Document YD3ejndmYZ92Mv09n4w38o5rn

FILE NAME: Electrical Insulation (ELEC) DATE: 1994 DOC#: ELEC017 DOCUMENT DESCRIPTION: Conference Presentation Your order details Our Order Ref: 01246847-001 Your Ref: 15NR0090 Despatched on: 1/7/2015 Your item details UIN: BLL01010512491 Title: TECHNICAL CONFERENCE- NETA. Publisher: ISSN: Year: 1994 Pages: Author name(s): VASCHIRIS J E Article title words: ASBESTOS IN CIRCUIT BREAKER & ALTERNATIVE AIR CHUTE MATERIALS Your shipping address: British Library Business Use Customer Services Internal Use Internal XX1 1XX . United Kingdom Comments British Library Business Use Customer Services Internal Use Internal XX11XX United Kingdom https://OnDemand.bl.uk Copyright Statement Unless out of copyright, the contents of the document(s) attached to or accompanying this page are protected by copyright. They are supplied on condition that, except to enable a single paper copy to be printed out by or for the individual who originally requested the document(s), you may not copy (even for internal purposes), store or retain any electronic medium, retransmit, resell, or hire the contents (including the single paper copy referred to above). However these rules do not apply where: 1. you have written permission of the copyright owner to do otherwise; 2. you have the permission of The Copyright Licensing Agency Ltd, or similar licensing body; 3. the document benefits from a free and open licence issued with the consent of the copyright owner; 4. the intended usage is covered by statute. Breach of the terms of this notice is enforceable against you by the copyright owner or their representative. This document has been supplied under our Copyright Fee Paid serviee. You are therefore agreeing to the terms of supply for our Copyright Fee Paid service, available at; http://www.bl.uk/reshelp/atyourdesk/docsupply/help/terms/index.htiril The British Library, On Demand, Boston Spa, Wetherb.y, United Kingdom, LS23 7BQ OnDemand.bl.uk ASBESTOS IN CIRCUIT BREAKERS AND ALTERNATE ARC CHUTE MATERIALS By James E. Vachria, M.E. Fabrication Specialty, Inc. As man explored and experienced all the wonders of this great planet, asbestos was discovered:. Here was a substance that, wouldn't burn. It could fee added to clays and cements.: Like straw added to mud for additional strength, asbestos was found to add body, substance, and additional strength to many materials. This was an acceptable additive, especially to. rigid clays that were used with fire. Asbestos was ideal; a natural. The resulting material would inherently be heat resistant. These properties were evident when electricity was harnessed to become another servant of man. As electric arcs began to burn -away primitive electrical insulations such as wood, paper, shellac, oil soaked paper, casein hard rubber, and vulcanised fibre, asbestos containing materials soon became the most durable and practical insulating and arc resistant material. In addition to its noncombustibilitf, asbestos does not easily conduct heat or electricity, The above outstanding thermal and arc resistant properties coupled with the relative low cost as well as adequate availability of the material easily prompted asbestos to become widely used in power switch gear. This extensive use of asbestos in electrical -apparatus began in the '20s and '30s and continued through the '70s (See Figure I ) . All this expansion in the. use of asbestos was without the general knowledge of the inherent hazardous circumstances. Once manufactured in thin sections, this material quickly found acceptance in arc splitters within arc chute assemblies. When the arc plasma contacts this combination of materials, the cement could glaze and the asbestos would not be consumed until confined 1400F was experienced or exceeded. Although the" arc plasma is extremely high In temperature (estimated to be greater than 220 0 F) , its proximity to these materials through the duration of the arc was acceptable, enabling many cement board asbestos insulated switches to render prolonged acceptable, service (See Figure 2). Electric switch gear, circuit breakers, and other equipment manufacturing progressed rapidly after World War II. In 1964 Dr. Irving Selikoff started research into the effects of asbestos related occupational problems and the asbestos health hazard began surfacing, 1/VACHRI5 ' - Page 25 Asbestos is friable material. All three major types- of natural mined asbestos? chrysotile, amosite, and crocidolite are friable. The National-: . :':^<wr Hazardous Air Pollutants (MISHAP) defines friiSiiitf''"of an ACM, asbestos containing material, as that quality wherein hand pressure can crumble or pulverize the material* Hdst;;#ttier, countries regulate asbestos by mineral types, but, in the Wilted States