Installation of quinterra wrapped coils in an elctrical motor - asbestos electrical insulation - Rosato (C) InspectApediaAsbestos Electrical Wire Insulation & Asbestos Electrical Insulation Products
Manufacture & Identification of Asbestos Electrical Insulation Products

     

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Asbestos electrical insulation:

History, manufacture, visual identification: how to recognize asbestos-based or asbestos containing electrical insulation materials in products & buildings - a visual guide to identifying asbestos in buildings.

Page top photograph: asbestos insulation on electrical wiring in a theater.

This articles series about the manufacture & use of asbestos-containing products includes detailed information on the production methods, asbestos content, and the identity and use of asbestos-containing materials. Page top photo shows asbestos used in an electrical motor.

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Asbestos Electrical Insulation Materials History & Manufacturing Processes

The following text is Adapted from Rosato (1959) p. 106-112 [1] © 2013 InspectApedia.com

Installation of quinterra wrapped coils in an elctrical motor - asbestos electrical insulation - Rosato (C) InspectApediaOne of the major uses for asbestos paper as well as for such forms of asbestos as yarn, tape, lap, and loose fiber is in the field of electrical insulation.

[Click to enlarge any image]

The main reasons for the use of asbestos are its fire and heat resistance, electrical insulation properties, acid resistance, and durability.

Electrical insulation is also used to protect the surfaces of conductors from such adverse conditions as moisture and chemicals, and to fill spaces where corona discharge is liable to occur.

In electrical applications, asbestos insulation is used with low iron content. All grades of crude and milled chrysotile fiber are predominately used.

The lowest iron content fibers for use in the electrical field are available from ore deposits in the North American Continent. ASTM specifications list the total iron content for electrical grade products. Details are
at ASBESTOS IRON CONTENT.

List of products using asbestos electrical insulation

Large quantities of asbestos are used to cover electrical wire in the traction type of electric motors and coils where there is a possibility of rising temperature damaging ordinary cotton coverings.

The general use of asbestos electrical insulation includes ordnance equipment (aircraft, missiles, etc.) oil burners, heating and cooking apparatus, lighting equipment, agricultural machinery, construction and mining machinery, hoists, oil field machinery, machine tools, portable tools, bakery machinery, food products 'machinery, textile machinery, paper industry equipment, pumps and 106 compressors, conveying equipment, blowers and fans, trucks and tractors, industrial ovens and furnaces, mechanical stokers, computers and cash registers, vending machines, laundry equipment, vacuum cleaners and units, refrigeration and air conditioning units, motors and generators, power transformers, switchgear controls, welding units, insulated wire and cable, lamps, radio, TV and radar units, x-ray units, railroad units, dental units, and signs and advertising displays.

Lightweight asbestos insulation is of primary importance on Naval and Maritime ships. Navy cable insulation is of particular importance; it is a combination of asbestos paper and textile products (lap, tape, etc.)

In the manufacture of multi-conductor cables, the single or paired conductors are cabled into required multiples, together with cushioning fillers in the valleys. These fillers are generally made with asbestos roving.

Specifications for Asbestos-Based Electrical Insulation Materials

Classification of electrical insulation by the American Institute of Electrical Engineers (AIEE) follows:

Classes of Electrical Insulation Materials

Class
Insulating Material
Maximum Temperature degF
O
Organic, not impregnated 195
A
Organic, impregnated 220
B
Inorganic, organic binder 265
H
Inorganic, silicone binder 355
C
Completely inorganic 355+
Notes:
Watch out: This data is circa 1959 from AIEE and is not current; therefore the table is provided for historic reasons and not as a current standard for electrical insulation products.

Another classification which includes asbestos-electrical insulated products is given by the Underwriter's Laboratories, Inc. This laboratory classifies asbestos electrical insulating material as asbestos-insulated wire (460 12) and as asbestos-varnished cloth wire (460 13).

