Document Rpbara8wzgGo4GOJ8OEbr0zpV

Mineral Wool--the Mining Industry': Fastest Growing Product PLAINTIFFS EXHIBIT JM 1066 By J. R. Thoenen Supervising Engineer, Nonmetal Mining Section, U. S. Bureau of Mines; Member, A.I.M.E. N five years mineral wool has I grown to a thirty-million-dollar industry from one whose output was valued, in 1933, at 81,700,000. Ten years ago, in 1928, there were only seven producing companies, with an annual output of but 50,000 tons. By 1936 fifty or more companies were producing half a million tons. The industry is still growing vigorously and will profit from the expected ac tivity in building in (1339,) for two- thirds of this material is used for building insulation and to assist in fire-retarding, in both new and old homes. It is as useful in the South, to protect against heat, as in the North, to keep out the cold, if one may speak nontechnically. It is a con Courtesy Ea*le-Pieher Sale* Co. Mineral wool insulation makes houses cooler in summert warmer in winter. Here it is being blown between joists in an unfinished attic. comitant of air conditioning, that new addition to the American standard of living that began in theatres, depart ment stores, and railroad dining cars, and is rapidly progressing down to small homes. Here, then, is an indus try that is only beginning to have a present, and one with an almost cer tain important future; one that de pends upon mining and the by-prod ucts of mining for all of its raw ma terials; one that every progressive mining man should know something about. Man has searched for comfort in his dwellings ever since his primitive ancestors built their first windbreaks. The thick-walled homes of colonial days gave way to thin pervious walls of modern construction because of their cheaper cost. Now comes min eral wool insulation to enable us to regain and even to add to the comfort of our immediate ancestors' dwellings. Sometime in 1788 a group of scien tists sent out by the United States Government visited the crater of Kilauea in Hawaii. As they climbed the side of the volcano, they noticed a soft, woolly substance floating in the G. C. Hall in Alexandria, Ind., in air that caught on foliage or rock 1897. fragments. The folklore of the native Mineral wool is a substance com Hawaiian accounted for the material posed of fine, interlaced mineral fibers by the story that when the Goddess having the appearance of loose wool Pele became angry she pulled out her or cotton. It is a fibrous, glasslike ma hair by the handful and threw it out terial composed principally of sili of the crater. Hence, the fine Huffy cates of calcium and aluminum, with stuff was known as Pele's hair. In other minor constituents. Mineral vestigation showed that Pele's hair wool is a generic term covering a was formed in the crater of Kilauea. number of similar products differenti by jets of steam blowing up through ated chiefly by the raw materials from molten lava. Samples of the material which they are made, as rock wool, were brought back to Washington slag wool, and glass wool or glass and tested in various ways. As a re silk. Rock wool, as its name implies, sult a process was devised for its com utilizes as raw materials limestone, mercial manufacture, but it apparent dolomite, shale, and clay, combined ly got little attention. Then in 1840 with silica in the form of sandstone, mineral wool was reported produced or quartz, or as an ingredient of the in Wales, and in Germany later. Stone other rocks. Slag wool is made from magazine, in its issue of November, slags resulting from the reduction of 1888, published an article describing iron, lead, or copper ores. Other ma the manufacture and use of rock wool terials, such as limestone or silica, near Cleveland. A dress made from' mayhave to be added depending on silica wool fibers was exhibited at the 'thechemical analysis of the original World's Fair in Chicago in 1893 and slag. Glass wool is made from the is still on display in the Toledo Art same materials that are required for Museum. The first successful and making glass. Basically, these are soda Published by permission of the Direc continuous manufacture of rock wool ash, limestone, and silica. The addi tor, Bureau of Mines. Not subject to copyrisrh' as a commercial venture is credited to tion or partial substitution of other FEBRUARY, 1939 101 MTC 017186 i i I melted to a fluid slag, a hole is punched in this opening, permitting the slag to escape in a small stream. It falls only a few inches before it is intercepted by steam or air issuing under high pressure from a trough V.l shaped orifice. This shears the fall ing slag stream into myriads of tiny globules and propels them through the air at high speed. As each globule rushes along, air friction forces its outer shell or surface layer into a long, fine, threadlike tail which cools and solidifies to form wool fiber. One manufacturer of rock wool has introduced a spinning disk in place Charging floor of a rock wool cupola. fnurtpy /?