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Electrical Arc FlashNFPA 70E

Introductions

Presented by:Ted Sommer

AgendaAgenda

TodayUnderstanding hazards of working around electrical energyArc flash hazard Approach boundariesPPE selection and useEquipment Labeling

What Causes an Arc Flash??What Causes an Arc Flash??

What is an Electrical Arc?What is an Electrical Arc?

NFPA 70E OverviewNFPA 70E OverviewNFPA 70E states that all facilities must provide the following:•A safety program with defined responsibilities for employees both (qualified and unqualified)

•Analysis for arc flash hazard degree

•Personal protective equipment (Clothing and tools, etc.) for all workers involved

•Training for all workers

•Correct warning labels on all electrical equipment

Some Statistics on Injuries and Some Statistics on Injuries and Why NFPA 70E has a Purpose!Why NFPA 70E has a Purpose!

•It is estimated that 5 –10 arc flash incidents occur each day in the United States

•350 Electrical –related fatalities annually

•4000 Non-disabling incidents from contact annually

•3600 Disabling incidents occur from contact annually

•2000 Admitted to hospitals with Arc Burns annually

There were several deaths and severe arc injuries in Wisconsin last year alone!

75-80% of all serious electrical injuries are related to electrical arcs created during short circuits and switching procedures.

Electrical Injuries That Can Electrical Injuries That Can OccurOccur

Low-voltage contact woundsHigh-voltage contact wounds (entry & exit)BurnsRespiratory difficulties (the tongue may swell and obstruct the airway; or vaporized metal or heated air may have been inhaled)

Infectious complicationsInjury to bone through falls, heat necrosis, and muscle contractionInjury to the heart (dysrythmia, cardiac arrest)Internal and organ injuriesNeurological injuryInjury to the eyes (cataracts may occur up to 3 yrs later)

A ten KA arc blast A ten KA arc blast can reach the can reach the

equivalent explosive equivalent explosive power of 8 sticks of power of 8 sticks of

dynamitedynamite

Milwaukee Incident Milwaukee Incident -- 20032003

“Safety has priority over service continuity, equipment damage or economics.”

Institute of Electrical and Electronic Engineers “Buff Book”

There are many hazards that exist as you approach

energized electrical equipment!

There are many hazards that There are many hazards that exist as you approach exist as you approach

energized electrical equipment!energized electrical equipment!

Arc FaultArc Fault

A BA B

BoltedShort Circuit

Electrical Arcs CreateElectrical Arcs Create

Pressure Waves

Copper Vapor:Solid to VaporExpands by67,000 times

Molten Metal

Intense Light

Hot Air-Rapid Expansion

35,000 °F

Shrapnel

Sound Waves

> Indicates Meter Pegged

Results: Test No.4Results: Test No.4

141.5 db @ 2 ft.

T2T2>225°C / 437°F

T3T350°C / 122°F

P1P1>2160 lbs/sq.ft

> 225°C / 437°F

T1T1

SoundSound

Incident ComparisonIncident Comparison

March 2001400A 480V Service EntranceSmall-Medium sized industrial facility (wood processing)Employee knew it was hotNo PPE Worn

Injuries sustained:2nd & 3rd degree burns to head, arm, handNearly lost earMed-evac from site to University HospOff work for a monthSeveral surgeries

Case #1 Town & Country

Case#1Case#1

Case #1Case #1

Case #1Case #1

July 2001480V 800A “slide in tub” gearLate night Preventive MaintenanceTelecommunications Provider

Injuries Sustained:

NONENONE

Incident ComparisonIncident ComparisonCase #2 Town & Country

Case #2Case #2

Case #2Case #2

Case #2Case #2

Case #2Case #2

Requirements for safe work practices, andaddresses all areas of electrical safety needs:

Shock HazardArc FlashInsulated ToolsOne-LinesLOTOQualified PersonsTrainingAll PPE NeedsLabeling Etc........

More than simply ArcFlash Protection!

