Fire Retardant (FR)Clothing NESC Compliance Brent McKinney, P.E. Manager – Electric T&D APPA Principal Member NESC Subcommittee 8
Disclaimer • Compliance with NESC, NEC, OSHA and / or all applicable codes and rules are the responsibility of each individual utility. This presentation merely provides background information so that each utility can make its own decision concerning compliance. Nothing contained in this presentation is intended to constitute legal advice. We recommend that you consult with qualified legal counsel regarding compliance with all codes, laws, and regulations.
Outline • Consensus Standard • NESC, NEC Scope • NESC Subcommittee Structure • NESC Subcommittee 8 FR Clothing History • NESC FR Clothing Compliance 2009 • NESC FR Clothing Compliance 2012 • Questions
Consensus Standard: Standard which is generally agreed upon by all entities affected. • NESC & NEC are Consensus Standards • NESC – IEEE • NEC – NFPA
NEC is primarily for non-utility companies past the meter. • NEC Utility Exemption – See NFPA 70E 90.1.B.5
NESC is minimum safety consensus standard for electric utilities. • States, cities may adopt. • Accepted as national safety consensus standard.
NESC is governed by 7 subcommittees • 1.Purpose, Scope, Application, Definitions and References • 2. Grounding Methods • 3. Electric Supply Stations • 4. Overhead Lines - Clearances • 5. Overhead Lines – Strength and Loading • 6. None • 7. Underground Lines • 8. Work Rules
NESC subcommittees made up of utility representatives, consultants, IBEW, NSPE, TelCom industry and others. • No one group can have more than 33% representation. • NESC Subcommittee 8 responsible for worker safety rules. • Responsible for FR clothing rules.
FR Clothing History • Change Proposal (CP) submitted to SC8 by IBEW in 2005 • OSHA told committee it needed consensus standard for new 1910.269 Rule • OSHA would use NEC 70-E if NESC did not pass FR clothing rule.
FR Clothing History – cont’d • Nearly all SC8 members now under OSHA • SC8 companies felt FR clothing rule must be passed • Significant disagreement among committee • Working group developed to write FR rule and bring back to subcommittee
FR Clothing History – cont’d • EEI, NRECA, APPA, OSHA, IBEW representatives on committee 8-10 people • Committee met three times
Issues • APPA and NRECA insisted tables be provided instead of requiring Arc hazard analysis. • Little and poor data on Arc hazard incidents and tests. • OSHA used ArcPro 2.0 to determine arcs.
Issues cont’d • What arc distance should be used? • Would regular jeans be allowed? • Would the heat stress of the clothes be more of a problem than the arc hazards? • Who should pay for the clothes? • When should the rule begin?
Issues cont’d • What do we do for arcs under 1,000V? • OSHA must accept.
Finally consensus reached, no one completely happy. • APPA votes to reject rule.
Rules 1. 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 (see Neal, Bingham, and Doughty [B59]), 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
Rules cont’d 2. When exposed to an electric arc or flame, clothing made from the following materials shall not be worn: acetate, nylon, polyester, or polypropylene. The effective arc rating of clothing or a clothing system to be worn at voltages 1000 V and above shall be determined using Tables 410-1 and 410-2 or performing an arc hazard analysis. When an arc hazard analysis is performed, it shall include a calculation of the estimated arc energy based on the available fault current, the duration of the arc (cycles), and the distance from the arc to the employee.
Rules cont’d 3. EXCEPTION 1: If the clothing required by this rule has the potential to create additional and greater hazards than the possible exposure to the heat energy of the electric arc, then clothing with an arc rating or arc thermal performance value (ATPV) less than that required by the rule can be worn. EXCEPTION 2: For secondary systems below 1000 V, applicable work rules required by this part and engineering controls shall be utilized to limit exposure. In lieu of performing an arc hazard analysis, clothing or a clothing system with a minimum effective arc rating of 4 cal/cm2 shall be required to limit the likelihood of ignition.
Rules cont’d 4. NOTE 1: A clothing system (multiple layers) that includes an outer layer of flame resistant material and an inner layer of non-flame resistant material has been shown to block more heat than a single layer. The effect of the combination of these multiple layers can be referred to as the effective arc rating. NOTE 2: It is recognized that arc energy levels can be excessive with secondary systems. Applicable work rules required by this part and engineering controls should be utilized.
