Injury from the pressure wave is minimal in contrast because the human body can survive up to 2 bar (30 psi) while most buildings can only withstand a 0.8 bar (12 psi) blast.The air around us already puts pressure on us to the tune of 14 pounds per square inchSurface areas or men 1.9m²For women 1.6m²1.9 square meter = 2,945 square inch/ 1.6 square meter = 2,480 square inchAnywhere from 20 to 40 added pounds per square inch can be fatal, depending on the time it takes to wash over the body.A wave of pressure that lasts less than .3 milliseconds leaves the eardrum no time to adjust to changes in pressure, and simply tears it. This can happen with pressure change as small as 5 psi.Pressure changes of 5 psi can cause 160 mile-per-hour winds. Changes of twenty psi can cause winds of 470 miles per hour.
There are MANY Global arc resistant testing guides and standards including:EEMAC G14-1IEC 62271-200 (Annex A)IEEE C37.20.7 (2007)IEC 61641 for LV manufactured in according to IEC 60439-1CSA C22.2 no. 22-11For global vendors, like Rockwell Automation, this creates a significant issue!IEEE C37.20.7, the most common used in North America, now includes internal arcing fault testing guidelines for equipment 38 kV and lowerLV MCC s - IEC 60439-1, IEC 60529, IEC/TR 61641:2008 for arcing durations up to 300 ms, KEMA certified (TTA), GOST-R certified (Russia), ASTA 61439 (Australia), CE conformance marked, CCC conformance marked (China), ABS Certification
First, the accessibility types in the various documents differ, and the working group wanted to make it clear that an accessibility type in one document might not be identical in performance to that in another document. In addition, the IEC identified types A, B and C, but types A and B concerned personnel safety whereas type C related to the amount of damage to the equipment during the test. Type C was thus considered as irrelevant to personnel safetySuffix C specifies that arcing does not cause holes in the freely accessible front, sides, and rear of the enclosure or in the walls separating the compartment in which the arc is initiated from all adjacent compartments. Suffix D: A modification of type 1 in which one or more of the enclosure surfaces is excluded from the arc resistant category. For example, type 1D-SR would indicate a design with arc-resistant functionality on the front and the right side only, with the rear and the left side considered inaccessible to personnel
NOTE THE DATE ON THE PICTURE 7 years ago!!!!
During arc-fault design tests, the energy release by an arcing fault is monitored by mounting racks of a black cotton material in panels covering the surface of the switchgear. This material is similar to 4.5oz/yd untreated t-shirt material identified as Hazard/Risk Category 0 per NFPA 70E Table 130.7(c) (11).The panels are mounted at 3.9 inches from all possible seams and one of the many acceptance criteria of ANSI C37.20.7 is that none of the cotton indicators ignites during or following a test. While the focus of NFPA 70E is the heat from the arc in medium-voltage switchgear, it is the pressure wave associated with the arc fault that dictates the design of the switchgear. The switchgear designed for arc-resistant protection requires heavy reinforcing of the entire structure.In conclusion, arc-resistant switchgear designs the hazard out of the tasks and reduces the level of risk for normal tasks to a zone 0 category. The result is a reduced need for PPE. The design focus of arc-resistant equipment is to provide the necessary enhanced safety features while requiring no addition maintenance, calibration, or final element tests to assure functionality
NFPA 70E 400.11 (also NEC 110.16 )
A new Section 110.6(D)(1)(f) has been added to the NFPA-2012 editionThis new section reads: “The employer shall determine through regular supervision and through inspections conducted on at least an annual basis that each employee is complying with the safety-related work practices required by this standard.” This mirrors similar language in OSHA 29 CFR 1910.269(a)(2)(iii).
The purpose of arc-resistant equipment certified to ANSI C37.20.7 is to eliminate the risk from the arc blast and the by-products (heat, pressure, shrapnel, and molten copper) during normal tasks performed on the equipment.
Rockwell Automaton does provide one of the broadest arc resistant product offerings in the marketplace.From NEMA and IEC 600V MCCs to full 7.2 kV and 15kV arc resistant control products
7% -None existent9% -Site written but just general2% -Direct quotes from OHSA, not specific to sites14% -Direct quotes from OHSA & NFPA-70E, not specific to sites26% -General Corporate ESP with site specifics42% -Site specific with specific instructions