Arc Flash Protective Personal Equipment (PPE)

Arc Flash Protection

Personal protective equipment, or PPE is designed to protect employees from serious workplace injuries or illnesses resulting from contact with chemical, radiological, physical, electrical, mechanical, or other workplace hazards. Besides face shields, safety glasses, hard hats, and safety shoes, personal protective equipment, or PPE includes a variety of devices and garments such as goggles, coveralls, gloves, vests, earplugs, and respirators.

In order to select the proper PPE, incident energy must be known at every point where workers may be required to perform work on energized equipment. These calculations need to be performed by a qualified person such as an electrical engineer. All parts of the body that may be exposed to the arc flash need to be covered by the appropriate type and quality of PPE. Proper PPE can include Flame Resistant clothing, helmet or headgear, face shield, safety glasses, gloves, shoes, etc. depending upon the magnitude of the arc energy.

What is my risk to being exposed to arc flash? The exposure to arc flash depends on the following:

• Number of times the workers perform a task involving exposed live equipment
• Complexity of the task performed, need to use force, available space, safety margins, reach, etc.
• Training, skills, mental and physical agility, coordination with helper
• Tools used
• Condition of equipment

Exposure to an arc flash frequently results in a variety of serious injuries and in some cases death. Workers have been injured even though they were ten feet or more away from the arc center. Worker injuries can include damaged hearing, eyesight, and severe burns requiring years of skin grafting and rehabilitation.

Equipment can be destroyed causing extensive downtime and requiring expensive replacement and repair. The cost of treatment for the injured worker can exceed $1,000,000/case. This does not include very significant litigation fees, insurance increases, fines, accident investigation, etc. This also does not include process loss to the employer.

Preventive maintenance, worker training, and an effective safety program can significantly reduce arc flash exposure. Preventive maintenance should be conducted on a routine basis to ensure safe operation. As part of a preventive maintenance program, equipment should be thoroughly cleaned and routine inspections should be conducted by qualified personnel who understand how to uncover loose connections, overheated terminals, discoloration of nearby insulation, and pitted contacts.

A comprehensive preventive maintenance plan should also include:

• Using corrosion resistant terminals and insulate exposed metal parts if possible
• Sealing all open areas of equipment to ensure rodents and birds cannot enter
• Verifying that all relays and breakers operate properly

Arc Flash first became popular in the early 1980’s with the publication by Ralph Lee titled, “The Other Electrical Hazard: Electric Arc Blast Burns.” Similar studies illustrated that too many people were suffering injuries as a result of arc flash incidents. Therefore, early adopters in the petrochemical industry took steps to establish the first set of practices designed to better protect employees and electrical contractors. Soon other industries recognized the need for additional protection against arc flash hazards. These new industry standards developed by the NEC and others were designed to keep electrical workers free from the hazards of shock, electrocution, arc flash, and arc blast.

Shock, electrocution, arc flash, and arc blast are responsible for hundreds of worker deaths and thousands of injuries per year in the U.S. alone.  Many of the deaths and injuries are completely preventable with the proper preformed arc-flash analysis and the correct level of personal protective equipment worn.  January 2009 is just around the corner and time is ticking for companies and their workers to comply with NESC (National Electrical Safety Code) rules 410A3 and 42012.  Per NESC Rule 410 A3, “If an arc-flash assessment determines a potential employee exposure greater than 2 cal/cm2 exists2, the employer shall require employees to wear clothing or a clothing system that has an effective arc rating not less than the anticipated level of arc energy.”