Asbestos-Insulated Wire (460 12) Labels & Classifications

  • Type A, with asbestos insulation
  • Type AA, with an asbestos braid and asbestos insulation
  • Type Al, with impregnated asbestos insulation
  • Type AlA, with asbestos braid and impregnated asbestos insulation

Asbestos-Varnished Cloth Wire (460 13)

  • Type AVA, An asbestos braid: an insulation consisting of varnished cloth and impregnated asbestos.
  • Type AVB, A plain [flame?] -retardent cotton braid: an insulation consisting of varnished cloth and impregnated asbestos.
  • Type ABL, A lead covering: an insulation consisting of varnished cloth and impregnated asbestos.

Data pertaining to electric shipboard cable which includes asbestos is given in the "Cable Comparison Guide," NAV- SHIPS 250-660-23 (1956) published by Bureau of Ships, Navy Department, Washington 25, D. C. and available through Government Printing Office.

The data pertains to Government procurement specifications MIL-C-915A (Ships), MIL-C-2194B (Navy), MIL-C-2681 (Ships), and MIL-W-16878B (Navy). All cables are identified by types.

The letters listed under types identify the first letters of the words used in describing the cable. Other letters identify construction of the cable. Some of these cables which incorporate asbestos are identified as follows:

  • DFPA, Double conductor, flame proof, armored: Natural rubber of asbestos-varnished cambric-asbestos insulation depending on size, cabled with fillers, belt, armored.
  • DHFA, Double conductor, heat and flame resistant, armored: Size 3, 4 and 9 with synthetic resin and felted asbestos insulation; sizes 14 and larger with asbestos-varnished cambric-asbestos insulation, cabled with fillers, belt, impervious sheath, armored.
  • DHFTA, Double conductor, heat and flame resistant, thin wall, armored: Thin wall synthetic and felted asbestos insulation, cabled with fillers, binder, impervious sheath, armored.
  • FHFTA, Four conductor, heat and flame resistant, thin wall, armored: Thin wall synthetic and felted asbestos, insulation, cabled with fillers, binder, impervious sheath, armored.
  • MFPP, Multiple conductor, flame proof, plain: Asbestosvarnished cambric insulation, cabled with fillers, binder, textile braid overall.
  • SFPA, Single conductor, flame proof, armored: Asbestosvarnished cambric-asbestos insulation, textile braid, armored.
  • TFPA, Three conductor, flame proof, armored: Asbestosvarnished cambric-asbestos insulation, cabled with fillers, belt, armored.

Asbestos Paper Products as Electrical Insulation

Asbestos papers are very popular for use in the manufacture of miniature electrical component units. Miniature transformers can use asbestos papers. A 30 per cent reduction in weight has been obtained in Class-B transformers.

World War II initiated many development projects specifically for developing inorganic paper products. Prior to 1940, no inorganic papers were commercially available. At present, there are four basically different types of inorganic papers commercially available; i.e., asbestos, mica, glass, and ceramic. Asbestos papers are manufactured by Johns- Manville, Inc. under the trade name "Quinterra" or "Quinorgo"; by Raybestos-Manhattan, Inc. under the trade name "Novabestos"; and by General Electric Co. under the trade name "Terratex."

These basic paper products are available in many different forms which include combinations of asbestos-glass, asbestos-mica, papers backed with or sandwiched between other types of papers or fabrics and held together by an oleoresinous varnish, shellac, silicone, rubber, or other composite insulation structures. These combinations provide for increased tensile strength which is desirable in many of the cable or wire taping operations.

The chief function of asbestos [in electrical applications] is that of a separator or as a wrapping for wire insulation. Untreated paper is roughly equivalent to air as an insulator; when it is completely dry its resistivity is good.

Untreated paper can contain moisture since it has the characteristic of absorbing moisture from the air—a characteristic typical of other paper products. It is usually treated with a varnish or lacquer in order to eliminate the moisture problem. Where high temperature requirements are of prime interest, the paper is treated with silicone varnishes or fluorocarbons.

In the manufacture of asbestos paper, there is always continued interest and development in producing open asbestos fibers. Various methods of manufacture and various equipment are used in order to fiberize bundles of asbestos fiber. By opening the fibers, entrapped undesirable magnetite can be removed.

