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FILE NAME: Oil Industry and American Petroleum Institute (API) DATE: 1935 Nov DOC#: API075 DOCUMENT DESCRIPTION: Journal Article - Mineral Wool and Vermiculite Insulation Mineral Wool and so that even now it is in an advanced state both in the build ing industry and in general industrial work. Today the training of a graduate in chemical engineering must include a study of thermal insulation since that subject is of as great importance to the chemical engineer us evaporation and distillation. Vermiculite as Insulation JOHN A. The Eagle-Picher Jppl in, Mo. Insulation in Air-Conditioning Percy Walker of the Bureau of Standards has stated that the greatest single development which will come out of the depression will be air-eonditioning: "Air-conditioning at the present time is in its infancy and there will 'be as much im provement in the next century in purifying the air we breathe as has been accomplished within the last century in purify ing the water we drink." In other words, he believes "that the inhabitant of our cities a hundred years hence will de mand clean air not only in his house but on the streets just as we demand clean, wholesome water delivered in our houses, whereas our ancestors of a hundred years ago used any water that was available without any real care to see that it was wholesome." _ T he relationship o f therm al insulation to air-conditioning is discussed. The con tributions o f the newer types of insulating m aterials (developed during th e p ast five years) to better the art of living are shown. T he characteristics o f various insulation m aterials for both dom estic and industrial in su latin g purposes are described and their physical properties com pared. 'NTEREST in thermal insulations should be universal, whether from a domestic I P- standpoint, which involves one's comforts throughout the year, or from an industrial standpoint, since every one engaged in industry is decidedly concerned with the control of temperature and heat flow. The obvious reason for domestic insulation is that of comfort and a saving of money in the heating of our homes. From an industrial standpoint the use of thermal insulations is to prevent the escape of heat, which is a direct loss in dollars. A reason which is less obvious, but is often of as great importance, is the fact that a well-operated plant depends to a large extent on the accurate control of temperature, since the tendency is toward chemical processes where definite temperature con trol is required. Where conditions are such th at temperature fluctuations are due to the cooling of heated surfaces, proper steps must be taken to reduce such heat variations to a Faced with a situation where the public is definitely be coming more insulation-minded, both from a domestic and an industrial standpoint, it is only proper to follow some of the advances which have been made during the past five years on this important engineering subject. The art of living has been materially bettered since thermal insulations have begun to play such an important part in the comfort of homes, offices, and places of entertainment. I t is today almost an economic impossibility to operate a theater or restaurant dur ing the summer months unless it is air-conditioned and properly insulated. The American Iron and Steel Institute estimates that the installations of air-conditioning equipment in 1934 required 28,000 tons of steel and it was the forecast that the 1935 de mand would be double that amount. The demand within the next 10 years was estimated by the institute as 450,000 tons of steel annually.2 Domestic insulations can be divided into three divisions: 1. The application of loose-fill insulation materials to build ings already erected. 2. The installation of insulation material in the form of bats between the studding in the walls of new houses or building; which are being erected. 3. The use of insulation board, applied either while the house is being built or after it has been built. Although several different types of loose-fill insulation ma terials have been employed for insulating buildings which are already standing, the greatest advance has been made in the use of mineral wool for such purposes. D a ta o b ta in e d from th e S t. L oui s Globe Democrat, F e b ru a ry 2 0 , 19J5. m inim um . , ' The insulation industry has been par ticularly active throughout the depression in not only developing new thermal insula tions, but likewise in improving those ma terials which had been used in the saving of heat loss prior to that time. Air-conditioning has com e to th e fro n t rapidly. One of the most important needs in proper air-conditioning is that of thermal insulation. T he in s u la tio n industry has kept pace with the needs of air-conditioning 1 Present address, Franklin and Marshall College, Franklin, Pa. A . Loose: U sed as loose fill on boiler a n d furnace walla, fireless cookers, ovens, and borne insulation. B . G ra n u la te d : used as loose fill for b o o insulation, overia, a n d furnace walls- F ig u r e 1. M ineral W ools: W eight, 8 P ounds per Cubic F oot; T h erm a l C o n d u c tiv ity , 0.27 1298 NOVEMBER, 1935 