Lockout Tagout and Arc Flash Shock Hazard Evaluation

When energy isolation by Lockout Tagout is to be performed on any point on energized conductor or circuit part, we need to evaluate the shock risk and accordingly determine the effective protection. We are thankful to Mr. Bhabani Mishra, a seasoned EHS Professional from Dalmia Group for sharing this article on ARC FLASH HAZARD.

Shock Protection Boundaries:

1. Your risk of being shocked by exposed energized electrical conductors or circuit parts depends in part on your distance to the conductor. Shock protection boundaries describe zones of risk depending on how far away you are from the conductors or parts.
2. The limited approach boundary is the radius within which a shock hazard exists.
3. The restricted approach boundary is the radius within which an elevated risk of shock from arc-over or inadvertent movement contact exists.

Shock Risk Assessment:

- A shock risk assessment determines the shock hazards, approach boundary distances, PPE requirements, and insulated tools and equipment for a specific electrical work task.

- To conduct a shock risk assessment, first determine the voltage to which you will be exposed.

- Then use the tables below Approach Distances to determine the radii of the restricted and limited approach boundaries for your voltage and current type.

- Once you have determined the approach boundary distances, select the proper PPE and insulated tools as per the requirement and equipment for work within the restricted approach boundary.

- You must wear electrical insulated gloves with an outer covering of leather for protection when working inside the restricted approach boundary.

- You must wear ASTM F2413 EH-rated or equivalent-rated electrical shock resistant safety shoes or boots when working within the restricted approach boundary.

- Record your shock risk assessment information, including approach boundaries and PPE requirements, on your energized electrical work permit form.

Work within the Limited Approach Boundary:

- Both qualified and unqualified persons may work within the limited approach boundary, but a qualified person must advise the unqualified person of the hazards and escort them while inside the boundary.

- The person responsible for the energized work activity shall ensure the limited approach boundary is marked using signs, barriers, or safety attendants.

- This person also shall ensure unqualified persons working near the energized work area are instructed to stay outside of the limited approach boundary.

Work within the Restricted Approach Boundary:

- Only qualified persons may work within the restricted work boundary.

- Qualified employees may not cross, work within, or extend a conductive object across this boundary unless they do all of the following:

1. a) Wear the insulated electrical safety gloves and other PPE and use insulated tools and equipment determined in their shock risk assessment.
2. b) Insulate the energized conductor from themselves and from all other conductive objects at a different potential by using an insulated cover or barrier, or confirm it is insulated already.

Arc Flash Boundary:

- The arc flash boundary is the radius within which a serious arc flash burn hazard exists. At the arc flash boundary, the energy from an arc flash, called incident energy, is 1.2 cal./cm2.

Arc Flash Risk Assessment:

In an arc flash risk assessment you determine whether an arc flash hazard exists, and, if it exists, you determine the arc flash boundary, the appropriate safety-related work practices, and PPE that you must wear within the arc flash boundary.