& <=\?> — W i Digitized by the Internet Archive in 2017 with funding from Columbia University Libraries https://archive.org/details/radialbrickchimnOOalph United Illuminating Co., Steel Point Station. Bridgeport, Conn. Chimney 175' x 12' 6 ". Red radial brick. Artificial stone trim. Built in 1921 This chimney duplicated at the same plant in 1973 Foundation—reinforced concrete piles Wes coll r" Xfapes, Engineers Alphons Custodis Chimney Construction Co. Radial Brick Chimneys 95 Nassau Street New York CHICAGO, ILL. PHILADELPHIA, PA BOSTON, MASS. ATLANTA, GA. DALLAS, TEX. Branch Offices DETROIT, MICH. BALTIMORE, MD SEATTLE, WASH. PORTLAND, ORE. ST LOUIS, MO. PITTSBURGH, PA CLEVELAND, O. RICHMOND, VA. MILWAUKEE. WIS. MINNEAPOLIS, MINN Custodis Canadian Chimney Co., Ltd. TORONTO, ONT. MONTREAL, P. Q VANCOUVER, B. C. 3 Copyright, July, 1921 Alphons Custodis Chimney Construction Co. 95 Nassau Street, New York 4 Foreword The construction of every chimney presents a problem of its own. In the following pages you will find information, formulae and other data helpful, even when not exactly applicable, in the study of most chimney problems. The development of immense boiler horse-power has made necessary tall and large chimneys. The ‘unprecedented in¬ crease in the size of engines and turbines in the past decade and the consequent increase in the size of boilers demanded the use of these large chimneys. Each of the five specific types of chimneys generally rec¬ ognized require calculations in twenty or more fields. This book discusses in detail all the factors commonly met with in chimney problems. But because the modern science of chimney construction has not yet been reduced to a text-book basis—-in the English language—the practice has been established of calling upon chimney construction engineers for authoritative information. This book is published to furnish engineers and architects the data essential to their study of design and size for the general chimney requirements. Views and designs are show n of chimneys illustrating most of the known requirements. It should, however, not be assumed that all data quoted fit exactly any given problem. We urge the engineers and architects to discuss with us the final, if not the lull, details of their specific chimney construction problem. 28106 Architect Two chimneys 200' x 8' 6" built in 191 Philadelphia General Hospital. Philadelphia, Pa 6 Gustodis Chimneys T HE Custodis perforated radial brick chimney is built of radial blocks formed to suit the circular and radial lines of each section of the chimney. This permits them to be laid with an even mortar joint and with regular smooth surfaces. In addition to being so shaped the blocks are moulded with vertical holes or perforations. There are several advantages in this. The perforations permit of a more thorough burning of the blocks in the kilns. This produces a more homogeneous block than could be obtained were they solid. Their density and strength are materially increased. The perforations also serve to form a dead air space in the walls of the chimney which tends to prevent rapid heating and cooling of the walls by conserving the heat inside. On account of their circular and radial form tight joints are obtained. This with the air space due to perfora¬ tions gives a maximum conservation of the heat inside of the chimney. (See illustrations showing radial blocks and the bonding of the Custodis wa Figs. 1, 2 and 3. It is very plain that with such shaped blocks a very strongly bonded wall can be built. It is very important not to make the perforations excessive in size. To retain the strength of the block, and to prevent the mortar from filling entirely these perforations, one and one-eighth of an inch square should be their maximum cross section. In general the perforations on the horizontal bed should not exceed 22 per cent, of the total area. The main principle of the perforated radial brick chimney is defeated in every attempt to make the perforations larger, in order to lighten the material and reduce their original cost and the cost of transportation. In laying the blocks the mortar is worked into the perforations about one (1) inch, locking them together on the principle of a mortise and tenon joint. Each course is keyed and the whole structure bound together practically in the same Custodis perforated radial brick const ruction Georgia School of Technology Atlanta, Ga. 206'6"x8'0". Built in 191' Atlanta Water Works Atlanta, Ga. 175' 0"x 8' 6". Built in 1920 Richmond Terminal Railway Richmond, Va. 110' 0" x 5' 0". Built in 1917 / f I 8 manner that steal dowels of a light-house hind the several courses of stone from its foundation to its top. I his produces the strongest bonded wall known to brick construc- t ion. It will be noted that the horizontal bed joints and the cross joints are not de¬ pendent alone on I he adhesion of the mortar to a flat surface. The blocks are corrugated on their sides in addition to being I >erforated ver tically. Fig. Details of bonding and jointing of CUSTODIS perforated radial brick construction The Custodis Company gives skilled supervision to the manufacture of its blocks. Only the proper mixtures of clays are used. None of the common clays or shale are used in Custodis blocks. Instead they are manufactured exclusively from clays that are high in alumina and high in silica, giving them not only high refractory powers but high crushing strength. They are burned at a temperature averaging 2000° F. and have a maximum crushing strength varying from 1000 pounds per square inch to 6000 pounds per square inch. Fig. 3 CUSTODIS perforated radial chimney blocks Idle illustration on this page shows five (5) different lengths of blocks. (Fig. 3.) All blocks have the stunt* dimensions on the face — namely, approximate!) 6 1 2 xTy§ inches. The lengths of the blocks vary in order to make possible the breaking of the joints horizontally and vertically in the walls. The combination of bonds with this type of block admits of a somewhat lighter wall and a lighter chimney. This not only reduces the cost of the foundation, but also produces a structure superior to, but less costly, than the common brick chimney where, on account of the uncertainty of the material in common bricks, it is general practice to line a common brick chimney to the top. On account of the high refractory powers of the blocks to resist heat, it is feasible to eliminate the long protective lining which is coninionh used in the ordinary common brick chimney. 10 W ith the selected clays used and the material burned to a temperature of at least 2000° F., a Customs block is produced, which is low in percentage of absorption of moisture, but high in crushing strength and refractory powers, acid-proof and of maximum density. The all important thing in the manufacture of radial blocks for chimney use is to mix different and suitable clays in the right proportion and burn I hem properly. This knowledge comes only through study and long experience. The Customs Company ships from twelve (12) brick yards in the United States and Canada. They are so geographically located that we can reach almost any part of the country without excessive freight rates. The building of a chimney requires not only that the work shall be of the best, but that it shall be done under exacting conditions and at altitudes to which ordinary masons are not accustomed. This is a special line of work requiring trained chimney foremen and workmen who are so employed constantly. We employ continually numbers of these men in organized and eflicient crews. It is only by such a system, accompanied by careful and frequent inspections which we maintain, that uniform perfect work in this line can be done. Chapter I STANDARD TYPES The application of the Customs Radial Brick Chimney to almost every possible condition where a chimney is required naturally calls for various and numerous types as illustrated in the following pages. “A.” FACTORY CHIMNEY There is the ordinary factory chimney for steam boilers i“or manufacturing plants, power houses, etc. In this case the chimney is built for the express purpose to produce an adequate draft to carry away a given volume of gas at a requisite velocity that the boilers may produce their maximum economical steam efficiency. These chimneys are designed to w ithstand temperatures ranging from 300° F., w hen economizers are used, up to 600° or 800° F., and are for boiler purposes alone. They usually lack decoration or ornamental design. Their diameter and height are determined solely by the amount of cubic feet of gases they must handle in a given time to produce a draft sufficient for the proper economical and thorough burning of the kind of coal used. The lining in this type of chimney is usually j short and is dependent, of course, upon the internal temperatures expected. It is ! generally not more than one-sixth (Veth) the height of the chimney. The chimney can be built either of an all round column construction for its full height, or in cases where the chimney is connected with the building wall, the lower portion may be built of common brick or of a brick to match that which is used in the walls of the power house. (See detail designs of the two types, pages 12 and 13. Figures 1 and 5. also illustrations.) li Arlington Mills Lawrence, Mass. 300' 0" x 19' O'' Built in 1917 Bush Terminal Co. Brooklyn. N. A. Two chimneys—200' 0"x 12' 0" built in 1907 and 275' 0"xl3' 0" built in 1921 All round column 12 University of Washington Seattle, Wash. 200' 0" x 10' 0" Built in 1921 Metropolitan Edison Co., Reading, Pa. Four chimneys like the above two Built in 1909, 1922 and 1923 Design of chimney Octagon base 11 •‘B.” DESKi NS F()R OFFICE BUILD1XGSJ K) PELS, ETC. The Ci stodis Kadial Brick Chimney is particular!) adapted for use in the modern office building'. These buildings in recent years reach the height of twenty or more stories. In the past steel stacks have been used, either running through the floors or banded to the outside walls. The steel stacks radiate heat to the offices when the stack is entirely within the building. When they run up the outside walls they are often adjacent to windows where their heat is objectionable. Furthermore, continual painting is necessary for their maintenance and preservation. When they run up through the building in a fireproof shaft they are often inaccessible to inspection and painting. The substitution of a CuStodis Radial Brick Chimney in these cases eliminates all these objections. They take up little or no extra space. No heat is radiated from them and when once in place require no inspection, painting or maintenance. Among the many excellent examples of this type are the Custodis Chimneys in the Hotel Commodore and 110 Wil¬ liam Street Building in New : York City. The design of the latter is shown. (Fig. 6.) This chimney is built in a fire¬ proof shaft running up through 22 stories. Note that there is no connection between it and the floor beams of the building, the w alls being carried to within approximately inch of the steel work. The chimney stands free on its own foundation. A small portion extends above the roof, just enough to clear the pent house. This portion only is exposed to wind pres¬ sure, so compression is the one stress of consideration in the structure. This admits of thin walls and very small spread. The chimney is plumb throughout, 310' 0" high and F 0" inside diameter at the top. In buildings of less height, the portion of the chimney entirely within the building may be plumb as above described, and that part extending above the roof, if of considerable height, may be given a taper for stability against wind forces. The form may not necessarily be circular. Many have been built elliptical or oval in section according to the shape of the space or shaft allotted for the chimney. In some instances it is more practical to carry the chimney up against the outside walls, close to the building. The plumb portion is banded with steel bands every 23 or 30 feet and fastened to the building wall by means of lugs. (See illustration, page 16, Fig. 7.) Fig. 6 Chimney, No. 110 William Street Bldg., New York— 310' high; 1' 0" inside diam¬ eter at the top. Running up through 22 floors. It is plumb throughout 15 16 Another special type applicable to hotels is shown in Figure 9. Here the chimney is divided into several compartments by means of interior walls, the main compartment taking the boiler gases, the others used for taking off the fumes from the kitchen, ventilating the dining room and carrying off the gases from a small incinerator. The Customs Company designed and built several chimneys for the Pennsylvania R. R. Company with partition walls running to the top. These were in connection with round houses and boilers. One compartment took the hot gases from a boiler plant while the other carried off the cooler smoke from locomotives in the round house. (Fig. 8.) In designs of this character it is important not to bond the partitions into the chimney walls, for their expansion is likely to crack the chimney walls. "The above are but a few of the designs showing the almost universal adap¬ tability of the Customs Chimney to meet almost every special case. “C.” CHIMNEYS WITH ARCHITECTURAL TREATMENT In connection with Museums, Libraries, Art Galleries, Memorials, Public Buildings, Institutions, Colleges, Universities, etc., architects often require the chimney to carry out in form and appearance a particular style or period of archi¬ tecture. They wish to depart from the plain shaft with its straight lines and commercial aspect. The Customs Company has many times been called upon to assist in the design of chimneys whose outer form adheres to the style of archi¬ tecture adapted for the building. A handsome example of this is the chimney show n on page 18, built for the Rice Memorial Play Field at Pelham Bay- Park, New ork. It is in the form of a fluted memorial column, surmounted by a terra cotta urn. The shaft is after the Greek columns of the Parthenon of Athens, period about fifth century, R. C. Within the stone design of the column is a Customs Chimney serving steam boilers. Some other examples are the chimneys built for the Betsy Head Memorial. Brooklyn, N. A., page 19. Also the State Capitol at Olympia, Wash.; General Electric Co.: National Lamp Works, Nela Park. Cleveland, 0.; Detroit Water Works, Detroit. Mich.; and others illustrated within I hese pages. The Rice memorial column particularly shows w hat can be done in constructing a proper and ellicient chimney within a shell, whose lines follow a definite style of architecture. 17 Architects , Herts (** Hotter!son, A lew York Rice Memorial Play Field. Pelham Bay Park, N. Y. 65' x 6' 2". Built in 1921 A chimney in the form of a memorial column on the top of which is a terra cotta urn. The shaft is after the Greek Doric Columns of the Parthenon of Athens. Period about 5th Century B. C. Within the stone facing is a Custodis Chimney 18 Detroit Water Works Detroit. Mich. Two chimneys 150' 0" x 12' 0" Built in 1921 An ornate chimney with ornamental head—stone trimmed \\ ilder df H hilc, Arch Her l Washington State Capitol Olympia. Wash. 1 IT' 6" x 6' 6". Built in 1920 An ornate Custodis chimney faced with cut stone _Herts if Robertson , I\'ew York, Architects Betsy Head Memorial Playground Brooklyn, N. Y. 88' 5" x 1' 0". Built in 1915 A Greek Doric Column built of Custodis radial chimney brick surmounted by a terra cotta memorial urn In a number of large power houses Custodis Chimneys of considerable size are built on the structural steel near the roof line. This conserves room in the station and often shortens the breechings from boilers to stack, lowering the cost of the latter as well as reducing the friction losses. Notable ex¬ amples of this type are the Cus¬ todis Chimneys at the Power Stations of the New \ork Central R. R. Co. at Port Morris and 5 onkers, New 'l ork, the interboro Rapid Transit Station at 59th Street, Nev 5 ork, the Municipal Electric Light Plant. Lansing, Mich., and Consolidated Gas, Electric Light & Power Co., Westport, Md. The illustration (Fig. 10). is typical and shows the foundation on steel. I'k Chimney on Consolidated Gas, Electric Light & Power Co., Westport, Md. Three chimneys. 