<vt PrnJvrtl of the steam jet, which is revolved at high speed on a vertical axis. The molten stream issuing from the fur ingredients changes the characteris tics of the glass; similar substitutions in the raw mix enable the manufac turer to alter the character of the wool blown. Just as the jets of steam issuing from the crater at Kilauea picked up bits of molten lava and blew them into the substance called Pele's hair so the manufacturer of today directs a stream of molten rock, slag, or glass to a jet of either steam or air and blows it into wool. Technically, how ever, the process is not so simple, since many factors enter into the proc ess, all of which must be under rigid control to assure a commercial prod uct. Merely projecting a molten stream of rock into a jet of steam does not always produce wool. Chem ical constituents of the raw material, degree of viscosity, and temperature of the slag, size of slag stream, length of fall, and the pressure of the steam or air are only a few of the many variables that must not only be con trolled individually but co-ordinated to make the process successful in pro ducing the kind of wool desired. fine silicate threads form the wool and are then collected and fabricated into many forms of insulating prod ucts. The cupolas are double-walled steel cylinders with open ends. They range from 26 to 72 in. in diameter and from 7 to 16 ft. in length. The thick ness between the double walls, or water jacket, ranges from 3 to 6 in. These cylinders or cupolas are set on end on brick or concrete foundations. The lower end is closed with a sheetiron plate and the upper end housed in a firebrick hood containing the charging opening and surmounted by a metal stack. Surrounding the lower portion of the cupola is a hollow, con centric metal ring from which several hollow arms or tuyeres extend radially to and through the cupola wall through which air is forced into the cupola. In starting operations, a few inches of sand or clay is placed on the bot tom plate. The cupola is then filled with coke to a point above where the tuyeres enter the walls. The coke is ignited, and when burning briskly, rock or slag is added to a depth of nace falls to the outer section of the disk, whence it is violently propelled through the air in a manner similar to the action of the steam jet. If conditions are not exactly right, part of the original globule will be cooled and solidified before it is drawn into fiber. Examination of most raw wools will show fibers still fastened to what is left of the original particle of molten slag. These solidi fied globules are known in the indus try as "shot," a waste product. The fine fibers, with their unfiberized particles, or shot, are either packed for shipment as loose wool or prepared for other types of fabrica tion. Recently other types of melting fur naces have been introduced success fully. One manufacturer uses a flat, reverberatory-type furnace fired with fuel oil. With this type of furnace, raw materials are first crushed and fed continuously. Another plant is reported to be using a similar type of furnace fired with natural gas. At still another plant, an electric furnace is used, with the electrodes immersed in the molten mass. several inches. The cupola is then Loose wool is not suitable for some THE usual process consists of mix filled with alternate layers of fuel and ing raw materials with coke in raw materials to the charging door alternate layers in a water-jacketedand the air is turned on at the tuyeres. forms of insulation. For example, wool used to insulate structures al ready built must be blown into the steel cupola, igniting the coke, melt The materials charged are in lump walls by air pressure. For this pur ing the rock or slag ingredients to a form to allow free passage of air and pose loose wool is "granulated," fluid molten slag, tapping the slag combustion gases; briquetting may be which involves passing it through one through a small aperture, allowing necessary for fine material. of several types of equipment rang the slag stream to drop to a steam jet, At one point near the base of the ing from small swing hammer mills and blowing the slag in tiny droplets cupola a round or square opening is to rapidly revolving ensilage cutters through the air, whereby friction provided through the wall and filled , to break up the fibers and separate elongates the droplet to a fine thread at