electrical - intelliquestmedia.com · – 1910.137 & 1926.97 for electrical protective...
TRANSCRIPT
9/30/2013
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ElectricalW o r k p l a c e S a f e t y
1910.269 Proposed Changes
Hugh Hoagland
ElectricalWorkplace SafetyElectrical Standards
OSHA 29 CFR 1910 .331-.335
.147
.137
.269
1926 .950
NFPA 70E –2012 (under revision for 2015)
ANSI/IEEE C2 -
NESC –2012 (under revision for 2017)
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ElectricalWorkplace Safety
Itishardtopredictthefuture,
especiallybeforeithappens.– MarkTwain
ElectricalWorkplace Safety1910.269 Changes
In January 2013 OSHA’s agenda indicated they would publish the new standard in March.
OSHA source indicates that it is on the OMB desk and would likely be out in two weeks to two months
Here are my predictions based on the June 2005 document and IEEE 516 and NESC 2007/2012.
Prepare for these since these are consensus standards but if your company is a “OSHA minimum” company (whatever that is), you might want to wait until the standard is published
9/30/2013
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ElectricalWorkplace SafetyCost/Benefit Analysis & Scope
• OSHA cites a $34m estimated annual cost
against$135m in annual benefits
• Proposed Revision June 15, 2005:– OSHA 29 CFR 1910.269 (Subpart R) and
– 1926, Subpart V (.950-.968)
– 1910.137 & 1926.97 for Electrical Protective Equipment
ElectricalWorkplace SafetyOSHA 29 CFR 1910.269
• Electric Power Generation, Transmission, and Distribution
– Final Rule –January 31, 1994
• Proposed Revision Federal Register
– June 15, 2005
• Anticipated Final Rule May 2013
– Scheduled for March 2013 in Jan OSHA Agenda
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ElectricalWorkplace SafetyOSHA Unified Agenda
http://www.reginfo.gov/public/do/eAgendaViewRule?pubId=201210&RIN=1218-AB67
ElectricalWorkplace SafetyDownload the Proposed Text
http://www.osha.gov/FedReg_osha_pdf/FED20050615.pdf
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ElectricalWorkplace SafetyMajor Changes
(a)(2) Training
(a)(4) Contractors
(i) Host…
(ii) Contract…
(c) Job Briefing
(e) Enclosed Spaces
(g)(2) Fall Protection
(l) Working on or near exposed energized parts
(m) Deenergizing lines and equipment for employee protection
(n) Grounding for the protection of employees
(p) Mechanical Equipment
(t) Underground electrical installations
(x) Definitions
ElectricalWorkplace Safety
• Updates to latest consensus standards
– NFPA 70E
– NESC
– ASTM
– IEEE
• Clarifying the Standard Changes
• Accident Cause Changes
Thrust of the Changes
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ElectricalWorkplace Safety(a)(2) Training Changes $1.2 million
(i) All employees shall be trained:
(A) Employees shall be trained in and familiar with:
safety-related work practices, safety procedures, and other safety requirements …that pertain to their …job assignments.
(B) Employees shall also be trained in and familiar with:any other safety practices…that are related to their work and are necessary for their safety.
(C) The degree of training shall be determined by the risk to the employee for the task involved.
(ii) Qualified employees shall also be trained and competent in:
(v) The recognition of electrical hazards to which the employee may be exposed and the skills and techniques necessary to control or avoid those hazards.
ElectricalWorkplace SafetyTraining is More Than Telling
The existing requirement for employers to certify that employees have been trained
would be replaced with a requirement for employers to determine that employees have demonstrated proficiency in the work practices involved
Plus a new note would be added to clarify how training received in a previous job would satisfy the training requirements.
– § 1910.269(a)(2)(vii) ---- § 1926.950(b)(7)
Auditing is also clarified (similar to NESC/NFPA 70E)
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ElectricalWorkplace SafetySupervision & Annual Inspection
(3) Supervision and annual inspection. The employer shall determine, through regular supervision and through inspections conducted on at least an annual basis, that each employee is complying with the safety related work practices required by this subpart.
