Arc Flash Work Safety: Understanding Hazard Risk Categories

-- End Ad Box --->minimum wear one of the following:
(Anchortex-AWS-2010-0001 - )flame-resistant long-sleeved shirt and pants, OR
The 2009 edition of NFPA 70E requires employersflame-resistant coveralls.
to label any electrical equipment likely to requireAdditional PPE Equipment: Employees in HRC 2
maintenance or examination while energized withsituations are also required to at minimum be
clearly visible warning labels that alert personnel towearing leather safety shoes, safety glasses, and
the hazard before they can be exposed to it. Thea hard hat with an arc-rated face shield. In certain
most common way of doing so is to list a HRCcircumstances, an 8+-cal/cm2 stocking hood or
(Hazard Risk Category) of required personalmulti-layer switching hood may also be required.
protective gear needed to service the equipmentMinimum Layer Requirements: HRC 2 requires one
in question. So what does this mean?to two layers of protective clothing.
Hazard Risk Category is defined within NFPA 70EMinimum Arc Rating in cal/cm2: 8 cal/cm2
as a general classification of hazard involved inHazard Risk Category 3 (HRC 3)
performing specified tasks. HRC typically rangesMinimum Clothing Requirements: In order to qualify
from zero to four, with zero denotingas covered under HRC 3, an employee must at
minimum-risk activities and four denoting high-riskminimum wear one of the following: a multi-layer
activities. Each category includes minimum safetyflash suit over FR long-sleeved shirt and pants
equipment required, the minimum number ofover natural fiber short-sleeved T-shirt and pants,
layers required to meet this requirement, and theOR a multi-layer flash suit over FR coveralls over
minimum arc rating of all required equipment in calnatural fiber short-sleeved T-shirt and pants.
cm2. The arc rating, in turn, is a value of theAdditional PPE Equipment: Employees in HRC 3
energy required to pass through a given materialsituations are also required to at minimum be
and cause a 50% probability of second to thirdwearing leather safety shoes, safety glasses, hard
degree burns. Arc ratings from multiple layers arehat, hearing protection, and a multi-layer switching
not cumulative.hood OR arc-rated goggle and stocking hood.
Hazard Risk Category 0 (HRC 0)Minimum Layer Requirements: HRC 3 requires two
Minimum Clothing Requirements: In order to qualifyto three layers of protective clothing.
as covered under HRC 0, a long-sleeved shirt andMinimum Arc Rating in cal/cm2: 25 cal/cm2
long pants made from natural fibers (untreatedHazard Risk Category 4 (HRC 4)
cotton, silk, wool, rayon, or blends of theseMinimum Clothing Requirements: In order to qualify
fibers), with a minimum fabric weight of 4.5as covered under HRC 4, an employee must at
ounces per square yard, is required. Polyester,minimum wear one of the following: a multi-layer
poly/cotton blends, and other artificial fibers areflash suit over FR long-sleeved shirt and pants
not permitted, as they will melt in an arc flashover natural fiber short-sleeved T-shirt and pants,
incident, increasing the potential damage.OR a multi-layer flash suit over FR coveralls over
Additional PPE Equipment: Employees in HRC 0natural fiber short-sleeved T-shirt and pants.
situations are also required to at minimum beAdditional PPE Equipment: Employees in HRC 4
wearing leather safety shoes, safety glasses, andsituations are also required to at minimum be
a hard hat.wearing leather safety shoes, safety glasses, hard
Minimum Layer Requirements: HRC 0 only requireshat, hearing protection, and a multi-layer switching
one layer of protective clothing.hood OR arc-rated goggle and stocking hood.
Minimum Arc Rating in cal/cm2: None. HRC 0 hasMinimum Layer Requirements: HRC 4 requires at
no minimum requirements on arc rating ofleast three layers of protective clothing.
material.Minimum Arc Rating in cal/cm2: 40 cal/cm2
Hazard Risk Category 1 (HRC 1)Depending on the specific tasks performed,
Minimum Clothing Requirements: In order to qualifyemployees may also be required to wear
as covered under HRC 1, an employee must atvoltage-rated gloves and use voltage-rated tools
minimum wear one of the following: denim jeansappropriate to the equipment being serviced.
and a flame-resistant long-sleeved shirt, OR aWhenever possible, energized equipment to be
flame-resistant long-sleeved sirt and pants, ORserviced should be put into an electrically safe
flame-resistant coveralls.work condition unless the employer can
Additional PPE Equipment: Employees in HRC 1demonstrate that de-energizing creates more
situations are also required to at minimum besevere hazards (such as when performing work
wearing leather safety shoes, safety glasses, andon life-support systems), or is not practical due to
a hard hat with an arc-rated face shield.limitations of equipment or operation (such as
Minimum Layer Requirements: HRC 1 only requiresduring testing of live equipment). Any service that
one layer of protective clothing.requires personal protective equipment should only
Minimum Arc Rating in cal/cm2: 4 cal/cm2be performed by qualified personnel following a
Hazard Risk Category 2 (HRC 2)documented plan approved by the manager
Minimum Clothing Requirements: In order to qualifyresponsible for the plan.
as covered under HRC 2, an employee must at