Rules cont’d 5. Employers shall utilize positive procedures to secure compliance with these rules. Cases may arise, however, where the strict enforcement of some particular rule could seriously impede the safe progress of the work at hand; in such cases the employee in charge of the work to be done should make such temporary modification of the rules as will accomplish the work without increasing the hazard. If a difference of opinion arises with respect to the application of these rules, the decision of the employer or the employer's authorized agent shall be final. This decision shall not result in any employee performing work in a manner that is unduly hazardous to the employee or to the employee's fellow workers.
NESC 2012 CP’s initial meeting • Low voltage working group developed update FR clothing rule including new table under 1000 Volts
Table 410- 23: Live-line tool work clothing and clothing systems—voltage, fault current, and maximum clearing time for voltages 46.1 to 800 kV 1 AC (See Rule 410A3) • Supporting Comments Currently, Rule 410A3 requires the use of clothing or clothing systems with a minimum effective arc rating of 4 cal /cm2 for voltages less than 1000 V, in lieu of performing an arc hazard analysis. • Subcommittee 8 established a Low Voltage Arc Flash Work Group (WG) to evaluate the necessary minimum clothing or clothing system requirements for employees working on energized lines and parts operating at voltages less than 1000V and to develop a Change Proposal, if needed, to revise Rule 410A3.
The WG’s initial evaluations concluded that aside from anecdotal evidence no technically substantiated data based upon specific industry testing existed to justify the creation of a new table, similar to existing Tables 410-1 and 410-2, for voltages less than 1000V. However, during the spring and summer of 2008, the Pacific Gas and Electric Company initiated and completed a series of scientific tests to determine the arc flash characteristics of 480V self-contained metering equipment by creating fault conditions at various kA levels (sans fault protection devices). • Based on PG&E’s test results and the application of an accepted industry standard (IEEE 1584-2002), the WG submitted a report to Subcommittee 8 which included revisions to Rule 410A3 and a new Table (410-1).
The revisions to Rule 410A3 seek to clarify the difference between performing an assessment and an arc hazard analysis, the conditions under which an arc hazard analysis is to be performed, and the employer’s requirements for determining the necessary clothing or clothing systems. • New Table 410-1 [Clothing and Clothing Systems (per cm2) for voltages 50 to 1000 V (AC)] and existing Tables (renumbered to 410-2 and 410-3) are cited in new text 410A3a to offer employers the option of using tabulated values for clothing and clothing systems in lieu of performing an arc hazard analysis.
The supplemental notes to new Table 410 -1 identify certainparameters that vary from the pre-existing tables (new 410-2 and 410-3). One such difference is the use of an 18 in. worker separation distance. On this particular topic, it should be noted that the supporting test results are based on the application of IEEE Std. 1584 test methodologies and typical working distances for low voltage motor control centers and panel boards (Table 3 p. 9). It seemed prudent to the workgroup to apply the 18 in. working distances to determine the cal/cm2 values for other listed equipment and for other voltage ranges, since Section 4.8 (IEEE 1584) states that arc flash protection is based on the incident energy level on the worker’s face and body, not the incident energy on the hands and arms. • The supplemental notes to new Table 410-1 also include statements identical to those in pre-existing tables (renumbered 410-2 and 410-3) that allow the user to apply different methods of calculating arc exposure values.
Revisions to Rule 410A3 • Effective as of January 1, 2009,tThe employer shall ensure that an assessment is performed to determine potential exposure to an electric arc for employees who work on or near energized lines, parts or equipment. If the assessment determines a potential employee exposure greater than 2 cal/cm2 exists (see Neal, Bingham, and Doughty [B59]), the employer shall: a. Perform a detailed arc hazard analysis, or use Table 410-1, Table 410-2, or Table 410-3 to determine the effective arc rating of clothing or clothing system to be worn by employees working on or near energized lines, parts, or equipment at voltages 50 – 800,000 volts. When anThearc hazard analysis is performed, it shall include a calculation of the estimated arc energy based on the available fault current, the duration of the arc (cycles), and the distance from the arc to the employee.
b. Require employees to wear clothing or a clothing system that haswith an effective arc rating not less than the anticipated level of arc energy. When exposed to an electric arc or flame, clothingor aclothing system made from the following materials, unless flame resistant, shall not be worn: acetate, nylon, polyester, or polypropylene.