(4) Additional training. An employee shall receive additional training (or retraining) under any of the following conditions:
(i) If the supervision or annual inspections required by paragraph (b)(3) of this section indicate that the employee is not complying with the safety-related work practices required by this subpart, or
(ii) If new technology, new types of equipment, or changes in procedures necessitate the use of safety-related work practices that are different from those which the employee would normally use, or
(iii) If he or she must employ safety related work practices that are not normally used during his or her regular job duties.
Using ANSI Z10 for continuous improvement of electrical safety is recommended by NFPA 70E and would help comply with this part of OSHA.
ElectricalWorkplace SafetyContract Employer(CE)/Host Employer(HE)
• Newly defined terms
• Similar Language to NFPA 70E
• (i) HE responsibilities. – The host employer shall inform CE’s of:
– Known hazards that are related to the CE's work,
– Information about the HE's installation
• The HE shall report observed CE-related violations of this section to the CE.
• CE responsibilities.– Shall ensure that each of his or her employees is instructed
in the hazards communicated to the contract employer by the host employer.
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ElectricalWorkplace SafetyMore CE/HE Relationship Regulation
• The CE shall ensure that each employee follows the work practices required and safety-related work rules required by the HE.– The CE shall advise the HE of:
• Any unique hazards presented by the CE's work,
• Any unanticipated hazards found during the CE's work that the HE did not mention, and
• The measures the CE took to correct any violations reported by the HE … to prevent such violations from recurring in the future.
• EEI has argued that this provision is without legal authority so this could be dropped but is still in NFPA 70E.
ElectricalWorkplace SafetySubstation Changes/Clarifications
• Fences must be grounded
• Gates of unattended must be locked
• Permanent guarding required
• Unqualified persons are also prohibited from areas containing live parts operating at more than 600 volts, unless the live parts are completely enclosed in metal enclosures or are installed at an elevation of at least 8 feet, 6 inches. The metal enclosures must be grounded, and the minimum height increases with increasing voltage.
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ElectricalWorkplace Safety
Arc-Rated Clothing § 1910.269(l)(6) [Revised] and (12) [New]. § 1926.960(f) and (g)
1926.960(g) Clothing.
(1) Hazard assessment
The employer shall assess the workplace to determine if each employee is exposed to hazards from flames or from electric arcs.
(2) Estimate of available heat energy
For each employee exposed to hazards from electric arcs, the employer shall make a reasonable estimate of the maximum available heat energy to which the employee would be exposed.
(3) Prohibited clothing.
The employer shall ensure that each employee who is exposed to hazards from electric arcs does not wear clothing that could melt onto his or her skin or that could ignite and continue to burn when exposed to the heat energy estimated under paragraph (g)(2) of this section.
ElectricalWorkplace Safety
HRC 4 – 40 cal/cm²
Either
4,8,12 cal/cm²
or
40 or 60 cal/cm² Suit
HRC 2 – 8 cal/cm²
Simplified and Fool-Proof PPE Program
Arc-Rated PPE
NESC/NFPA 70E Simplified PPE programs –Use the Two-Category Approach
(Annex H.2 or NESC options)
18
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ElectricalWorkplace Safety
Reducing the Arc Hazard Proposed § 1926.965
Arc blast blanketsCan totally contain energy.
ASTM F2676
Arc equipment shields attach to hot stick/shotgun stick or racking screw and cut energy by 50%.
ASTM F2522
Electrical Hazards – Arc Flash 19
ElectricalWorkplace SafetyShoes Recommended & Required…
EH Rated(recommended for dry conditions)
• Lower Voltage, Lower Risk Exposure
• 130.7(C)(8)Secondary Protection Only
• (ASTM F2413 or CAN/CSA Z195, 14kV, Test Soles only)
• Wet conditions (i.e. DC Battery Rooms, electrolytic cell rooms)
• Required “equipment grounding near power lines” NFPA 70E 130.8(F)(3)
• Common for walking downed powerlines.