the start with firebrick or clay. \ them from the attached shot. This before it has time to solidify. These When the charged material haa been Vgranulated wool is then passed to an 102 MININS AND METALLURGY MTC 017187 ordinary revolving trommel or in the same fluidity or viscosity. Viscos clined shaking screen where the shot ity alone, however^ is not the only passes through the wire mesh and the controlling factor. The furnace freed fibers are collected and rolled charges of different composition, up into small pellets or balls. In this when brought to the same viscosity form, the wool is an ideal product at the same or different temperatures, for blowing into house walls. may produce entirely different wools, Glass wool is made in regenerative- or it may even be impossible to blow type glass tanks fired with natural gas. one into wool. No published results The molten glass flows over a perfor covering the relationship between ated forehearth, and the fine streams chemical composition, temperature, of glass passing through the perfora viscosity, and ability to produce wool tions are attenuated by steam pressure have appeared as yet, so the manu and blown into wool. facturer must rely on his own research to determine the best procedure with MANY factors must be more or his particular raw materials. For less rigidly controlled to assure various reasons, this combination of a finished product that will meet thvaeriables can be controlled more ac rapidly narrowing limits of consumer curately in the manufacture of glass requirements. The first of these is wool, so the characteristics of the the chemical composition of the raw wool itself can be varied to a con materials, which exhibit a wide range. siderable extent at will. It has been proved experimentally Another variable is the diameter that a combination of pure calcium of the molten stream when cut by the carbonate and silica without other in steam jet and the length of fall from gredients can be blown into wool. draw hole to steam jet. Obviously the However, all manufacturing plants greater the length of fall the smaller use alumina in some form, and in will be the diameter of the stream. most mixtures some magnesia is There will probably also be a corre present. Some operators attempt to sponding change in temperature achieve and maintain a chemical bal which in turn may change viscosity. ance between acids and bases. Others Whatever effect a change in length contend that this is not necessary and or diameter may have, operators have that better wool results when there found that wool blown from a stream are more acids than bases, or vice 6 in. long will have different charac versa. It is sufficient here to point teristics from that blown with the out that similar chemical composi steam jet cutting the stream 3 in. or tions in the furnace charge may be 9 in. from the taphole. In fact, some obtained by combining two, three, manufacturers are using this differ four, or more of a large number of ence in length of stream to blow wool natural or waste materials and that to meet different specifications. the chemical composition of the Production of shot seems to be a charge is reflected in the chemical necessary evil. Shot itself has no in composition of the wool. sulating value so the wool with the The next variable is the tempera lowest percentage is the best in ture of melting and blowing. This, sulator, other conditions being equal. however, is directly coupled with the Therefore, the constant aim of the viscosity or fluidity of the molten ma manufacturer is to produce wool with terial and to a large extent may be as little shot as possible. A change in influenced by the chemical composi any one of the previously discussed tion of the charge. Melting tempera variables may be directly reflected in tures range from 2300 to 3400 F. the amount of shot. Various schemes Blowing temperatures, or the tempera have been devised to remove all the tures of the molten stream when cut shot from the wool, and some promise by the steam jet, are somewhat lower, success. Granulation is the process ranging from 2000 to 2850 F. A generally applied. This, however, greater amount of heat is required breaks the wool fiber into short pieces to melt some minerals than others, so thus destroying the binding effect of one combination of raw materials will long fiber. The process of spinning need a greater amount of fuel and wool seems to produce Iong-fibered must be raised to a higher tempera wool singularly free from shot but ture than another mixture, to obtain whether this is attributable directly to spinning or to other elements in the process is difficult to determine from casual observation. Glass wool ordinarily