215' 0" x 20' 2". Built in 1913, 1917 and 1918 Chimneys on structural steel 90' from ground 20 Illinois Glass Co., Bridgeton, N. J. 170' x T Built in 1921 J. E. U oodwell, Engineer Moores Park Station City of Lansing, Michigan Two chimneys 200' \ PI' 0" Built in 1923 Chimney on structural steel If. L. Doherty df Co., Engineers Public Service Co. of Colorado Valmont, Col. 350' x 16' Built in 1921 1 “D.” HIGH TEMPERATURE CHIMNEYS "These chimneys are used in connection with furnaces, smelters, incinerators, garbage destructors, etc., where, in addition to providing draft, they must stand high internal temperatures. As stated heretofore, chimneys used in connection with steam boilers where the temperatures range between 300° F. anti 600° F. it is necessary to line only a portion of the chimney. Where the boilers are pushed to an overload of 150 or 200 per cent, or more above normal, in the absence of economizers or other appara¬ tus that would lower the temperature of the gases before entering the chimney, higher stack temperatures may be expected. If these do not reach over 1000° F. it is not necessary to line the chimney to the top, but it is well to increase the length of lining above the customary one- sixth (i/gth) the height. Should tin* chimney temperatures run over 1000° F. and up to 1200° F., it is good practice to line it with sectional lining of Custodis Radial Brick for its lull height. The lining is supported on corbels built out from the main walls at intervals of approximately 20 feet vertically, with an air space of not less than 2 inches between the lining and the walls. For temperatures ranging from 1200° to 1500° F., where no destructive acids are present, we recommend an independent lining of Custodis Radial Brick for the full height of the chimney with an ample air space between it and the chim¬ ney wall. The lining should have no connection with the main walls and be abso¬ lutely free to expand at the top. It is advisable to use mortar composed of lime, sand and cement when the above or less temperatures are present. Fire clay is not recommended, for the lime, sand and cement mortar gives a stronger bond and answers the purpose. If the internal temperatures expected are above 1500° F. and up to 2000° F., an independent lining of solid radial lire brick for the full height of the chimney shall be employed. In this case we recommend that the solid radial fire brick lining be laid up in lire clay with a small quantity of cement. Internal steel bands should be built into the walls of the chimney at every change of section to assist in taking up the thermal strains. (See Fig. 11.) The internal ladder generally used should be eliminated in chimneys subjected to these high temperatures, for the reason that if the ladder step irons are built through the lining and into the main walls, when the lining expands they are liable to crack both the lining and the chimney. Chimneys subjected to temperatures over 2000° F. should be constructed with an independent solid radial fire brick lining laid in fire clay mortar as described above. In addition to the independent lining an additional lining of the very best obtainable high refractory lire brick should be constructed in the lower portion inside the independent lining, but not bonded to it. Under continued temperatures over 2000° F. the lire brick in the lower portion, particularly in the vicinity of 99 The Don Incinerator Toronto, Ont.. Canada 175' 0" x 7' 6". Built in 1916 This chimney subjected to temperatures Chimney for high tem¬ peratures up to 2000° F. Independent lining of solid lire brick Section A \ Fig. 12 of F ig- 12 Chimney for temperatures over 2000° F. t\ ith independent solid radial fire brick lining to top and removable fire brick lining in lower portion 25 o'- o' _ V_ 14-'- the flue, wil 1 in time burn out. This necessitates the removal and replacement of this removable portion. The fact that it is not bonded to the main lining makes its removal and renewal possible without disturbing the main lining. We would further recommend building on the outside of the chimney steel bands at intervals of between 8 and 10 feet vertically. (See drawing illustrating this type, Fig. 12.) RESISTANCE TO EARTI[QUAKES, EXPLOSIONS AND SHOCK It has been demonstrated many times that the Custodis radial brick chim¬ neys resist successful!\ such unusual shocks as concussions due to explosions and earthquakes, as well as shocks from heavy rock blasting, and vibrations from hydraulic or steam hammers. Although there were a number of these chimneys in Ihe area covered by the San Francisco earthquake, they were not damaged. The well-remembered explosion of TAT in the Harbor of Halifax in December, 1017. during the World War, wrecked many structures and buildings in Halifax and Dartmouth, N. S. On the day of the explosion the Custodis Company had practically finished six radial brick chimneys for The Imperial Oil Company at Dartmouth. These chimneys were practically green. Structures and buildings were wrecked all around them, but the chimneys themselves were not injured in the least. They stood within a mile of the explosion. There were some fifteen older Custodis chimneys within this area and none of them were injured in the slightest degree. The Black Tom explosion during the W orld W ar, at Communipaw, N. J., also wrecked structures and buildings in that vicinity. In this area there were a large number of Custodis chimneys. These chimneys withstood the concussion and none of them were injured in any way or developed defects since. There are a number of installations of Custodis chimneys in the vicinity of quarries where they are blasting continually. These chimneys have not been affected. Many Custodis radial brick chimneys stood within the area covered by the tropical cyclone and hurricane of September, 1915, in southern Louisiana and Mississippi. Their heights ranged from 165 feet to 200 feet. The L nited States Weather Bureau reports an extreme wind velocity in certain areas of over 130 miles per hour, and further say that pulsating gusts of a few seconds' duration were at times undoubtedly much greater than the extreme velocity of 130 miles per hour. The Custodis chimneys, in this area, were in no way affected by this extreme and practically unprecedented wind. These incidents are ample proof that the factors used by the engineers of the Custodis Company in designing their chimneys are conservative and safe, and, furthermore, that the design of the whole structure in taper, spread, wall thickness and weight are of the best that long experience and good judgment can produce. :■ -. 24 Chicago & Northwestern Railway Co., Chicago, 111. 203' 0" x 12' 0". Built, in 1916 On March 19th, 1921, the grain elevator in t lie Yards of the C. & N. \\ . Railway blew up. The concrete elevator, elevator buildings, power house, loading and welfare buildings were completely wrecked. The Custodis radial brick chimney adjacent to the elevator was the only structure that withstood the shock and remained intact. A demons!ration of the stability, durability and strength of the modern Custodis radial brick chimney. St. Paul & Tacoma Lumber Co., Tacoma, Wash. Two chimneys 150' 0" x 9' 0". Built in 1920 Replacing two steel stacks which have since been removed American Woolen Co. Shawsheen \ illage Andover, Mass. 250' 0" x 12' Built in 1921 U. S. Public Health Hospital W alla Walla, Wash. 127' 0" x 4' 6" Built in 1922 Edison Lamp Works Harrison, N. J. 175' 0" x 7' 6" Built in 1918 Name built into chimney with while enamel brick. Each letter approximately 4' 7" high. NAMES, LETTERS, DECORATIONS Many firms take advantage of their chimney to use it as a means of adver¬ tisement by placing the firm name or initials in a vertical position on the column. Some have a taste for a decorative pattern at the top. Illustrations of the use of names, letters and decorations are shown on pages 27 and 28. These are formed by building into the structure radial chimney blocks the color of which is in marked contrast with the body color of the shaft. On a chimney buff in color, blocks of dead black are usually used. During their manufacture a black preparation is put on the faces of the blocks when green. It is then burned permanently into them as they are fired in the brick kilns. This makes the black absolutely permanent, as well as weather and heat proof. If the chimney shaft be red then blocks of light buff color may be used. They make a striking contrast with the dark red background. A very handsome and effective appearance is obtained by forming the letters with glazed enamel brick of different colors—such as white enamel on a red chim¬ ney and dark brown, dark maroon or deep dark blue on a buff chimney. The glazed surface of the enamel brick is not easily discolored. What little soot does gather on them is quickly washed off by the rain, and the surface is again bright and clear. The size of the letters varies with the size of the chimney. The larger the chimney, the larger the letter which can be used with effect. They range in height from two feet eleven inches to seven feet or more. Elevated as the letters are on a tall chimney, they attract marked atten¬ tion. Compared with the same size letter put on by a sign painter the cost is not large. Furthermore, paint in time will wear off. while the built-in letters are absolutely permanent. Were the sides of the letters made straight with separate bricks or blocks, they would not break joints and the strong bond of the Custodis chimney would be destroyed. For that reason the letters are worked out in broken lines. PROTECTIVE AND DECORATIVE HEADS The standard head for factory chimneys is shown in Fig. 13. The tops of acidproof chimneys are protected w ith a cap made of material not affected by the particular acid the chimney handles, as show n in Fig. 15. Ornamental heads are exemplified in Figs. 16 and 17 and can be furnished at slight additional cost. Many different styles of heads may be designed to suit the architecture of the building or the particular taste of the owner or architect. 26 Vancouver Lumber Co. 17.V' x 9" Vancouver B. C. Built in 1922 \\ bite enamel brick letters each o' 5" high Length of name 102 feet The Buda( io., Harvey, Ill. 200' 0" x 9' 0" Built in 1917 Northwest Paper Co., Cloquet, Minn. Two chimneys 175' x 9' 0". Built in 1914 250' x 14' 0". Built in 1922 -i f- r/ Atlanta Terra Cotta Co. Perth Amboy, N. J. 110' 0" x 5' 6" White Provision Co. Atlanta, Ga. Built in 1922. Light BUFF col¬ umn with deep BLUE enamel letters and decoration 125' 0" x 7' O'' Built in 1923. RED column with WHITE enamel brick letters. Note cored concrete sub-base and foundation Patterson Realty Co. Nashua, N. H. 70' 0" x 3' 0" s T R A T F O R D O A K U M 4h Stratford-Oakum Co. Jersey City, N. J. 125' 0" x 4' 0" Built in 1922. Light BUFF col¬ umn with BLACK letters. Note cored concrete sub-base and foun¬ dation Built in 1919. Dark RED column with WHITE enamel brick letters 28 Fig. 13 Slandaril head Head with concrete capping Fig. 15 Mead of chimney with lining to top showing lend cap FLUE OPENINGS For structural reasons avc recommend a line opening rectangular in shape, and of an area equal to the total area at the top of the chimney plus ten per cent (10%). This will develop the full working horse-power of the chimney. Fig. 20 Section through t ypical flue opening Fig. 21 Section through all-round chimney located on side of building Fig. 24 Section through octagon base chimney located in corner of building Fig. 22 Section through square base chimney located in corner of building Fig. 25 Section through chimney showing baffle w all Fig. 23 Section through square base chimne; located on side of building Fig. 26 Elevation of baffle wall Reinforcing piers are built out on each side of the opening from the main walls. The faces of the piers are a plain surface vertical to the ground. The masonry above the opening is supported by heavy I-beams. It is further rein¬ forced top and bottom by means of steel bands built into the chimney walls. See section of Hue opening, page 29. Fig. 20. To maintain a safe moment of stability, the width of Hue opening is limited for round chimneys approximately to one-third the width of the chimney at the point where the Hues enter; for octagon, seven-sixteenths; for square, one-half. We recommend certain widths and heights for dilferent inside top diameters of chimneys. These sizes are given in table 1. page 30, and it is well not to exceed them. The sizes given will develop the full working horse-power of the chimney. Where the chimney is designed for two line openings on the same elevation and directly opposite, a bailie wall is necessary to prevent interference of the two gas streams and to assist in their upward trend. See page 29, Figs. 25 and 26. The bailie wall should be set at an angle of 15 degrees with the entering lines. It may start two feet below the openings and extend three or four feet above them. When not resting on the foundation the bailie wall may be supported on I-beams and built against the lining, but not bonded to it nor to the main walls. Table 2, below, gives the proper sizes of two line openings entering a chimney where the Hue openings are of equal capacity. TABLE i SINGLE FLUE SHOWING MAXIMUM WIDTHS OF FLUES AND SIZES OF FLUE OPENINGS FOR STACKS OF VARIOUS DIAMETERS Diara. FLUE DIMENSIONS Diam. FLUE DIMENSIONS ol ol Chimney Square Rase Octagon Base Round Col. Chimney Square Rase Octagon Base Round Col. 2'-6" 2'-0'x 2'- 9' 2 -0’x 2'- 9' 2'-O'x 2'- 9' 1 1 -6' 8'- 6'x 13'- 5' 8'-0'x 14'- 6' 7'-3"xl5'- 6' 3-0' 2'-6'x 3'- 2' 2'-6'x 3'- 2' 2-6'x 3'- 2' 12-0' 8'- 6'x 14 - 7' 8'-0'x 15'- 7' 7'-6'xl6 - 0' 3-6' 3'-0"x 3'- 6’ 3'-O'x 3 - 6' 2'-9'x 3-nr 12-6' 8'-11" x 15'- 5 ' 8'-4'x 16'- 3' 7'-9'xl7'- 5' 4-0' 3-3'x 4'- 3' 3 -3'x 4 - 3' 3'-O'x l'- 7' 13-0' 9'- I'xl5'-10” 8'-8'x 1 6'-l 1" 8'-0'x 18'- 3' 4'-6" 3'-6'x 5'- 2' 3'-6'x 5'- 2' 3-3’x 5'- 6' 13-6' 9'- 9'x 16'- 3' 9'-0'x 17'- 6' 8'-3'xl9'- 1' 5-0" 4'-0'x 5'- 5’ 4'-O'x 5'- 5’ 3'-6’x 6'- 2' 14-0' 10'- 2'xl6- 8' 9'-4'x 18'- 2" 8'-6'x 19'-11' 5 '-6" 4'-6'x 5'-l0" 4'-3'x 6'- O' 4'-O'x 6-7' 14-6' 10'- 7'x 17'- 2' 9'-8"x 18-10' 8'-9'x20'- 9" 6'-O’ 5'-0’x 6'- 3’ 4'-6'x 7'- 0’ 4 '-3’x 7'- 5' 15-0' 11- 0'xl7'- 8" lO'-O'x 19'- 6' 9'-0'x21'- 7" 6'-6" 5'-6’x 6'- 8’ 4'-9'x 7'- 9' 4 '-7'x 8'- 2’ 15-6' 11'- 5'x 18'- 2' 10'-4'x20- 2' 9'-3'x22'- 5' 7'-0’ 5'-9'x 7'- 5' 5-3'x 8'- 6' 5 -O'x 8'- 6' 16-0' 1 1 '-10'x 18'- 8' 10'-8'x20'-10' 9'-6"x23'- 3' 7 -6" 6-O'x 8'- 1 5-6'x 8 -10' 5 -3'x 9 - 4' 16-6' 12 - 3'x 19'- 2' 1 l'-0'x21'- 5' 9'-9'x24'- 1' 8'-0’ 6'-6'x 8'- 6' 5 -9'x 9'- 8' 5'-6'x 10'- O' 1 7'-0' 12'- 8'x 19'- 9’ ll-4'x22'- 1 10'-0'x25'- 0' 8'-6' 7 '-0*x 9 - 0' 6 -3'xlO'- O' 5'-9'xl0'- 9' 17-6' 13'- 1 ”x20'- 3' 1 l'-8'x22'- 9' 1 0'-3"x25'-10' 9'-0" 7'-6'x 9'- 3* 6-6'x 1 O'- 9’ 6-'0'xll'- 8' 18-0' 13'- 6'x20'- 9' 12'-0'x23'- 4' 10'-6"x26'- 8' 7'-9’xl0'- O' 6'-9'xll'- 6" 6'-3'x 12'- 6' 18-6' 13 -11 "x21 - 3' 12'-4'x24'- O' 10'-9'x27'- 6' lO'-O" 8-CxiO'- 9’ 7'-0'xl2'- 4" 6-6'x 13'- 3' 19'-0' 1 1- 4'x21- 9' 12'-8'x24'- 8" 1 l'-0"x28'- 5" 10'-6" 8 -6'xll'- 3' 7'-0'x 13'- 7" 6-9'xll- r 19-6' 1 1 - 9"x22'- 3' 13'-O'x25'- 4' 1 1 '-3'x29'- 3' 1L -0" 8'-6"xl2'- 3' 7'-6'xl3'-10' 7'-0'xl4'-10' 20'-0" 15'- 2"x22'- 9” 13'-4'x26'- 0' 1 l'-6'x30'- 1' TABLE 2 TWO FLUES OF EOUAL SIZE. EACH FOR HALF CAPACITY, SHOW ING MAXIMUM W IDTHS OF FLUES AND SIZES OF FLUE OPENINGS FOR STACKS OF VARIOUS DIAMETERS Diam. FLUE DIMENSIONS Diam. FLUE DIMENSIONS ol ol Chimney Square Rase Octagon Rase Round Col. Chimney Square Rase Octagon Base Round Col. 2'-6' U- 9"x2'- 0’ 1- 9'x2'- 0' 1'- 9'x2'- 0' 11-6' 7'- 2'x 8'- 0' 6'- 3'x 9'- 3’ 5'-10'xl0'- 0" 3'-0" 2'- 0'x2'- 3' 2'- 0'x2'- 3' 2'- 0'x2 - 3’ 12-0' 7'- 6'x 8'- 4' 6'- 6'x 9'- 8' 6 - O'x 10'- 5' 3 '-6" 2'- 3"x2'- 9’ 2'- 3'x2'- 9' 2'- 3'x2'- 9' 12'-6* 7'- 7'x 9'- 0' 6'- 7'x 10'- 4' 6'- 2'x 11'- 1' 4'-0" 2'- 6'x3'- 2' 2'- 6"x3'- 2' 2'- 6'x3'- 2' 13'-0' 7'- 8'x 9 - 7' 6'- 8'x 11- 0' 6'- 3'x 11'- 9' 4'-6' 2'- 9”x3'- 6" 2'- 9'x3'- 6' 2'- 8'x3'- 7' 13-6' 7'- 9'xl0'- 2' 6'-10'xl 1'- 8" 6'- 4'xl2'- 7' 5'-0" 3 - 1 'x3'- 9' 3 - l’x3- 9' 2'-l 1 'x4'- O' 14'-0' 7 -1 1'xlO - 9' 7'- O'x 12'- 3' 6'- 5'xl3'- 2' 5'-6" 3’- 4’x3'- 0' 3'- 4’x4'- 0” 3'- l'x4'- 6" 14'-6' 8'- l'xll- 4' 7'- 2'xl2'- 9' 6'- 7'x 13'- 9' 6'-O’ 3'- 7"x4'- 6" 3'- 7'x4'- 6' 3'- 3'x5'- O' 15'-0' 8'- 3'xir-Il' 7'- 5'x 13'- 4' 6'-10’xl4'- 4' 6'-6" 3'-ll"x4'-10' 3'-10’x4'-ll' 3'- 6'x5'- 5' 15 '-6' 8 - 5'x 12'- 6' 7'- 7'x 13'-10’ 7'- 0'xl4'-ll' 7'-0' 4'- 2"x5'- 2' 4'- 0’x5'- 5' 3'- 9'x5'-10' 16'-O' 8'- 6'x 13'- 1" 7'- 9'xl4'- 4' 7'- 2'xl5'- 6' 7'-6" 4'- 6"x5'- 6" 4'- 3'x5'-10" 4'- 0'x6'- 2' 16-6' 8'- 8'xl3'- 8' 7'-ll'xl4'-ll* 7'- 4'x 16'- 1' 8'-O’ 4'-10"x5'-10' 4'- 6'x6'- 3' 4'- 3'x6'- 8' 17-0' 8'-10'xl4'- 3’ 8'- l'xl5'- 5' T- 6'xl6'- 8’ 8-6' 5'- l"x6'- 2' 4'- 9'x6'- 8' 4'- 6'x7'- 1' 17 '-6 ’ 9 - 0'xl4'-10' 8 - 4’x 16'- 0' 7'- 8'xl7'- 3' 9'-0' 5'- 5"x6'- 6’ 5'- O'x7'- 1" 4'- 9'x7'- 7' 18-0' 9 - 2'x 15'- 5' 8'- 6'xl6'- 6' 7'-ll'xl7'-10' 9-6' 5'- 9'x6'-10" 5'- 3'x7'- 6' 5'- 0'x8'- 0' 18'-6' 9 - 4'xl5'-Il' 8 - 8'xl7'- 1' 8'- l'xl8 - 5' 10 '- 0 ' 6 - l"x7'- 2" 5'- 6"x8'- 0" 5'- 3"x8'- 6' 19-0' 9 - 9'xl6'- 2" 9'- O'x 17'- 5' 8'- 3'x 19 - 0' 10'-6' 6'- 5"x7'- 5' 5'- 9"x8'- 5' 5'- 6'x9'- 0' 19-6' 10'- 2"xl6'- 4' 9- 4'xl7'- 9" 8'- 5'xl9'- 7' 11'-0* 6'-10"x7'- 9" 6'- 0'x8'-lO' 5'- 8"x9'- 6' 20'-0' 10'- 6'xl6'- 6' 9'- 7'x 18'- 1' 8'- 7'x20'- 2' 30 Imperial W ire & Cable Co . Montreal. P. 0. 