INDUSTRIAL AND ENGINEERING CHEMISTRY 1299 machine and is then carried by compressed air FIG. 2 to the place to be insulated. The mineral wool settles to its natural density with a thickness of m etho d fo r insulating A HOUSE ALREADY BUILT 4 inches. The attic of a dwelling is insulated in the same manner. Because of the very low conductivity of mineral wool, a 4-inch layer is ample for proper insulation. Figure 3 shows the difference in the physi cal characteristics of glass wool and mineral wool. The glass wool consists of long, com paratively thick fibers, whereas the mineral wool contains very fine threads admixed with larger fibers, scarcely any of which has the diameter size of glass wool. Glass wool is also rather brittle and tends to break on handling. In insulating buildings during their construc tion, a different procedure is followed. Here it is far more satisfactory to use mineral wool formed into a bat (Figure 4) of the proper size, usually 15 inches X 18 inches X wall thick ness and weighing 8.0 pounds per cubic foot. The insulation bats are placed in- the space between the studding before the lath and plaster are applied. This gives a perfectly insulated wall. The same practice is .used in insulating; the M ineral Wool Insulation attic, which is of great importance. A house so treated is cooler in summer, warmer in winter, and sound-proof to a Chemically, mineral wools are calcium silicates or calcium- certain extent, and can be maintained at a comfortable iron silicates. They are made by melting the silicates in a temperature in winter with an actual saving of 20 per cent short cupola furnace, using coke as the fuel with the addition in fuel. Its greatest convenience is in the summer months, of lime or iron in proper proportion to yield a fusion which is since buildings can be kept warm in winter but cannot so easily fusible. The molten material issues from a small hole successfully be kept cool in summer. The attic is the at the bottom of the furnace. The stream of molten ma worst offender because in the daytime it stores up a large terial is blown into fibers by a jet of high-pressure steam. supply of heat which it dissipates to the rooms below during These fine fibers are collected by settling in large chambers the night. ' ~ from which they are periodically removed for further process The use of insulation board, either applied after a building ing. When the silicates are derived from native rock, the has been erected or during the process of erection, is not con wool produced is designated as rock wool (calcium-magnesium sidered as highly efficient as the other .methods of insulation. silicates) with properties similar to mineral wool. I t is difficult to obtain a proper thickness of requisite insula The properties .which make mineral wool (Figure 1A) tion when insulation board is used. Certain insulation unique in the field of domestic insulations are its low conduc boards, however, have a rather low heat conductivity; for tivity (0.27 at room temperature), its ability to withstand example, vegetable fiber board has a conductivity of only high temperatures, and its stability. This material is prac tically unattacked by dilute mineral acids or alkalies. Sul fur dioxide and other corrosive gases have but little effect on 0.33. I t has been predicted that within five years practically no modem homes will be erected which are not insulated, if not it. It retains its original form and has good insulating value entirely air-conditioned. The same will also hold true for up to its fusion point of 1800 F. This material is probably office buildings. . the only insulating material which combines low conductivity While we find mineral wool being most largely used in the with ability to withstand elevated temperatures. Basic insulation of buildings, it has other important applications. magnesium carbonate dehydrates and calcines when heated. Mineral wool serves as the raw material for the manufacture Asbestos, which has a rather high conductivity, decomposes because of dehydration upon heat ing. The animal and vegetable products can not withstand high temperatures, since they bum and are completely destroyed. The problem of using this desirable insulat ing material in buildings already erected de veloped slowly bu t in such a way as to be highly efficient. For domestic in s u la tio n , mineral wool is nodulized by shredding the loose mineral wool and rolling the shreds into small pellets. In the nodulized or granulated form (Figure IB), mineral wool is well adapted for blowing into the space between the studding in build ings which are a lre a d y e re c te d . Figure 2 shows the method of using nodulized or granu lated mineral wool in insulating a building. A., Mineral wool Glass wool The nodulized mineral wool is fed into a blowing F igure 3. P hotomicrographs of F iber (X 52) of blankets (Figure 4), used to insulate furnace and boiler walls, bubble or clay F igure 5. M ineral. W ool Cement refinery towers, and any flat or slightly curved surface. Pipe covers (Figure 4) consist essentially of mineral wool felted between various metal fabrics, and are used for insulating pipe lines exposed ' to weather. The important feature of such