Manufacturing processes have also been developed which permit uniform blending of asbestos fiber with such synthetic fibers as glass. These types of products are used by electrical insulation manufactures and by the manufacturers of reinforced plastics and filters.

"Quinterra" is a pyrolysis-resistant electrical insulation made of highly purified asbestos. These electrical insulations greatly extend the life of electrical equipment. By permitting magnetic units to operate at higher temperatures, they promote savings in space, weight and materials.

The asbestos products enable electrical apparatus to withstand higher overloads; thus, they reduce the necessity for standby equipment. Their thin layers require less time and labor to apply and occupy less space than the extra thicknesses formerly employed to compensate for the loss of dielectric strength caused by heat. (Courtesy Johns-Manville Corp.)

Installation of quinterra wrapped coils in an elctrical motor - asbestos electrical insulation - Rosato (C) InspectApedia

Figure 6.1. Installation of Quinterra wrapped coils in electric motor armatur e[click to enlarge]

In transformers, their uses include barriers, core tubes, spacer sticks, end packings, interlaminates, interlayers, and wrappers. They have replaced metal cores in some resistors and conserve insulation in others.

In magnets, they insulate the ribbon coils, and form liners, spacers, and wrappers. Both wires and cables are wrapped with "Quinterra" and "Quinorgo" Typical motor wire insulation is shown in Figure 6.1.

Patent 2,626,213 describes a unique method of dispersing and forming asbestos papers. The Novabestos paper products produced are characterized by their ability to stretch and distort, both dry and wet, to a much greater extent than ordinary paper. The smooth asbestos fibers in the paper allow more flow and better packing properties than the commercial organic paper products.

The Novabestos paper machine developed specifically for producing asbestos paper is similar in many respects to the conventional Fourdrinier machine. The asbestos pulp is picked up by a wire screen and carried over flat boxes operating under a vacuum of 2 to 8 in. mm.

The flat boxes remove 60 to 70 per cent of the water from the slurry. The next step in drying is a suction transfer roll operating under a vacuum of 12 to 15 in. mm. In this operation, another 5 to 10 per cent of water is removed. From the suction transfer roll, the paper goes over a steam-jacketed drying roll and then over a windup drum. The finished paper product has the appearance of snowy white paper.

Reader Question: did house wiring ever contain asbestos?

I was wondering if house wiring ever contained asbestos. The wiring in my home appears to have an asphalt impregnated type covering almost looks like a snake skin. Could this contain asbestos? - D.T., Canada 10/4/2013

Reply: yes

A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer about wiring (noting any markings, exact composition of its insulation, and perhaps data about its age) than we can give by email alone. You will find additional depth and detail in articles at our website.

That said I offer these comments:

Asbestos was indeed used in electrical wiring insulation, as discussed in the article above
(ASBESTOS ELECTRICAL INSULATION)
and appears in our lists of asbestos-containing materials found
at ASBESTOS LIST of PRODUCTS
and
at ASBESTOS PHOTO GUIDE to Materials

Asbestos was in particular, more widely used in a more pure form in certain electrical wires exposed to high risk (inside of heaters, toasters, electric stoves, theatre wiring).

I would like to see sharp photos of your wiring, its external jacket, cross section of the insulation, and if occasion permits, an actual sample - those details would permit further comment or even testing of the material.

Depending on the age and appearance of the wiring about which you ask, it may be appropriate to treat it as PACM - presumed asbestos containing material. But don't panic. Usually asbestos hazards are minimized by leaving PACM alone unless it is friable, already damaged and / or subject to damage and is in an occupied space.

I suspect that unless  there is a demolition project in progress, the asbestos exposure hazard from asbestos-containing residential electrical wiring is very low, perhaps below the limits of detection, both because of low friability of the typical (excluding my list above) application and insulation materials, and because wiring is normally enclosed in wall, floor, or ceiling cavities.

Reader Question: asbestos used in vacuum cord SVT electrical cords?

(May 2, 2014) Frank d said:
Does vacuum cleaner cord SVT have abestos? Or has it ever contained abestos?