225'xlO" Built in 1910 General Electric Co. (National Lamp W orks) Nela Park (Cleveland Two chimneys 86' 1" x 7' 0". Built in 1911 and 162(1 Note the entasis in the round shaft J. Delawanna. N 165' 0"x 7' Built in 1919 Top decoration built of white enamel brick 31 II’ one Hue opening serves less boiler horse-power than the other, the sizes should be proportioned accordingly. Within limits, a chimney may be economically and safely built sufficiently large to take care of future additional boilers. In this case we recommend that the Hue opening in tlie chimney be built tlie full size. The breeching, for a few feet from the chimney, is made the full size of the opening, then properly reduced in section to take the gases of the lirst boilers installed. In this manner, when additional boilers are added, they can be connected to the full size breeching at the chimney without disturbing the masonry in the chimney. Provision should he made in the breeching for the future connection of additional boilers. University of Washington. Seattle. Wash., plant shut clown eight hours while [tutting new chimney in service AN OLD STACK CAN BE REPLACED BY A NEW CHIMNEY WITH A SHUT DOWN OF ONLY A FEW HOURS Power plant owners often have to face the problem ol renewing old stacks or of building a larger chimney. It is possible, but not generally practicable, to build a masonry chimney around an old steel stack to avoid a shut down, but we recommend against this procedure. A ery often the new chimney can be located close to the old one. In that case the old stack can be kept in operation until the new one is entirely completed with Hue opening ready to be connected up. With the new breeching and con¬ nections already fabricated and on the ground, the old stack may be cut out on a Saturday or a holiday and the new chimney connected up in a few hours, after which the old stack may be removed. The Custodis Company has built new chimneys directly behind old chimneys, connected the new chimneys up by means of a breeching directly through the old stacks and put the new chimneys in operation directly after shutting down the old ones. See illustration, page 32. Our Engineers are experts in all such difficult and apparently baffling chimney problems. We solicit an opportunity to solve them for you. REPAIRS TO AND HEIGHTENING OF OLD CHIMNEYS In addition to crews of expert chimney builders, the Custodis Company maintains organized crews of expert steeplejack masons, who recondition old chimneys, repair and renew the heads, repoint the weathered surfaces of old structures for their preservation and longer life, straighten chimneys that lean and repair those struck by lightning. They also demolish old chimneys, repair and renew lightning rods. Many old chimneys are capable of being heightened. We accomplish this work, if necessary, while the chimney is in operation without interruption to the plant. See illustration, page 34. Calculations should lie made to determine whether or not the chimney is capable of being heightened without impairing its stability. The foundation and old brick work should be examined to determine whether they will stand the additional weight and wind stresses. If such a proposition is under consideration, send ns a plan of the old chimney and our Engineers will determine how much, if at all, the chimney can safely be heightened. If a plan is not available, advise us the cross section, whether octagon, square or round, the height above the foundation, the inside diameter at the top, the outside dimensions at the foot and, as nearly as possible, the lop outside measurements, and also the wall thickness at the bottom. This last may often be obtained through the cleanout door. NEW OPENINGS CUT IN OLD CHIMNEYS It is often found necessary to cut new openings in a chimney where changes or additions are made in a plant, but this should never be attempted without first obtaining expert advice. The reduction of cross sectional area may impair the stability of the chimney. This can be determined only by careful calculations. The position of the new Hue opening w ith respect to the old is an important factor in determining whether or not it is safe to cut the new flue opening. Our Engineers are prepared to make such calculations for you and advise you not only as to the safety, but as to the maximum size opening possible and its best position. 33 If a second opening is cut and the original opening left in operation, a baffle wall is sometimes a necessity to prevent the gases from the two Hues interfering with each other and impairing the draft. See page 29. An extension of the inner lining may also be necessary. When it is determined that such openings can safely be cut, the work should not be done by inexperienced workmen. Our chimney crews are trained to safely accomplish such work without injury to the structure. Great care and a certain routine method are necessary. Reconditioning an old chim¬ ney. This can be done while chimney is in operation if necessary Note platforms for determining chimney performance Oregon Agricultural College Corvallis. Ore. 17^'vlfl' "R.iiH in 1 Q93 Showing the heightening of two chimneys while the chimneys are in operation. 34 Cornell University, Ithaca, N. Y. 225' 0" x 11' 0". Built in 1922 Note ladder, experimental plat¬ forms and openings for taking observations Henry It. Kent & Co., Engineers Rutherford, N. J. Built in 1905 This chimney stood in the area covered by the tropical cyclone and hurricane of September. 1915, in Southern Louisiana and Missis¬ sippi. It remained in perfect condition Interboro Bapid Transit Co. 74th St. Station, New ^ ork Four chimneys 278' 0"x 17' 0" Built in 1900 Five others 162'xl5'—59th St. Station. Built in 1902 One 162'x 20'—59th St. Station Built in 1923 These last six built upon the structural steel of the building Geo. H. Pegram , Engineer New OrleansPumpingStation New Orleans, La. 35 West Virginia Pulp & Paper Co., Covington, Va. 250' 0"xl2' 0" Built in 1920 Turners Falls Power & Electric Co. Chicopee Falls, Mass. 250' 0" x 13' 0" Built in 1917 John Stevens, Engineer Virginia Bailway & Power Co., Richmond, Va. 234' 0"xl3' 0" Built in 1912 I I 36 Chapter II CHIMNEYS SUBJECTED TO ACID GASES A chimney is called upon to perform many varied duties in addition to pro¬ ducing draft for steam boilers. This multiplicity of duties presents many chimney problems. Ymong them are the determination of proper height, size and particular design where they are connected with chemical plants, dye works, smelters, paint color factories, silvering industries with their pickling and plating departments, the picture film industry, sintering plants, celluloid factories and innumerable industries, all of which are confronted more or less with the handling of some form of acid gases. Many of these gases are destructive to ordinary brick and mortar, steel, tile and concrete. Many are destructive at certain temperatures and harmless at other temperatures; destructive with certain conditions of moisture, but harmless with others. The subject is an extremely diversified one requiring not only a knowledge of the mathematical and mechanical features, but a knowledge of chemistry, thermo¬ dynamics, ceramics and subjects dealing not alone with the How of gases, but with the effects of different kinds of acid gases under different degrees of concentration and different conditions of moisture and temperature on a chimney. A chimney to handle noxious and acid gases must be designed and built not only for adequate capacity and draft, but also to resist the destructive effect of the particular acid gases, dust, fumes and temperatures and in addition to resist the dynamic wind forces that tend to fell it. Many of these chimneys are not operated in connection with steam boilers, but are connected directly with roasting kilns, furnaces and other apparatus used in the production of chemicals, acids, reduction of ores, the manufacture of colors, photo films, celluloid products, etc. 1 he smoke streams emitted from such chimneys contain acids in both liquid and gaseous form. I hey are often reputed to be a nuisance to a community. Some are supposed to be detrimental to vegetable and animal life. Whether or not they are depends entirely upon the degree of concentration. Plants of this nature are faced with the disposition ol these gases, which of necessity must pass ofl from their apparatus. Among the methods which have been used to remove acid gases fume and flue dust from the smoke are washing the smoke streams in scrubbers, the use of sprays and baffle chambers, bag houses for filtration and electrical precipitators, all more or less successful in reducing the quantity of fumes and dust. None have so far been successful in eliminating all the objectionable elements before entering the chimney. Some of the above mentioned methods tend to materially reduce the stack tem¬ peratures. Some contribute moisture to the gas stream, increase the acid mist and sometimes add to the undesirable activity of the dust and fume. Chimneys 350 to nearly 600 feet in height, discharging the gases at high elevations above the surrounding country where they become diffused and diluted before reaching the earth, have become common. American Smelting & Refining Co. Tacoma, Wash. 57T high x 25' inside diameter at the top. Built in 1917. This chimney handles acid gases Eastman Kodak Company Rochester. N. Y. Two chimneys—366' O'x 9' 0" built in 1906 and 366' 0"xl3' 0" built in 1911. These chimneys handle acid gases as well as gases from steam boilers Anaconda Copper Mining Co. Anaconda, Mont. The largest and tallest brick chimney in the world—585' 0" above ground—60' 0" inside diameter at the top. Built in 1918. This chimney handles acid gases ! 38 They may not serve the purpose perfectly, but their continued use is e\idence that the results are not entirely unsatisfactory. In chemical or industrial plants where the fumes are not acid, noxious or harmful, but yet are disagreeable in their odor, the gases are easily disposed of by means of a comparatively tall chimney. The smoke stream having no destructive content, no precautions need be taken against acid action. The fumes are carried to an altitude where their diffusion in the atmosphere greatly reduces any objec¬ tionable odors, if not entirely eliminating them. The line dust coming from roasting kilns, horizontal rotary kilns in the burning of lime, pyrites, sintering processes, etc., may be diffused to a marked degree by emitting the dust carrying stream at a high altitude. Of the many gases coming from these industries, such as those of the sulphur, nitric, chlorine, fluorin, lead and arsenic groups, the sulphur group is the most frequently encountered. Those of the carbon family give little concern as they are not particularly detrimental to a community nor do they tend to disintegrate a brick stack. Sulphur trioxide, sulphur dioxide, compounds of lead and arsenious oxide are noxious and objectionable. The lirst of these at tack to a marked degree common brick and ordinary mortar, concrete and steel and can not be discharged safely through the ordinary chimney designed for use in connection with steam boilers burning coal. Sulphur dioxide gas in the pure state will condense to a liquid at about 1 1° F. At any temperature above this it remains a gas and will not combine to form a damp acid mist nor liquid acid. If present in small quantities in the smoke stream at atmospheric pressure the condensation point is much lower. Therefore, I his particular gas has little or no effect on a brick chimney. At the present date it seems that the only solution for the elimination of the effect of sulphur dioxide is to see that the sulphur dioxide content of the smoke stream is so diluted before it reaches the ground that it is harmless. This is being done through the use of tall chimneys safeguarded against the corrosive action of the gases by means of auxiliary furnaces to raise I he temperatures. This is practiced by the American Smelting & Refining Company at such plants as require it, and is being adopted by other companies. Unlike sulphur dioxide, sulphur trioxide in the presence of water vapor so common in the smoke stream of the industries mentioned, even in extreme low concentrations, will combine with the water vapor and form what may be called a fog of sulphuric acid or even liquid sulphuric acid on the walls of the chimney. Of that which passes out of the chimney, some may eventually settle to the ground in the lorni of sulphuric mist or dew under certain atmospheric conditions, but the amount is so small in any properly constructed plant as to cause no trouble. It is a fact that the temperatures at which an acid gas will become an acid liquid depends largely upon the concentration of water vapor and acid gases in the smoke stream. The greater the concentration of sulphur trioxide and water vapor 39 -t A-* ^ m, - =-i- _L Arizona Copper Co., Clifton, Ariz. 300' 0" x 22' 0". Built in 1912 A chimney handling acid gases Consolidated Kansas City Smelting & Refining Company El Paso, Texas ■100'x 30'. Built in 1916 This chimney handles acid gases. The platform gives access to open¬ ings in which instruments are in¬ serted and gas samples are taken Anaconda Copper Mining Co. Great Falls, Mont. 506' 0" x 50' 0". Built in 1908 This chimney handles acid gases 40 r the higher the temperature at which lhe condensation will lake 1 place. I nfortu¬ nately, in general, the sulphur gases handled are rather dilute and in the presence of moisture are more active than a stronger concentrated gas. As long as they remain a gas, or in other words, as long as the sulphur trioxide is kept at a tem¬ perature over 100° F. they have little effect upon hard burned impervious brick or so-called commercial acid-proof mortar. Some authorities give the condensation point of the sulphur trioxide under the above conditions as low as 275° F. The best practice is to maintain a temperature of the smoke stream of 400° F. or over. It will be noticed that these temperatures are above the boiling point of water. The fumes of chlorine and nitrous oxide under certain conditions attack common brick and mortar, concrete, unvitrified tile, steel and the common metals. The effect on these materials, particularly in the presence of moisture and low temperatures, is practically the same as the effect of sulphur trioxide. A structure to stand up against them should follow the same general design and use of materials as one built to resist the action of sulphuric acid. The disposition of the chlorine and nitrous oxide fumes, by emitting them at high altitudes, is common practice. Here, too, if the products of combustion carrying these two gases have a low r temperature, auxiliary furnaces lired at the foot of the stack are employed to raise the temperature, give impetus or added velocity to the smoke stream, decrease its density and cause it to raise to considerable heights above the top of the chimney. The diffusion in the atmosphere is thus more completely accomplished. The most important thing in handling acid gases in a chimney is to maintain a high internal temperature. This often destroys the detrimental effect of the gases on the masonry. Furthermore, the higher the temperatures of the emitted gases at the top of the stack, the higher the fumes and fine acid dust will ascend, consequently their greater diffusion before reaching the ground. This is a most important fact to the management of smelters and chemical plants, especially where they have sulphur dioxide to contend with. A wet or damp acid smoke stream in contact with ordinary mortars made of cement, lime and sand, or sand and cement, and certain commercial mortars which do not contain cement and lime, produces a swelling and puffing of both the bed and cross joints accompanied by a tremendous pressure. The swelling amounts at times to 25 to 30 per cent. A chemical change takes place at first on the surface. The mortar becomes soft and of the consistency of mud. As time goes on this softening and swelling w orks entirely through the w alls, causing the brick w ork to bulge and crack. Steel bands are useless, even on the outside, for the masonry will bulge betw een the bands and in time the bands will give w ay. If the temperatures are raised or the chimney dries out the inner portion of the joints may become hardened but still remain swelled. If the brick is not hard and impervious the exposed portion becomes soft and flakes off. This process continues until the whole brick is changed into a soft mass. n Design of chimney for acid gases. Indepen¬ dent acid-proof lining in the round column. Acid-proof corbel lining in the base. Corbels and air space protected with lead aprons. Lead cap on the head and top of lining Fig. 28 —- Chimney with sectional lining for handling acid gases C. K. Williams & Co. Easton, Pa. 375' 0" x 7'. Built in 1911 This chimney handling acid gases Cases have been observed where the swelling of llie joints is quite uniform in the circumference of the chimney and irregular bulging of the structure hardly discernible. The disintegration takes the form of vertical cracks. These usually appear first at the top where the walls are thinnest and in time they work downward to the base. The vertical cracks are due to the swelling of the joints causing cir¬ cumferential strains as the diameter tends to increase. These strains are greater than the strength of the masonry. It is further observed that the cracks increase more rapidly and become larger on the prevailing windward or weather side. This is to be expected, for on that side the rain and snow are driven more frequently, and more forcibly, against the surface and into the interior of the initial small cracks. The water enhances the disintegration of the acid-soaked joint. Once the joints are soaked with the acid, the swelling will continue as long as they can take up any moisture, and by capillary attraction this continues to spread through large areas. Even if the acid fumes are not wet, but are dry, certain of them will attack the above mentioned mortars, destroy the cement or any binder that contains an element which will combine with the acid fumes, turning the joint into a weak sandy mass. Bricks not vitrified and impervious share the same fate. The effect on concrete is a rapid disintegration of the whole mass, due to the breaking up of the cement content, and the acid action on certain aggregates. Acid action has been observed from the smoke stream resulting from the burning of certain fuel oils under boilers. This is particularly in evidence w here the sulphur content of the oil is high and steam atomizing burners are used. In these installations, especially in connection with economizers resulting in low Hue tem¬ peratures, and when the chimneys are high, the protection of the upper portion should have the attention of a designing engineer. It all depends upon the sulphur content of the oil and the tine temperatures. Smoke from many fuel oils has no effect on the brick lining designed for coal burning steam boilers. In designing a chimney for acid duty it is necessary to perfectly protect the main walls by an independent lining for the full height of the structure, with an ample air space between it and the main walls. An air space of not less than 3 or 4 inches at any point is recommended. In fact the design is a chimney w ithin a chimney. See drawing, Figure 27, page 42 The independent inner lining must be built of impervious, practically vitrified, brick, very low in lime and laid up in acid-proof mortar: i. e., an acid-proof mortar made to resist the particular kind of acid in the smoke stream. The thinnest pos¬ sible joint is imperative. The bricks should be thinly buttered or dipped and struck tightly into place. Many commercial acid-proof mortars are acid-proof against certain acids so long as the acid gases are dry and of a comparatively high temperature. These are often composed of a mixture of pure clay, silica sand or