fabrication is the fact that, since no binding agents are added, the low conductivity of the wool is not impaired. Such fabricated products are used ex tensively in insulating h ig h -p re ssu re steam lines, oil refinery lines, furnace and boiler lines, and many flat or curved surfaces. They have the added ad vantage of being rather light in weight F igure 6 . P hotomicrograph o f M ineral Wool Cement (X 2.2) F igure 7. M onolithic M ineral W ool Cement U sed for I nsulating I rregu and of su cc essfu lly w ith s ta n d in g moderately high temperatures. For these uses, mineral wool blankets and pipe covering are superior to 85 per cent magnesia lar Surfaces, F urnace and B oiler Walls, P ipe Lines, and P ressure K ettles blocks and pipe covering because they are able to withstand much higher service temperatures, and at the same time have lower thermal conductivity. after application (Figure 6) with a magnification of 2.2 di ameters and (Figure 7) as a dried block, clearly reveal the character of the cement after it has been dried. . M ineral Wool Cem ent A definite method has been worked out for the application of highly efficient insulating materials where insulations must Another important use for mineral wool is that of serving be applied where exposed to the'weather. The proper method as the basic raw material for the manufacture of mineral woo! of insulating such equipment is to use first a mineral wool cement (Figure 5). Such cement has as its base granulated blanket and then to apply a thin layer of mineral wool insu or nodulated mineral wool, mixed with long-fiber asbestos lating cement. This insulating cement is: in turn protected and bonded with a suitable binder, usually clay. When from the weather by an asphaltic weather-proofed material mixed with water to the proper consistency, it can be readily which yields a permanent installation. Figure 8 shows a applied to either hot or cold surfaces. Its greatest advantage cross section of such an installation. This method of in is its convenient form since it can be readily applied to any sulation is highly efficient, for the heat is retained by the >irregular-shaped body, such as furnace and boiler walls and original mineral wool application (with a thermal conductivity will dry to a monolithic coating. The cement consists of of 0.27) and the insulating cement aids in preventing heat small nodules of wool fiber surrounded by a binder. None of loss and provides a base for the final weather-proofed layer. the binder appears to penetrate the wool nodules so that the original good properties of the wool are preserved in the dried cement. Such insulating cement has a weight per V erm lcu lite cubic foot of 35 pounds, yet has a thermal conductivity value of 0.6. There is quite a tendency towards the use of such cements for monolithic insulations. As its name implies, it gives one continuous coating and thereby eliminates the es cape of heat through joints such as would be found in an insulation built up of blocks and similar forms. A new type of insulation material has come to the fro n t rapidly during the past five years.: This material, which is used as a base for many insulation products, is the mineral vermiculite. I t is a micaceous, alteration product of biotite, which is found rather widely distributed throughout the United States, and has the peculiar property of expanding The illustrations, showing the structure of the cement itself rapidly when subjected quickly to high heat, because of an 1300 NOVEMBER. 1935 INDUSTRIAL AND ENGINEERING CHEMISTRY 1301 jjuiost immediate expulsion of water of constitution. Fig rather high heat conductivity. The weight per standard ure 9 shows the volume increase upon heating (the two quan brick is 33 ounces and the thermal conductivity is 0.80. tities shown have the same weight). I t is not unusual to Another type of insulating brick (Figure 11) has only re jjd vermiculite which will expand from fifteen to eighteen cently been developed. The principle involved is to create times its original size. The insulating value of vermiculite voids in the brick itself, thereby lowering conductivity with depends largely upon the degree of exfoliation which will out great loss of strength. The same ordinary materials are take place upon fumacing. Such expanded vermiculite used as are utilized in the manufacture of fire brick, and are adapts itself well to the manufacture of insulation products. admixed with certain organic substances which volatilize ]t has a thermal conductivity of 0.48. Its weight per cubic at moderate temperatures. After the brick are made, through foot of a medium sized product is between 6 and 8 pounds. the process of firing, the volatile constituents disappear' and It does not decompose readily when exposed to heat and is leave voids in the brick. Because the base for making such suitable for use as a base material in products which must brick is highly refractory material, the brick will withstand withstand temperatures up to 2000 F. While used as a as high temperatures as are found in fire brick of the ordinary raw material for the insulation of dwellings,.it is not quite as type (up to 2600 F.). Here again structural strength is sacri