Electrical Arc Flash:

Protecting against residual risk - DuPont‘s “4 P“ Approach

Alsico Academy
A plus A

Elaina Harvey ...
DuPont’s Methodology for Approaching Arc Risk Hazards
YES

Re-evaluate

Predict
Severity

Can we apply
further
prevention
...
Usually an inadvertent contact between
an energised conductor with another
conductor or an earthed surface.

What is an El...
Determination of the Thermal effects of an Electric Arc on PPE
IEC 61482-2 (Draft EN 61482-2)
Requirements for Material Pe...
Ensuring Fit-for Purpose Garments for Your Situation
Arc Rating*

Body Protection

ATPV > 4 cal/cm2
Box Test Class 1

ATPV...
Examples In DuPont’s Thermal Industrial Guide

•

Using Nomex® provides lightweight
comfortable layering to the relevant
l...
Wish To Find Out More Information?
• www.arcguide.dupont.com
• www.nomex.co.uk/solutions
• Ask an Alisco Specialist
• Visi...
Disclaimer Notice
This information corresponds to our current knowledge on
the subject and may be subject to revision as n...
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Protecting against residual risk - DuPont‘s “4 P“ Approach

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  • The DuPontTM 4 P Approach is structured around the principles Predict, Prevent, Protect & Publish.
    Predict – determine the severity of the thermal effect of an arc flash by the amount of “incident energy” that a person, standing at a given distance away from the arc, could receive. “How big will the bang be?”. Also calculating the distance boundary at which the predicted incident energy reduces to a level of 1.2 cal/cm2 beyond which the thermal effects of the arc will not be sufficient to cause injury. This can be achieved by carrying out an arc flash study and DuPont can put you in touch with organisations to carry this out.
    Can the end user apply further Prevention techniques?
    Prevent - design out, eliminate or remove the hazard at its source by engineering means or changes to work practices so to prevent it from happening and reduce the level of injury.
    Re-evaluate the severity of the arc again (Predict) and if no other Prevention techniques can be made then customers then move to
    Protect - where the risk cannot be controlled by prevention or where there is a residual risk of injury then it may be necessary to consider as a mitigation technique the use of personal protective equipment (PPE) to prevent injury to the worker. PPE should be used as a last resort!
    Publish - communicate and document results of site arc flash to those who are at risk including European warning labelling on switch gear
  • Electric arc flash is usually caused by inadvertent contact between an energised conductor, such as a bus bar or wire, with another conductor or an earthed surface.
    The video shows the effect of an arc flash
    This video is from the US and has been discussed on many web forums and is available in the public domain. There are no confirmed details about why this incident occurred and what happened to the person involved in the arcflash. Some say it was in Bogota Columbia in April 2007 and that the breaker being racked in had been in storage for a long time in a damp location allowing the fibreglass insulation to absorb moisture. The breaker is being placed back in service and racked in for the first time, no one tested the breaker before installation, when the line side disconnects it contacted the buss, the damp insulation allowed a phase to phase fault to occur.
    It is believed that the person was racking in a breaker standing approx 1 metre from the door hinge out of the way of the blast - this is standard switching procedure in the US. The workers appear to be wearing NFPA 70 E category 2 FR PPE 8 cal/cm2 PPE because the worker racking in the breaker adds eyewear and pulls down his visor. This video is purely for demonstration purposes to show the potential effects of an arc flash.
     