silex, kaolin, asbestos fibre, china clay, graphite products, ground gypsum and the like. A common binder is silicate of soda. These mixtures are not always acid-proof and often 43 break up under the action of moisture. They soften, swell and disintegrate under a wet acid. So the mortar must not only be acid-proof but be moisture- proof. Sand only of practically a pure silica content should be used. The top of the chimney should be protected with a cap, covering both the lining and the main walls, and made of material not affected by the par¬ ticular kind of acid under consideration. Ample room should be allowed for the lining to expand upward and outward. Furthermore, the cap should be so designed that no dust, fumes or moisture can find their way down between the main walls and the lining. It will be noted, with this design, the lining has room to ex¬ pand upward without lifting the cap. The air space is protected. See drawing, Fig. 29. With certain acid conditions the cap may be made of lead. On the other hand certain acids wi lead—not necessarily disintegrate it, but cause it to buckle. With other acid conditions a cap of monel metal has been used with success. The choice of material is dependent entirely upon the nature of the acid. The gases coming from the top of a chimney are often blown down the outside for distances varying from 25 to 100 feet. For that reason the same acid-proof mortar used in the lining should be used on the outside joints of the upper portion of the main walls. Since this surface is exposed to the weather it is most necessary that the mortar be weather-proof. Common building lime should never be used in any part of the structure. In some cases where the temperature of the acid smoke stream is continually high, and the acids not very active, the same brick and mortar may be used and a sectional lining constructed in place of an independent lining. See drawing, Fig. 28, page 42. This form of construction is less ex¬ pensive. The corbels built out at intervals from the main walls and supporting the lining should have the inner joints pointed with acid-proof mortar. On the top of each corbel an apron of an acid-proof material should be set in such a manner that the lower lip projects down over the top of the section of lining below. The air space is then protected. In addition to this the Note expansion space at top of lining -At- 11 affect — v- X \AN , \ V\ z: \V 4. \ Fig. 30 Detail of supporting corbel showing protecting apron and expansion space for lining 44 upper 12 inches or so of the air space under each corbel should he packed with flexible material not affected by the particular acid encountered. See drawing, Fig. 30, page -11. Where lightning rods are installed on acid chimneys, the upper 50 feet or more of the complete rod should be sheathed to protect the copper from effects of the acid. Lead covering is in most cases effective. All chimneys handling acid gases should be equipped with an outside ladder, the upper portion of w hich should be covered with lead or an acid-resisting material. Chimneys that have been in practically continuous service for years without show ing any effect from the smoke stream have been observed to develop defects, particularly in the upper portions, after they have been shut down for a protracted period. Although the conditions of temperature, dilution, acid mixture and the like may be such as not to cause damage while the chimney is in operation, yet an accumulation of dust on the inner walls, which is deliquescent by virtue of its acid content, may tend to do damage when the chimney is not in operation. The weather, rain, fog, snow or a heavy humid atmosphere furnishes the necessary w ater within the chimney to convert the previously inert dust with an acid content into a liquid acid which immediately becomes active. It is, therefore, wise when the chimney is shut down for a period to cover the entire opening at the top with a temporary weather-proof lid. This can be made in sections of light wood easily placed and removed. Lugs protected against acid action should be built into the head to which the sections of the temporary lid may be fastened. A good arrangement in designing a plant in which acid fumes are to be carried off is to locate the boiler house so that the gases from the boilers and the acid fumes from the apparatus can be put in the same chimney. Such an arrangement is in use at the Murray Plant of the American Smelting & Refining Company and at the Eastman Kodak Company, Rochester, N. Y. The boiler gases not only keep the temperatures up, but they dilute the smoke stream containing acid gases. No haixl and fast rules can be laid down which will apply to every case where chimneys handle acid gases. The problem of design and materials used can be solved only by an intimate knowledge of the nature and effect of the particular fumes or dust to be disposed of. 45 The Tallest and Largest Chimneys in the World Have Been Built by the Alphons Custodis Chimney Construction Company. Most of These Chimneys Handle Vcid Gases. Anaconda Copper Mining Company, Anaconda, Mont. 585' above grade. 60' inside diameter at top. Built in 1918. American Smelting & Refining Co., Tacoma, Wash. 571' 0" x 25' Built in 1917. Anaconda Copper Mining Co. Great Falls. Mont. 506'x 50' Built in 1907. Federal Bead Company, Federal, Ill. 450' x 17' 0" Built in 1923. United \ erde Extension Mining Co., Jerome, Ariz. 425'x 30' 0" Built in 1918. United Verde Copper Co., Clarkdale, Ariz. 430' x 29' 0" Built in 1922. Consolidated Kansas City S. & B. Co., El Paso, Texas. 400'x 30' 0" Built in 1916. American Smelting & Refining Co., Hayden, Ariz. 300' x 25' 0" Built in 1911. American Smelting & Refining Co., E. Helena, Mont. 400' x 16' 0" Built in 1917. American Smelting & Refining Co., Garfield, Utah. 300' x 30' 0" Built in 1905. Garfield Smelting Company, Garfield, Utah. 350' x 22' Built in 1913. C. K. Williams Company, Easton, Pa. 375' x 7' Built in 1911. Eastman Kodak Company, Rochester, N. Y. 1-366'x 9' Built 1-366'x 13' Built 1-350'x 17' Built in 1906. in 1911. in 1920. Heller Mertz Company, Newark, N. J. 350'x 8' Built in 1904. Public Service Co. of Colorado, Valmont, Col. 350' x 16' Built in 1923. Magna Copper Company, Superior, Ariz. 300' x 20' New Jersey Zinc Company, Austinville, Ya. 350' x 5' Built in 1923. Built in 1920. General Chemical Company, Claymont, Del. 300'x 8' Built in 1912. Nichols Chemical Company, Brooklyn, N. Y. 300' x 12' Built in 1905. Pyrites Company, Wilmington, Del. 300'x 12' Built in 1919. 46 r I I I Federal Lead Co., Federal, Ill. 450' x 17' Built in 1923 This chimney handles acid gases United Verde Copper Co., Clarkdale, Ariz. 430' x 29' Built in 1922 This chimney handles acid gases H. .1. Heinz Co., Pittsburgh, Pa. 250' x 10' Built in 1919 Pacific Mills, Groce. S. C. 175' x 9' Built in 1923 Chapter III ELEMENTS IN DETERMINING THE PROPER SIZE OF CHIMNEY FOR A SPECIFIC INSTALLATION The subject of draft, draft losses and the proportioning of chimneys is one upon which an entire volume could be written. As a book of this nature does not admit of an exhaustive discussion, we will set forth only the basic principles of theory and modern engineering practice. Most of the formulas for determining chimney sizes are empirical. These generally give satisfactory results provided they are used within the limits of the assumptions upon which they are based, or in other words, one must have definite knowledge applicable to the specific problem. The height and diameter of any chimney is determined by considering: first, the amount of draft required; second, the requisite and economical velocity; and third, the maximum quantity of gas that must pass out ol the chimney. The available draft is equal to the difference in the weight of the cold column of external air and a like 1 column ol hot gas in the chimney minus the loss due to internal friction and the loss due to accelerating the gases. I he height therefore depends upon the available draft required and may be influenced by the diameter. The theoretical draft of a chimney 100 feet high at sea level is given in Table 3, expressed in inches of water. I liese values were calculated from the lormula: MTD = H Where MTD =the maximum theoretical draft H = height in feet Ti=average absolute temperature (° F.) of the flue gases T = absolute temperature (° F.) of outside air. The absolute temperature (° F.) is equal to the temperature reading (° F.) plus 161 F. The formula is based on the fact that the theoretical draft is equal to the difference in the weight of the cold column ol air outside the chimney and the hot column of gas inside the chimney—i. e., the theoretical draft = H (weight per cubic foot of the outside air at the given temperature minus the weight per cubic foot of the flue gas at the given temperature) X0.192; where 0.192 is the constant for converting to inches of water from pounds per square foot. TABLE NO. 3 THEORETICAL DRAFT PRESSURE IX INCHES OF WATER IN A CHIMNEY 100'0" HIGH Temp, in | Temperature of External Air (Barometer 30') Chimney Fahr. 0° 10° 20° 30° 40° 50° 60° 70° 80° 90° 100° 200° .453 .419 . 384 .353 .321 .292 .263 .234 .209 . 182 .157 220° .488 .453 .419 .388 . 355 .326 .298 .269 . 244 .217 . 192 240° .520 .488 .451 .121 . 388 . 359 .330 .301 . 275 . 250 • 225 260° .528 .484 .453 .420 .392 .363 . 334 . 309 .282 . 267 280° .584 .549 .515 .482 .451 . 122 .394 . 365 .340 .313 . 288 300° .611 .541 .511 .478 .419 .420 .392 .367 . 340 . 315 320° .637 .603 . 568 .538 . 505 .476 . 447 .419 .394 . 367 . 342 340° .662 .638 .593 .563 . 530 .501 .472 . 443 .419 .392 . 367 360° .687 .618 .588 . 555 .526 .497 468 .4 44 .417 .392 380° .710 676 .641 .611 .578 .549 .520 . 192 .467 .440 .415 400° .732 .697 662 .632 .598 .570 .541 .513 488 . 461 . 436 420° .718 .684 .653 .620 .591 .563 . 534 . 509 .482 . 457 440° .774 .739 .705 .674 .641 612 .584 . 555 . 530 .503 .478 460° .793 .758 .724 .694 . 660 .632 .603 .574 . 549 .522 . 497 480° .810 .776 .741 .710 .678 .649 .620 .591 . 566 . 540 .515 500° .829 .791 .760 .730 .697 .669 .639 .610 .586 . 559 . 534 .863 .828 .795 .762 .731 .700 .671 . 64 1 .618 . 593 . 585 600° 908 .87.3 .839 .807 .776 .746 .717 .690 . 663 . 638 .613 48 Iii Table 3, for any oilier height of chimney, multiply these values by where II is the height in feet. The weight of gas which will pass up the chimney increases as the temperature of the flue gas increases, but maximum is reached according to Rankin at about 622° F., as at any internal temperature above that, the gas velocity increases less than the density of the gases decreases. In the draft formula the average temperature is used because tests show that the temperature of the gases at the top of the chimney is less than it is at the bottom. The amount of drop in temperature depends upon the dimensions of the chimney, the material of which it is built and the volume of the gases. In tall chimneys of large diameter the drop in temperature is usually less than it is in tall chimneys of small diameter. In unlined steel stacks the drop is greater, especially with low external temperatures. Unfortunately there have not been many tests made to determine actual chimney performance and the engineering profession is in need of further infor¬ mation on this subject. Facilities for observation have been provided by the Custodis Co. at three elevations on the chimney 225' x 11/ 0" constructed in 1 ( >2.> at Cornell University, Ithaca, N. \., on the chimney 175'x 10'0" constructed 1923 at the Oregon Agricultural College, Corvallis, Ore., on the chimney ot the Public Service Co. of Col., Valmont, Col., 350' x 16' 0" built in 1921 and also on the common brick chimney 150'x 7'0" constructed in 1911 at Johns Hopkins Uni¬ versity, Baltimore, Md. Figure 31 gives some results of the observations on the drop in temperature as the gases move upward in Custodis brick chimneys deduced Irom observations by Peabody and Miller and J. C. Smallwood. Height of chimney in feet Fig. 31 Average temperatures of gases in per cent of entering temperature according to height 19 Example I. — To determine the maximum theoretical draft produced by a circular brick chimney 200 feet high at sea level, average temperature of hue gases 600° F., and the outside air temperature 60° F. Atmospheric pressure at sea level = 11.7 pounds per square inch MTD = H (^4r~~ \ T Ti W here T = 60+ 161 =521 Ti =600+461 = 1061 MTD =200 7.61 7.95 \ 521 1061/ MTD =1.134" At atmospheric pressure and an external temperature of 60° F. the values of the expression 7.61 7.95 521 T, have been calculated and tabulated for various Then MTD = HJ internal chinmex temperatures and max be found in Table 1. where J is the table x alue. TABLE I /7.6 I 7.95\ \ alue of ( - 0 j — I for \ arious Internal Temperatures for One Foot of Height Temperature of External Air—60° F. Barometer—11.7 Pounds per Square Inch Temperature in Chimney.. . . . . 200° 220° 210° 260° 280° 300° 320° 340° 360° (7.61 J.97,\ .00263 .00298 f 521 Ti / Temperature in 380° 400° 420° 1 10° 460° 480° 500° 550° 600° 7.95X .00520 .00541 .00563 .0058l j .00603 00639 i 1 521 'l l ) The available draft in a well-designed chimney at the breeching opening may be safely assumed as 80% of the theoretical. A small number of tests on com¬ paratively high chimneys gave results close to this value. The coefficient of friction in masonry chimneys has not been definitely ascertained. In view T of this, the xmlue of ”80%" is probably as nearly correct as the values calculated from the numerous formulas. It is hoped that tests at Cornell University, Oregon State Agricultural College and Johns Hopkins University will give some further light on this subject. The formula then, for maximum available draft, at sea level is MAD =HJX 0.80 Where MAD = maximum available draft The ax ailable draft required is determined by taking draft gauge readings on installations similar to the one proposed. In the event that this is not possible, the proposed installation should be analyzed in the light of past experience and the available draft required estimated. 50 II' the chimney is located near a high hill or building, it may be necessary to increase the height because the wind may decrease the available draft when it blows from the direction of the barrier. The required area is obtained by dividing the volume of gases emitted by the assumed velocity. With the total weight and analysis of the fuel burned and the Hue gas analysis known, the total weight or volume of the Hue gases can be calculated. For ordinary calculations the following velocities have been recommended. They may be safely used for the following quantities of gases without undue friction losses in the chimney or prohibitive cost of construction. Gases, Lbs. per Hr. 3,600. 55,750. 120,900. 2 17,000. 559,000. 1.105,000. Velocity, Ft. per Sec. 10 15 20 25 30 35 CHIMNEY AT ALTITUDES ABOVE SEA LEVEL As the altitude above sea level increases the barometric pressure decreases, or in other words, I lie weight of air per cubic foot is less. There is some difference of opinion as to the correct method for calculating the height of chimney at alti¬ tudes. However, the method commonly used of multiplying the height required at sea level by the ratio of the barometer reading at sea level to the barometer reading at altitude has given good results. The number of pounds of air required to burn a pound of any given fuel is the same, regardless of the altitude. Therefore it is obvious that the volume of air furnished for combustion and I he resultant volume of Hue gas must increase as the barometric pressure decreases. It is evident that w hen the height of I he chimney and volume of gas are increased, the friction loss is increased. In order that the same draft may si ill be available as at sea level, it will be necessary to increase the diameter proportionately. Reliable authorities state that the diameter should vary as the two-fifths power of the ratio of the barometer reading at sea level to the barometer reading at altitude. Table 5 has been compiled, giving the barometric pressure at different eleva¬ tions, the ratio of the pressures and the value of the two-fifths power of the ratio. It is observed that the drop in barometric pressure affects the height very much more than the diameter. Up to the altitude of 2,500' or 3,000', though the height should be increased, no increase of diameter is necessary for practical purposes. Where the altitudes are unusually high, the available draft required is reduced by changing the plant design, lowering the combustion rate and increasing the size of tire flues. If this were not done, a very large chimney would be required to give the desired results. TABLE 5 CHIMNEYS AT ALTITUDES ABOVE SEA LEVEL Correction Factors Altitude in Feet Above Sea Level Barometer Beading in Inches R Relative Gas Volume R 2/5 Ratio Chimney Diameters Altitude in Feet Above Sea Level Barometer Reading in Inches R Relative Gas Volume R 2/5 Ratio Chimney Diameters 0 30.00 1.000 1 000 4,500 25.45 1.180 1 068 500 20,46 1.019 1 008 5,000 21 98 1.201 1 076 1,000 28 92 1.037 1 015 5,500 24.53 1.224 1 084 1,500 28 40 1.057 1 023 6,000 24 08 l 246 1 092 2,000 27.88 1.076 1 .030 6,500 23.65 1.269 1 100 2,500 27.38 1.006 1 , 038 7,000 23.22 1.292 1 108 3,000 26.88 1,116 1 045 8,000 22.38 1.340 1 124 3,500 20.10 1.137 1.053 9,000 21 .58 1.390 1 111 4.000 25 01 1.158 1 060 1 0.000 20 80 1 442 1 158 Example II. —To determine the size of chimney required at an elevation of 6500, assuming that a given installation requires a chimney 180' x 7' 6" at sea level and the available draft required is the same. Normal barometer at sea level =30.000 Barometer at 6500' =23.65 Ratio between the pressures R = 1.269 Height of chimney = 180 X 1.269 =228 feet. The two-fifths power of ratio of the two pressures = 1.100. Diameter of chimney =7.5 X 1.100 =8' 3" Hence a chimney 228'x8' 3" is