• High Voltage, High Risk Exposure
• (ASTM F1117, Test to ASTM F1116 20kV, Tested wet on whole shoe/boot)
Shock » Protection » PPE
DI Rated(required when…)
20
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ElectricalWorkplace Safety
Energy Calculations Appendix F to § 1910.269 [New] & Appendix F to Subpart V
Note 1: Appendix F…provides guidance on the estimation of available heat energy.
Standard for Electrical Safety Requirements for Employee Workplaces, NFPA 70E-2004, Annex D, ``Sample Calculation of Flash Protection Boundary.''
Doughty, R.L., Neal, T.E., and Floyd II, H.L., ``Predicting Incident Energy to Better Manage the Electric Arc Hazard on 600 V Power Distribution Systems,'' Record of Conference Papers IEEEIAS 45th Annual Petroleum and Chemical Industry Conference, September 28-30, 1998.
Guide for Performing Arc Flash Hazard Calculations, IEEE 1584-2002.
Heat Flux Calculator, a free software program created by Alan Privette (widely available on the Internet). (factors required for 3Phase & Box)
ARCPRO, a commercially available software program developed by Kinectrics, Toronto, ON, CA. (factors required for 3Phase & Box)
The employer should require each exposed employee to have no more than 10 percent of his or her body unprotected.
ElectricalWorkplace SafetyFlame Resistant Clothing Minimum
(4) Flame-resistant clothing. The employer shall ensure that an employee wears clothing that is flame resistant under any of the following conditions:
(i) The employee is subject to contact with energized circuit parts operating at more than 600 volts,
This could go away. NESC 2007 said 1000V, 2012 no exclusion.
(ii) The employee’s clothing could be ignited by flammable material in the work area that could be ignited by an electric arc, or
(iii) The employee’s clothing could be ignited by molten metal or electric arcs from faulted conductors in the work area.
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ElectricalWorkplace SafetyFlame Resistant Clothing Rating
(5) Clothing rating. The employer shall ensure that each employee who is exposed to hazards from electric arcs wears clothing with an arc rating greater than or equal to the heat energy estimated under paragraph (g)(2) of this section.
ElectricalWorkplace SafetyTagOut vs. LockOut
• Utilities have long had tagout vs. lockout issues with the law and this continues.
• Expect OSHA to continue to push for lockout especially in power plants.
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ElectricalWorkplace SafetyJob Briefing
(1) Before each job. (i) provide the employee in charge of the job with available
information necessary to perform the job safely.
(ii) ensure that the “employee in charge” conducts a job briefing … with the employees involved before they start each job.
(2) Subjects to be covered. The briefing shall cover at least the following subjects:
hazards associated with the job, work procedures, special precautions, energy source controls, and PPE requirements.
(3) Number of briefings. (i) At least one job briefing shall be conducted before the start of
the first job of each day or shift.
(ii) Additional job briefings shall be held if significant changes, which might affect the safety of the employees, occur during the course of the work.
ElectricalWorkplace SafetyJob Briefing
(4) Extent of briefing. (i) A brief discussion is satisfactory if the work involved is
routine and if the employees, by virtue of training and experience, can reasonably be expected to recognize and avoid the hazards involved in the job.
(ii)A more extensive discussion shall be conducted:(A)If the work is complicated or particularly hazardous, or
(B)If the employee cannot be expected to recognize and avoid the hazards involved in the job.
Note to paragraph (c)(4) of this section: The briefing must always touch on all the subjects listed in paragraph (c)(2) of this section.
(5) Working alone. An employee working alone need not conduct a job briefing.
However, the employer shall ensure that the tasks to be performed are planned as if a briefing were required.