In order for workers to be protected with the correct level of personal protective equipment, an arc flash hazard analysis must occur.  The analysis will identify the arc flash protection boundary, the proper ppe necessary, and also appropriate safety-related work practices.  Included in the process is a study of short circuits to determine the available “bolted” fault current at each location.  The study will gather all relevant overcurrent protection device data to accurately predict the clearing time of the arc fault current, and the calculation of arc flash protection boundaries and incident energies, which are used to determine PPE categories.  NFPA 70E (Electrical Safety in the Workplace) is a standard of the National Fire Protection Association that addresses electrical safety requirements for employees. Defined by NFPA 70E, the categories of personal protective equipment workers are required to wear for the work to be performed, based on the incident heat energy calculated at the appropriate working distance are the following:

Category      Cal/cm²      Personal Protective Equipment

0                 1.2            Untreated cotton
1                 5               Flame retardant (FR) shirt and FR pants
2                 8               Cotton underwear, FR shirt and FR pants
3                 25             Cotton underwear, FR shirt, FR pants and FR coveralls
4                 40             Cotton underwear, FR shirt, FR pants, and double layer switching coat and pants

We must keep in mind, the purpose of the new rules is to keep people safe.  Yes, it is tedious, yes it costs money and yes, it can be a nuisance to prepare your company.  The purpose of the NESC is the practical safeguarding of persons during the installation, operation, or maintenance of electric supply and communication lines and associated equipment.  The organization does not create rules to be a nuisance.  Chuck Woodings, a member of the NESC SCC8 subcommittee states, “The intent of the rules is to protect the employee from catastrophic injury and minor injuries if a flash occurs.”

Here at Texso Instruments, our goal is to provide the necessary personal protective equipment for workers, and to help ensure companies are compliant with this deadline.   We offer many types of PPE, and all categories of clothing to protect from arc flash dangers.    A lot of confusion exists regarding proper protection and categories of clothing.  January 1, 2009 is quickly approaching, and compliance is mandatory, not a choice.  Let us help keep workers protected and ensure compliance.

Contact:

Gary Phillips
Texso Instruments
(760) 444-0032
http://www.texsoinstruments.com

In North Carolina, a local electric company sent a request for a replacement of a high voltage distribution switch for an underground system with another switch that included a disconnect on the load side.   The existing switch had only been in service for one year, but a new switch was needed, stemming from rapid growth of the area.  The new switch would allow the isolation of circuits on the load side independently of each other.

Shortly before 9:00am on a crisp spring morning, two electricians showed up to make the switch.  When they arrived, no one from the electric company was present.  They discussed whether or not the distribution switch was de-energized.  They opened the door of one of the cabinets, and one of the men started guiding a tic tracer.  He allowed it to make contact with a 23,000 volt source, sending 13,200 volts through the ground and into his body.  Paramedics arrived quickly on the scene, but he was pronounced dead at 10:20am.  The other worker received minor flash burns of the eyes and face and stated that he was “electrified,” shaken, and proceeded to run.

When the investigation of the incident was performed, it was determined the man who did not survive was not wearing the required personal protective equipment.  The system was not de-energized or properly grounded.  Written company work procedures require both of these factors.  To add to the tragedy, both workers were present at a safety demonstration that discussed the exact job being performed only two days prior to this incident.  Laws can be written and procedures outlined, but it is up to every individual to follow the rules and guidelines.  Personal protective equipment is designed to prevent accidents like this from happening.  It will do no good if it is not worn when needed.

Arc Thermal Performance Value (ATPV): This value is presented in calories per square centimeter and represents the maximum capability for arc-flash protection of a particular garment.  This rating also applies to fabrics.  A garment made from more than one layer of arc-flash rated fabric will have a calories per square centimeter rating greater than the sum of the ATPV ratings of the original fabrics.  The calories per square centimeter rating of most arc-flash protective suits, coveralls, and coats is commonly sewn into the fabric in large letters on the outside of the garment.

Flame Resistant (FR): Flame resistant can describe a fabric naturally resistant to burning but also can represent a material with special treatment applied to the fabric.  Occasionally, the letters FR are used to represent flame retardant. This can lead to some confusion because a flame-retardant treated fabric is flame resistant, but a flame-resistant fabric is not necessarily flame retardant.