required. At 2000' altitude the chimney height would be 180x1.076 = 194 feet, with practically no change in diameter necessary. The fuels generally used in the United States are coal, oil and wood. Coals are classilied in several ways, but for the purposes of this article they can be designated as anthracite, semi-bituminous, bituminous, and lignite. Anthracite coal contains approximately 92% fixed carbon and 6% volatile matter and has an approximate heat value of 15,000 R. t. u. per pound of com¬ bustible. Anthracite coal is in great demand for domestic purposes and only the smaller sizes are available for industrial uses. Some form of forced draft is ordi¬ narily used to burn the line sizes of anthracite coal now available. Semi-bituminous coal contains approximately 79% fixed carbon, 2'2y 2 c / 0 volatile matter, and has a heat a alue of approximately 1 4,000 R. t. u. per pound of combustible. Bituminous coal varies widely in composition, ranging from 45% to 70% fixed carbon and 25% to 50% volatile matter. It has a heat value ranging from 9,000 B. t. u. to 14,500 B. t. u. per pound of combustible. It does not stand handling v r ell and the fine sizes or slack frequently have to be burned. If so, ample draft should be provided. Lignite coal also has a varying composition ranging from 25% to 35% fixed carbon and 27% to 32% volatile matter. It lias a heat value ranging around 12,500 B. t. u. [KT pound of combustible. Lignite coni contains a large amount ol moisture and is likely to air slack. Coal is burned upon hand lired grates, in stokers and in the pulverized form. The quantity of air theoretically required for combustion is practically constant in the ratio of 7.6 pounds of air per 10,000 B. t. u. However, the percentage of excess air required increases rapidly as the quality of the coal decreases, except in the case of pulverized coal. The percentage of excess air required for pulverized coal is very low, as the combustion is readily completed. The heat value of commercial fuel oil ranges from 17,500 B. t. u. to 19,000 B. t. u. per pound, and that of crude oil ranges up as high as 22,000 B. t. u. Crude oil is seldom used, as it is much more expensive. The oil burners atomize the oil into a very finely divided spray, consequently only a small per cent of excess air is required. The quantity of air theoretically required for combustion varies with the amount of hydrogen in the fuel. Approximately 14 pounds of air per pound of oil are required for this purpose. Wood shavings, sawdust, tan bark and bagasse are by-products having varying heat values depending upon their origin. In the average plant burning by-product fuels the calculation of the volumes of resultant gases to a fine degree of accuracy is hardly possible. The fuel has no commercial value; as a result no great attempt is made to operate efficiently. This means widely fluctuating excess air percentages. In addition to this the quality of fuel varies widely from time to time in the same plant. The determining of the volumes of resultant gases is, therefore, largely a matter of experience with the peculiar conditions under consideration. The various kinds of by-product fuel are generally burned in extension furnaces provided with large combustion space and plenty of heated brickwork to radiate heat to the fuel bed and evaporate the moisture. The ordinary practice is to allow the fuel to pile up in cones three to six feet high. One very successful furnace employs forced draft under the grates. CHIMNEYS IN CONNECTION WITH STEAM BOILER PLANTS BURNING COAL The accuracy of formulas to determine stack sizes for boiler plants evolved by early authorities depended mainly upon the value of certain constants. The fixing of proper values for these constants with any degree of accuracy is almost an impossibility. Consequently it has not been found practical to apply them generally to chimney design. For this reason many engineers have resorted to rule of thumb with results not entirely unsatisfactory, yet they may err one way or the other. The well-known and generally accepted formulas of W m. Rent, frequently applied, accord well with the good results of actual practice, particularly when overloads are not high. The dimensions of a chimney should not be taken from a table or calculated from a formula and be accepted as final without computing the size on a maximum gas basis and total draft loss basis, using the method previously discussed. Yet it is helpful and interesting to compare a tabulated 11. P. size with one computed on the above-mentioned basis. The formulas of Wm. Kent applied to the determination of the chimney area, horse-power and height are based upon the following assumptions: 1. The draft power of the chimney varies as the square root of the height. 2. The retardation due to friction between the ascending smoke stream and the chimney walls is taken care of on the assumption that there is a layer of gas two inches thick against the walls which has zero velocity. 3. The power varies directly as the effective area. So H. P. =3.33 Evil, H = f °' 3 W here A = total area in square feet, horse-power, II = height in feet. The coefficient 0.6 may be used for the case of the latter the diameter of the From these formulas Tables 6, 7 and ne\ s, w ere computed. P-Y E- — — R \ II F =effecti\ e area in , E = A-0.6vA square feet, H. P. = both square and round chimneys, and in actual section. 8. giving the boiler horse-power of chim- TABLE6 SIZES OF CHIMNEYS FOR STEAM BOILERS Calculated by Mr. W in. R. Kent, From His Formulae Given on Page 51, Assuming 5 Lbs. Coal Required Per Boiler Horse-Power Hour Diarn.. Inches Area, Sq. Ft. Effect. Area HE IGHT OF CHIMNEY Equiv. Square Chimney Side, Inches 50' , 60' 70' 80' 90' 100' 110' 125' 150' 175' 200' 225' 250' 275' .300' COMMERCIAL HORSE POWER OK BOILE RS 30 4.91 3.58 84 | 92 100 107 113 119 27 33 5 94 4 48 1 15 125 133 141 149 30 36 7 07 141 152 163 173 182 191 204 32 39 8 30 183 196 208 219 229 245 35 42 9 62 7.76 216 231 245 258 271 289 316 38 48 12 57 10 44 311 330 348 365 389 126 43 54 15 90 13.51 127 449 472 503 595 48 60 19 64 16 98 565 593 632 692 748 54 23.76 20.83 694 728 776 849 918 981 59 28 27 25 08 835 876 934 1023 1105 1181 1253 64 78 33.18 29.73 10.38 1107 1212 1.310 1400 1485 1565 . 70 84 38 48 34.76 1211 1294 1418 15.31 16.77 17.36 1830 1919 2005 75 90 44 18 40.19 1496 16.39 1770 189.3 2008 21 16 2219 2318 80 96 50.27 46 01 1713 1876 2027 2167 2298 242.3 2511 2654 86 102 56.75 52.23 1944 21.70 2300 2459 2609 2750 2884 .7012 91 108 63.62 58.83 2190 2392 2592 2770 2939 .3098 .3249 .7.39.7 96 111 70 88 65 83 2685 2900 3100 .3288 .3466 3635 3797 101 120 78.54 73.22 2986 3226 .3448 .3657 .7855 4043 4223 107 132 95 03 89 18 36.37 .3929 4200 4455 4696 4925 5144 117 144 113.10 106.72 4352 4701 5026 53.31 5618 589.3 6155 128 132 72 125 82 5542 5925 6621 6948 7256 138 168 153.94 146.50 6454 6899 7.318 7713 8090 8449 149 180 176.71 168.74 74.33 7916 8429 8884 9.318 97.32 160 192 201 06 192.56 9068 9619 101.38 10633 1 1105 170 204 226.98 217 94 10263 10885 1 1 175 12035 12569 181 216 254 47 244 90 12233 L2891 135 ’ 5 14123 191 228 283 53 273.53 1 1396 15099 15768 202 240 31 1 16 303.53 16761 17505 213 51 T\BLE 7 SIZES OF CI11\INE\ S FOR STEWI ROIEERS Calculated !• rom M r. \\ m R. Kent’s'Table, Assuming 1 00 Lbs. Coal R ■quired ’er Boil er Horse-Power 1 lour I )iam., Area (A). HEI(BIT OF CHIMNEY Equi v. Sq. Chi in. 50' 60' 70' 80' 90' 100' 110' 125' 150' 175' 200' 225' 250' 300' S(|. 1 1. HORSE-POWER—3.25 A V ii Side, In. 18 1.77 42 46 19 52 16" 21 2.41 55 02 65 68 19" 24 3.14 72 78 85 91 98 22' 27 3 98 91 mi tor 111 124 24' 30 4.91 114 124 133 143 153 159 27' 33 5.94 1 19 163 172 182 192 202 30' 36 7.07 179 192 205 218 228 211 257 32' 39 8 30 224 241 257 270 283 302 35' 42 9.62 263 282 296 312 332 351 390 39' 48 12 57 304 387 no 129 458 510 43' 54 15.90 491 517 543 579 647 683 48' 60 19.64 605 637 669 715 797 845 54' 66 23 70 774 809 865 965 1021 1092 59' 72 28.27 920 962 1051 1 l 17 1215 1300 1378 61' 78 33 18 11 3 1 1206 1349 1459 1524 1 0 1 9 1 706 70' 81 38 48 1310 1 till 1563 1654 1768 1 875 1976 2H>5 i 5' 90 44 18 1609 1 794 1 898 2031 2155 2269 2186 80' 96 50 27 1830 2041 2101 2311 2451 2584 2831 86' 102 56 75 2067 2304 2434 2607 2766 2915 3195 91' 108 63 62 2314 2584 2734 2925 3101 3269 3578 96' 114 70 88 2879 3045 3257 3455 30 43 3901 101' 120 78.54 3191 3374 361 1 3829 4037 4420 107' 132 95.03 3861 4082 4368 46.31 1882 5350 117" 144 113 11) 4596 4859 5200 5515 58 1 1 6367 128" The formulas and tables of Win. Kent just discussed are based in part upon the results obtained in a large number of power plants. For comparatively small installations operated at moderate ratings, they are sufficiently accurate for layouts and estimates. Mr. Kent himself states that the tables give the boiler horse-power the chimney will serve only when the draft losses are not excessive. To determine the required height, the loss of draft must be ascertained, due to all causes, from the ashpit to the point where the flue enters the chimney. TABLE 8 SIZES OF CHIMNEYS FOR STEAM BOILERS Calculated From Mr. Wm. IL Kent’s Table, Assuming 3.86 Lbs. Coal Required Per Boiler Horse-Power Hour Diana., Inches Area, Sq. Ft. HEIGHT OF CHIMNEY Equiv. Square Chimney Side, Inches Effect. Area 50 ' 60' 70' 80' 90' 100' 110' 125' 150' 175' 200' 225' 250' 275' 300' COMMERCIAL HORSE-POWER OF BOILERS 30 4.91 3.58 109 119 130 139 146 154 27 33 5.94 4.48 149 162 172 183 193 202 30 36 7.07 5.47 183 197 211 224 236 217 264 32 39 8 30 6.57 237 254 269 281 296 317 35 42 9.62 7.76 280 300 317 334 351 374 409 38 48 12.57 10.44 403 427 150 472 501 43 54 15.90 13.51 553 582 01 1 651 715 770 18 60 19.64 16.98 695 732 768 820 896 97(1 54 66 23.76 20.83 900 913 I 005 1 099 1188 1270 59 28.27 25.08 1080 11.35 1209 1325 1 131) 1530 1623 61 78 3.3. 18 29.73 1342 1433 1570 1698 1811 L924 2025 70 81 38.48 34.76 1571 1678 1835 1984 2120 2246 2370 2 is i 2600 75 90 44.18 40 19 1940 2120 2292 2151 2600 2710 2870 3000 80 96 50.27 46 01 2220 2 130 2625 2805 2975 31 10 3300 3 110 86 102 52 23 2520 2760 2980 3180 3380 3561 3710 3900 91 108 63.02 58 83 2810 3100 3360 3585 3800 4010 1210 1 100 96 114 70.88 65.83 3 180 3760 4012 4260 1 190 4710 1920 101 120 78 54 73.22 3870 1220 1 160 1730 1990 5240 5180 107 132 95 03 89.18 ITOil 5090 6 140 5775 6075 6 180 6650 117 144 1 13 10 100.72 5650 6100 6520 6900 7280 7625 7 1 »7 128 156 1.32.73 125.82 7170 7675 8110 8590 9000 9 100 138 108 153.94 1 to 50 8360 8925 9480 11)000 In 17ii l 0920 1 19 180 176.71 108.71 9630 10280 10920 11500 12060 12600 160 192 201.06 192.56 117 10 12450 13130 13790 1 1100 170 201 226 98 217.94 13290 1 l LOO 1 1850 1 '.(.ini 16280 131 216 254.47 24 l.90 15850 L6700 17500 18 100 191 228 283 53 273 53 18650 L9550 20 100 202 240 311 16 303.53 21700 22650 213 The maximum available draft required for a given installation may be expressed by the formula 55 MAD = LG+LI+LB +LF + LT +LE, L, etc. W here MAD = maximum available draft required. LG =the loss through the fuel bed necessary to produce the required rate of combustion. L I = the loss to provide furnace vacuum, etc. LB=the loss through the boiler at the rating assumed as the maximum required. LF=the loss through tlie Hue. LT =the loss due to the turns or bends in the path of the smoke stream after leaving the boiler. LE = tlie loss through the economizer if used. L, etc. =the loss through any other apparatus in the path of the gases* such as settling chambers, baffles, super-heaters, etc. The draft loss in the flue or breeching depends upon its length, its cross section, the material it is built of and the number of bends. The smoother the inside of the flue, the straighter it is, the nearer it approaches to a circle in cross section, the less the loss at a given gas velocity. Sharp right angle bends, sudden changes in area or shape of section, are to be avoided and all changes of direction made easily. If the chimney can lie placed in the geographical center of the batteries of boilers, minimum lengths of flues are generally obtained. As a general rule in steel Hues of circular section there will be a loss of 0.10 of an inch per 100 feet of length with normal gas velocities. Each right angle bend represents a loss of 0.05 of an inch. If the flues are square or rectangular there will be an average additional loss ranging up to 25%. The loss increases as the ratio of height to width increases. If the flues are built of masonry there will be a further loss unless the walls are smooth. Hdie loss of draft through the boiler itself, i. e., from the top of the fire to the point where the gases leave the boiler and enter the flues, depends upon a number of factors and varies widely. The factors are—the size and type, the number of tubes and the way they are set, the type of grate, the method of baffling, and rating at which the boilers are operated. This loss may vary from 0.15" to 0.25" at rating, to 0.80" or 0.85" for a maximum of 250% or more rating. It is advisable for the engineer to cooperate with the boiler manufacturer in determining the loss of draft to be assumed through the particular type and setting of boiler at maximum rating required. With natural draft stokers and hand fired furnaces there is an additional loss through the fuel bed, dependent upon its thickness, the kind of fuel and the type of grate. There is a certain draft over the fuel bed that will give the best results for every combustion rate and kind of fuel. Again, it is advisable for the engineer to cooperate with the boiler and stoker manufacturer in determining the loss of draft to be assumed through the fuel in order to produce the best results from a specific fuel and type of boiler fired at the desired ratings. 56 With Ihe forced draft type of stoker the re([iiireineirt is somewhat different, for Ihe reason that the air is forced through the fuel bed by fans, relieving the chimney of this duty. It is considered good practice to allow 0.05 inch to 0.15 inch draft over the lire in all forced draft installations to prevent Ihe formation of positive pressures in Ihe furnace. If this allowance is not made, there is a possibility of overheating the furnaces and fronts; also there is the possibility of objectionable gases being forced out into the boiler room. If economizers are used betw een the boilers and chimney there is an additional loss in draft, due to friction through the economizer. This friction loss varies within wide limits, depending upon the type of econ¬ omizer, the number of tubes, the length and the velocity of the gases passing between the tubes. The efficiency of the economizer is dependent upon the gas velocity. The economizer reduces the temperature of the flue gases. This reduces materially the available draft, or in other words affects the required height of chimney. With low r stack temperatures and economizers, to depend upon natural draft alone would require a ridiculously high chimney, especially with a fine grade of coal and boilers operated at high ratings. In this case the best modern practice in isolated plants, w here overloads from 200% to 250% or more are contemplated, is to provide a chimney of ample height and diameter to operate the boilers when the economizers are cut out; then to provide induced draft fans to furnish the additional draft needed with the economizers in service. Mistakes have been made in the past by trying to reduce the chimney heights in such cases. This resulted in the sluggish movement of gases through the boilers and economizers, with inefficient and incomplete burning of the coal and disappointing results as to capacity. Therefore, to meet heavy peak loads with economizers the chimney should be of ample height supplemented with induced draft fans to overcome all Ihe pre¬ viously cited losses, so that there is a constant flow of gases from ashpit to chimney. W here many boilers are connected to one chimney the temperature and quantity of' flue gas depends upon the number of boilers in service and the ratings at which they are operated. Therefore the available draft varies. Accordingly w hen a few boilers are operated at high ratings to carry t he over¬ load the flue gas temperatures are higher and the available draft is increased. On the other hand, operating a majority of the boilers at low ratings decreases the temperatures and the draft falls off. The varied conditions expected should be studied to determine the proper size of chimney and whether more than one chimney should be installed. The economy and efficiency of operation during the life of the plant, rather than first cost, should be given due weight in making this decision. It may be that property limits will restrict the available space so that there is only one solution of the problem. Radial 1 trick chimneys ranging from 275 feet to 350 feet high, with diameters in proportion, are economically and successfully operated in many large power plants. It will he noted we have assumed an outside air temperature of 60° F. in making the draft calculations. In northern climates, for months, the temperatures are often below freezing and there are periods when the temperatures are far below 0° F., while in summer the temperature may be above 90° F. The available draft is greater in winter and may vary 75% throughout the year. In selecting a chimney size due allowance should be made for the most adverse atmospheric conditions. These occur when the outside air temperatures are highest and the barometer low est. When designing a chimney to serve a heating plant located in northern lati¬ tudes it is customary to assume that the temperature of the outside air will be somewhat less than 60° F. However, it is wise to be conservative in reducing stack heights and to recommend ample dimensions w here there is any doubt. The boiler cannot lie operated efficiently or at high ratings unless the chimney is properly proportioned. Many power plant