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ElectricalWorkplace Safety
Safety-Related Work Practices
• Timing – Before starting each job
– Before any change in job scope
• Type– Field
– Formal
• Outline (Annex I)– Identify
– Ask
– Check
– Know
– Think
– Prepare for emergencies
Job Briefing
NFPA 70E 110.3(G)
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ElectricalWorkplace SafetyNew Definition: Entry
Entry (as used in paragraph (e) of this section).
The action by which a person passes through an opening into an enclosed space. Entry includes ensuing work activities in that space and is considered to have occurred as soon as any part of the entrant's body breaks the plane of an opening into the space.
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ElectricalWorkplace Safety
Enclosed Space Changes More Like Confined Space
• Add a definition of “entry” and remove associated note
• Requirement to provide an attendant if there is reason to believe that a hazard exists
• Require test instruments to have an accuracy of ±10 percent of what you are measuring
• Require employer to demonstrate that ventilation is sufficient
• Will require sufficient lighting never addressed for daytime
ElectricalWorkplace SafetyFall Protection
• Clarify that fall arrest equipment used in aerial lifts must meet Subpart M of the construction standards (OSHA 1926)
• Update the requirements for work positioning equipment (through a reference to Subpart V) (also OSHA 1926)
• Possible requirement to decrease fall distance from 6 ft. to 2 ft.
• Will require ASTM F887 which includes arc testing of harness
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ElectricalWorkplace Safety
Site Specific Considerations
Make sure a fall protection assessment is completed and the appropriate safety precautions in place before you work at an elevated level.
Fall Protection
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ElectricalWorkplace SafetyWorking on or Near Energized Parts
(2)(i) The employee is insulated from the energized part
– Employee is insulated from the energized part (insulating gloves or insulating gloves and sleeves
– Provided that the employee has control of the part in a manner sufficient to prevent exposure to uninsulated portions of the body)
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ElectricalWorkplace SafetyWorking on or Near Energized Parts
(3) Type of insulation.If the employee is to be insulated from energized parts by the use of insulating gloves…insulating sleeves shall also be used
Some exceptions
(4) Working position. (i) The employer shall ensure that each employee, …
works in a position from which a slip or shock will not bring the employee's body into contact with exposed, uninsulated parts energized at a potential different from the employee.
ElectricalWorkplace Safety(6) Conductive Articles
– 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, such as key or watch chains, rings, or wrist watches or bands, unless such articles do not increase the hazards associated with contact with the energized parts.
This is less restrictive than NFPA 70E
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ElectricalWorkplace SafetyDo Not Wear Conductive Articles
Arc-Rated PPE – Non-Conductive 35
ElectricalWorkplace SafetyUnderground Installations
• Paragraphs (3), (7), and (8) have been revised and expanded for clarity
• Apply all provisions to manholes and underground vaults
• Added requirement to de-energize cables or protect employees if the work could cause a fault
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ElectricalWorkplace SafetyMAD Distances
• NESC has had the term MAD since early 1900’s
• OSHA adopted the term in 1910.269
• IEEE 516 IEEE Guide for Maintenance Methods on Energized Power Lines (Phase to Ground)
– MAID – Minimum air insulation distance
– MTID – Minimum tool insulation distance
– MAD – Minimum approach distance
– MAD for tools – MAD with tool in air gap
– MHAD – Minimum helicopter approach distance
ElectricalWorkplace SafetyTwo Types Of Boundaries: Shock & Arc
Protection Strategies
Arc Flash Boundary
Shock Protection Boundaries EnergySource
Limited “Public Safety Boundary” Person in Charge Boundary: NESC 421.B.1 OSHA 1910.333 & .269 (w)(6)(ii)
Restricted “Shock PPE Boundary”Minimum ApproachDistances (MAD) NESC 431
Arc Flash At 2 cal/cm² PPE is Required: NESC 410.A.3
NFPA 70E NESC
38
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Phase-to-ground
Graph courtesy Jim Tomaseski, International IBEW Safety Director
ElectricalWorkplace Safety
New Class of Rubber Gloves (Voltage Rated Gloves)
• Section 1910.137 would be revised to include Class 00 rubber insulating gloves.