Changes for 2004 NFPA 70EChanges for 2004 NFPA 70E

New NFPA 70E was released in April of 2004Added Multi-Employer language for the first timeRequires host employers and contractors to work together to address electrical hazards

MultiMulti--Employer LanguageEmployer Language

110.4 Multiemployer Relationship.(A) Safe Work Practices. On

multiemployer worksites (in all industry sectors), more than one employer may be responsible for hazardous conditions that violate safe work practices.

Outside personnel Outside personnel (contractors, etc.).(contractors, etc.).

(B) Outside Personnel (Contractors, etc.). Whenever outside servicing personnel are to be engaged in activities covered by the scope and application of this standard, the on-site employer and the outside employer(s) shall inform each other of existing hazards, personal protective equipment/clothing requirements, safe work practice procedures, and emergency/evacuation procedures applicable to the work to be performed. This coordination shall include a meeting and documentation.

Determination and Monitoring of Determination and Monitoring of Work on Live Systems.Work on Live Systems.

The onsite employer or its designee shall decide whether electrical contractor or maintenance work on lines and systems is to be performed in an energized or de-energized manner.

Qualified PersonsQualified Persons

(2) Unqualified Persons. Unqualified persons shall be trained in and be familiar with any of the electrical safetyrelatedpractices that might not be addressed specifically by Chapter 1 but are necessary for their safety.

Qualified PersonsQualified Persons

(1) Qualified Person. A qualified person shall be trained and knowledgeable of the construction and operation of equipment or a specific work method and be trained to recognize and avoid the electrical hazards that might be present with respect to that equipment or work method.

What are these “accessible to What are these “accessible to qualified personnel” spacesqualified personnel” spaces

Rooms, Vaults, balconies or similar enclosures accessible only to qualified personnel etc.

If the access is possible thenIf the access is possible then

The conductors and the equipment need to be in an “electrically safe condition”

Electrically Safe Work Condition. A state in which the conductor or circuit part to be worked on or near has been disconnected from energized parts, locked/tagged in accordance with established standards, tested to ensure the absence of voltage, and grounded if determined necessary.

As a minimum you need:As a minimum you need:

Signs to warn those unqualified (other trades) of the hazardsBarricades (to keep them out.)And if that is not effective then an attendant to ensure that they stay out of the area.Remember the plumber with the copper pipe that walked into the electrical bus bar in Brookfield????

110.16 Flash Protection. Switchboards, panelboards, meter socket enclosures, industrial control panels, and motor control centers in other than dwelling occupancies, that are likely to require examination, adjustment, servicing, or maintenance while energized, shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.

FPN No. 1: NFPA 70E-2004, Electrical Safety Requirements for Employee Workplaces, provides assistance in determining severity of potential exposure, planning safe work practices, and selecting personal protective equipment.

FPN No. 2: ANSI Z535.4-1998, Product Safety Signs and Labels, provides guidelines for the design of safety signs and labels for application to products.

Reprinted from NEC® 2002

2005 National Electrical Code Book States:

WARNING!Arc Flash and Shock Hazard

Appropriate PPE Required per NFPA 70E

Basic Arc Flash LabelTo Warn Personnel

Example of Basic Labeling Applied to Electrical Equipment

Safety relies on employees to fully understand the hazards associated with each piece of equipment

24 inch Flash Hazard Boundary3 cal/cm•2 Flash Hazard at 18 inches1DF PPE Level, 1 Layer 6 ozNomex ®,

Leather Gloves Face shield480 VAC Shock Hazard when Cover is removed42 inch Limited Approach12 inch Restricted Approach - 500 V Class 00 Gloves1 inch Prohibited Approach - 500 V Class 00 Gloves

Equipment Name: Slurry Pump Starter

WARNING!Arc Flash and Shock HazardAppropriate PPE Required

Courtesy E.I. du Pont de Nemours & Co.

