The line worker was out viewing a repair job at a northern US utility. The presumption was that a single unit in a three-phase transformer bank had been struck by lightning during a storm. One of the three transformers had been replaced but the secondary line was still not energized. The crew was replacing the second transformer. And the line worker was standing below the scene watching the progress of the work when the conductor apparently broke at the point where the lightning struck and fell. It landed away from his feet but created an electric arc as it fell apart. The radiated heat from the arc hit his arc and flame resistant shirt and caused little damage to his upper torso but it ignited his denim jeans and burned them completely off of his body except for a bit of denim jean fabric underneath his leather belt.
He had first and second degree burns on the front of his legs but mostly third degree burns on the back of his legs and hips. The arc may have blown the front of his jeans off quickly so that the front of his legs were not as severely burned by the fire which swept over his lower torso as the heavy jean material continued to burn. Wally Benhke, retired DuPont scientist, and one of the developers of the copper calorimeter currently used in burn prediction, once told us something that came home in this accident: “Heavy cotton is good until it ignites, and the ignition energy is almost directly proportional to the weight of the cotton material, but once the heavy cotton ignites you just have more fuel to burn on the body.” The line worker would have been much better protected with a pair of an arc and flame resistant jeans that he could have selected in the company’s clothing allowance program.
Clothing allowance programs, purchase programs, rental programs and other creative solutions to getting the right clothing on the backs (and fronts) of workers are becoming more and more important in the utility industry. Hazard assessment is moving from art to science and software programs and now “turn key services” are making it easier to MATCH the hazard and the task in order to provide for worker protection. However, new concerns continue to arise as we move forward toward the “right stuff ”.
Clothing and the Arc
When OSHA promulgated the CFR 1910.269 standard in the US, the clothing portion of the standard put many utilities in an uproar. There was concern over the necessity of moving to arc and flame resistant clothing and there were, and to some extent still are, questions about when and where conventional clothing can be used by utility workers.
Most utilities today provide some arc and flame resistant (FR) clothing be it an FR shirt or an FR jacket. Most electric utilities in the US and Canada now provide arc and flame resistant raingear also. Since melting FR raingear does not do well under many arc conditions, more utilities are moving to the new F1891-00 a standard which eliminates most of the “FR” raingear containing melting materials Non-flame resistant winter wear continues to be an issue due to melting linings and non-flame resistant shells which are frequently observed to melt and/or ignite when in arc accidents. Even with increased regulation, new electrical safety standards, and more workers in arc and flame resistant clothing, the arc accident rate has not decreased.
Why no Drop in the Accident Rate?
Why, with the new regulation and safety standards has there not been a drop in the accident rate. FR clothing cannot prevent accidents but it can eliminate or greatly decrease the severity of the injuries sustained by workers. Most line workers and electricians exposed to the electric arc hazard wear an FR shirt and many wear FR pants. But the clothing doesn’t prevent injury unless it covers all skin and has a rating equivalent to the arc hazard level. When an arc accident occurs, exposed skin has a high probability of injury as does inadequately protected skin. The intent of the OSHA standard was to reduce injuries from igniting clothing and melting materials, and this has been somewhat successful.
The OSHA standard succeeded in motivating scientific evaluation of clothing exposed to the electric arc, and in motivating manufacturers to seek creative solutions for arc protection scenarios. The driving force behind the standard was utility and union desire for standard rules and worker protection, and the clothing portion of the standard was based on the best test information available at that time. The weaknesses utilities have encountered in implementing the OSHA standard are the lack of knowledge and guidance in protective clothing selection and the lack of the knowledge on performing a hazard assessment. In the hazard assessment area, although exposure energy from single phase arcs has been well researched, there is a lack of scientific information on the hazards produced by three-phase arcs and arcs that are confined within switchgear. To fill this void the IEEE-PCIC (Institute of Electrical and Electronics Engineers Petrochemical Industrial Conference) group has been attempting to fund an arc testing project aimed at assessing the arc exposure intensity for various pieces of equipment from MCC’s (motor control centers) to switchgear. Further funding contributions are required to enable this work to cover a wide range of arc exposure scenarios. (For further information contact Craig Wellman craig.m.wellman@usa.dupont.com)
Another Issue Of Arc Hazard Assessment
Several tools are available for arc hazard assessment today. The standard, ARCPRO (Version 2.0) developed by Kinectrics (formerly Ontario Hydro Research), provides a user-friendly interface to compute radiated heat energy and compare the hazard to the arc rating of FR clothing. In addition, EDSA (www.edsa.com) has now built arc hazard assessment into their Power System Design Software. Many companies are finding that with the lack of available and qualified power system engineers, there is a need for system assessment packages. Consultants are available to provide utilities with the power system engineering computations and the clothing selection analysis. For more information on system assessment, contact the authors.