is free from shot but fre quently has enlarged fibers with hooked ends instead. Production of shot in wool blown from a cupola is an industrial waste, since the shot cannot be returned to the cupola for remelting for it would restrict the flow of combustion gases. Shot can, however, be remelted in the reverber atory furnace but even so, its produc tion is a waste because of the extra heat and fuel required to remelt it. The diameter of the wool fibers is another variable that requires con stant control. The value of mineral wool as an insulator lies in the great number of minute air spaces confined within the interlaced fibers. Obvi ously the finer the fiber the greater in number and smaller in size these little air spaces will be. A change in chemical composition, temperature, viscosity, or possibly steam pressure may be reflected by a change in diam eter of the fiber. Ordinarily manu facturers try to hold fiber diameter between 4 and 10 microns, or 0.00016 and 0.0004 in. but this is not easy. Random samples that I have taken and measured under the microscope showed fibers in one sample ranging from 2 to 25 microns, though in an other no fiber was under 4 and none over 8 microns in diameter. ALONG-FIBERED wool is prefer able because of the greater strength of its interlaced fibers. For reasons previously mentioned it seems to be difficult, by the customary methods, to obtain long-fibered wool which at the same time is shot-free. However, greater knowledge and im proved processes will undoubtedly yield such a product. The manufac turers of glass wool. and spun-rock wools already seem to have ap proached a solution of this problem. There are other less obvious vari ables, the effect of which may or may not be serious, for example, the shape of orifice from which the blowing steam issues. Ordinarily this is Vshaped, but the shape or dimension of the V is seldom the same in dif ferent plants, and in some plants the customary V has been discarded in preference for some other shape. In dicative of how the shape of the FEBRUARY, 1939 MTC 017188 103 sleam orifice affects the product is the assertion by one operator that the molten slag stream must fall in the exact center of the V for best re sults; another is equally emphatic Table 1. Density and Conductivity of Insulating and Building Materials Materid. Density lb. per cu.fl. Conductivity, Mean tem K, B.T.U. perature, per hr. per sq.ft. deg. F. per deg. F. per in. Authority that better shearing effect is obtained by cutting the slag stream by one side of the steam trough. Balsam wool............ . . 3 Felted cattle hair. . . . 11 Loose mineral wool. 8 Rock wool................ . . . 10 0.255 Weiss' 90 0.26 Bur. Standards' 103 0.27" Bur. Standards" 90 0.27 Bur. Standards* Fabrication Methods Diatomite in powder form 10.6 86 0.308 Bur. Standards4 Cork, regranulated . . . . 8.1 90 0.31 Bur. Standards' Fiber board, from sugar PROBABLY the first step in fabri cane .................. .. 13.5 70 0.33 Pebbles" cation is the application of a light, Vermiculite, exfoliated . . 8 100 0.48 Research lab., Eagle-Picher high-fiash-point paraffin oil to theCorrugated asbestos board 20.4 110 0.48 Lead Co. Willard, Litchy, Harding9 wool. This serves two purposes: it. 85% magnesia, 15% as- keeps the extremely fine fibers from bestos board 19.3 86 0.51 Bur. Standards' flying around the plant as dust and acts as a lubricant between fibers, reducing internal friction and making the wool more resilient. This oil is applied in various ways. In some plants it is added in the steam line. In others the oil is sprayed or al lowed to drip slowly into the wool stream a short distance beyond the steam jet. This application of oil Wood (while pine) Brick, common Concrete, typical 31.2 86 0.78 5.00 12.00 Bur. Standards' A.S.H.V.E. Guide, 1935' A.S.H.V.E. Guide, 1935' `Chum. & Met. Eng., 29, 534-7 (1923). - Tests based on samples submitted by manufacturers as shown in American Society of Heating and Ventilating Engineers Guide, 1935. Direct communication. ' Report of the American Society of Refrigerating Engineers Insulating Committee, A.S.R.E. Circular No. 1. 