosted: Thu May 31, 2012 6:33 am 
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Joined: Thu May 31, 2012 6:27 am
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Location: Warrensburg, Missouri
I am a maintenance man in a battery manufacturing plant. I don' find any direct references in 70E or IEEE1584 that relate to the safety and PPE requirements for individuals connecting, monitoring and disconnecting strings of batteries during their formation. Our formation area is open air inside our plant. Our associates wear polyester uniforms and no other PPE. Does anyone know of any standards that i could review for safety information?


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PostPosted: Fri Jun 01, 2012 4:16 pm 
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Location: North Carolina
Yes. 70E-2012 has quite a bit of information. Article 320 contains extensive rules for handling battery enclosures/rooms with regards to the chemical hazards and gives a long list of references to other IEEE standards (70E is a work standard). Also in 2012, they have a DC shock hazard table which is a DC adaptation of the work methods in IEEE Std 516 adapted to other than distribution work. Second, Annex D.8 contains a calculation method for performing arc flash calculations for DC systems. It is one of many similar equations that have been recently presented in papers at the IEEE ESW and PCIC conferences. Essentially the formula is constant x volts x amps x time / (distance in mm)^2. In other words, power x time = energy, and then calculating the thermal energy at a distance (based on area of a sphere). This is a formula based on very basic theoretical underpinnings only.

Now then, in the examples you are citing, battery series resistance is probably the most critical since it limits output current, followed by the resistance of the rest of the system (the probes, cables, meters, etc.). You can then substitute V^2/R for the volts x amps calculation above. In practice I have not yet found a case where the incident energy exceeds 1.2 cal/cm^2 but considering your environment you may have much larger batteries than I have seen in the field. The arcing time is potentially unlimited with DC (or at least only limited by battery capacity) but most practitioners use the "2 second escape" clause as an upper cutoff which is specified in IEEE 1584 for the case you are describing. The idea is that the potential victim will either attempt to flee the area or will be blown from the area by the explosion and will be out of harms way within 2 seconds assuming there is an escape route. In addition the key area of concern with arc flash is exposure to the face/chest area which is the area where very little exposure (around 10% of total body surface area) is enough to cause a significant fatality risk even with only second degree burns. IEEE recommends 455 mm (18") as the shortest distance to this area for a working distance usually applied to equipment such as panelboards. Depending on the equipment/task configuration though you may want to vary this. Remember that distance is inverse squared...so small changes in working distance have a huge impact.

Regardless, the biggest concern even if it's a small arc is that the burn injuries that can occur from melting/burning fabrics can vastly exceed the initial thermal energy. There are plenty of Youtube videos demonstrating this in lab tests where the clothes on the dummy light on fire. That is why 70E specifies that for "H/RC 0" (1.2 cal/cm^2 or less arc flash hazard), nonmeltable fabrics are required. NESC also states the same thing, and even OSHA regulations specify this. So polyester is a really, really bad idea and is not acceptable in OSHA 1910 regulations (I forgot the exact section...look in 1910.33x).

So...I suggest in summary you review IEEE 70E, in the 2012 edition. Also review OSHA 1910.3xx (which was based on a much older version of 70E). Look through the references in Article 320 of 70E for further information specifically on batteries. These are all relevant to what you are doing. Battery safety by the way is an active area of review/research in some of the IEEE committees. Most of the information is pretty dated and likely to be updated in the next couple years. I just don't have any contact information for that.


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PostPosted: Mon Jun 11, 2012 10:08 am 

Joined: Tue Jun 02, 2009 1:40 pm
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OSHA 1910.335 and 1910 Subpart I


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PostPosted: Wed Jun 13, 2012 7:15 am 
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MikeMc wrote:
OSHA 1910.335 and 1910 Subpart I


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PostPosted: Wed Jul 11, 2012 11:54 pm 
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Location: Hammond, IN, United States
You can go for OSHA 1910.55 and 1910 subpart and for more information consult www[.]osha[.]gov/SLTC/etools/battery_manufacturing/engineering/index[.]html


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PostPosted: Thu Jul 12, 2012 5:54 am 
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From what i see 29 CFR 1910.52-55 were eliminated in 1990.


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