Tracking Arcs
Another issue that has surfaced with FR clothing has been tracking arcs, i.e. arcs that move or track along a surface like, for example, the surface of the skin. In one instance, a worker experienced a tracking arc on the skin surface and thought the FR material may have contributed in some way to arc tracking on the skin. It is unlikely that FR clothing is a contributor, but with non-FR clothing when the arc does track on the skin (or sweat on the skin) the clothing is often ignited due to the closeness of the arc and the entrance and/or exit of the arc through the clothing. Once the non-FR clothing has ignited, the evidence from the tracking arc would quickly be lost as the fabric is consumed. With arc resistant clothing the evidence remains, since the clothing doesn’t ignite or continue to burn. Arc and flame resistant clothing actually lessens the severity of burns in these incidents since the clothing does not contribute. In two accidents of this nature involving FR clothing there were burns along the path of the tracking arc, i.e. in one case the burn was just a jagged “streak” across the chest and at the entry point, but in both cases there were NO clothing burns. This is a major improvement from what would likely have happened in the past due to the ignition of non-FR clothing.
System Assessment Problems
There is sometimes an assumption that most faults clear “instantaneously” and that the fault current is the most critical factor in system assessment. Since the fault current availablity drops dramatically with the conductor distance, it might be assumed that system assessment would focus on the substation level. An experienced engineer who kept up the fuse curves for the distribution system and has illustrated the relationship between fuse curves and the operation of “instantaneous” breakers has given insight into something critical in understanding of the arc hazard. Since instantaneous breakers are set for a specific fault current, they do not “see” faults below that “set” amperage. If the instantaneous breaker is “set” for 4000 amps, it will not “see” a fault of 3936 amps and that fault will have to clear with a fuse or in another manner. This may be amplified on the secondary side of the system where the amperage required to trip the primary breaker is higher amplified by the transformer. At a particular substation, the fault could be 8000 amps and would clear in less than 10 cycles and generate less than 10 cal/cm2 of energy but still enough to ignite most 100% cotton shirts. One mile from this substation, the fault current is only 3936 Amps thus insufficient to “trip” the “instantaneous” breaker. Going to the fuse curves for this particular part of the system, the clearing time is 20 cycles and at 8 inches away from the work a 12 inch arc can deliver 18 cal/cm2. This is sufficient to ignite most non-FR clothing, even the magical 11 oz/yd2 cotton that some still believe OSHA endorses. The surprise here is that lower fault current creates a higher exposure due to the extended clearing time of the device at lower fault currents.
New Moves in Worker Protection
One ongoing “new” practice in worker protection is the use of blast blankets. Actually, blast blankets have been used for 40 years attempting to absorb, dissipate and deflect energy of an electric arc especially in underground cable vaults on network systems. Some of these blast blankets are currently being manufactured specifically for electric utilities. Many utilities have been involved in testing and developing materials and designs for additional worker protection. There is currently no standard for testing blankets but testing at KEMA labs and BC Hydro have influenced testing methodology which may become a standard someday. There was a need for more information on the effectiveness of these blankets, and the utilities that have been testing have made much progress on this front. Additional testing on new materials and material configurations at Kinectrics lab is planned for the next few months.