5 Tests conducted at Armour Institute of Technology, based on samples submitted by manufacturers. "Tests conducted at University of Illinois. : Recommended conductivity for computing heat-transmission coefficients. "Since 1935, glass and rock wool have been reported having a "K" value as low as 0.22. should not be confused with the water proofing process. Other types of oil or other materials are used for water proofing, but the materials used and methods of application for water proofing are trade secrets. In most plants the wool is blown into wool rooms as it leaves the steam jet. These rooms vary greatly in size and construction. Modern practice, however, requires a moving conveyortype floor. Some wool rooms have elaborate ventilating systems, where as others have no such provision. The wool collects on the moving floor and is carried out of the room in a blan ket of quite uniform thickness, the latter being regulated by the rate of They are then packed in cartons for shipment. Wool intended for other types of products is usually gathered from the conveyor and sent to the granulator, after which the shot is removed. These fine, shot-free fibers are bagged for shipment as granu lated wool for blowing into the walls of houses already constructed. Granulated or loose wool is also mixed with suitable binders and pressed or molded into insulating board, pipe covering, or other shapes. Mixed with clay or bentonite and asbestos, loose or granulated wool is sold as insulation cement. Mixed with water to form a paste, it can be wool is literally deposited by the blowing process on a moving con veyor which delivers it to the fabri cating rooms. Rock wool made by the spinning process is thrown across the end of a large sheet-metal pipe, into which it is drawn by an exhaust fan and blown to the fabricating rooms. The shot made in the spinning process are thrown beyond the pipe orifice and collect in the spinning room. House Insulation INSULATION of houses against excessive summer heat or the es cape of internal heat during the winter blowing and the speed of the con formed around irregularly - shaped provides the greatest market for veyor. As the blanket emerges, it objects as an insulating cover. Loose mineral wool. The best insulator of usually passes under a heavy idler wool as taken from the conveyor is all is empty space, as illustrated by roll which further compacts it to uni frequently placed between chicken the vacuum bottle. The next best, form thickness. ~ In some plants the wire or steel lath and sold in blanket practically, is still air. In modern blanket, as it emerges, is sprayed form as insulation for steam gener frame construction, the walls of with a liquid binder to increase its ating units in furnace walls and on houses contain a dead air space be structural strength or to promote ducts and bridgings, and in petroleum tween the outside sheathing and in ease in handling the various shapes refining for insulating process ves side plaster separated into vertical into which it may be cut. sels and heat exchangers. Railway panels by the studding. In masonry Blankets intended for immediate cars and annealing ovens offer other or brick construction similar dead air fabrication are cut both longitudi outlets. Insulating board or blocks is found in the furring spaces. Even nally and transversely by knives or are made up to any specification size if all these dead air spaces were revolving disks into the sizes required and thickness for stove or refrigera hermetically sealed movement of air for batts to be used in wall insula tor insulation. within each panel would occur, thus tion between studding. These may be In the manufacture of glass wool, reducing its insulating value. But covered on one or both sides with the operators have greatly reduced when filled with mineral wool, the plain or moisture-proofed paper. the size of the wool rooms, and the original space is converted into mil- 104 MINING AND METALLURGY MTC 017189 lions of tiny air pockets entrapped |iv the interlaced wool fibers. The libers thus prevent air currents or, in fact, any air movement. Mineral wool thus converts the dead-air ..paces of house construction to stillair spaces. Table 1 presents the relative in sulating values of various materials as published in 1935 in Industrial & Engineering Chemistry. The "K" value or measure of conductivity is the inverse of insulating value, hence a higher figure in that column repre sents a lower insulating value. Thickness of various building materials required to give equal insulating values. The increasing demand for house insulation and the application of air conditioning to residences have con centrated the attention of architects and builders on proper design for the best use of insulation. There were numerous complaints from early in stallations of mineral wool because walls so insulated absorbed moisture and either caused construction mate rials to rot or resulted in unsightly walls or ceilings because of conden sation. These complaints led to ex tensive research, the results of which have been published. That conducted by Frank B. Rowley, of the Univer sity of Minnesota, to determine the best type of insulation construction developed the following points: (1) Moisture is produced indoors by