Flame Retardant: This term could be used to describe a fabric made up of a flammable fabric treated in such a way that it will provide arc-flash protection.

Fabric Weight: This is usually represented in one of two ways: ounces per square yard or grams per square meter. Both of these values essentially refer to the thickness of the fabric. The more ounces per square yard, the more material exists in the same square yard of fabric.

Heat Attenuation Factor (HAF): This is the amount of heat blocked by the fabric. Even though a fabric may be 100 per cent flame resistant, that does not mean it will block all of the heat to which it is exposed. An HAF of 85 percent means that it will block 85 percent of the heat the fabric encounters. This applies to a short burst of heat – typically less than one second. In the event of prolonged heat exposure, the HAF would be much lower.

Calories per Centimeter Squared: This is a number identifying the amount of energy that can be delivered to a point at a particular distance from an explosion. Once this value is known, the ATPV rating of the required for work at that distance from the potential flash hazard is also known.

Energy Break-Open Threshold (EBT): Primarily, this addresses the physical strength of the fabric with respect to thermal energy and at what value the fabric will fail.

Hazard Risk Category (HRC): This is a 2004 NFPA 70E rating of exposure levels for particular types of equipment. The values range from zero to four, with a zero HRC with a zero HRC not requiring any ATPV-rated. The minimum ATPV rating for Categories One through Four are as follows:

• Category One: five calories per square centimeter
• Category Two: eight calories per square centimeter
• Category Three: 25 calories per square centimeter
• Category Four: 40 calories per square centimeter

Arc flash clothing has been around for years now.  Early personal protective equipment was typically made of one or two fabric layers.  Heavier clothing was used when the need for greater protection existed.  Today’s arc flash clothing is made with a multi-layered construction, making the clothes lighter and easier to wear.  Wearing layers of clothing increases the ability of the PPE to dissipate the heat from arc flash.   It is important to view PPE as a system, because of the need to use individual articles of clothing and equipment together to improve performance against arc flash hazards.

A general guideline is that for every layer of clothing worn under arc-rated clothing, heat will drop by fifty percent per layer.  Keep in mind this is for bodily areas that are covered.  The air between the layers of clothing will increase the ability of the arc-clothing to dissipate heat.  Now, if a person wears an underlayer made of meltable fabrics such as spandex, the chance greatly increases of residual burns from arc flash.  Spandax, being a synthetic fabric can melt even at 180 degrees F. temperatures.    Enough heat can transfer through arc-rated clothing to melt underlayers.  For this reason, cotton underlayers are recommended in most cases although fire resistant underlayers are ideal.

Understanding the importance of a layered system of protective clothing and additional PPE is part of being a qualified electrical worker as well as providing protection in the case of electrical incident.  Layering clothing provides extended performance of arc-rated clothing and offers a method to minimize burns to heat transfer during an arc flash.

A new law regarding arc flash, established by the NESC states, “Effective as of January 1, 2009, the employer shall ensure that an assessment is performed to determine potential exposure to an electric arc for employees who work on or near energized parts or equipment.  If the assessment determines a potential employee exposure greater than 2 cal/cm2 exists, the employer shall require employees to wear clothing or a clothing system that has an effective arc rating not less than the anticipated level of arc energy.”

This law will require workers to wear arc flash suits when exposed to an exposure greater than 2 cal/cm2.  Arc flash is the result of a rapid release of energy due to an arcing short circuit between two or more adjacent conductors.  The cause of the short normally burns away during the initial flash, and the arc fault is then sustained by the establishment of a highly conductive plasma.  Arc flash produces temperatures above 35,000 degrees and statistics say 2000 people are admitted to the hospital every year because of arc flash injury.  The risk of arc flash has contributed to new laws such as the one stated previously beginning in 2009.  It is imperative to protect yourself from the dangers of arc flash by wearing the proper personal protective equipment when working anywhere a potential exists for arc flash.