we treat them all the same. Approximately SSI of asbestos products have been produced using chrysotile. Because of friability' they are all hazardous, When asbestos fibers are loose and dispersed they can become airborne, inhaled, or ingested and remain in' the body, most commonly in the lungs. Asbestos fibers are also dangerous because they are so small and airborne capable. This ales them difficult to detect without instrumentation. Additionally, they break in length and width at the same time multiplying the hazard, The most dangerous fibers are l to 5 microns long* A micron is 1/25,000 inch. Early in his study of 1,760 ship workers', Dr. Selikoff found that 8 0 % had an asbestos related ailment. In addition, 40% of the immediate family members of these workers also had some asbestos related ailment (ARA). Asbestosis, a nott cancerous but often fatal scaring of the lungs,* mesothelioma, cancer of the lining of the lungs or abdominal cavity; pleural plagues, fluid between the chest cavity and the thickened lining of the lungs; and lung cancer, especially among cigarette smokers were-the major problems. In 1972 the Occupational Safety Health Act (OSHA) limited asbestos exposure without protection at 5 fibers/cubic centimeter. In 1973 the Environmental Protection Agency (EPA) banned asbestos in buildings for thermal and sound proofing insulation. By 1976 OSHA reduced asbestos exposure to 2 fibers/cubic centimeter; but, in 1986 it was further reduced to a Permissible Exposure Limit (PEL) of .2 fibers/cubic centimeter. The wide spread use of Asbestos Containing Materials (ACMs) in fire-proof curtains, fire boxes of furnaces,' floor tiles, ceiling tiles, plaster, brake linings, gaskets, pipe wrapping, as well as cement boards, put ACMs in many applications and. locations. An ACM is defined as a material containing greater than 1% asbestos by area. The materials worked well in these uses. Unfortunately the major ABAs mentioned have a minimum dormancy of ten years. Asbestosis has a latency period of 15 to 30 years; Mesothelioma and Pleural Plaques, 20 to 40 years; and lung cancer varies from 10 to 30 years. Smoking while exposed to asbestos increases the risk of lung cancer by 90 times. It was these extended latency periods that delayed wide spread industrial awareness of t h e .ACM' hazards until the mid-sixties. 2/VACHRIS Page 26 In order to protect workers in occupations where they are exposed to airborne concentrations of asbestos fibers, OSHA established regulation 29 CFR 1926.58, ' This U.S. Department of Labor ruling was published in the Federal Register on June 20, 1986. It set forth definitions, exposure limits, monitoring, compliance, protection, communications, housekeeping, medical surveillance, and record keeping. This regulation spells out an "Excursion Limit" (EL) of 1.0 fibers/cc for short-time exposure of 30 minutes? an "Action Level" (AL) of .1 fibers/cc requiring special medical surveillance along with proper employee training and the "Permissible Exposure Limit" (PEL) of .2 fibers/cc. For both the AL and PEL airborne concentrations of asbestos are measured over an eight hour time-weighted average (TWA) period. Asbestos fiber airborne concentrations are measured using air samples taken through special filters examined using Transmission Electron Microscopy (TEM) or Phase Contract Microscopy (PCM). Using PCM, fiber count is possible. With TEM the fibers can be identified, one from another? asbestos type determined as well as fiber count down to .002 microns in diameter. Such microscopic analysis is expensive and must be conducted by EPA recognized labs. Hopefully most electrical testing and inspection work will be conducted where experienced airborne asbestos levels . are considerably less than the excursion limit (EL) of 1.0 fibers/cc. Therefore, In the field when checking., out breakers a "half ask" respirator with High Efficiency Particulate Air (H1PA) filters should be worn. This should provide adequate protection if any burned out or loosened fibers should be blown towards the inspector while the apparatus is opened. During this time the protected worker can gently break off a small portion of the suspected worn out asbestos insulation and place it in a 6 mil polyethylene bag, A "critical seal" should be established by tape sealing the bag and placing it into another 6 ail poly bag and tape sealing the second bag. Additionally, the area from which the "bulk sample" was broken off should also be sealed with a suitable encapsulant. The encapsulant adhesive matrix creates a. membrane over the disturbed broken surface or penetrates" the material binding its components together reducing the friability of the ACM. Any repair of previously encapsulated asbestos containing materials ay include