Svt cord is a type of UL cord that they use in vacuums it's probably highly unlikely that they use asbestos in this type of application. Ami I right?

Reply:

Asbestos was used in some electric wire insulation such as high temperature wiring in heating devices and stoves and in theater wiring.

Dillon (1942) and other of our citations given below describe widespread use of asbestos in electrical appliances, devices, and in their wiring and line cords.

So SVT electrical cords are basially a cord with a thinner insulating jacket, intended for use on vacuum cleaners - appliances that often want to use a spring-loaded spool to re-wind and store the cord when it's not in use. That thin-ness limits the use of the power cord to just certain applications.

Weber (1997) cites SVT components in older guitar amps that did contain asbestos but that asbestos use was in the amplifier's structure.

I don't know that that application speaks to being able to assert the use or non-use of asbestos whatsoever. My OPINION is that where heat is an extra concern (such as toasters) we might be more likely to find that asbestos was used in an appliance electrical cord. Heat may indeed be a concern, or rather heat tolerance, in a power cord that has also to use a thin insulating jacket for other reasons. The specifications for electrical wire insulation have much to do with tolerating heat as well as other factors (flexing in power cords, moisture resistance, etc).

Asbestos was in fact mixed with rubber in some applications.

You might approach the question of whether a specific power cord contains asbestos more easily by stating the product's name, model, and date of manufacture, and if available the manufacturer could certainly answer the question. The alternative is to have a sample tested.