effective as mineral wool because of its higher thermal con ficed to gain lower heat conductivity, but the brick is suf ductivity. I t serves well as a base for the manufacture of ficiently strong for industrial purposes. insulating pipe coverings for high-pressure and oil refinery Table I gives data from standard authorities to show the lines, and insulating blocks (Figure 10), particularly those ' density and conductivity of certain insulating and building subjected to a high temperature, such as insulation for fur materials. naces, oil towers, and other flat or slightly curved surfaces. Figure 12 shows the value K (thermal conductivity factor) Such blocks and pipe coverings are made with vermiculite ... for a number of building materials which are used today for as the base material, asbestos fiber, and a suitable binder. both insulating and building purposes. Figure-13 shows the They have a thermal conductivity of 0.65. density of various insulating materials in pounds per cubic Insulating bricks made from vermiculite are used exten foot. Comparison of Figures 12 and 13 shows that certain sively in industrial operations. The bricks are of two types. materials of low conductivity have a high density. This com The light-weight type is made purposely to obtain the low parison is of interest since it has been the general conception est possible conductivity by sacrificing structural strength that low density per cubic foot is always accompanied by (Figure 10). Such brick are used largely in open-hearth fur low conductivity. naces over arches where no structural strength is required, Figure .14 is a three-dimensional chart-based on mineral particularly where the brick must be used repeatedly. The wool where the thermal conductivity is a function of density weight per standard brick is 24 ounces, and the thermal con and temperature. The conductivity of insulating materials ductivity is 0.7. Where strength is needed in a vermiculite brick, it is always necessary that heat conductivity be sacri ficed since it is impossible to maintain low heat conductivity with high structural strength. To produce such high-strength brick (Figure 10) a binder has to be added. These brick can be used for building purposes, such as insulation for fur nace walls where structural strength and fairly low conduc tivity are required to replace ordinary brick which have a 'S I Figure 8. T ypical I ndustrial Applica tion of M in er a l W ool I nsulation Bottom layer, blanket insulation; center layer monolithic wool cement; top <layer, asphaltic weather-proof coating Figure 9. Volume Increase of Vermiculite upon H eating Figure 10. F orms of Vermiculite I nsulation I 1302 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 27, NO. H is naturally affected by the density of the prod uct as well as the temperature at which the th e rm a l conductivity determination is made. On such a three-dimensional graph the conduc tivity of mineral wool can be plotted packed to any given d en sity and dependent upon any given temperature; the optimum packing re quired to obtain the minimum conductivity for a given temperature can be determined. A three-dimensional graph of this type can be used for comparative purposes in determining the thermal conductivity as a function of the density and mean temperature; Figure 15 shows the relationship between mineral wool and glass wool. The upper surface is the three-dimensional graph for glass wool, and the lower surface is that for mineral wool. T abus I. D ensity and Conductivity of Insulating and B uilding M aterials M aterial Den sity M ean Temp. Con- ductivity, K A uthority Lb./cu, ft. F. B. t. u ./h r ./ $q. f l . / F ./in . ' Balsam wool Felted cattle hair Loose mineral wool 3 0 .2 5 5 Weiss 11 ` 0 .2 6 Bur. Standards* S 103 0 .2 7 Bur. Standards* Rock wool (fibrous m aterial m ade from rock) 10 90 0 .2 7 Bur. Standards* D iatom ite, in powder form 10.6 86 0 .3 0 8 B ur. Standards'* Cork, regranulated 8.1 90 0.31 Bur. Standards* Fiber board, from sugar cane 13.5 70 0 .3 3 Peebles Verxniculite, exfoliated 8 100 C orrugated asbestos board 20.4 n o 85% m agneaia-15% asbestos 0 .4 8 0 .4 8 Research lab., Eagle-Piche; Lead Co. W illard, Litchy, H arding/ , b o ard W ood (w hite pine) Brick, common Concrete, typical 19.3 86 0 .5 1 31.2 86 0 .7 8 . 5 .0 0 . . . 12.00 Bur. Standards* Bur. Standards* A. S. H . V. E . G uide, 19359 A S- H . V . E . G uide, 1935? Chem. < M et. E ng., 2 9 534-7 (1923). # T e s ts based o n sam ples su b m itte d b y m an u fa c tu re rs as show n in A m erican Society of H eating and V entilating Engineers Guide, 1935. 