What is Arc Flash? Arc Flash is an electrical short circuit, where a high level of current passes through air. Arc Flashes cause electrical equipment to explode, resulting in an arc- plasma fireball with temperatures exceeding 35,000° F (the surface of the sun is 9000° F). These high temperatures cause rapid heating of surrounding air and extreme pressures, resulting in an arc blast. An arc blast is the explosive expansion of both the surrounding air and the metal in the arc’s path. In an arc blast, vaporized solid metal conductors expand several thousand times their original volume, and can travel at speeds in excess of 700mph. The result of this violent event is usually destruction of the equipment involved, fire, and severe injury or death to any nearby people. The explosion takes less than one second and produces a brilliant flash, intense heat, and a pressure blast potentially equivalent to several sticks of dynamite. Personal Protective Equipment, “PPE” PPE is used to limit the injury incurred during a fault to a level no greater than the exposure of bare skin to an open flame for approximately 1 second (approx 1.2 cal/cm^2, a curable 2nd degree burn). If an Arc Flash study has not been performed at your installation, NFPA 70E has several tables that your “qualified personnel” should apply when determining PPE. In some cases the PPE worn by your “qualified personnel” is oversized for a certain task in a specific location. In other cases where improper equipment is installed or existing equipment is maintained improperly, the Arc Flash energy could be MUCH GREATER than what their PPE can protect them from. If a fault has an Arc Flash energy greater than 40 cal/cm^2 the pressure wave will be so great that PPE can no longer provide adequate protection. Our Arc Flash study provides suggestions on how to reduce Arc Flash energy to safer levels, and it also points out improperly maintained and installed equipment. How to Reduce Arc Flash Energy There are three ways that Arc Flash energy can be decreased. First, the available short circuit current from the utility could be decreased (probably not possible). Second, the impedance in the local power distribution system could be increased (may be difficult and/or expensive). Third, the trip time of protective devices could be decreased. One of the more common suggestions that we have made to reduce Arc Flash energy is circuit breaker trip adjustment. The adjustment of circuit breaker tripping devices can decrease the amount of Arc Flash energy that is the result of a fault. Care must be taken when implementing this solution, as protective device coordination may be affected when reducing the trip time of protective devices. A benefit of decreasing the Arc Flash energy is that it could lower the level of PPE required. Why should we perform an Arc Flash Study for you? An Arc Flash study is not required by the NEC, but Arc Flash equipment warning labels are. If you do not have any Arc Flash labels now, you need to install them. These labels are included in our Arc Flash study. An Arc Flash study may be required by the NFPA70E. If your system falls outside the boundaries set for the NFPA70E PPE tables, then an Arc Flash study is required. We provide calculated Arc Flash energy values and labels that will be a key part of your Electrical Safety training. If your electrical personnel do not know what level of PPE is required for a task, as per NFPA70E, you need to inform them. We inform you of the required NFPA70E PPE level and provide a detailed Arc Flash label which can be placed on equipment. Do you have improperly maintained or installed equipment that would cause the increase of Arc Flash Energy or increase the potential for a fault to occur? Your system will be thoroughly analyzed as a part of the Arc Flash energy calculations. The following are common areas of concern: Circuit breaker trip settings Using Motor Circuit Protectors “MCPs” as feeder breakers Under-rated or improperly sized fuses and circuit breakers Under-rated Motor Control Center “MCC” buss bracing Under-rated MCC starters and feeder breakers Under-rated Switchgear, Switchboards, and Panelboards So, why not let us give you a quote to perform a detailed study that will include the required labels, required level of PPE details, and suggestions on how to decrease the available Arc Flash energy? Links: NIOSH ARC-FLASH AWARENESS IRISS White Papers and Technical Articles IRISS (World Class IR Solutions) |
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Do you need an Arc Flash Study for NFPA70E
Compliance?
The NFPA70E clearly states electrical equipment
should not be worked on while in an energized state.
However, the equipment is considered to be energized
until verified it has been de-energized. During the
verification process the employee is potentially
exposed to energized electrical parts. This exposure
of the employee to energized parts places a
requirement on the employer to provide Personal
Protection Equipment (PPE). The NFPA70E outlines
what type of PPE is required to be provided by the
employer. The employer has two options to determine
the type of PPE that complies with the NFPA70E:
1. NFPA70E, 2004, article 130.3 states, “A flash
hazard analysis shall be done in order to protect
personnel from the possibility of being injured by an
arc flash.”
This option requires the employer to provide either an
independent outside source or a qualified internal
source to perform this analysis in accordance with the
calculations defined by the NFPA70E or IEEE 1584.
This option defines what level of PPE is required.
2. NFPA70E, 2004, article 130.7(C-9) “Selection of
Personal Protective Equipment” states, “When PPE is
selected in lieu of flash hazard analysis, Table 130.7
(C-9a) shall be used to determine the hazard/risk
category for a task.”
This option requires the employer and the employee
to make the determination of what level of PPE is
required. This option shall NOT be used if the system
has a short-circuit capacity or fault clearing times
greater than what the tables were designed for.
The NFPA70E requirements take into consideration
that the electrical system should have been installed
and maintained in accordance with the NEC. If the
system has been improperly maintained or has
underrated equipment installed, it is a VIOLATION of
the NEC. Therefore, the guidelines provided by the
NFPA70E may not adequately protect your employees.
Compliance?
The NFPA70E clearly states electrical equipment
should not be worked on while in an energized state.
However, the equipment is considered to be energized
until verified it has been de-energized. During the
verification process the employee is potentially
exposed to energized electrical parts. This exposure
of the employee to energized parts places a
requirement on the employer to provide Personal
Protection Equipment (PPE). The NFPA70E outlines
what type of PPE is required to be provided by the
employer. The employer has two options to determine
the type of PPE that complies with the NFPA70E:
1. NFPA70E, 2004, article 130.3 states, “A flash
hazard analysis shall be done in order to protect
personnel from the possibility of being injured by an
arc flash.”
This option requires the employer to provide either an
independent outside source or a qualified internal
source to perform this analysis in accordance with the
calculations defined by the NFPA70E or IEEE 1584.
This option defines what level of PPE is required.
2. NFPA70E, 2004, article 130.7(C-9) “Selection of
Personal Protective Equipment” states, “When PPE is
selected in lieu of flash hazard analysis, Table 130.7
(C-9a) shall be used to determine the hazard/risk
category for a task.”
This option requires the employer and the employee
to make the determination of what level of PPE is
required. This option shall NOT be used if the system
has a short-circuit capacity or fault clearing times
greater than what the tables were designed for.
The NFPA70E requirements take into consideration
that the electrical system should have been installed
and maintained in accordance with the NEC. If the
system has been improperly maintained or has
underrated equipment installed, it is a VIOLATION of
the NEC. Therefore, the guidelines provided by the
NFPA70E may not adequately protect your employees.