Hoods and Faceshields
Hoods and face shields are making a major impact on worker protection in the past few years. Since the invention of the arc resistant face shield things have been heating up. Paulson Manufacturing (used by Steelgrip, and many other manufacturers) and Oberon now use this technology in arc resistant face shields, and many people are using amber-green polypropionate shields alone and in hoods for face protection. Though a face shield cannot protect fully from some arc exposures, in situations where the arc may be focused on the face, a face shield adds important protection, and the arc resistant shields work well for many situations. When hoods are used there is an issue with oxygen supply which some companies are addressing with supplied air. Also Steelgrip is offering a Nomex® mesh hood with the open mesh being in the top of the hood over the hard hat for better air flow with little risk of increased burn potential.
Another trend is focused on multi-layered approaches to protect in high amperage exposures. Usually you will get more protection for a given cost and weight by using more light weight layers versus a single heavy weight layer. For example, in recent testing, a multi layered system using UltraSoft® and a Nomex®-Kevlar® lining provided an arc rating greater than 50 cal/cm2 at a weight less than 15 oz/yd2.
Nomex® and Nomex®-Kevlar systems have been performing in the 40 to 100 cal/cm2 range for years. Many utilities use arc and flame resistant raingear in conjunction with a single layer of FR clothing to provice 20-50 cal/cm2. The raingear becomes a dual-purpose garment of both rainwear and the outer layer of an arc and flame resistant clothing system. Multi layer systems play a key roll in worker protection as exposure energy increases.
New Laws Requiring Arc and Flame Resistant Clothing
Another new trend in arc and FR clothing is emerging now in Minnesota. A new Minnesota law which takes effect next year requires ANSI 107-1999 compliant High Visibility Clothing in roadway work zones exposed to vehicular traffic. This will also affect line workers since the law also requires the clothing to meet the NFPA 70E electrical safety standard for situations which also involve an electric arc hazard. Currently, clothing which meets both these requirements is limited to two types of materials. Many companies are now making vests of these new materials from SSM and Performance Textiles. The materials are Fluorescent Lime-Yellow mod-acrylic which meets the F1506-2000 standard AND the ANSI 107-1999 standard. Westex also has a Valzon® which meets F1506-2000 and although offers some degree of high visibility, does not meet the ANSI 107-1999 standard fully at date of publication. Bulwark, MWG Apparel, Steelgrip, Tyndale and Workrite all make vests compliant with either or both standards.
Peru is the first country to require FR clothing for all electricians. More info on international regulations regarding the electric arc hazard will be forthcoming as the effect of US, ISO and IEC standards begin to impact North American industry.
Flash Fire Clothing New NFPA 2112 and 2113 Standards at the Door
This new standard will be affecting utilities soon. Scheduled to be published in September 2001 NFPA 2112 and 2113 could assist gas utilities and all petrochemical businesses since this voluntary standard assists in the selection, care and use of flame resistant clothing when industrial workers are exposed to potential flash fire hazards. Most materials which meet this standard will also meet electric arc standards. The challenge will be in high visibility fabrics since none to date can meet ANSI 107-1999 AND NFPA 2112.
New standards, laws and breakthroughs in arc protection are helping companies with workers exposed to the electric arc and flash fire to better comply with standards and to inform their workers on clothing choice. Prudent utilities are addressing the issues and keeping up on the literature on new clothing systems as they are proven in the field. Clothing is getting more comfortable and as the systems improve, there are more incentives to provide the right system for utility workers exposed to electric arc. Doing an electrical system hazard assessment, choosing comfortable, arc resistant clothing matched to the hazards and providing effective worker training on how to wear arc resistant and worker provided clothing are good steps in the right direction.
