Archive for March, 2011

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Friday, March 18th, 2011

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Arc Flash Work Safety: Understanding Hazard Risk Categories

Saturday, March 5th, 2011

The 2009 edition of NFPA 70E requires employers to label any electrical equipment likely to require maintenance or examination while energized with clearly visible warning labels that alert personnel to the hazard before they can be ex

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osed to it. The most common way of doing so is to list a HRC (Hazard Risk Category) of required personal protective gear needed to service the equipment in question. So what does this mean?

Hazard Risk Category is defined within NFPA 70E as a general classification of hazard involved in performing specified tasks. HRC typically ranges from zero to four, with zero denoting minimum-risk activities and four denoting high-risk activities. Each category includes minimum safety equipment required, the minimum number of layers required to meet this requirement, and the minimum arc rating of all required equipment in cal/cm2. The arc rating, in turn, is a value of the energy required to pass through a given material and cause a 50% probability of second to third degree burns. Arc ratings from multiple layers are not cumulative.

Hazard Risk Category 0 (HRC 0)

Minimum Clothing Requirements: In order to qualify as covered under HRC 0, a long-sleeved shirt and long pants made from natural fibers (untreated cotton, silk, wool, rayon, or blends of these fibers), with a

minimum fabric weight of cheap viagra canada 4.5 ounces per square yard, is required. Polyester, poly/cotton blends, and other artificial fibers are not permitted, as they will melt in an arc flash incident, increasing the potential damage.

Additional PPE Equipment: Employees in HRC 0 situations are also required to at minimum be wearing leather safety shoes, safety glasses, and a hard hat.

Minimum Layer Requirements: HRC 0 only requires one layer of protective clothing.

Minimum Arc Rating in cal/cm2: None. HRC 0 has no minimum requirements on arc rating of material.

Hazard Risk Category 1 (HRC 1)

Minimum Clothing Requirements: In order to qualify as covered under HRC 1, an employee must at minimum wear one of the following: denim jeans and a flame-resistant long-sleeved shirt, OR a flame-resistant long-sleeved sirt and pants, OR flame-resistant coveralls.

Additional PPE Equipment: Employees in HRC 1 situations are also

required to at minimum be wearing leather safety shoes, safety glasses, and a hard hat with an arc-rated face shield.

Minimum Layer Requirements: HRC 1 only requires one layer of protective clothing.

Minimum Arc Rating in cal/cm2: 4 cal/cm2

Hazard Risk Category 2 (HRC 2)

Minimum Clothing Requirements: In order to qualify as covered under HRC 2, an employee must at minimum wear one of the following: flame-resistant long-sleeved shirt and pants, OR flame-resistant coveralls.

Additional PPE Equipment: Employees in HRC 2 situations are also required to at minimum be wearing leather safety shoes, safety glasses, and a hard hat with an arc-rated face shield. In certain circumstances, an 8+-cal/cm2 stocking hood or multi-layer switching hood may also be required.

Minimum Layer Requirements: HRC 2 requires one to two layers of protective clothing.

Minimum Arc Rating in cal/cm2: 8 cal/cm2

Hazard Risk Category 3 (HRC 3)

Minimum Clothing Requirements: In order to qualify as covered under HRC 3, an employee must at minimum wear one of the following: a multi-layer flash suit over FR long-sleeved shirt and pants over natural fiber short-sleeved T-shirt and pants, OR a multi-layer flash suit over FR coveralls over natural fiber short-sleeved T-shirt and pants.

Additional PPE Equipment: Employees in HRC 3 situations are also required to at minimum be wearing leather safety shoes, safety glasses, hard hat, hearing protection, and a multi-layer switching hood OR arc-rated goggle and stocking hood.

Minimum Layer Requirements: HRC 3 requires two to three layers of protective clothing.

Minimum Arc Rating in cal/cm2: 25 cal/cm2

Hazard Risk Category 4 (HRC 4)

Minimum Clothing Requirements: In order to qualify as covered under HRC 4, an employee must at minimum wear one of the following: a multi-layer flash suit over FR long-sleeved shirt and pants over natural fiber short-sleeved T-shirt and pants, OR a multi-layer flash suit over FR coveralls over natural fiber short-sleeved T-shirt and pants.

Additional PPE Equipment: Employees in HRC 4 situations are also required to at minimum be wearing leather safety shoes, safety glasses, hard hat, hearing protection, and a multi-layer switching hood OR arc-rated goggle and stocking hood.

Minimum Layer Requirements: HRC 4 requires at least three layers of protective clothing.

Minimum Arc Rating in cal/cm2: 40 cal/cm2

Depending on the specific tasks performed, employees may also be required to wear voltage-rated gloves and use voltage-rated tools appropriate to the equipment being serviced. Whenever possible, energized equipment to be serviced should be put into an electrically safe work condition unless the employer can demonstrate that de-energizing creates more severe hazards (such as when performing work on life-support systems), or is not practical due to limitations of equipment or operation (such as during testing of live equipment). Any service that requires personal protective equipment should only be performed by qualified personnel following a documented plan approved by the manager responsible for the plan.