Of the many workplace safety hazards and risks found in industrial environments, electrical arc flash ranks among the most serious. Injuries from arc flash events are usually acute and often fatal, potentially affecting multiple victims. These incidents also cause damage to plant and equipment, impeding an organisation’s ability to conduct business.
Given the potential for harm, a thorough risk assessment and hazard management program – including provision of suitable personal protective equipment (PPE) – should be a top priority for safety teams in environments where arc flash risks are present
What is arc flash?
An arc flash is a type of electrical fault or short circuit, where current leaves its intended path and travels through the air from one conductor to another or to the ground. The energy released leads to a rise in both temperature and pressure and creates an arc blast.
Arc blast events generate radiant heat up to 20,000˚C – a temperature four times higher than the surface of the sun – and arc plasma, a form of ionised gas that reaches around 5,000˚C and often presents as a ‘fireball’. Additional by-products of an arc blast include a pressure wave capable of knocking a worker off their feet, loud noise, flying shrapnel and other debris including molten metal droplets and vapour.
The potential for injury is significant, with anyone located nearby at risk of serious harm. Likely injuries include external and internal burns – including damage to the lungs and other organs – hearing loss, eye damage and severe fragmentation wounds.
An arc blast will ignite flammable materials including non-arc rated clothing and personal protective equipment (PPE) that is insufficient for the application, which will continue to burn after the event, potentially causing even more harm that the initial incident.
Common causes of arc flash
There are many common causes of arc flash, which range from human factors – including workplace culture, lack of training or skills deficit and distraction or carelessness – through to physical causes including the presence of foreign materials or dust, loose connections, exposed parts, and incorrectly designed or rated preventative equipment, to name but a few.
Given the magnitude of the risk and broad range of potential causes, it’s best to adopt an offensive stance toward arc flash injury. A thorough risk assessment is essential, but it is only part of the picture. Workers must have access to adequate training and the organisation must also provide suitable safety equipment and procedures (including supervision where necessary) as part of the risk reduction process.
Risk Assessment and hazard management
The Electrical Arc Flash Hazard Management Guideline suggests that ‘when workers are required to work on or near electrical equipment, all reasonably practicable measures should be taken to protect workers from the harmful effects of electric arc flash hazards through hazard elimination and risk reduction’.
The recommended hazard management process to achieve that goal follows a generally prescribed format, with the addition of specific arc flash-related considerations as follows:
- Understand the hazard
- Identify assets or asset groups with arc flash hazard potential
- Quantify the hazard (calculate the arc flash incident energy on each asset or asset group)
- Assess the risk (using your organisation’s risk management framework)
- Develop and implement risk treatments using the hierarchy of controls
- Validate control effectiveness
- Monitor and review
Among the risk treatments for arc flash hazard, measures include:
- Where possible – and as a principle – work on dead equipment only
- De-energise and stringently maintain all electrical equipment
- Use suitable current protection including circuit breakers and fuses
- Utilise remote or robotic operators for high-risk activities
- Implement barrier controls including lockable containers and vaults, fences and other barricades
- Educate and adequately train staff and ensure appropriate supervision.
Hierarchy of controls
WHS regulation requires that safety and operations managers work through the hierarchy of controls to manage risk. Where it is not possible to eliminate the risk entirely, replace it with a safer option, isolate the hazard from people, reduce risk through engineering controls or change work practices to avoid it, then PPE that offers the appropriate level of defence must be supplied.
When working on or near electrical equipment, the following types of PPE may be required, dependent on the present risk:
- Arc-rated clothing and/or protective suits
- Hand protection
- Face and head protection including arc flash hoods
- Eye protection
- Ear canal inserts
The Electrical Arc Flash Hazard Management Guideline provides guidance on appropriate PPE types, identified from least to highest risk based on work activity and corresponding tasks, providing a useful starting point for selection.
In the case of hand protection, opt for industrial rubber insulating gloves (RIGs) designed specifically for electrical hazards. RIGs fall under one of six classes (from 00 to 4), which indicate voltage resistance capability. When choosing the right glove, it is important to determine the maximum voltage to which the worker will be exposed and select a class of glove rated at or above that voltage.
Standards
As always, PPE must comply to the applicable PPE regulations and be safe for its intended use. This can be done using harmonised or mandated standards or technical specifications. To be suitable for use against arc flash injury, PPE must protect against the relevant risk presented by following existing standards. Some of these standards are designed for protective clothing and some for protective gloves, although in some instances a standard existing for clothing can also be applied to gloves, depending on the test method described in these standards:
Be flame resistant-rated (FR) or arc flash-rated (AR), as determined under the following standards and testing methods:
- ASTM F1506 Standard performance specification for flame resistant and electric arc rated protective clothing worn by workers exposed to flames and electric arcs
- ASTM F2675-13 Standard test method for determining arc ratings of hand protective products developed and used for electrical arc flash protection
- EN 61482-1-1/IEC 61482-1-1:2019 Protective clothing against the thermal hazards of an electric arc
- Part 1-1: Test methods - Method 1: Determination of the arc rating (ELIM, ATPV and/or EBT) of clothing materials and of protective clothing using an open arc
- EN 61482-1-2/IEC 61482-1-2:2014 Live working - Protective clothing against the thermal hazards of an electric arc
- Part 1-2: Test methods - Method 2: Determination of arc protection class of material and clothing by using a constrained and directed arc (box test) and;
- IEC 61482-2 Protective clothing against thermal arc hazards of an electric arc
FR protection resists ignition, limiting burn injury and insulating the wearer from thermal hazard. AR protection is inherently flame resistant but also includes a measure of insultation to arc flash, which is expressed as Arc Thermal Performance Value (ATPV) or Energy Break-open Threshold (EBT). ATPV is the amount of energy that PPE can support before the wearer suffers second-degree burns, while EBT is determined when breakopen occurs before the onset of a second-degree burn. While the values are expressed differently, they are essentially functional equivalents in terms of protection.
Monitor and Review
The catastrophic nature of arc flash events calls for a rounded approach to risk minimisation. Hazard management should include the provision of suitable training to ensure that workers have the appropriate knowledge and skills to work safely. It must also include development of adequate testing procedures and the provision of appropriate tools and other equipment – including PPE – to safely work on electrical equipment. As a final consideration, work processes and procedures, along with control measures, should be monitored and regularly reviewed to ensure they continue to offer the highest levels of safety.
For further information, view the Ansell Electrical Glove Selection Guide here