Hugh Hoagland consultant in arc and flame resistant clothing and PPE working with electric utilities and clothing manufacturers to develop, test and educate workers about the electric arc and clothing. Hugh’s company, ArcWear.com also provides consulting in cooperation with several electrical engineering firms to provide fault studies and hazard analysis of electrical systems. You may contact Hugh at hugh@arcwear.com
Dr. Stephen Cress Principal Engineer – Distribution at Kinectrics Inc. (formerly Ontario Hydro Technologies) where the majority of North American arc testing of clothing has been conducted. He is co-developer (H. Morrison and B. Gu) of the ARCPRO computer program. You may contact Stephen at Stephen.Cress@kinectrics.com
Tom Neal consultant in the areas of protective clothing selection for flash fire and electric arc hazards, accident investigation and hazard assessment. Following his retirement as the Thermal Laboratory Technology Manager at DuPont in 1999, Tom established his own consulting company, Neal Associates Ltd. and can be reached at nealassoc@earthlink.net
He had first and second degree burns on the front of his legs but mostly third degree burns on the back of his legs and hips. The arc may have blown the front of his jeans off quickly so that the front of his legs were not as severely burned by the fire which swept over his lower torso as the heavy jean material continued to burn. Wally Benhke, retired DuPont scientist, and one of the developers of the copper calorimeter currently used in burn prediction, once told us something that came home in this accident: “Heavy cotton is good until it ignites, and the ignition energy is almost directly proportional to the weight of the cotton material, but once the heavy cotton ignites you just have more fuel to burn on the body.” The line worker would have been much better protected with a pair of an arc and flame resistant jeans that he could have selected in the company’s clothing allowance program.
Clothing allowance programs, purchase programs, rental programs and other creative solutions to getting the right clothing on the backs (and fronts) of workers are becoming more and more important in the utility industry. Hazard assessment is moving from art to science and software programs and now “turn key services” are making it easier to MATCH the hazard and the task in order to provide for worker protection. However, new concerns continue to arise as we move forward toward the “right stuff ”.
Clothing and the Arc
When OSHA promulgated the CFR 1910.269 standard in the US, the clothing portion of the standard put many utilities in an uproar. There was concern over the necessity of moving to arc and flame resistant clothing and there were, and to some extent still are, questions about when and where conventional clothing can be used by utility workers.
Most utilities today provide some arc and flame resistant (FR) clothing be it an FR shirt or an FR jacket. Most electric utilities in the US and Canada now provide arc and flame resistant raingear also. Since melting FR raingear does not do well under many arc conditions, more utilities are moving to the new F1891-00 a standard which eliminates most of the “FR” raingear containing melting materials Non-flame resistant winter wear continues to be an issue due to melting linings and non-flame resistant shells which are frequently observed to melt and/or ignite when in arc accidents. Even with increased regulation, new electrical safety standards, and more workers in arc and flame resistant clothing, the arc accident rate has not decreased.
Why no Drop in the Accident Rate?
Why, with the new regulation and safety standards has there not been a drop in the accident rate. FR clothing cannot prevent accidents but it can eliminate or greatly decrease the severity of the injuries sustained by workers. Most line workers and electricians exposed to the electric arc hazard wear an FR shirt and many wear FR pants. But the clothing doesn’t prevent injury unless it covers all skin and has a rating equivalent to the arc hazard level. When an arc accident occurs, exposed skin has a high probability of injury as does inadequately protected skin. The intent of the OSHA standard was to reduce injuries from igniting clothing and melting materials, and this has been somewhat successful.
The OSHA standard succeeded in motivating scientific evaluation of clothing exposed to the electric arc, and in motivating manufacturers to seek creative solutions for arc protection scenarios. The driving force behind the standard was utility and union desire for standard rules and worker protection, and the clothing portion of the standard was based on the best test information available at that time. The weaknesses utilities have encountered in implementing the OSHA standard are the lack of knowledge and guidance in protective clothing selection and the lack of the knowledge on performing a hazard assessment. In the hazard assessment area, although exposure energy from single phase arcs has been well researched, there is a lack of scientific information on the hazards produced by three-phase arcs and arcs that are confined within switchgear. To fill this void the IEEE-PCIC (Institute of Electrical and Electronics Engineers Petrochemical Industrial Conference) group has been attempting to fund an arc testing project aimed at assessing the arc exposure intensity for various pieces of equipment from MCC’s (motor control centers) to switchgear. Further funding contributions are required to enable this work to cover a wide range of arc exposure scenarios. (For further information contact Craig Wellman craig.m.wellman@usa.dupont.com)
Another Issue Of Arc Hazard Assessment
Several tools are available for arc hazard assessment today. The standard, ARCPRO (Version 2.0) developed by Kinectrics (formerly Ontario Hydro Research), provides a user-friendly interface to compute radiated heat energy and compare the hazard to the arc rating of FR clothing. In addition, EDSA (www.edsa.com) has now built arc hazard assessment into their Power System Design Software. Many companies are finding that with the lack of available and qualified power system engineers, there is a need for system assessment packages. Consultants are available to provide utilities with the power system engineering computations and the clothing selection analysis. For more information on system assessment, contact the authors.