    Outcome of the person: not known, some say he may have died, the other is he was Okay since he was standing to the side (US switching procedure for just this reason) the bulk of the energy missed him and the PPE that he had on was sufficient to protect while he was jumping back.
    The resulting short circuit current will melt the conductors, ionise the air and create a conducting plasma fireball with temperatures in the core of the arc that can reach upwards of 20,000 degrees centigrade. (But the temperature of the surfaces exposed to the heat generated by the arc will be “only” a few hundred oC) Arc flash injury can include external burns to the skin, internal burns from inhaling hot gasses and vaporised metal, hearing damage and eye damage (such as blindness from the ultraviolet light of the flash). Inevitably, the consequences can include Health & Safety investigations resulting in prohibition notices, improvement requests, fines and corporate/individual prosecutions, severe equipment damage, lost production and loss of company reputation.
    When an arcing fault occurs, the result can be extremely high temperatures, a tremendous pressure blast and shrapnel hurling at high velocity. An accidental slip of a tool, or a lose part tumbling across live parts can initiate an arcing fault in the equipment. If a person is in the proximity of an arcing fault, the flash can cause serious injury or death. The point of the 110.16 warning label is to remind qualified workers of the arc flash hazard when working on electrical equipment.
    This slide identifies some of the effects of an arcing fault including:
    Extreme Heat, Pressure waves, Loud sound waves, Molten Metal
    Copper vapor, Intense Light, Shrapnel
    A phase to ground or phase to phase arcing fault can quickly escalate into a three phase arcing fault due to the expansive cloud of conductive copper vapor which can engulf all phase conductors .
  • The International Electrotechnical Commission (IEC) has developed a series of standards for clothing to protect against the thermal hazards of an electric arc. However, these standards do not address electric shock hazards, effects of noise, UV emissions, air pressure, shrapnel or other possible projected substances such as hot oil, the consequences of physical and mental shock or the toxic influences of an electric arc.
    The IEC 61482-2 is the garment standard which allows the use of two ways to technically assess the fabric and garment performance in an electric arc, i.e. assess its arc rating. The CENELEC version of this IEC standard, is still at the committee level for being finalised and then published as EN 61482-2.
    The two ways that an “arc rating” is achieved is either by the
    i) Open Arc Test (EN 61482-1-1) which provides the “Arc Thermal Performance Value” (ATPV) and “Breakopen Threshold Energy” (EBT50) – which ever is the lower of both values being taken as the arc rating
    And/or by the
    ii) Box Test (EN 61482-1-2) which evaluates whether it passes the “Class 1” or the more severe “Class 2” simulated arc exposure environments.
    (EN ISO 11612 uses the same test methods for assessing the arc rating of fabrics and garments.)
    Our technical clothing experts can help advise which Nomex® fabric system will be most appropriate to your needs and hazards
    Further Information
    IEC 61482-2 is the adopted IEC performance standard for arc protective clothing, and it has been intention of having it adopted by CENELC as an EN standard with the number EN 61482-2. However it has become unlikely that it will be published in it’s present form as an harmonised EN standard.
    Nevertheless, some Notified Bodies are already accept garments submitted by manufacturers to be CE certified and labelled to this standard.
    Garment manufacturers must go through the following process:
    a) Select materials that have been tested and classified according to IEC/EN 61482 part 1-1 or part 1-2
    b) Materials must also meet the Flame Spread and Physical requirements of IEC 61482-2.
    c) Construct garments compliant to the Design requirements of IEC 61482-2.
    d) Have garments tested to, and pass, the relevant garment test of IEC/EN 61482 parts 1-1 or 1-2.
    e) Marking (labelling) and User Information must meet the requirements of IEC 61482-2, and any relevant legislation.
    f) For the European Economic Area (EEA), garments must undergo the relevant procedures of the PPE Directive, 89/686/EEC. As these garments are generally considered to be Category III, this has to include Article 10 (EC Type-examination) and Article 11 ( Checking of PPE manufactured and/or manufacturer’s quality assurance system of PPE).
    For other territories, different Certification or Verification schemes may apply.
    IEC 61482:2 Material Flame / Physical Testing
    All materials in a compliant garment must meet the Flame Spread requirements of IEC 61482-2 after cleaning pre-treatment:
    The flame spread is tested to ISO 15025 and classified to ISO 14116:
    All single layer garments must be of Index 3 material.
    All multi-layer garments must have Index 3 material as the outer and inner layers. Any enclosed middle layers must be at least Index 1.
    Outer materials must also meet the Physical requirements of IEC 61482-2. These are:
    Tear strength at least 20N (fabrics 220 g.m-² and above) or at least 15 N (fabrics 150 to 220 g.m-²), tested to ISO 13937-2.
    Tensile strength at least 400 N (fabrics 220 g.m-² and above) or at least 250 N (fabrics 150 to 220 g.m-²), tested to ISO 13934-1.
    Burst strength for knitted fabrics at least 200 kPa, tested to ISO 13938-2.
    Dimensional change of outer not more than 3% (woven) or 5% (knitted) after the specified cleaning pre-treatment.
  • Where the risk cannot be controlled by prevention or where there is a residual risk of injury then one has to consider mitigation to prevent injury to the worker.
    In general, if the prospective incident energy exposure at a given location is below 1.2 cal/cm2, no additional thermal protection is required for the worker. This is achieved by the determination of a boundary beyond which the incident energy is less than 1.2 cal/cm2 or through shielding or application of properly designed specialist PPE capable of withstanding the thermal effects of the arc. Where protection against the thermal effects becomes necessary it must be emphasized that PPE does not prevent the accident happening in the first place.
    Personal Protective Equipment (PPE) used for arc flash protection includes garments are made from Nomex®. Flame Resistant (FR) fabrics are designed to provide a thermal barrier and limit the incident energy exposure at the skin surface to no greater than 1.2 cal/cm2. It also must not break or burn open and expose the skin directly to the heat or incandescent or flaming debris caused by an electric arc.
    As a result of the risk assessment, layering up in Nomex® provides an excellent lightweight and comfortable solution matching the customer’s required protection without the need for heavy switching suits. If switching suits are required, Nomex® multilayer assemblies offer a lightweight solution.
    * In Europe there are not ATPV category classes like there is in the USA according to NFPA 70
  • Protecting against residual risk - DuPont‘s “4 P“ Approach