EXCEPTION 1: If the clothingor clothing system required by this rule has the potential to create additional andor greater hazards than the possible exposure to the heat energy of the electric arc, then clothing with an arc rating or arc thermal performance value (ATPV) less than that required by theis rule canmay be worn.
NOTE 1: Assessmentsperformed to determine potential exposure to an electric arc considerthe affected employee’s assigned tasks and/or work activities. NOTE 12: A clothing system (multiple layers) that includes an outer layer of flame resistant material and an inner layer of non-flame resistant natural fibermaterial has been shown to block more heat than a single layer. The effect of the combination of these multiple layers canmay be referred to as the effective arc rating. NOTE 23: It is recognized that arc energy levels can be excessive with secondary systems. Applicable work rules required by this part and engineering controls should be utilized. Engineering controls can be utilized to reduce arc energy levels and work practices can be utilized to reduce exposure levels.
New Table 410-1 Table 410-1: Clothing and Clothing Systems (per cm2) for voltages 50 to 1000 V (AC) (See Rule 410A3.) Nominal Voltage Range and Calories/Cm 2 Equipment Type 50 – 250V251 – 500V501 – 1000 V Self-contained Metering Pad-mounted transformers/ Panels & cabinets 42 204 308 CT Meters and control wiring 42 45 68 Metal-clad Switchgear / Motor Control Centers 83 406 608 Subsurface/ Pedestal- mounted Equipment 42 87 12 8 Open Air (includes lines) 42 42 68
Notes: 1. This table is based on maximum fault current of 51kA. Calculations are based on an 18-in separation distance from the arc to the employee. See IEEE 1584-2002. Other methods are available to estimate arc exposure values and may yield slightly different but equally acceptable results. The use of the table in the selection of clothing is intended to reduce the amount or degree of injury but may not prevent all burns. • Industry testing by two separate major utilities has demonstrated that voltages 50 - 240V will not sustain arcs for more than 0.5 cycles thereby limiting exposure to less than 4 calories/cm2. • Value based on industry test results and IEEE Std. 1584-2002 formula for Motor Control Centers. (Gap = 1 in.) (Xd = 1.641) (18 in. distance) 51kA (Based on a 208V, 1000kVA, 5.3% Z, served from a 500mVA system) Maximum duration (from tests) is 10 cycles: 46.5 cal/s/cm2 * 0.167 sec = 7.8 cal/cm2 4. Industry testing on 480V equipment indicates exposures for self-contained meters do not exceed 20 calories/cm2.
Industry testing on 480V equipment indicates exposures for CT meters and control wiring does not exceed 4 calories/cm2. • Value based on industry test results and IEEE Std. 1584-2002 formula for Motor Control Centers. (Gap = 1” and Xd = 1.641, 18 inch distance) 12.7kA at 480 V (worst case energy value from testing). Maximum duration from tests is 85 cycles: 26.2 cal/s/cm2 * 1.42 sec = 37 cal/cm2 • Incident analysis on this equipment indicates exposures do not exceed 8 calories/cm2. 8. Incident analysis and industry testing indicates that applying a 150% multiplier to the 480V exposure values provides a conservative value for equipment and open air lines operating at 501 – 1000V.
Questions?Contact Information: Brent McKinney Manager, Electric T&D City Utilities of Springfield Phone: 417/831-8762 Email: firstname.lastname@example.org Nathan Mitchell Director of Engineering Services American Public Power Association Phone: 202/467-2925 Email: email@example.com Mike Hyland VP of Engineering Services American Public Power Association Phone: 202/467-2986 Email: firstname.lastname@example.org
Additional Information Available at: • E&O Conference – March 22-25, 2009 Austin, Texas • The 14th Edition of the APPA Safety Manual – Available Now at APPAnet.org