Tracking Arcs
Another issue that has surfaced with FR clothing has been tracking arcs, i.e. arcs that move or track along a surface like, for example, the surface of the skin. In one instance, a worker experienced a tracking arc on the skin surface and thought the FR material may have contributed in some way to arc tracking on the skin. It is unlikely that FR clothing is a contributor, but with non-FR clothing when the arc does track on the skin (or sweat on the skin) the clothing is often ignited due to the closeness of the arc and the entrance and/or exit of the arc through the clothing. Once the non-FR clothing has ignited, the evidence from the tracking arc would quickly be lost as the fabric is consumed. With arc resistant clothing the evidence remains, since the clothing doesn’t ignite or continue to burn. Arc and flame resistant clothing actually lessens the severity of burns in these incidents since the clothing does not contribute. In two accidents of this nature involving FR clothing there were burns along the path of the tracking arc, i.e. in one case the burn was just a jagged “streak” across the chest and at the entry point, but in both cases there were NO clothing burns. This is a major improvement from what would likely have happened in the past due to the ignition of non-FR clothing.
System Assessment Problems
There is sometimes an assumption that most faults clear “instantaneously” and that the fault current is the most critical factor in system assessment. Since the fault current availablity drops dramatically with the conductor distance, it might be assumed that system assessment would focus on the substation level. An experienced engineer who kept up the fuse curves for the distribution system and has illustrated the relationship between fuse curves and the operation of “instantaneous” breakers has given insight into something critical in understanding of the arc hazard. Since instantaneous breakers are set for a specific fault current, they do not “see” faults below that “set” amperage. If the instantaneous breaker is “set” for 4000 amps, it will not “see” a fault of 3936 amps and that fault will have to clear with a fuse or in another manner. This may be amplified on the secondary side of the system where the amperage required to trip the primary breaker is higher amplified by the transformer. At a particular substation, the fault could be 8000 amps and would clear in less than 10 cycles and generate less than 10 cal/cm2 of energy but still enough to ignite most 100% cotton shirts. One mile from this substation, the fault current is only 3936 Amps thus insufficient to “trip” the “instantaneous” breaker. Going to the fuse curves for this particular part of the system, the clearing time is 20 cycles and at 8 inches away from the work a 12 inch arc can deliver 18 cal/cm2. This is sufficient to ignite most non-FR clothing, even the magical 11 oz/yd2 cotton that some still believe OSHA endorses. The surprise here is that lower fault current creates a higher exposure due to the extended clearing time of the device at lower fault currents.
New Moves in Worker Protection
One ongoing “new” practice in worker protection is the use of blast blankets. Actually, blast blankets have been used for 40 years attempting to absorb, dissipate and deflect energy of an electric arc especially in underground cable vaults on network systems. Some of these blast blankets are currently being manufactured specifically for electric utilities. Many utilities have been involved in testing and developing materials and designs for additional worker protection. There is currently no standard for testing blankets but testing at KEMA labs and BC Hydro have influenced testing methodology which may become a standard someday. There was a need for more information on the effectiveness of these blankets, and the utilities that have been testing have made much progress on this front. Additional testing on new materials and material configurations at Kinectrics lab is planned for the next few months.
Hoods and Faceshields
Hoods and face shields are making a major impact on worker protection in the past few years. Since the invention of the arc resistant face shield things have been heating up. Paulson Manufacturing (used by Steelgrip, and many other manufacturers) and Oberon now use this technology in arc resistant face shields, and many people are using amber-green polypropionate shields alone and in hoods for face protection. Though a face shield cannot protect fully from some arc exposures, in situations where the arc may be focused on the face, a face shield adds important protection, and the arc resistant shields work well for many situations. When hoods are used there is an issue with oxygen supply which some companies are addressing with supplied air. Also Steelgrip is offering a Nomex® mesh hood with the open mesh being in the top of the hood over the hard hat for better air flow with little risk of increased burn potential.