ow ners have saved thousands of dollars and avoided embarrassment by having ample stack height and capacity. It is impossible to predict the quality of coal which can be secured at all times or when a stoker or boiler w ill require repairs or overhauling. There is a reserve in every unit of a well-designed power plant, its stokers, its boilers, its pumps, its engines or turbines, and that principle should be carried straight through to the chimney. If not, the reserves back of the chimney will fall short of their purpose. Each installation is a study of ils own. The important problem is the deter¬ mination of the available draft required at the point where the flue enters the chimney, giving careful consideration to the draft losses through all the equipment. Practical experience, good judgment and a study of the equipment are required for each installation and no one can lay down fixed rules to apply to all cases. The diameter of the chimney is determined on a gas basis as previously described. CHIMNEYS IN CONNECTION WITH STEAM BOILER PLANTS BURNING OIL The sizes of chimney to be used where fuel oil is burned are determined in the same w ay as w hen coal is used as fuel. For several reasons calculations will result in a chimney of less height and smaller diameter. There is no fuel bed loss; in fact some types of burners have a certain forced draft action. Less weight of air per horse-pow er is required; consequently, the pressure drop through the boiler and fines is less than when coal is burned. Some reduction in 53 the height of the chimney is, therefore, permissible, but it should be borne in mind that the flue gas temperatures are lower when oil is burned. I bus reducing the available draft. The height should be sufficient to furnish the draft required at peak loads and no more. This is much more important in the burning of oil than in the burning of coal. In the lat ter case there is little or no danger of too much draft. In the former great loss in economy may result from excessive draft during the periods of light load. This is especially true in plant operating a\ i11 1 a fluctuating boiler load. Automatic control does much to eliminate this evil. It permits the proper height to be used without undue losses. This is as it should be. Always determine the height of chimney for maximum boiler requirements. Several authorities state that good results are obtained by reducing the area from 35 to 45% below that required for coal burning. This is merely an arbitrary assumption. Such a method is not recommended. The diameter is dependent entirely upon the volume of gases to be moved at a given velocity. This volume is dependent upon the calorific value, the composition, and amount of the oil burned, together with the percentage of excess air. Some boiler manufacturers give tables of chimney sizes suitable for various oil-fired boiler plants. They are useful only as a check after the size has been determined by method previously described. In proportioning chimneys for oil-fired furnaces, consideration should be given to the possibility of having to turn to coal for fuel, due to scarcity and high price of oil. CHIMNEYS IN CONNECTION WITH STEAM BOILER PLANTS BURNING WOOD REFUSE AND OTHER BY-PRODUCTS FUELS The determination of sizes of chimney used for steam boiler plants with these fuels is more a matter of experience than of calculation, for the data is very meager concerning the performances of boilers burning them. This applies particularly to the determination of the diameter. The height, however, admits of a more exact determination by calculating the pressure drops. However, it should be borne in mind that with wood refuse these are likely to be considerably higher than they are in t he case of coal or oil on account of the abnormal quantities of excess air passing. Also, as is always the case w hen the percentage of excess air is high, the flue gas temperatures are much higher than they are with coal or oil and this should be borne in mind when making draft calculations. The loss through the lire is generally less with by-product fuels than it is with coal, because most of the combustion is surface combustion. However, the determination is largely a matter of experience. Example 111. Determine the height and diameter of a circular masonry chimney for the following conditions: \\ ater tube boilers, hand fired, builder's rating 1500 H. P., burning Virginia semi-bituminous coal, calorific value 13.000 B. t. u., boiler rated at 10 sq. ft. heating surface, ratio of heating surface to grate surface 50 to 1, length of circular steel breeching 40 feet, 2 right-angle bends, outside air 60° F., average internal stack temperatures 560° F.. location sea level, boilers operated at a maximum of 150% of rating. W ith this equipment, a combined efliciencx of 65% may reasonably be assumed, f nit of evaporation =972 B. t. u. One boiler H. P. is equivalent to 34.5x972=33,534 B. t. u. 33 53 j Pounds of coal burned per boiler horse power hour - ! =3.97 1 1 13,000x0.65 Boiler H. P. developed 1500x1.5 =2250 1500x10 Square leet ol grate surface -—-= 300 1 & 50 Total pounds coal burned per hour 2250x3.97 =8933 Pounds of coal burned per square foot grate surface =29.78 Summing the draft losses up, we have Loss through lires and grates.0.40" Loss through boiler, depending upon type and setting.0.45" Loss in steel flue circular section 70'— 0.10 per 100'.0.07" Loss in two right angle turns.0.10" Total.X02 77 , 1.02 1 heoretical draft required — _ =1.275 inches 1 .80 . ... / 7.64 7.94\ H = 187 feet. To determine the diameter. Our assumption was that Virginia semi- bituminous coal was to be burned. Pounds air required per 10,000 B. t.u. (U. S. Bureau of Mines) =7.6. Pounds of air per pound of coal = 7.6 | ^——0=9.88. Assume an allowance for excess air of 90% to provide against possible holes 60 in fire, defective sellings, leakage and adverse conditions, giving 19 pounds of air per pound of coal. The total weight of coal burned per hour =8933 pounds. The total weight of flue gas per hour = 20.0 X 8933 = 178,660. Weight of Hue gas per second =19.5 pounds. Density of gases at 580° F. (see Fig. No. 2) =0.0410 pounds per cubic foot. 49.5 Total volume ol flue gases per second = — = 1208 cubic feet. Assume that the economical velocity is 22.5 feet per second. 1208 I he minimum effective area required = =53.7 square feet. 22.o The minimum diameter required =8' 3". On the assumed premises select a chimney 187' 0"x8' 3". 00 200 300 400 500 600 700 800 900 Temperature Deg. Fahr. Fig. 32 Weight of flue gas per cubic foot at various temperatures Referring to table No. 8, which is based upon the assumption that 3.86 pounds of coal are burned per boiler horse-power hour, it is seen that there are several chimney sizes given as capable of serving 1500 rated boiler horse-power. If any of the chimney sizes were selected which had a height appreciably less than 187 feet it would be impossible to operate the boiler at 150% of rating, and if the height were appreciably more than 187 feet the chimney would not be of the most economical dimensions for this particular case. It is, therefore, evident that the only safe method to employ is to compute the height and diameter in accordance with the principles laid down in the sample problems heretofore given and to ignore all tables and formulas. Example IV. Assume the same conditions as before except that the boilers are operated at 200% of rating with forced draft stokers. Determine the height and diameter of the required chimney. 61 The draft required through the fuel bed is taken care of by the fans with forced draft stokers. The volume of gas formed per second will increase as the horse-power developed increases. Consequently the draft loss through the boiler increases. Summing up the draft losses we have: Initial draft over fires for furnace, vacuum, etc. 0.10 Loss through boiler at 200% rating, depending upon type of boiler settings, baffling, etc. 0.70 Loss through flue (as before). 0.07 Loss in two right angle bends. 0.10 Total. 0.97 Theoretical draft required .97 .80 1.21 inches. \t 200% of rating assume the average temperature in the chimney to be 580° F. with outside air 60° F. 1.21 11 11 = 173 feet. An assumption of a combined efficiency of 70% is reasonable. Pounds of coal burned per boiler 11. P. per hour = 1 1 13.000X.70 = 3.68. Boiler H. P. developed = 1500x2 =3000. Pounds of coal burned per hour = 3000x3.68 = 11,010. With forced draft stokers it is usualh safe to assume 18 pounds of air per pound of coal burned. Total weight of flue gas per hour = 19x11.0 10 = 209,760 pounds. Weight of flue gas per second =58.3 pounds. Density of gases at 580° F. (see Fig. 32) =.010. Total volume of gases per second 58 .3 .04 = 1157 5 cubic feet. Assume that the economical velocity is 21 feet per second. rhe minimum effective area required 1457.5 21 = 60.8 square feet. The minimum diameter required =8' 10". On the assumed premises select a chimney 173'X8' 10". The height is less, as it is not necessary for the chimney to furnish the draft for drawing the air through the fuel bed. The draft loss through the boiler plus the draft loss for furnace vacuum is less than the loss was through the boiler and grates in the case of hand firing. 62 The height of chimney calculated in the examples is the net height, or that measured above the boiler damper. If the breeching is level, the height will, of course, be measured from t lie point where the breeching enters the chimney. The total height of the chimney will be the net height plus the distance from the datum point to the top of the chimney foundation. Chapter IV CALCULATION OF STRESSES IN CHIMNEYS We have set forth in the previous chapter the principles for determining the height and diameter of a chimney for a specific installation. The laws of Mechanics determine the structural design, due consideration being given to securing the most economical stable structure that will resist the action of the wind, weather and internal gases. Many engineers and architects prefer to leave the design of the chimney to the chimney company. For the benefit of those who desire to prepare their own plans and specifications the following is a brief resume of the principles involved and methods employed. Let us consider the chimney shown in Fig. 33, with no wind blowing. In any horizontal section of the chimney the dead w eight of the superincumbent portion is uniformly distributed over the bearing walls and therefore the pressure on each horizontal unit of area in the section is the same, that is to say the “fiber stress " in the brickwork is a uniform compression. \\ hen a wind of a given velocity blows against the chimney it exerts a certain force (pressure) on the windward side. Assume for the present that the intensity of this force is uniform from the top to the bottom. The force created by the wind tends to push the shaft over iu the direction of the wind. As a consequence, the intensity of the compression on any hori¬ zontal section due to the dead weight of the superincumbent portion is increased on the lee side and decreased on the w indward side. The decrease may be larger than the pre¬ existent intensity, in which case the net result will be a tensile stress. We then have a structure supported at one end. acted upon by r two forces: one, the dead weight applied along its longitudinal axis, the other, the wind load applied perpen¬ dicularly to that axis. From the above description it is evident that the well-known cantilever beam formulas apply provided the material is not stressed beyond its elastic limit. Notation.—I n the following let A = area of horizontal section under consideration in square feet; 63 G= weight of brickwork of superincumbent portion of chimney in tons; W=wind pressure on that portion in tons; L = distance from section to resultant of wind pressure in feet; M = bending moment at the section in foot tons; S' = intensity of stress at lee side in tons per square foot; S" = intensity of stress at windward side in tons per square foot; P= intensity of wind pressure in pounds per square foot of projected area; a = distance from the center of the section to where the resultant of the weight and wind pressure cuts the section, “eccentric distance”; 1 = second moment (moment of inertia) of area of section about an axis through the center and normal to the direction of the wind. In the case of a circular chimney let Di=outside diameter at top of chimney in feet; 1) = outside diameter at section in feet; R = outside radius at section in feet; r= inside radius at section in feet; II = height of superincumbent section in feet; then D + Di PH 2 2000 (1) D +2Di H D+Di 3 (2) M = \\ L = bending moment. (3) Applying the cantilever beam formulae, we obtain: Also S' = S" = w g” G MR A + ^~ (4) G MR (5) A 1 a M L ° r ” = G (6) If we assign values for allowable tension and compression we can proceed with the structural design. The strength of masonry in tension is low compared with its strength in compression. The strength in tension may be reduced to almost zero through poor workmanship. To design masonry structures other than chimneys without tension does not greatly increase the total cost, and specifications generally do not permit tension in such masonry. In chimney construction, the cost may be greatly increased by designing to eliminate all tension. We will, therefore, investigate further on the assumption that tension may safely exist within certain limits with the object of producing the most economical stable design. The “fiber stress” is considered to be a uniformly varying stress and in Ihe case of a uniformly varying stress we learn in Mechanics that: (1) The average unit stress tor any portion of the section equals the unit stress at the centroid (center of gravity) of that portion; and (2) The total force is equal to the product of the average unit stress and the area of the portion of the section; or (3) The total force is equal to the product of the lirst moment of the area of the portion of the section and the intensity of the stressat a units distance from the neutral axis; and (1) Idie resultant of the stress on any portion of the section has its point of application at a distance from the neutral axis equal to the ratio of the second moment of the portion of the section about the neutral axis to the first moment of the portion of the section about the same axis. The following principles in Mechanics will also be used: (5) I he first moment of an area about an axis in its plane is equal to the product of the area and the distance from the axis to the centroid of the area. (6) ddie second moment of an area about an axis in its plane is equal to the second moment of the area about a parallel axis through the centroid of the area increased by the product of the area and the square of the distance between the axes, or mathematically expressed In = I <7 Tl 2 A in which l n = the second moment of the area about the required axis. h/ = the second moment of the area about a parallel axis through the centroid of the area; I =the distance between the axes; A = area under consideration. Note. — The mathematical development of the foregoing principles is as follows: Let \ = F = / = f- x F = r/A = X = I hen in = F = area under consideration; total force acting on area; the intensity of stress at a unit's distance from the neutral axis; average unit stress; the distance of the point of application of the resultant of the total force to the neutral axis; differential element of area parallel to the neutral axis; distance from neutral axis to differential element of area; f xdA = first moment of area about neutral axis; f xd A _ B =l A A =ffxd\- .fxA A the distance of the centroid of the area from the neutral axis; fxA=fm (Principle 3). =fx (Principle 1). By comparing F =fx A with / =fx we have F =/A (Principle 2). By principle of moments Jr/J xdA =/j x-dA or _ I x F = — (Principle 1), m where I = j x-dA, the second moment of the area about the neutral axis. c . m Since x = ir m = xA 65 W1 len there is no wind blowing (see Fig. 34) S' =S" = S 0 = — (7) Direction ofWiad "f So 25c Fig. 34. Stress Distribution, no wind blowing—Neu¬ tral Axis at Infinity. Fig. 35. Stress Distribution, wind blowing—Neu¬ tral Axis Tangent to Section. Fig. 36. Stress Distribution, wind blowing—Neu¬ tral Axis through Cen¬ ter of Section. G Suppose now that the wind pressure is such that S" =0 and S' =2 — =2S 0 in which case the neutral axis will be tangent to the section as shown in Fig. 35. Let the value of a under these conditions be designated by k, then from principles 4 and 6 we have k + R = which reduces to k = or I =kRA. (8) o • f c.