filling damaged areas with suitable non-asbestos substitutes followed by re-encapsulating, The total t i m e 'for any such exposure should not exceed 30 minutes, A "half face" air purifying respirator provides the minimal protection factor for the wearer. ` 3/VACHRS Page 27 1 The bulk sample in its "critical seal" can subsequently be analyzed in the laboratory using Polarized Light Microscopy (PLM.J. This will determine the type of asbestos and the percentage by volume, if asbestos is indeed1present. If the breaker apparatus is subsequently shipped to your facility for repair, the same precautions are required. Additionally, a high efficiency HRPAv a c vacuum should be used to remove any loose a s b e s t o s :dust and fibers before working on the unit. Since there are specific IPA regulations concerning the disposal of what the HEPA-VAC collects and specific OSHA regulations concerning its handling;, it is highly recommended that you contact your state Environmental Protection Agency for local guidance. Many states may not permit' a half mask** for certain excursion levels because the protection factor of that respirator is only 10. Pot -gross removal of asbestos containing material a Supplied Air Respirator {SAR) or a Powered Air Purified Respirator (PAPR) may be required. If so , the wearer must foe pre-trained after passing medical tests including chest x-ray, pulmonary, and a complete base line occupational physical. After .being licensed by your state .IPA, medical surveillance continues for that worker's term of employment plus 30 years. Additionally, the work must be performed in a restricted area, under constant negative air pressure with a CPR qualified asbestos licensed supervisor present -- all in accordance with applicable EPA and OSHA regulations. It was for these reasons that Fabrication Specialty, Inc.; (FSI) was established as a subsidiary of Franklin Fifere-Lamihek orp. FSI has 6 licensed asbestos workers, including this author, with another man in training as this paper was being written. Because of this special facility and appropriately trained" and licensed workers, we can properly remove and dispose of the ACMs in an arc chute assembly. Once removed, we can also replace the arc splitters (See Figure 3) and the chute assembly with several non-asbestos insulating materials (See Figure 4), Mica is the nearest alternative to asbestos. Chemically, Phlogopite Mica Mg? AL*' Si6 O20 (OH}, and Amber Mica H, KMg5 AL (Si04}3 contain potassium, aluminum, and magnesiasilica similar to asbestos M g 3 Si* (0H)4 0* Hydrous Magnesium Silicate, Mica has potassium and aluminum added to a very similar chemical structure as asbestos, but unfortunately, does not have the high tensile strength of asbestos. It is readily available, but comes in thin small transparent sheets, the smaller .sizes of which are usually ground into powder. A weak mica paper can be made from the mica grindings. Mica's better thermal conductivity and corona resistance is offset by its poorer processability. Thermal rating Page 28 4/VACHRIS of mica composites may be limited by the binder systems employed to produce more usable sizes. Research and development is being done to enhance many mica containing materials, Franklin Fibre* Laraitex Corp, is producing Lamitex Grade #136 (See Figure 5} in many round and square tubular shapes from mica/epoxy. As a high pressure laminate, it has strengths close to NEMA G-7 Glass Silicone with arc, corona, and thermal resistance limited by the epoxy binder. Other mica containing material that is used and considered for certain arc chute replacements is Xndularc(TM) i*-21 mica cement, for lower voltages and D.c. applications. Insular(TM) XM .glass bonded mica is considered for medium voltage (4,16 to 13.8 I?). InsularcfTM) XC mica bonded sheet is for high' voltages. Mica melts at 18QGF t 20GG*F and can expand in volume at I0G0F; cement vitrifies at 1500F and glass bonded mica can expand in volume at 80-0F to 90:GF. The uses of any of these materials should be tested in actual usage. Machinable ceramics, porcelain type materials, and zirconia have been used in some of these applications. Mineral ceramic alumina talc and clay composites are under development and should withstand approximately 2300C>F and higher voltages. Each design and proximity to the arc, as well as voltages, time, AC/DC, and types of contacts used, are variable factors making the specific use of these materials totally not guaranteed without full tests conducted in the appropriate apparatus under actual or closely simulated conditions. 5/VACHRIS Page 29 F igura 3. Swaferielyh a r e aabestos arc stil'l in c ia se t teo, i a*ya* j of Page 30 Figsr# 2 a sb esfeo s cernent board and asbestos ciotb aelamine arc runners. Page 32