What is Arc Flash? Answering The Common NFPA 70E Basics
“Anything That Can Go Wrong Will Go Wrong”
– Murphy’s Law
Believed to only be a rare event, arc flash can happen to any employee at any point when dealing with electrical equipment or machinery. The right conditions can cause a catastrophic event. It’s important employees and employers understand what arc flash is, how it happens, and what can be done to help prevent such disasters.
What is Arc Flash?
Arc Flash is the powerful rapid release of energy when current travels or arcs between two live conductors through the air (or grounds) causing an arc fault. This type of electrical discharge results from a low impedance (low-frequency resistance to a current). As the temperature of the arc increases the electrical resistance decreases which can draw more current. This results in a high-intensity electrical explosion that will cause serious harm or damage not only to employees in the area but machines and equipment as well. The immense heat and light are known as the Arc Flash while the pressure wave that’s caused by this explosion is known as the arc blast.
The intense release of concentrated energy and hot gases create temperatures that reach 35,000 °F (19,400 °C). For reference flowing lava can get up to 1,600 °F (871 °C) and the surface of the sun is 9,000 °F (4,982 °C). This makes the release of energy caused by an Arc Flash almost twenty-two times hotter than lava and four times hotter than the surface temperature of the sun.
What Can Cause An Arc Flash?
There are multiple factors that can create an environment that will harness an arc flash event. The following are ways this can happen.
- Dropped tools or equipment when working on an electrical system
- Condensation which can be caused by humidity
- Dust/ Dusty areas
- Accidental contact
- Water Leakage into electrical machinery
- Faulty installation (improperly installed electrical equipment)
- Machine or equipment failure
- Damaged wires (bent, stripped, corroded, etc.)
What Kind Of Injuries Could You Experience?
Electrocution is the first thing that comes to mind when you think of an arc flash injury. Yes, an employee does face that risk but there are other injuries that can be sustained if proper precaution isn’t taken. Below are some other ways that individuals can be hurt when exposed to an arc flash event.
- Electrical Skin burns from direct exposure
- Thermal burns from the arc flash or blasts
- Injury to the retina of the eye from the high-intensity ultraviolet flash
- Severe Hearing damage due to explosion (can reach 140 dB)
- Bodily Trauma from molten metal shrapnel, flying debris or projectiles
- Internal burns from inhalation of hot gases and vaporized metals
- Being Tossed By Blast Pressure (2,000 lbs per square foot)
The severity of injuries employees can face are influenced by different factors present during an arc flash event. The following are five primary factors that determine the severity of injuries.
- The heat coming from an electrical arc is known as “incident energy.” This incident energy is made up of convection heat and radiated heat. The more distance between an employee and the arc, the safer they are.
- Temperatures from an arc flash event can vaporize metals and have been recorded at 35,000 °F (19,400 °C). The closer a person is to this radical event the more danger they face.
- Longer arcs create more incident energy or heat as opposed to shorter arcs. High-voltage systems present a greater risk, however low voltage systems have been known to fail and be just as destructive.
- The duration of an arc flash event is the second largest factor when it comes to injury severity. Even a small increase in duration can be sinister. The longer the incident energy lasts the more time there is for trauma.
- It’s important that employees wear approved articles of clothing and PPE when working around electrical equipment. The weight of clothing layers and the type reduces heat and burns to the body.
How To Avoid Arc Flash
It all starts with a strong safety training foundation and company enforcement of procedures. Below are several steps that an employer can take to prevent an Arc Flash incident in the workplace:
- First and foremost initial electrical and arc flash training should be the top priority. It’s important that all employees are trained on the procedures and safe work practices that align with OSHA standards as well as NFPA 70E (Standard for Electrical Safety in the Workplace).
- The appropriate arc-rated Personal Protective Equipment (PPE) must be supplied for the task at hand. The rating of the PPE needed will be determined in the arc flash assessment. Employees should also be trained on the dangers of wearing conductive jewelry, electronics or clothing. They should know that wearing layers that can melt underneath arc-rated outer layers (synthetic fibers) is a danger. Those kinds of fibers can lead to second and even third-degree burns if worn.
- Provide workplace warning labels and signage on high-voltage machinery, power lines, and power panels. This is not only very important but ensures that all employees working on or near these elements are cautious and taking the correct preventative measures.
- Whenever maintenance or repair work must be done to equipment or machinery employees must de-energize those devices before initiating those repairs. There are situations when it’s infeasible to de-energize equipment and that includes when de-energizing the equipment can cause other risks or hazards.