\ M 1 , , , M By equation (6) a = ~~ but a =k, hence k = — . G G Equating, w e have I M RA G The value of k obtained under these conditions will be referred to as the radius of the first kern. If now we place M=aG from equation (6) and I=kRA from equation (8) in equations (4) and (5) we obtain (9) ( 10 ) 66 A necessary condition to prevent overturning is that the resultant of the forces of the wind and weight must fall within the base; therefore, the fact that tension exists does not of necessity indicate that the structure is unstable. On the above principle it may be concluded that the two prime requisites for stability in a chimney are: (1) The resultant must fall well within the base. It is arbitrarily assumed that the resultant must fall inside an area such that there is no tension beyond an axis through the center of the section normal to the wind, that is to say that the leeward half of the section will be under compression and that there will be no stress on the w indw ard half. (2) The maximum compression must not exceed the safe limit of the masonry. The radius of the area described under requisite (1) we will refer to as the radius of the second kern and designate same by e. This condition is shown in Fig. 36; the neutral axis passes through the center of the section, and the shaded area represents the area under compression. In this case we have, applying principle 4, m W here m is the first moment of the shaded area about the neutral axis NN. .. . , ^ S'm , RG By principle 3, G = or S comparing with equation (11) / _ Ill (12) 2eRG (13) S' I substituting I = kRA from equation (8) in equation (13) 2e G e we obtain S' = — -= 2S 0 — • k A k (14) It now remains to show how r to determine the value of a for positions of the neutral axis intermediate to those shown in Figs. 35 and 36. Deflection of Resultant Fig. 37 Value of Stress for Various Positions of the Resultant 07 In Fig. 37 the horizontal axis represents the various positions of the resultant (in terms of a \\ ), and the vertical axis through point 0 the corresponding unit stresses. A\ hen the deflection of the resultant is zero there is no wind pressure acting and the unit compressive strength is S 0 . Plotting this value the point F is obtained. When the deflection of the resultant is equal to k, the radius of the first kern, there is no tension and the unit compressive stress at the lee side is 2S 0 . Plotting this value we obtain the point B. The straight lines FBC and FB'C' may now be drawn. The line FBC will then represent equation (9), the unit stress on the lee side, and the line F'B'C' equation (10), the unit stress on the windward side after replacing a a k by in these equations, k 1 B For values of a > k or when the distance of the point of application of the resultant from the center is greater than the radius of the first kern, S" becomes negative, indicating tensile stress on the windward side; hence, in accordance with our previous assumption that the tensile stress no longer exists, the compressive stress S' must be increased by some definite amount for each position of the resultant beyond the first kern. This assumption will produce a new curve start¬ ing at 1:» and passing through II. which point is determined by equation (14) and which will lie on the straight line OBH. The equation of the curve BHQ is closely approximated by the equation between k and e. by means of which S'" can be found for values of a FOUNDATIONS In making calculations for the maximum compression on the soil in foundation designs it is assumed that the compression varies in accordance with the straight line law. It is good practice to provide sufficient weight in the foundation and chimney to eliminate any tendency for the windward toe to lift. The cantilever formula is then applicable. Soil pressure G A ± M V where G = total dead weight above bottom of foundation: A = area of bottom of foundation; V = section modulus of bottom of foundation; M = bending moment at the foot of the foundation. If the tension in the outstanding cantilever portion of the foundation exceeds sixty pounds per square inch, reinforcement is necessary. The foundation is generally considered as being similar to a column looting. I lie outstanding cantilever portion of the base is acted upon by the upward earth pressure so that tension exists on the lower side, while the remainder may be con¬ sidered as a fixed plate with tension on the upper side. It is customary to de¬ termine the bending moment per unit of width and calculate the amount of steel required in accordance with the formula given below. In making these calcula¬ tions, account should be taken of the fact that the soil pressure does not vary uniformly. M =jdA s s where d = distance from the compressive face to the plane of the steel; M = resisting moment as determined by steel; j = constant which may be taken as 0.875; A s = area of cross-section of steel; (Note. — For octagons use 55% of computed value) s=unit fiber stress in steel. I he shearing stresses should also be examined to see that they are within safe limits. The punching shearing stress is equal to the total upward soil pressure on the area under consideration, divided by the shearing area of the foundation. Foundations supported on piles are treated in accordance with the general cantilever formula, except that the second moment for a system of piles is found in accordance with the principle stated on page 65. Foundations supported on piles having large bearing power should have the reinforcing designed to take care of both the circumferential and radial bending moments. Before proceeding with design and static calculations it is necessary to assign certain values, such as the values of wind pressure, stresses allowable in the brick¬ work, as well as the weight of the brickwork in place. Also consideration must be given to the thermal stresses set up in the walls. These are rather involved subjects upon which there has been, and still is, a great diversity of opinion. They will, t herefore, be treated under separate headings, setting forth the combined results of the best known modern investigators, as well as the experience of the Custodis Company covering a period of over forty years. WIND PRESSURE Winds are due to the differences in the atmospheric density produced l>\ the sun in its unequal heating of the earth and its surrounding atmosphere. These differences constitute a condition of unstable equilibrium. The air immediately moves to restore equilibrium and as a result sets up vertical and horizontal wind currents. Ihe differences in density which are produced depend upon the geographical location and climatic conditions. Flic wind velocities attained, therefore, vary widely in the different parts of the world. The United States W eather Bureau for a long period has kept a daily record of wind velocities. The map on page 71 shows the maximum recorded velocities in the various parts of the United States. A study of this map shows that recognition should be given to regional differences in maximum wind velocity in chimney design. The maximum velocities indicated are the recorded velocities from the Robin¬ son Anemometer. They are not the actual velocities. Mr. P. C. Day, Meteorologist Weather Bureau, Department of Agriculture, writes under date of Oct. 29, 1923: “The relation between indicated velocity as published and actual velocity of the wind has been recently made the subject of experiments in the wind tunnel of the Bureau of Standards. The results may be taken from the following tables: Miles per I lour Indicated velocity. 10.0 20.0 30.0 40.0 50.0 60.0 Actual velocity. 9.1 17.1 21.9 32.2 39.5 17.0 Indicated velocity. 70.0 80.0 90.0 100.0 110.0 120.0 Actual velocity. 54.3 61.7 69.0 76.3 83.6 91.1 Indicated velocity. 130.0 140.0 150.0 Actual velocity. 98.5 106.0 113.3” _ In predicting the probable maximum wind velocity which the chimney will have lo withstand, consideration should be given to the fact that the recording instruments are recording rather than integrating, so that it is possible that the velocities of occasional gusts are 60% higher than those recorded. The development of aviation necessitated an exhaustive and comprehensive study of wind velocities and pressures. It is a fact that the velocities increase with the height above ground. This must be considered in the design of all chimneys, more especially the very tall ones. Some very accurate data has been secured through careful experiments at AIcCook Field, Dayton, Ohio, of which Mr. E. A. Fales, Aeronautical Engineer, writes under date of Nov. 16. 1923: “A reasonable velocity gradient curve can be given only for the case of Hat unobstructed ground. To consider this curve a straight line seems consistent for practical use in chimney design. “McCook Field experiments with pilot balloons (1921-22) indicated that the velocity at altitudes up to 5,000 ft. was represented by the equations V = / 2400 1) ^ 1 ^ 0r avera & e w i n d s V = (—r—hi) Vi for highest winds observed V 8550 / 8 Where Y = velocity at an altitude Vi = velocity near the ground h = height in feet." 70 71 The velocity of the wind near the ground depends largely upon the nature of the surrounding terrain. The determination of what pressure a wind of given velocity produces on a given surface has been a subject of controversy for many years and there are many different values published in the various hand books on engineering. The reason for this lack of agreement is well explained by Mr. Tales, who says, “The wind force on chimneys cannot be determined in any other manner than by actual empirical measurement. It cannot be computed from known laws of physics; for the behavior of air flowing past any sort of object is not well understood.” The method in the past has been to determine values for flat surfaces, then apply a correction factor for the various forms of profile. Among the values most frequently found are P — .0032\ ■ on flat surfaces (Stanton) P = .0040v 2 on flat surfaces (U. S. Weather Bureau) P = .0023v 2 on flat surfaces (Welsbach) P = .0021 lv 2 on flat surfaces (Mariotte) P = .00535v 2 on Hat surfaces (French Government) Regarding this Mr. P. C. Day of the Weather Bureau says: “ A careful study of wind pressures, w ith special reference to their application to aviation, was made by Mr. E. Eiffel. Paris, and a translation by Hunsaker, assistant naval constructor, U. S. Navy, published 1913, will no doubt be available in a local library. The general formula for small plates exposed normal to the wind is: P =0.0033SV 2 in which P equals the pressure in pounds, S equals the area of the surface in square feet, and \ equals the true velocity of the w ind in miles per hour. This result is somewhat lower in value than that determined by some experiments made by the W eat her Bureau some years ago in which the factor 0.004 was adopted, it seems quite likely that with the better appliances used by Mr. Eiffel, his value is the better one.” For round surfaces, American engineers use values for the projected area ranging from one-half to two-thirds, while continental engineers use two-thirds. Mr. Fales has investigated this matter and writes under date of Nov. 16, 1923: “ As affects cylinder resistance, sufficient work has been done to show that a maximum value of the resistance coefficient may be reasonably used where the cylinder is of large diameter as in the case of a chimney. “Theory and experiment indicate that the resistance coefficient within certain . i , «„ , , , T , . / Velocity X Diam. \ ranges depends upon the Kevnolds Number 17 :-:-——- • & 1 1 ‘ \Viscosity Coefficient/ “If the coefficient be plotted against this ‘ Reynolds Number’ the curve, as the velocity or diameter increases, first drops 25%, then rises back to its original value and then drops off. approaching a minimum value when velocity X diameter reaches 70.0 (velocity in ft. per sec., diameter in ft., viscosity coefficient remaining the same throughout). Now in the case of large cylinders whose length is great enough to make the end effect negligible, the Reynolds Number is 5 to 50 times greater than this. The indications are that no further rise takes place in the coefficient as VxD is increased beyond 70.0. Therefore, the best information available from different sources indicates that this coefficient represents I he maxi¬ mum resistance to be expected in large diameters and high wind velocities. “ There results the following formula which may be applied to circular chimneys, with the satisfaction of knowing that there is no better coefficient obtainable from any source whatsoever: It = .0022 DV 2 where (It) is the resistance per linear foot of chimney. (D) is chimney diameter in feet (V) is wind velocity in miles per hour. This coefficient has been arrived at from study of various tests, and in particular those of Dry den (see paper 394, U. S. Bureau of Standards).” It is interesting to note that using a profile correction factor of 2/3 Mr. Bales checks Mr. Eiffel exactly. For octagon surfaces American engineers use values for the projected area of 0.75, while continental engineers use 0.71. COMPRESSIVE STRENGTH OF BRICKWORK The compressive strength of brick masonry depends upon the quality of the brick, mortar and workmanship. A study of the behavior of various specimens of brick masonry under com¬ pression in a testing machine shows that tendency is for the individual brick to fail by flexure due to the non-uniform distribution of the test load. This non- uniform distribution is due to the irregularity in the shape of the bricks, the human equation in the jointing of the specimen pier, and the displacement of the mortar under load. Many formulas are available in the engineering handbooks for calculating the strength of common brick piers. The formulas given by the U. S. Bureau of Standards are P = Ivp (1) P = KR (2) Where P = unit ultimate compressive strength of pier Where p=unit ultimate compressive strength of single bricks Where R = unit transverse strength of modulus of rupture of the single bricks K = constant depending upon the kind of mortar used. The following formula for the strength of perforated radial brick masonry was derived from the results secured at the Royal Mechanical Technical Institute of Tests at Chariot tenburg. K =. 26Ivs 1 + 8 Km \ Ks ' Where K = compressive strength of masonry in kg. per sq. cm. Km = compressive strength of mortar in kg. per sq. cm. Ks = compressive strength of brick in kg. per sq. cm. It is, therefore, evident that compressive strength of the brickwork depends to a large extent upon the strength of the brick used. Care, therefore, should be taken to see that the brick are of good quality. To that end the C.ustodis Company frequently test their brick and know the crushing strength of all their materials. Different experimenters often obtain widely varying results in testing the same quality brick. This is because the values obtained depend upon the dimen¬ sions of the specimen tested, the method of preparation and the method of applying the test load. The samples should have their faces ground so that they are abso¬ lutely parallel or else imbedded in plaster j tar is or portland cement and the load applied gradually. Good judgment is, therefore, needed to interpret the results obtained in the tests of the individual bricks. In compression the mortar is invariably weaker than the brick. Consequently under excessive loads it yields and is displaced. Therefore, the mortar to a con¬ siderable extent determines the strength of the brickwork. Theoretically the thinner the joints the nearer the strength of the brickwork approaches the strength of the single bricks. In practice the joints must be thick enough to properly bed the brick to an even bearing. If the joints are very thin the brick are liable to absorb enough water from the mortar to prevent its proper hardening. Brick with low absorption power are not always desirable in chimney work. They are difficult to hold in position on the wall and, furthermore, they do not absorb enough water to give the maximum adhesion between mortar and brick. Soft bricks, on the other hand, rol) the mortar of water, defeating the hardening process. It is specified at times that the compressive stress on the brickwork shall not exceed one-tenth the ultimate strength of the single bricks. In chimney work to limit the compression to 350 pounds per square inch is good judgment. WEIGHT OF MASONRY All self-supporting brick chimneys are dependent upon the force of gravity to prevent overturning by wind pressure. Therefore, the unit weights of the masonry which are used in determining the stresses should be the accurate results of experience and experiment, otherwise the results of stability calculations will be of little value. It is obvious that the weight of the brickwork depends entirely upon the weight of the various materials of which it is composed, namely, the weight of the bricks, the sand, the cement and the lime. The weight of the 74 mortar varies somewhat, hut not between as wide limits as the brick itself. The weight of brick is dependent upon the nature of the clay, the porosity of the finished product, the method of manufacture and the hardness of burn. The weight of sand varies, depending upon its composition, its coarseness and geological origin. The weight of cement and good, pure, wood-burned lime is comparatively constant, the cement especially being manufactured under laboratory supervision. The products of different brickyards vary in texture, density and weight. It is, therefore, a fallacy to compare the weight and stability of a radial brick chimney, built of radial bricks, light in weight, approaching the structure and hollow form of partition fireproofing with a radial brick chimney built of dense, hard burned, impervious, heavy, properly designed radial brick. The design of the radial brick itself as well as its physical characteristics should be given careful consideration of all who propose building a radial brick chimney. TEMPERATURE STRESSES The walls of a brick chimney are heated on the inside by the hot flue gases, while the outside portion of the walls remain practically at atmospheric temperatures. The drop in temperature through the wall is practically uniform. This results in the inner portion of the wall expanding circumferentially and vertically, while the outer portion endeavors to remain in its original position, setting up tension in the outer ring and compression in the inner ring. The magnitude of the stresses depends upon the temperature of the smoke stream and upon the modulus of elasticity of the mortar and the brick. If the circumferential temperature stresses on the outside exceed the ultimate strength of the masonry in the outer ring a rupture will occur. Lime mortar is more compressible and more elastic than a sand cement mortar. It is for that reason, in construction of chimneys, a goodly quantity of lime is used with the cement in the mortar. This increases the elastic limit of the joint and thereby greatly reduces the ten¬ sile stresses in the outer ring. To further assist in taking up the hoop stresses, steel bands are built at intervals in the outer portion of the chimney wall. For this same reason adequate amount of lining is advocated to insulate the main walls of the chimney, thus protecting the inside portion from excessive tem¬ peratures. This is the governing factor in the design of high temperature chimneys, the object being to reduce the temperature gradient between the inner and outer portions of the main walls. The tendency of the inner portion of the walls to expand vertically is taken up by the elasticity of the lime cement mortar and the strong bond of the perforated radial brickwork. Ruptures in the main walls of the chimneys due to vertical expansions are practically unknown; the circumferential stresses, however, should be given careful consideration. In general this is a complicated subject on which little exact information is available, but the Custodis Company’s many years of experience enable them to readily cope with these temperature stresses. It is therefore essential that the maximum temperature expected be known and the chimney be designed accordingly. SAMPLE OF CALCULATIONS Factory chimney 150' 0" high by 8' 6" inside diameter at top serving a boiler plant at Binghamton, New York. The chimney and various types of foundation are shown in figures 88. 