6 D irect com m unication. - < 4 R eport of the A m erican Society of Refrigerating Engineers Insulation Committee A. S. R . E . C ircular N o. 1. T ests conducted a t A rm our In stitu te of Technology, based, on sam ples su b m itted by m anufacturers. , . ^ / Tests conducted at U niversity of Illinois. # - t Recom m ended conductivity for com puting heat transm ission coefficients. F igure 11. H igh-R efractory Insulating B rick Ba l s a m w o o l j FEl TED c a t t l e h a ir FIG.tZ. THERMAL CONDUCTIVITY OF VARIOUS INSULATING MATERIALS LOOSE M INERAL WOOL ROCK WOOL, FIBROUS MATERIA. MADE FROM RCC* O V trO M ffZ , FONDER FORM 1 ' CORA, REGRANULATEO V E R M K U LfTE , B t'C L U T O CORRUGATED ASBESTOS BOARD BSZMAGNESIA - tS X ASBESTOS BOARO FLAKED GYPSUM wood, w n tte fa h e ' BRACK, COMMON (CO ND U C TIVITY VALUE -S O O ] CONCRETE , TYPICAL (CO ND U C TIVITY VALUE - UJDO) Q 04 02 03 04 05 06 7 08 09 IO CONDUCTIVITY VALUE The photomicrographs of Figure 3 show that because of the larger fiber size of glass wool, larger air cells are present than are found in the smaller fibered mineral wool. This characteristic is also exemplified in Figure 13 where the coarser fibered glass wool, even at a lower density, shows a higher conductivity than mineral wool. It is particularly notice able that conductivity increases rapidly with increase in tem perature in the case of the glass wool. The reason is that convection within the air cells plays an important part as the conveyor of heat through the material, particularly at elevated temperatures. By taking a given density of 5 pounds per cubic foot and a mean temperature of 220 F. in both the case of glass wool and mineral wool, Figure 13 shows that the thermal conduc tivity of the glass wool will be approximately 0.5, whereas in the case of mineral wool at the same density and mean tem perature a thermal conductivity of approximately 0.4 is ob tained. _ Using the same densities with a mean temperature of 420 F., the mineral wool will have a thermal conductivity of ap proximately 0.63 as compared to approximately 0.97 for glass LOOSE M INERAL WOOL VE R M IC U LITE ,EYFGLIATED CORA, REGRANULATED F IG 13. DENSITY OF VARIOUS INSULATING MATERIALS OUfTOANTE, >N POWDER FORM FELTED C A T T L E HAIR F IB E R BOARO FR O M SUGAR CANE B S MAGNESIA - 1 5 2 A S B E S T O S BOARO CORRUGATED ASBESTOS BOARO GTPSUM ,FLAKED WOOD MANTE PIN E ( U t LBS PER CUBIC FO O T) io is 25 POUNDS PER CUBIC FOOT F igure 14. T hree-D imensional Chart S howing Conductivity of M ineral W o o l a s a F unction of D ensity and M ean T emperature 3. II j NOVEMBER, 1935 6 INDUSTRIAL AND ENGINEERING CHEMISTRY 1303 j ; \ i i Picher i ing/ 1935 19350 iety of ; m itte | ted by | F igure 15. T hree-D imensional Chart Comparing M ineral W ool with Glass W ool and Showing Conductivity as a F unction op D ensity and M ean T emperature -___ ise of esent wool. This clearly illustrates the effect of convection in the This larger air cells found in glass wool. jarser , gher It is difficult to cover even partially the field of thermal otice- : insulations in a paper of this length. All that can be done is torn- : to stimulate interest in thermal insulations as a necessary i that adjunct to the building industry, both from a domestic and an industrial standpoint. The fact that these industries are growing so rapidly makes it imperative that engineers and architects be familiar with this field. So many data have been published on the subject of thermal insulation!; that it can be called a definite branch of engineering. R eceived A pril 27, 1935. - irt as ! ly.sit 0 ' . ' ~~ ' - t and wool nduceas in i tem- , is ob- ' f 420 of ap r glass Preservatives and Antitermite Protection of Timber C. DEM ERE E. L . B ruce C om pany, M em phis, T enn. ' Som e new wood preservatives and a new m ethod o f applying th ese preservatives to the wood have resulted from recent research and developm ent work. These new pre servatives are designed to m eet th e require m ents o f those phases o f building w hich are not satisfactorily served by other preserva tives and m ethods o f application. This brief sum m ary has n ot attem pted a de tailed treatm ent o f th e num erous consid erations involved in th e developm ent o f im proved wood preservatives b u t has endeav ored to show w hat one group o f investi gators is doing to solve th e problem s in volved.. . L k NUMBER of wood preservatives, such as / \ creosote and zinc chloride, are excellent -L j for outside use for treatment of erossties, bridge timbers, poles, etc., since they are cheap and effective. The field for new preservatives has its basis in the limitations of these old types. Creosote's limitations are its persistent and sometimes objectional odor, the fact that its fumes under certain conditions may be injurious to human health, its dis coloration of the wood, and the difficulty of painting wood after treatment with creosote. Zinc chloride and other pre servatives of the same general type use water as a carrying agent. The application of water causes wood to expand and become distorted and, when it is dried to the moisture con tent satisfactory for use, the grain tends to raise, the wood tends to check and warp, and some woods become discolored. The need for new preservatives for use in the building in dustry is most clearly recognized in the field of home con struction and for certain uses in other building construction, packing houses, dairy buildings, farm buildings, textile plants where the humidity is high, and refrigerator, box car, and auto mobile construction, etc. A program of research, which has resulted in the develop ment of a series of new preservatives, was begun by the laboratories of the E. L. Bruce Company in 1927.. After careful study it was decided that a preservative to meet the