Research Citations Indicating Use of Asbestos in Electrical Wiring & Components

  • Avidiya, James E. "Combination door and ironing board." U.S. Patent 3,170,417, issued February 23, 1965. used asbestos in its electrical outlet.
  • Baddour, Joseph S. "Electrical face treating mask." U.S. Patent 2,028,889, issued January 28, 1936. used asbestos on electrical conductors in this product.
  • Baisch, Thelma E. "Electrically heated gravy warming ladle." U.S. Patent 4,005,310, issued January 25, 1977. The gravy warming ladle included asbestos wire insulation.
  • Bakke, Allan P. "Electric blood warmer utilizing a metallic ribbon-flow cartridge." U.S. Patent 4,782,212, issued November 1, 1988. included use of asbestos
  • Booker, Aylwin R. "ELECTRICALLY CONDUCTIVE." U.S. Patent 2,715,668, issued August 16, 1955. describes production of electrically conductive asbestos panels
  • Burt, Guy H. "Electrical plug." U.S. Patent 2,128,883, issued August 30, 1938. used asbestos in the cord plug as an insulator
  • Callahan, James J., and John P. Snow. "Electrical cable adapted for use on a tractor trailer." U.S. Patent 3,993,860, issued November 23, 1976. used asbestos in the electrical cable.
  • Cunningham, James D. "Electrically operated impact tool." U.S. Patent 4,323,127, issued April 6, 1982.
  • DICK, TALBEBT M. "Face mask or like." U.S. Patent 1,820,602, issued August 25, 1931. used asbestos
    Excerpt:
    4. Embedded in the face and neck portion ofthe mask is a circuit of resistance wire 13 extending in spaced. convolutions 90 throughout the area. of the face and neck-portions and which has its length of coil construction wound around a cord 14 of asbestos or like flexible material. B this arra ment of parts the convolutions will not only t completely surrounded by the rubber portion of the invention but will be held apart one from the other.
  • Dillon, Ernest E. "ELECTRIC VACUUM FLUE CLEANERS." U.S. Patent 2,281,144, issued April 28, 1942. Describes use of asbestos in the vacuum cleaner motor assembly:
    Excerpt: An asbestos sheet 30 is interposed between the housing rear wall I4 and the housing fiange i5 and is provided with a central opening 3| through which the motor shaft 24 projects. The asbestos sheet prevents heat from gaining access to the motor and damaging the windings.
  • Dublirer, Kobert. "Collapsible heating pad for travelling." U.S. Patent 3,130,289, issued April 21, 1964. Describes use of asbestos wrapping in electrical components of a heating pad
  • Elsenheimer, Charles W. "Electric flatiron and the like." U.S. Patent 2,353,151, issued July 11, 1944. Cites asbestos electrical cord insulation as an exgternal sheath
  • "Electrical steam generator." U.S. Patent 2,140,516, issued December 20, 1938. Cites asbestos used in electric heater elemnents and wicks.
  • Governale, Anthony J., and Rolf A. Zurwelle. "RADIANT ENERGY WARMER-DRIER FOR TEXTILE ARTICLES." U.S. Patent 3,626,152, issued December 7, 1971. used asbestos sheets that were electrically conductive
  • Grabner, Floyd V. "Electrically heated bath drying device." U.S. Patent 3,418,452, issued December 24, 1968. describes use of asbestos on electrical components
  • Heiser, Myron G., and Wheeler C. Gilbert. "Attachment plug." U.S. Patent 2,343,664, issued March 7, 1944. used asbestos fluffed up layers
  • Herbert, William J., Bruce E. Klipec, and Clifford R. Stine. "Wire and cable." U.S. Patent 4,096,346, issued June 20, 1978. Describes use of asbestos electrical wire insulation as a fire barrier.
  • Irrgang, Louis J. "Strain relief for electrical conductors." U.S. Patent 2,420,826, issued May 20, 1947. Cites use of asbestos tape around electrical conductors.
  • Kalichmann, Isidore, and David Weissberger. "Mechanized electrically heated windshield cleaner." U.S. Patent 3,935,425, issued January 27, 1976. used an asbestos scraper
  • Lewis, Edward H. "Electric cord set." U.S. Patent 2,091,824, issued August 31, 1937. Cites use of asbestos electrical cord insulation.
  • Musgrave, Harrington Le B. "Electric heating devices and the like." U.S. Patent 2,889,439, issued June 2, 1959. Cites asbestos electrical panels in electric heaters.
  • Pedlow, J. Watson. "Electrical arc and fire protective sheath, boot or the like." U.S. Patent 4,018,983, issued April 19, 1977. Cites asbestos used in electrical cabling and power cords
  • SACKERMAN, ERNEST A. "DEVICE FOB." U.S. Patent 1,316,190, issued September 16, 1919. used asbestos components in a devie for thawing frozen pipes
    Excerpt: Extending over the entire inner face of each section and suitably fastened thereto, is a layer of asbestos 6 or other heat nonconductive material. Stretched over the outer face of the asbestos layer to extend longitudinally thereover and substantially parallel to each other are a number of coiled incandescent wires 7 suitably fastened in position and insulated by suitable means (not shown) from the sections or shells 1, 1, which coils constitute the heating means and correspond with those usually employed in the well known bread toasters or other electric heating devices. These wires, when an electric current is passed therethrough, will be heated to red heat which will be utilized for thawing the gas or water pipe.
  • Scott, Mindy. "Electrically heated vaporizing device." U.S. Patent 3,152,240, issued October 6, 1964. used asbestos as follows:
    Excerpt: The insulation should be adequate to prevent the heating element 23 from causing the transmission of an unsafe quantity of heat to the bottom support 15, top flange 21 or to base 14. I prefer to use a layer of /8 inch thick ness asbestos 27 in conjunction with a layer of inch thickness spun glass 28 for this purpose.
  • Shomphe, George J. "Electrical resistance heating articles." U.S. Patent 3,417,229, issued December 17, 1968. Cites unraveling asbestos insulation exposing heater elements. Walter, Jacobsen. "Electrically heated flying suit." U.S. Patent 2,329,766, issued September 21, 1943. Cites use of asbestos padding in an electrically-heated flying suit.
  • Weber, Gerald. Tube Amp Talk for the Guitarist and Tech. Hal Leonard Corporation, 1997 Cites asbestos board used in guitar amps.
  • Werner, Arthur M. "Cordless electric iron." U.S. Patent 2,714,650, issued August 2, 1955. used asbestos in the iron stand
  • Williamson, Val K. "Combined table and food warmer." U.S. Patent 2,866,956, issued December 30, 1958. used asbestos in electrical components in heating plates of this electrical appliance.

 

 

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