• Class 0 was all that was mentioned in previous versions.
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ElectricalWorkplace Safety
Ignition Limits on Voltage-Rated (VR) Gloves
Arc-Rated PPE – Gloves
53.5
41.9
31.2 30.4
21.4
0
10
20
30
40
50
60
Black Blue Yellow Red NaturalRubber
50% Ignition
Tests conducted on Salisbury gloves.
31 31.2
17.4
22.1
0
5
10
15
20
25
30
35
Black0.7mm
Blue0.7mm
Blue0.5mm
Orange0.65mm
50% Ignition
Class 00 Rubber GloveResults (cal/cm²)
Best Practice Class O Blue or Black
Class 0 Rubber Glove Results (cal/cm²)
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ElectricalWorkplace SafetyNew Arc Rated Glove Standards
• ASTM Standard will not require testing of Rubber Insulating Gloves or Leather Protectors– Most mfg. have already tested and may label even though
they are excluded from the standard in a compromise to get a standard.
– Non protector gloves and arc flash work gloves can be rated when ASTM releases the standard.
• IEC Standard began last month and will be unlikely to exclude rubber and leather.
• New Protector Glove standard will begin next cycle in ASTM and may produce more comfortable protector gloves. – OSHA does not preclude other protector gloves today.
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ElectricalWorkplace SafetyQuestions Asked of OSHA April 2013
What is the potential date now?
Any time now. OMB asked for another analysis -- could be in as soon as 2 weeks to 2 months. Likely faster since analysis was not over a controversial issue. In January, March looked very doable. Things change.
What will be the compliance time?
90-120 day, training and clothing minimum.
What are the effects on the 1910 non-269 world?
Mainly the addition of 00 gloves and removal of EH shoes as protection while still recommended. They save lives but you only know if they don’t work.
Tree trimming will change substantially in regulations to prevent deaths.
NFPA 70E & NESC compliant companies will find nothing new but agreement.
ElectricalWorkplace SafetyQuestions Asked of OSHA April 2013
How much has the auditing been focused on?
This is not focused on in citations but can be used effectively in defense.
Leading indicators vs. lagging indicators.
What about proficiency? Is that only for 269?
Definitely not. Qualified depends on the job duty and it really means proficient FOR THE TASK.
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ElectricalWorkplace SafetyBiggest Impacts
• Construction (1926) and Maintenance (1910) will be harmonized so compliance will be simplified.
– Many companies followed the more restrictive anyway.
– Different policies for different work will disappear.
• Arc Rated Clothing will be law for Generation, Transmission and Distribution work (LV and HV)
• EH shoes will be eliminated from OSHA language in 1910.136 to eliminate the possibility of people believing that EH shoes remove the need for rubber gloves, blankets or sleeves.
– This could be interpreted that they are unhelpful but this is not the case. NFPA 70E just added them as recommended for dry environments.
• DI shoes will still be needed if you have step potential
– This is the NFPA 70E language anyway but most don’t follow this requirement.
• Locking snap hooks on positioning devices (Most already made this way in anticipation)
• Arc Tested Harnesses ASTM F887-04 or later listed as required.
ElectricalWorkplace Safety
Questions? Want More Information?
ElectricalWorkplace Safety
www.e-hazard.com Email: [email protected]
Phone: (502) 716-7073
For a FREE* copy of our newsletter:
Text: “Newsletter” withyour e-mail address to:
925-Arc-Wear(925-272-9327)
Clothing in Arc Flash
Four Types of Arc Exposure and the Effect of Moisture on
Garment Appearance After an Arc Event
Hugh HoaglandMikhail GolovkovClaude Maurice
Phillip Clark
2013 IEEE, IAS Electrical Safety Workshop 1
4 Types of Arc Exposure
2
Tracking Arc
• Plasma next to body• Can cause clothing ignition
in an electrical contact• Usually at higher voltages
4. Open Air Arc
• Mostly radiant energy
1.