    1. 1. Electrical Arc Flash: Protecting against residual risk - DuPont‘s “4 P“ Approach Alsico Academy A plus A Elaina Harvey - Electric Arc End User Specialist - Nomex® The DuPont Oval, DuPont™, The miracles of science™, Nomex® and ArcMan® are registered trademarks or trademarks of DuPont or its affiliates
    2. 2. DuPont’s Methodology for Approaching Arc Risk Hazards YES Re-evaluate Predict Severity Can we apply further prevention techniques? Results NO START Predict Publish Publish Results & Training Prevent Protect Apply Protection Measures Residual Risk
    3. 3. Usually an inadvertent contact between an energised conductor with another conductor or an earthed surface. What is an Electric Arc? 2 7 3 1 8 6 5 Possible causes of electrical arcs: • Accidental contact with energized parts • Contamination (e.g. dust) on insulating surfaces • Wiring errors • Corrosion of equipment parts and contacts • Improper work procedures 4 1 Plasma 2 Molten Metal 3 Pressure Waves Sound Waves 4 Shrapnel 5 Hot Air-Rapid Expansion 6 Intense UV Light and Infra Red Radiation 7 Copper Vapor: Solid to Vapor Expands 8 Radiant and Convective Heat 20’000 °C. (Temp on surfaces only a few hundred oC) Arc flash Incident
    4. 4. Determination of the Thermal effects of an Electric Arc on PPE IEC 61482-2 (Draft EN 61482-2) Requirements for Material Performance & Garment Design, Marking & User Information in accordance to Determination of the Incident Energy EN / IEC 61482-1-1 (Open Arc Test) Thermal Resistance: Arc Thermal Performance Value (ATPV) or Breakopen Threshold Energy (EBT50) (Value is > Prospective Incident Energy identified during risk assessment) scenarios EN / IEC 61482-1-2 (Box Test) Arc Protection Classes: Class 1 (4kA) Class 2 (7kA) Pass/Fail Protect DuPontTM Arc-Man® Two different ways of testing Protective Clothing & Materials Simulation of defined
    5. 5. Ensuring Fit-for Purpose Garments for Your Situation Arc Rating* Body Protection ATPV > 4 cal/cm2 Box Test Class 1 ATPV > 8 cal/cm2 Box Test Class 1 Long Sleeved Long Sleeved Jacket Business Shirt Polo Shirt Coat PT IO NA L Coverall O O PT IO NA L ATPV > 12 cal/cm2 Box Test Class 1 Trousers ATPV > 25 cal/cm2 Box Test Class 2 ATPV > 40 cal/cm2 Box Test Class 2 * In Europe there are not ATPV category classes like there is in the USA according to NFPA 70 Weather Jacket & Trouser
    6. 6. Examples In DuPont’s Thermal Industrial Guide • Using Nomex® provides lightweight comfortable layering to the relevant level of protection • Ensures worker is not restricted from cumbersome clothing 4 to > 40 cal/cm2 / Class 1 & Class 2 systems available
    7. 7. Wish To Find Out More Information? • www.arcguide.dupont.com • www.nomex.co.uk/solutions • Ask an Alisco Specialist • Visit the DuPont Stand Hall 5 A40 • Questions? elaina.harvey@dupont.com +44 7881 836588 7
    8. 8. Disclaimer Notice This information corresponds to our current knowledge on the subject and may be subject to revision as new knowledge becomes available. It is your responsibility to investigate other sources of information on this issue that more appropriately addresses your product and its intended use. DuPont makes no warranties and accepts no liability whatsoever. This information is not intended for use by you or others in advertising, promotion, publication or any other commercial use. 8

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