NFPA 70E Boundaries NFPA 70E Boundaries 70E70E--2004 130.22004 130.2

Shock Protection BoundariesLimited Approach Boundary

Entered only by qualified persons or unqualified persons escorted by qualified person

Restricted Approach BoundaryEntered only by qualified persons required to use shock

protection techniques and equipmentProhibited Approach Boundary

Entered only by qualified persons requiring same protection as if direct contact with live part

Flash Protection BoundaryLinear distance established to prevent serious injury from a

potential arc-flash. Established at a distance to prevent flash burns above first degree or bad sunburn.

The Established Flash Boundary should fall withinthe Limited Approach Boundary.

Shock Hazard Approach BoundariesShock Hazard Approach Boundaries(from NFPA 70E-2000)

70E-2000 P. 51Column Number (1) (2) (3) (4) (5)

Nominal SystemVoltage Range

Limited approach Boundary RestrictedApproachBoundary

ProhibitedApproachBoundary

ExposedMovable

Conductor

ExposedFixed

Circuit Part

IncludesInadvertentMovement

Adder

IncludesReduced

InadvertentMovement

AdderPhase-to-Phase

Energized Part to Employee - Distance in feet - Inches

50 V and less Not Specified Not Specified Not Specified Not SpecifiedOver 50 V, not over 300 V 10 ft. 0 in. 3 ft. 6 in. Avoid Contact Avoid ContactOver 300 V, not over 750 V 10 ft. 0 in. 3 ft. 6 in. 1 ft. 0 in. 0 ft. 1 in.Over 750 V, not over 15 kV 10 ft. 0 in. 5 ft. 0 in. 2 ft. 2 in. 0 ft. 7 in.Over 15 kV, not over 36 kV 10 ft. 0 in. 6 ft. 0 in. 2 ft. 7 in. 0 ft. 10 in.

Limited Shock Boundary: Qualified or Unqualified Persons** Only if accompanied by Qualified Person

Prohibited Shock Boundary: Qualified Persons Only. PPE asif direct contact with live part

Restricted Shock Boundary: Qualified Persons Only

Note: shock boundaries dependent on system voltage level

Flash Protection Boundary (FPB)Must wear appropriate PPEFPB dependent on fault level and time duration.

Flash Protection Boundary (FPB)Must wear appropriate PPEFPB dependent on fault level and time duration.

Equi

pmen

t

Methods of Assessing Arc Flash Methods of Assessing Arc Flash HazardHazard

Two methods are recognized by the industry.Both methods are based upon the understanding that hazards vary from one piece of equipment to another.Therefore, both require assessment of each piece of equipment to be worked on.

Method #1: Arc Flash CalculationMethod #2: Use NFPA 70E Table

Proper Hazard Assessment??Proper Hazard Assessment??

All personnel must be trainedAvoid overly general policiesPPE should be specific to the level of the hazard

Formula Example for Arc Formula Example for Arc Incident EnergiesIncident Energies

Calculating Arc Thermal Energy in a BoxEMB = 1038.7 x DB

-1.4738 x tA x [0.0093F² -0.3453F + 5.9675]

EMB = Max 20-inch cubic box Arc Thermal Energy in Calories / cm²DB = Distance to worker’s torso in inches (valid for 18” or greater)tA = arc duration in secondsF = bolted fault short circuit current in kA (valid for 16 to 50 kA)

How Arc Flash Levels Can VaryHow Arc Flash Levels Can Vary

91.5 cal/cm²53.8 cal/cm²26.9 cal/cm²20000

66.8 cal/cm²39.3 cal/cm²19.6 cal/cm²15000

43.4 cal/cm²25.5 cal/cm²12.8 cal/cm²10000

34.3 cal/cm²20.2 cal/cm²10.1 cal/cm²8000

25.5 cal/cm²15.0 cal/cm²7.5 cal/cm²6000

16.8 cal/cm²9.9 cal/cm²5.0 cal/cm²4000

8.3 cal/cm²4.9 cal/cm²2.5 cal/cm²2000

Multi Phase Arc with arc

enclosed in box: factor = 3.4

Single Phase Arc with arc

enclosed in box: factor = 2

Single Phase Arc in open air

Fault Current (amperes)

Calculations based on 10 cycle exposure, arc length = 12”, 12” to worker, and 4200 Volt system

NFPA 70E PPE TablesNFPA 70E PPE TablesAllows “quick” assessment of needs for highly qualified employees.Uses tables broken down by task to determine protective clothing.PPE is often based upon worse-case assumptions.Often over protective in nature.Very difficult to manage for companies with many employees.