Arc-in-a-Box
• Mostly convective energy
3. Ejected Arc
• Mostly arc plasma• Convection at short
distance• Radiant further away
2.
2013 IEEE, IAS Electrical Safety Workshop
Radiant Energy Results from Open Air Arc Event
3
Open Air Radiated Arc with Convection
Open Air Arc1.
2013 IEEE, IAS Electrical Safety Workshop
Convective Arc Energy is Forced Out Through an Opening (arc-in-a-box)
6Arc-in-a-Box 3.
Arc-in-Box from disconnect
Tracking on Sweat
2013 IEEE, IAS Electrical Safety Workshop 9
2500V through sweat across wire with 8 inch gap
Tracking or Pop-Out Arc
2013 IEEE, IAS Electrical Safety Workshop 10
7500V 8kA with small wire to start arcArc stays in clothing for 2 cycles then moves
Water Effect on Arc Exposures
2013 IEEE, IAS Electrical Safety Workshop 13
Dry T-shirt with Tracking Arc Underneath
Wet Arc-Rated T-shirtwith Tracking Arc
Just Add Water
0
10
20
30
40
Dry/Dry Dry/Wet Wet/WetATPV 24 18 12.6EBT 23 24 35.6
Cal/cm2
2013 IEEE, IAS Electrical Safety Workshop 14
Layer 2 (Brown)
5.4 oz/yd² (183 g/m²) Jersey Knit
75%15%10%
ModacrylicCottonNylon
AAD: 5.8 oz/yd² (197 g/m²)
Layer 1 (Med Blue)
2x1 Twill80%15%
5%
ModacrylicCottonPara-Aramid
AAD: 7.0 oz/yd² (237 g/m²)
AAD = Actual Areal Density
Less Burn Protection, Increased Fabric Integrity
Recommendations
• Choose arc rated PPE for all common electrical work
• Choose arc rated undergarments for higher voltage work– especially for upper torso
2013 IEEE, IAS Electrical Safety Workshop 15
Design/Installation Considerations
• Recommend changes to NEC – Require disconnects to be placed for safe operation
from the side (not against a wall so worker must operate from front).
• Design >480V equipment so it can be operated from a safe side/zone
• Mark a safe zone for equipment operation when possible.
2013 IEEE, IAS Electrical Safety Workshop 16
Work Practice Considerations
• Standing to side of equipment
• Use non-ignitable clothing in all work situations – especially with voltages greater than 1000V
• Use properly installed arc flash blankets – Rated for the fault current and clearing time which
meet ASTM F2676
• Use arc deflecting shields to shunt all plasma and up to 50% of the radiated & convective energy in an arc flash event when arc shields can be used
2013 IEEE, IAS Electrical Safety Workshop 17
Questions?
Hugh Hoagland
502-333-0510
Mikhail Golovkov
502-333-0510
Claude Maurice
416-207-6350
2013 IEEE, IAS Electrical Safety Workshop 18
Arc-Rated PPE & Contamination Study
Hugh Hoagland, Mikhail Golovkov,
Rob Pailing, Lionel Smith,Cecil Burton,
Claude Maurice
ASTM F1959 Adapted for Contamination Study
• The standard measures energy on a panel.
• We began with the base and wet ratings.
ASTM F1959 Adapted for Contamination Study
We drew a specific area
which covered the
calorimeters for the
contamination area.
ASTM F1959 Adapted for Contamination Study
Next we measured the mass of the
contaminants placed in each
area for the test to have
mass per unit area.
ASTM F1959 Adapted for Contamination Study
• Then we tested each contaminant.
• Some like transformer oil would continue to burn if we reached the ignition temperature.
• Here panel A ignites, the other two do not ignite.
• Each panel records the temperature rise and we compare this to the Stoll curve.
• In this exposure, panel A which ignited would have caused 2nd and 3rd degree burns on part of the body.
ASTM F1959 Adapted for Contamination Study
Last we did statistical
analysis of the data points to
predict the ATPV of the fabric with
contamination.
