Determine the Right Arc Flash Protective Clothing for Each Application

Safety SPI

May 6, 2020

The risk of electric explosion and arc flash injuries is high, from superficial burns to fatalities. The leading causes of occupational accidents are deficient maintenance and inspection of installations as well as unsafe practices due to inadequate training.

It is essential to wear AF clothing when there are arc flash risks. Wearing AF and fire-resistant clothing will protect the workers from injuries generally caused by momentary and continuous ignition of non-flammable clothing. As AF clothing is self-extinguishing, it limits possible injuries.

To select the right work gear, incident energies must first be estimated. Only after estimating how many calories per square centimeter is performed that the worker is able to make an informed choice.

AF clothing is divided into four different categories: category 1, category 2, category 3 and category 4. The right clothing category for a particular application must be determined by the estimated incident energy that is calculated and according to the requirements of the standard CSA Z462-2018.

• Category 1: clothing with minimum arc index of 4 cal/cm2
• Category 2: clothing with minimum arc index of 8 cal/cm2
• Category 3: arc-rated clothing of at least 25 cal/cm2
• Category 4: arc-rated clothing of at least 40 cal/cm2

At Bulwark, most monolayer clothing used for low and high-voltage power line work provides a minimum protection of 8 calories per cm2. If all estimates are fewer than 8 calories per cm2, category 2 clothing is sufficient. For installations with risks higher than 8 cal/cm2, simply increase the distance between the work and the arc (until obtaining an estimated 8 cal/cm2 or lower) or add additional clothing layers until reaching the right protection level for incident energy.

Multi-layer system

The multi-layer system proposes putting on two layers or more of AF clothing in order to reach a higher protection level. It is mandatory that the outer layer is AF approved and the inner layer is made of natural fibres. Sometimes, two lighter layers of lesser categories may offer a better protection than a single layer of a higher category. However, it is not simply a matter of adding up layers to increase the protection level. The efficiency of all layers together must be tested in order to assess the overall protection. It is with this in mind that the Bulwark Arc Rating Calculator becomes an important tool. This calculator proposes the best AF clothing combination according to a pre-selected clothing item and the arc flash protection needed.

In the example shown below, there are 35 possible combinations with the item MPU8 for an estimated arc of 20. It is also possible to refine the search by specifying the desired category and fabric type. A valuable tool to make safe choices.

This article was first published online by SPI Health and Safety; The company’s mission is to be the single most valuable partner for companies that value health and safety in their work environment.

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