several means, including cooking, washing, and operation of humidi fiers. (2) This internal moisture can pass as vapor through almost all building materials, including wood, plaster, brick, and ordinary building papers. The vapor will pass through materials that prevent air movement. (3) Since internal moisture can penetrate the walls of ordinary house construction, it will accumulate in the wall unless the outer covering is such as to allow it to pass on through to the outdoors. Moisture-proof paper on the outer wall, as is commonly used in building construction in the North, will tend to trap the moisture in the wall. (4) To prevent condensation in the walls, provision must be made to prevent moisture moving into the wall at all. If this is impossible, then provision must be made to allow easier egress of moisture to the outer air than from the interior of the house to the wall. (5) To prevent moisture entering the wall it is necessary to use a mois ture barrier on the warm side of the wall. This is accomplished by stretching moisture-proof paper on the studding before the lath and plas ter are applied. Several moistureproof papers have been developed and are on the market. (6) To remove any moisture in the wall which may get past the inner barrier it is only necessary to be sure that the outer paper covering is of such nature that it will allow moisture to pass through. Ordinary slater's felt is such a material. (7) In houses already constructed and insulated and which have experi enced wall condensation, this trouble can be corrected by removing some of the siding and replacing a strip of the waterproof paper with a windproof but porous paper. (8) The same type of moistureproof barrier should be installed on the underside of the rafters when the roof is insulated or on the underside of the attic floor joists when the attic floor is insulated. (9) The moisture movement in summer in a hot, humid climate in the reverse direction through an in sulated wall is not objectionable be cause the temperature differential be- Table 3. Heat Loss From a Typical House Equivalent House with Heat Loss, B.T.U. Tons of Coal No insulation ... 38,000,000 1-in. rock wool.... 18,700,000 1.6 0.8 3%-in. rock wool.. 8,600,000 0.4 Heat loss calculated through 1000 sq. ft. of wall consisting of clapboard on sheathing with building paper between, 2 by 4 studs set at 16-ln. intervals, and an Inner wall of wire lath and plaster. The calculation was made for a 15-m.p.h. wind velocity, 200 days' heating season, 30* average temperature difference, and 24- hr. load. tween the house interior and the in side of the wall is not sufficient to cause condensation in the wall. (10) Some mineral wools are treated on one side by a moisture proofing process. This is good prac tice but insufficient to prevent the passage of moisture. The inner mois ture-proof barrier should be used, as with untreated wools. Even with the best type of insula tion, properly applied, all possible heat losses are, however, not stopped. Assuming the total possible heat loss of any building as 100 per cent, about one-third occurs through walls and roof; another third is due to air leakage around windows and doors; and the rest escapes through the glass of doors and windows. These pro portions, of course, depend upon the type of construction and will vary widely. Table 2. Fuel Savinc Under Various Conditions. Fuel Saving, Building with Per Cent No insulation but weather-stripped 15 to 20 Same as above but fitted with dou ble windows .................................25 to 30 1-in. insulation, not weather- stripped ...........................................30 to 40 1-in. insulation, weather-stripped. 50 1-in. insulation, with double win dows .......................................... 60 The National Bureau of Standards has estimated the fuel savings due to proper prevention of heat losses as shown in Table 2. On this basis, it is apparent that about one-third of the heat losses occur from air leak age around doors and windows, which can be reduced by weather stripping. Loss through window glass accounts for one-sixth and is reduced by adding winter or storm sash. At least one-half of the heat loss is then accounted for through walls and roof, which can be reduced by insulation. Another set of tests, the results of which are shown in Table 3, showed that in a certain case use of 3%-in. (wall thickness) of rock wool would reduce the heat loss 75 per cent. About two-thirds of the heat enter ing a house comes in through the roof. The importance of attic-floor insulation, coupled with adequate attic ventilation, is thus apparent in providing a cooler house interior dur ing a hot summer. FEBRUARY, 1939 MTC 017190 105