Another trend is focused on multi-layered approaches to protect in high amperage exposures. Usually you will get more protection for a given cost and weight by using more light weight layers versus a single heavy weight layer. For example, in recent testing, a multi layered system using UltraSoft® and a Nomex®-Kevlar® lining provided an arc rating greater than 50 cal/cm2 at a weight less than 15 oz/yd2.
Nomex® and Nomex®-Kevlar systems have been performing in the 40 to 100 cal/cm2 range for years. Many utilities use arc and flame resistant raingear in conjunction with a single layer of FR clothing to provice 20-50 cal/cm2. The raingear becomes a dual-purpose garment of both rainwear and the outer layer of an arc and flame resistant clothing system. Multi layer systems play a key roll in worker protection as exposure energy increases.
New Laws Requiring Arc and Flame Resistant Clothing
Another new trend in arc and FR clothing is emerging now in Minnesota. A new Minnesota law which takes effect next year requires ANSI 107-1999 compliant High Visibility Clothing in roadway work zones exposed to vehicular traffic. This will also affect line workers since the law also requires the clothing to meet the NFPA 70E electrical safety standard for situations which also involve an electric arc hazard. Currently, clothing which meets both these requirements is limited to two types of materials. Many companies are now making vests of these new materials from SSM and Performance Textiles. The materials are Fluorescent Lime-Yellow mod-acrylic which meets the F1506-2000 standard AND the ANSI 107-1999 standard. Westex also has a Valzon® which meets F1506-2000 and although offers some degree of high visibility, does not meet the ANSI 107-1999 standard fully at date of publication. Bulwark, MWG Apparel, Steelgrip, Tyndale and Workrite all make vests compliant with either or both standards.
Peru is the first country to require FR clothing for all electricians. More info on international regulations regarding the electric arc hazard will be forthcoming as the effect of US, ISO and IEC standards begin to impact North American industry.
Flash Fire Clothing New NFPA 2112 and 2113 Standards at the Door
This new standard will be affecting utilities soon. Scheduled to be published in September 2001 NFPA 2112 and 2113 could assist gas utilities and all petrochemical businesses since this voluntary standard assists in the selection, care and use of flame resistant clothing when industrial workers are exposed to potential flash fire hazards. Most materials which meet this standard will also meet electric arc standards. The challenge will be in high visibility fabrics since none to date can meet ANSI 107-1999 AND NFPA 2112.
New standards, laws and breakthroughs in arc protection are helping companies with workers exposed to the electric arc and flash fire to better comply with standards and to inform their workers on clothing choice. Prudent utilities are addressing the issues and keeping up on the literature on new clothing systems as they are proven in the field. Clothing is getting more comfortable and as the systems improve, there are more incentives to provide the right system for utility workers exposed to electric arc. Doing an electrical system hazard assessment, choosing comfortable, arc resistant clothing matched to the hazards and providing effective worker training on how to wear arc resistant and worker provided clothing are good steps in the right direction.
Hugh Hoagland consultant in arc and flame resistant clothing and PPE working with electric utilities and clothing manufacturers to develop, test and educate workers about the electric arc and clothing. Hugh’s company, ArcWear.com also provides consulting in cooperation with several electrical engineering firms to provide fault studies and hazard analysis of electrical systems. You may contact Hugh at hugh@arcwear.com
Dr. Stephen Cress Principal Engineer – Distribution at Kinectrics Inc. (formerly Ontario Hydro Technologies) where the majority of North American arc testing of clothing has been conducted. He is co-developer (H. Morrison and B. Gu) of the ARCPRO computer program. You may contact Stephen at Stephen.Cress@kinectrics.com
Tom Neal consultant in the areas of protective clothing selection for flash fire and electric arc hazards, accident investigation and hazard assessment. Following his retirement as the Thermal Laboratory Technology Manager at DuPont in 1999, Tom established his own consulting company, Neal Associates Ltd. and can be reached at nealassoc@earthlink.net