Panel boards 240V and belowPanel boards 240V and belowIns

toolsIns

glovesHaz Cat

TASK

NN0Opening hinged covers to expose bare, energized parts

NN1Removal of bolted covers to expose bare, energized parts

YY1Remove/install CB or fused switch

YY1Work on energized parts, including voltage testing

NN0CB operation w/ covers off

NN0Circuit Breaker operation w/ covers on

Panelboards or Switchboards Panelboards or Switchboards 240V 240V –– 600V600V

Ins tools

Ins gloves

Haz Cat

TASK

YY2*Work on energized parts, including voltage testing

NN1CB operation w/ covers off

NN0Circuit Breaker operation w/ covers on

600V MCCs600V MCCsIns

toolsIns

glovesHaz Cat

TASK

NY3Insertion or removal of individual starter “buckets” from MCC

YY2*Work on control circuits with energized parts > 120V

YY0Work on control circuits with energized parts 120V or below

YY2*Work on energized parts, including voltage testing

NN1Reading a panel meter while operating a switch

NN0Circuit Breaker or starter operation w/ covers on

Hazard PPE MatrixHazard PPE Matrix

4024 – 30Above plus double layer switching coat / pants4

2516 –20Cotton Underwear, FR Shirt / Pants plus FR coverall3

89 – 12Cotton Underwear plus FR Shirt / Pants2

54.5 – 8FR Shirt / Pants1

N/A4.5 – 7Untreated Cotton0

Minimum ATPV (cal/cm2)

Total Weight (ox/yd2)Clothing Description

Hazard Risk

Category

OSHA’s Stand on Clothing:OSHA’s Stand on Clothing:Apparel. (i) When work is performed within reaching distance of exposed energized parts of equipment, the employer shall ensure that each employee removes or renders nonconductive all exposed conductive articles. . .(ii) The employer shall train each employee who is exposed to the hazards of flames or electric arcs in the hazards involved.(iii) The employer shall ensure that each employee who is exposed to the hazards of flames or electric arcs does not wear clothing that, when exposed to flames or electric arcs, could increase the extent of injury that would be sustained by the employee.

08/19/1995 Standard Interpretation – Guidelines for the Enforcement of the Apparel Standard

Effects of Electric Arc Flash on Cotton Clothing

Effects of Electric Arc Flash on Synthetic Clothing

Secondary ProtectionSecondary Protection

Fabric SelectionFabric Selection

Arc Thermal Performance Value (ATPV) –Amount of heat energy in calories/cm² a fabric or garment is rated to protect the wearer from a second degree burn.

1910.335(a)(i): Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed.

1910.335(a)(2)(ii): Protective shields, protective barriers, or insulating materials shall be used to protect each employee from shock, burns, or other electrically related injuries while that employee is working near exposed energized parts which might be accidentally contacted or where dangerous electric heating or arcing might occur.

If you can’t feasibly (????????) If you can’t feasibly (????????) dede--energizeenergize

1. Evaluate what the hazards are2. Select the right person to do the job

a.Trained in the process, and this means any helper assigned to assist must be qualified*. b. Give that person the PPE required based upon calculations or the table in 70E but read the footnotes.

3. Use tools that are appropriate alsoDO NOT INTRODUCE A HAZARD INTO A HAZARDOUS AREA!

For More Information:For More Information:

Check out:NFPA 70ENFPA 70 (National Electrical Code)www.arcflash.comwww.whsalisbury.comwww.bussmann.com/services/safetybasicswww.westexinc.com