ASTM F1959 Adapted for Contamination Study
The Baseline: Wet & Dry Fabric
10.4
5.5
0
2
4
6
8
10
12
Dry Fabric Wet Fabric
Baseline Protection cal/cm²
The wet fabric was worst case scenario 2X weight of the dry. We soaked and wrung out the excess only. VERY wet.
Wet Contaminants cal/cm²
5.1
75.9
11.3
13
0
2
4
6
8
10
12
14
FloculentSlime
Grease HydaulicOil
CaOHSlurry
WetCement
Wet Contaminants
Dry Fabric 10.6 cal
Wet Fabric 5.5 cal
Diesel & Transformer oil ignited causing greater burns.Grease, hydraulic oil did not ignite less than 11 cal/cm² but did lower protection . All hydrocarbons will ignite causing greater burn than their thermal conduction reflects here.
Dry Contaminants cal/cm²
10.6
12.9
11.5 11.5
0
2
4
6
8
10
12
14
Carbon Dust Dry Cement Dry Lime PalladiumDust
Dry Contaminants
Dry Fabric 10.6 cal
Wet Fabric 5.5 cal
Summary Graph
Die
sel
fuel
Flo
ccu
len
t S
limes
Wat
er
Hyd
rau
lic o
il
Gre
ase
Tran
sfo
rmer
oil
Bas
e ra
tin
g
Car
bo
n d
ust
Slu
rry
Pal
lad
ium
du
st
Dry
lim
e
Dry
cem
ent
Wet
cem
ent
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
Rel
ativ
e R
atin
g (
to b
ase
rati
ng
)
Contaminants
Liquids
Solids and heavy saturatedmixes
Reduction in protective properties
Arc Rating Conclusions• Hydrocarbons can ignite at some level.
• Water/sweat does decrease protection but does not increase risk of ignition.
• Mixes of contaminants did not provide the negative consequences thought possible.
• Small percentages of hydrocarbons mixed with other non-flammable contaminants were not as dangerous as the pure contaminants.
Method of Areal Resistance Measurement: two electrodes at contaminated area edges, 5 kV DC megger as a voltage source
2 inch
12 inch
Electrical Conductivity
Conductivity and arc ratingContaminant
Areal Resistance Change cal/cm²
Wet Dry Wet Dry
Cement 15.6X103 Ohm >10X109 Ohm +2.6 (25%) + 2.5 (25%)
Flocculent Slimes (86-91)X103 Ohm - 5.3 (50%)
Slurry (44-54)X103 Ohm +0.9 (10%)
Grease (4.2-4.4)X109 Ohm -3.4 (35%)
Sweat <10X103 Ohm - 4.9 (50%)
Palladium Dust (6.7-9.0)X109 Ohm + 0.9 (10%)
Carbon (7-10)X109 Ohm +0.2 (2%)
Dry Lime >10X109 Ohm +1.1 (10%)
Transformer Oil >10X109 Ohm -3.2 (30%)
Hydraulic Oil 6.8X109 Ohm - 4.5 (45%)
Dry Contaminants on log Ohms
1
10
100
1000
10000
100000
1000000
10000000
00000000
1E+09
1E+10
Cement PalladiumDust
Carbon Lime
Saline
Dry Contaminants
Dry Fabric
Wet Contaminants on log Ohms
1
10
100
1000
10000
100000
1000000
10000000
00000000
1E+09
1E+10
WetCememt
Flocculent CaOHSlurry
Grease Trans Oil HydraulicOil
Saline
Wet Contaminants
Dry Fabric
Practical Conclusions
• No correlation to conductivity and arc rating of contaminants.
• Wet state is often worse than dry state but only ignitable contaminants are worse than sweat/water.
• Most dry soils and many wet ones seem to be good for protection from arc flash.
• A small amount of hydrocarbons is unlikely to be life threatening.
• Proper cleaning should be regular but not need not be excessive.