39, 40 and 41, page 77. It is built of radial brick on foun¬ dation of concrete. 1 cubic foot of radial brick masonry weighs.120 pounds 1 cubic foot of concrete weighs.150 pounds The method of calculations and the symbols used are the ones shown in the pre¬ ceding pages. The wind pressure is taken as 22 1 2 pounds per square foot of projected area. The foundations are designed so that there is no tendency to lift, on the wind¬ ward side. ClIIMMA CALCUL\T1(>NS (1) olume Section Length 1 20' 9 20' 3 20' 1 20' 5 20' 6 20' ( 20' 8 10' 2) Weight p 5874x120 2000 353 tons (Slide Rule t sed) \\ all Thickness \ olume of Section ~Vs 351 cubic feet m 118 cubic feet 10 Xs 576 cubic feet 13 736 cubic feet 15 886 cubic feet 17 1012 cubic feet 18Vs 1170 cubic feet 20 y 8 665 cubic feet 5874 cubic feet (3) \\ ind Pressure W 9.69 + 11.19) X 150x22.5 2x2000 (4) Lever arm of resultant wind pressure [14.49 + (2 X9.69)] X150 = 20.12 tons L (9.69 + 14.49) X3 = 70.0 feet O -07 y-fpw? (5) W ind moment at foot of chimney M =20.42 xTO.O = 1430 feet tons (6) Radius of resultant » 1430 f . A - =1.0o leet 353 (7) Radius of first kern (For hollow circular section R = .250 1 + f J R R = .250 £ 1 + J 7.245 =2.88 feet (8) Radius of second kern 1 - For hollow circular section e = 3tt 16 r R r R R e = 16 5.565 7.21.5 5.565 x 55245 7.215 = 5.09 feet (9) Net area at foot A= 7r (7.245 2 — 5.565 2 ) =67.5 square feet (10) Stress intensity at foot lee side S" = 1 + = 12.60 tons per square foot 67.5 \ 2.88/ (11) Stress intensity at foot windward side s „ = 3o3 , ^ 4.05 \ = —2.12 tons per square foot 67.5\' 2.88/ (12) Maximum stress intensity at foot lee side S'" = 1: [2.60 —r—2.12 ( I =13.2 tons per square foot J_ \ 5.09—2.88/ _J FOUNDATION CALCULATIONS Solid type—no steel reinforcing—For dimensions See Fig. 39, page 77 Maximum allowable soil pressure =2}/£ tons per square foot 78 (13) Weight of foundation = 151 tons (1 f) W eight of chimney, lining, foundation and lill =556 tons (15) Wind moment at foot of foundation = 1552 foot tons (16) Area of foundation =438.2 square feet (17) Section modulus of foundation = 1332.3 feet 3 (18) Soil pressure = 3 _ + =2.43 tons per square foot 438.2 1332.3 (19) Tension in concrete M 6550 _ , , . , p = = =57.1 pounds per square inch V 11 o2 Reinforced concrete type. For dimensions, see Fig. 40, page 77 (20) Weight of foundation = 128 tons (21) Weight of chimney, lining, foundation and lill =509 tons (22) Wind moment at foot of foundation =1522 foot tons (23) Area of foundation =419.3 square feet (24) Section modulus of foundation =1247.3 feet :! (25) Soil pressure (26) Tension on concrete 509 1522 + 1247.3 = 2.43 tons per square foot p = y = = 8d.O pounds per square inch (27) Reinforcing steel required 4.00x4860x24 As = V 8 X 4X12X16000 X .55 = .38 square inch PILE FOUNDATIONS Same foundation with concrete piles capable of sustaining a load of 25 tons per pile. (See Fig. 41, page 77) (28) Dead load on piles = 509 tons (29) Number of piles = 38 (30) Dead load per pile —^r— =13.35 tons 38 (31) Wind moment at foot of foundation = 1522 foot tons 79 Moment of inertia of system of piles about the horizontal axis = 1398 e. g. pile #1 1 + (1 X10 2 ) = 101 (33) Section modulus of system of piles about the horizontal axis = 139.8 1522 Live load per pile = - = 10.85 tons 1 1 139.8 (35) Total load per pile = 13.35 + 10.85 =24.20 For the convenience of the designer, we give the following tables showing the dimensions of Custodis radial brick chimneys and foundations: TABLE 9 CHIMNEY DIMENSIONS AND WEIGHTS Following dimensions and weights are approximate and must not be used as final Boiler Chys. Normal Conditions. Temperatures not above 800 degree Fahrenheit A B c D E Lining Total Wt. Erect. (Dead) Approx. H. P. 1 lb. C. A B c D E Lining Total Wt. Erect (Dead) Approx. H. P. 4 lb. C. 80' 3' 8'- 1V 15 V 7V 15' 69 Tons 205 225' 7' 17'- 6V 28" 7V 40' 655 Tons 1875 80' 4' 8'- 9" I5V' 7 \A" 15' 78 “ 364 225' 8' 17'-10V 28" 7 V 40' 688 “ 2451 100' 4' 9'-10 V 19" 7 V 15' hi “ 410 225' 9' 18'- 3V 28" 7 V 40' 716 “ 3101 100' 5' 10'- 8" 17" 7!+" 15' 124 “ 637 225' 10' 18'- 9A" 28" 714" 40' 7 57 3829 100' 6' 10'-I 1V 17" 734* 15' 132 “ 920 225' 12' 19'- 7 V 27" 8V 40' 830 “ 5515 L10' 4' 10-11 19" 7 20' 113 “ 429 250' 8' 19'- 1%" 29" 714" 45' 844 “ 2584 110' 5' 11'- 2" 10" 7V 20' 148 “ 669 250' 9' 19'- 6 V 29" 714" 45' 880 “ 3269 110' 6' 11'- 5M" 19" 7 V 20' 157 “ 962 250' 10' 20'- <>V 29" 714" 45' 925 " 4037 125' 5' 11-11" 21" 7 34" 20' 185 “ 715 250' 12' 20'-10V 28" ny H " 45' 1003 “ 5811 125' 6' 12'- 2 V 21" 7 V 20' 193 “ 1051 250' 14' 22'- IV 97 " a A" 45' 1068 “ 7940 135' 5' 12'- 4 34" 21" 7V 20' 213 “ 744 275' 9' 20'- 9A" 30" 7 14 " 50' 1065 “ 3440 135' 6' 12'- 8V 21" 734" 20' 221 “ ] 092 275' 10' 21 3 V 30" 7 J4" 50' m2 “ 4243 150' 5' 13'- 2" 23V 734" 25' 263 “ 797 275' 12' 22'- IV 29' 8%" 50' 1192 “ 6090 150' 6' 13'- 5 V 23 A" 7 34 " 25' 273 “ 1 147 975' 14' 23'- 4 V 28" ;; . 50' 1262 “ 8300 150' 7' 13'- 9 V 23 V 7V 25' 292 “ 1563 300' 14' 24'- 7 A" 30" 8 % " 50' 1480 “ 8670 150' 8' 14'- >%" 23 V 7V 25' 31 1 “ 2041 300' 15' 25'- 2 A" 30" 8 - 50' 1550 “ 9940 160' (V is'-mr 23 V " 7 V 25' 310 “ 1185 300' 16 '-6" 25'- 8 32" 10 V 50' 1688 “ 1221(1 160' 7' 14'- 3V 23 V 7 V 25' 330 “ 1615 300' 18' 27'- 8" 40" L0V 50' 2113 “ 14360 160' 8' 14'- 73 s " 23 V 25' 349 “ 2102 300' 20' 30'- 4" 38" ny 4 " 50' 2235 “ 17700 175' 7' 15'- 0 V 25" 714' 30' 395 “ 1654 325' 14' 25'-10V 34' 8 55' 1746 “ 9025 175' 8' 15'- 4%" 25" 734" 30' 416 ' 2161 325' 15' 26'- 6A" 34" HA" 55' 1820 “ 10370 175' 9' 15'- 9 A" 25" 714" 30' 441 “ 2734 325' IO'-6" 27'- 2%‘ 34" 10 y H " 55' 1960 “ 12750 175' 10' 16'- h 3 V 26 A" 714' 30' 494 “ 3374 325' 18' 31- 2" 32" 10%' 55' 2020 “ 14920 200' 7' 16'- 3v 26 A" 7 V 35' 516 “ 1768 325' 20' 31- 4" 40" 11 V 55' 2620 “ 18440 200' 8' 16'- 73 s " 26 A" 7V 35' 540 “ 231 1 350' 15' 27'- 9 V 36" av 60' 2120 “ 10750 200' 9' 17'- 0 A" 26 V 714" 35' 570 “ 2925 350' 16 '-6" 28'- 2 3 k" 36" 10 V 60' 2280 “ 13200 200' 10' 17'- 6k>" 26 V 35' 605 “ 361 1 350' 18' 33'- iy 2 " 36" 10V 60' 2520 “ 15500 200' 12' 18'- -IV 8 " 25" 8H' 35' 675 “ 5200 350' 20' 32'- 4" 44" 11%' 60' 3075 “ 19150 TABLE 10 FOUNDATION DIMENSIONS AND VOLUMES Two Ton Two and One-Half Ton Three Ton Depth No. Weight Size Type in of of l op Dia. Bottom Cu. Yds. Cu. Yds. 1 op Dia. Bottom Cu. Yds. Cu. Yds. 1 op Dia. Bol tom Cu. Yds. Cu. Yds. Feet Slabs Chimney Dia. Cone. Excav. Dia. Cone. Excav. Ilia. Cone. Excav. 80'x 4' 4 9 9' 0" 12' 0" 16.7 21.4 9' 0" 11' 0" 15.0 17.9 80'x 4' 4 9 10' 6" 13' 6" 17.9 99 4. 90'x 5' Sq. 4 9 10' 6" 13' 0" 20.7 25.0 10' 6" 12' 6" 19.8 23.2 90'x 5' Oct. 4 2 11'9" 15' 0" 22.3 27.6 100'x 4' 4 2 10' 6" 14' 0" 22.6 29.1 10' 6 " 13' 0" 20.7 25.0 100'x 4' Oct. 4 2 12' 0" 15' 6" 23.6 29.5 100'x 6' Sq. 4 2 132 tons 11' 9" 15' 0" 26.9 33.3 11' 0" 14' 0" 23 5 29.0 11' 0' 13' 0" 21.5 25.0 100'x 6' Oct. 4 9 13' 9" 17' 0" 29.4 125'x 5' Sq. 5 3 185 tons 12' 6" 17' 6" 42.4 56.6 12' 6" 16' 0" 38.0 47 4 12' 6" 15' 0" 35.2 41 7 125'x 5' Oct. 5 3 185 tons 13' 0" 19' 6" 11 2 58.3 13' 6" 18' 0" 38.4 49.7 12' 6" 17' 0" 33 8 44.3 125'x 7' Sq. 5 3 225 tons 13' 6" 18' 6" 48.2 63.5 13' 6" 17' 0" 43.4 52.5 13' 6" 16' 0" 40.5 17 1 125'x 7' Oct. 5 3 225 tons 15' 6" 20' 6" 50.2 64.6 15' 0" 19' 6" 55 3 58 3 14'0" 18' 6" ID 8 52.5 150'x 4' Sq. 6 3 255 tons 14' 0" 20' 0" 65.5 89.0 14' 0" 18' 0" 57.5 72.0 14' 0" 17' 0" 53.8 64 1 150'x 4' Oet. 6 3 255 tons 15' 6" 22' 0" 66.6 89.1 15' 0" 20' 6" 59.5 77.5 14' 0" 19' 0" 51.0 66 5 150'x 6' Sq. 6 3 273 tons 15' 0" 21' 0" 73.4 98.0 15' 0" 19' 0" 64 9 77.0 15' 0" 18' 0" 61.0 19 9 150'x 6' Oct. 6 3 273 tons 17' 0" 23' 6 " 76.8 101.5 16' 0" 21' 6" 65.6 85.2 15'6" 20' 6" 64 0 77 5 150'x 8' Sq. 6 3 311 tons 16' 0" 22' 0" 81.6 107.6 16' 0" 20' 0" 72.6 88 9 16' 0" 19' 0" 68 4 80.3 150'x 8' Oct. 6 3 311 tons 18' 0" 24' 6" 84.5 110.8 17' 6 " 23' 0" 76.3 97.7 16' 0" 21' 6" 65.7 83 5 175'x 7' Sq. 7 3 395 tons 16' 0" 24' 0" 106 1 149.9 16' 0" 22' 0" 95 1 123.5 16' 0" 20' 0" 84.8 103.7 175'x 7' Oct. 7 3 395 tons 19' 0" 26' 6" 113.0 150.6 18' 0" 24' 6" 98 3 128.9 17' 0" 23' 0" 87.0 1 1 1 11 175'x 9' Sq. 7 3 441 tons 17' 6" 25' 6" 122.0 169.2 17' 0" 23' 0” 105.0 137.2 16' 6" 21' 0" 91.8 114.2 175'x 9' 7 3 441 tons 200'x 7' Sq. 8 4 516 tons 18' 0" 27' 6" 158 0 224.5 16' 6" 25' 0” 130.8 183.3 16' 6" 23' 0" 117.2 157.0 200'x 7' < >ct. 8 1 200'x 9' Sq. 8 4 570 tons 19' 0" 29' 0" 177.0 249.7 17' 6" 26' 0" 143.0 199.8 17' 6" 24' 0' 129.6 170.5 80 Chapter V FOUNDATIONS Just as the determination of the proper height and diameter of a chimney for a particular case is invariably a problem of its own, so the foundation design is one to properly meet the soil conditions encountered as well as the general conditions in reference to building walls and structures in the immediate vicinity. A chimney is a structure subjected to shock due to the sudden increases and decreases in the velocity of the wind. These abrupt changes of wind pressure produce the dynamic effect of a sud¬ denly applied load. The soil then must have sufficient bearing power to resist this in addition to the dead load and pressure produced by the wind force. For this reason in the case of chimneys we counsel more conservative loadings than are allowed in ordinary foundations, especially if the soils are low in bearing power. All soils are compressible to some extent. The design, therefore, should aim to reduce settlement to a minimum and provide so that if there is any settlement, it will be uniform. Silty soils, mud and quicksand have low bearing power and are liable to squeeze out in every r direction when a heavy load is applied, and should never be relied on for a foundation. Clay soils vary widely in their bearing power, as they range from shale down to soft clay which oozes under slight pressure. The bearing power of clay soils is lowered by the penetration of water and it is desirable to provide drainage for the foundation. Where soft clay is encountered care should be taken to see that there is no possibility of the soil escaping by flowing into ad jacent foundations. Hard, stiff, dry clay in.thick beds generally has a bearing capacity of 2§ tons per square foot. 11 ‘ Soft, wet clay dannot be relied on to carry more than 1 ton per square foot. Instances will be encountered where a reinforced spread foundation on weak soils of this kind would be more practical and economical than going down to greater depth for a more solid soil. Here the spread foundation may be made of such dimensions that the soil pressure is reduced to as low as I ton per square foot. (See Fig. 51. page 85.) Sand if confined and dry is almost noncompressible and makes an excellent foundation. However, it is best to be conservative and not apply a load of more than 2 tons per square foot. Compact gravel may be loaded to 3 tons per square foot. Hard pan, coarse gravel cemented with dry clay r may be loaded to 3 tons per square foot. For airy soil condition, other than solid bed rock, we recommend against a loading of over 3 ] ^ tons per square foot. Solid bed rock can safely carry any load which may be imposed by the chimney. This may run as high as 18 to 20 tons per square foot. If the rock 81 lies at an angle the slope should be cut into steps to prevent the concrete mass from sliding. The surface of the rock should be thoroughly cleaned and dis¬ integrated soft portions removed. The surface should be thoroughly wetted down before placing the first layer of concrete. (See design, page 85, Fig. 44.) In the case of spread foundations, precautions should be taken to ascertain if the soil encountered in the bottom of the excavation continues the same for a considerable depth. It should be made certain that the hard strata encountered is not a thin strata overlying a soft one, such as cpiicksand, soft, wet, silty clay or wet muck. The bearing capacity of the soil may be determined by driving down an iron rod, making borings with a soil auger, sinking a hollow pipe by means of a water jet, or by applying a test load on a mast and recording the settlement. Holes may be dug at several points in the foundation. In general should the same or better soil be encountered through a depth of 8 or 10 feet, the foundation soil may be considered safe to build on. The nature of the soils for a considerable depth in the vicinity of the founda¬ tion may often be determined by observing nearby excavations or by records of foundations supporting other structures in the neighborhood. On page 85 are illustrations of several different designs of the most common foundations (Fig. 42). They are built of concrete, made of a mixture of one part by volume of Portland cement, three parts coarse clean sharp sand and five parts crushed 234 -inch graded concrete stone or suitable gravel. We recommend the American Society of Civil Engineers’ specifications for the proportioning, mixing and laying of mass concrete. The table on page 80. is given to enable the Engineer or Architect to make his approximate preliminary layout, and should not be taken as final in all cases. The exact pressure should be calculated and the foundation determined for the particular size and design of chimney, for the reason that a chimney of the same height and diameter may vary in weight according to the type, the lining and other specifications. Where the necessary depth of excavation to firm soil is greater than the required thickness of the concrete foundation to safely resist shear and bending yet not deep enough to make piling imperative, a foundation with a sub-base and earth fill is the most economical. (See page 85, Figs. 47-48-49-50.) We call attention to the drawing of the reinforced spread foundation where the thickness is materially reduced. This type may be used when deeper excava¬ tions are expensive and the cost of sheet piling, pumping or cribbing is more than the additional cost of steel reinforcement. The steel should be designed to resist the shear or bending that may occur in the thin slab of concrete. When a chimney foundation is built adjacent to a building wall we recommend, if possible, there be no connection between it and the wall footings. The chimney footings for the chimney should be carried down to at least the depth of the wall footings. 82 Underground flues are not uncommon. A design of this type is illustrated by a typical drawing (page 85, Fig. 50). This condition occurs where the boiler room floor is some distance below ground or where the chimney is used in con¬ nection with brass f urnaces or similar melting furnaces. A unique solution of a chimney foundation is shown in Fig. 43 on page 85. The chimney was built adjacent to a stone quarry where continued heavy blasting is carried on. This subjected the chimney to two forms of shock other than wind shock. First—The concussion waves through the ether from the explosions. Second—- The shock carried through the underlying rock to the foundation. The former was easily met by an extra heavy column design. The latter was more of a problem and was solved in the following manner: An excavation 18' 3" square and 6' deep was made in the solid rock. This was lined on the bottom and four sides with 12" of concrete in which were imbedded steel rods. In this concrete box was laid clay 24" thick, tamped hard in separate thin layers. This formed a clay cushion upon which the concrete chimney founda¬ tion was constructed. Between the sides of the chimney foundation and sides of the concrete box a l 1 2 joint was left and filled with asphalt. In this manner the clay cushion was absolutely confined within the concrete walls. The chimney has stood for years, withstanding the shocks from the blasting. By their long and varied experience the Engineers of the Custodis Com¬ pany are prepared to solve any chimney foundation problem, no matter how diffi¬ cult or baffling. PILE FOUNDATIONS Where soft unreliable soil, such as quicksand, wet clay and harbor muck is encountered piles are frequently found necessary. There are tw o classes of piles in common use, w ood piles and concrete piles. Wood piles are more frequently used. They are very satisfactory if installed so that they are always wet and are protected against attacks of the marine borers. It is highly important that wood piles be cut off so that they w ill always be sat¬ urated or submerged. In determining the point of cut off consideration should be given to possible future lowering of the water level. Concrete piles have several advantages over wood piles—among which are immunity from decay and greater bearing capacity and in some cases lower first cost than wood piles. There are two general types of concrete piles: first, the “cast in place” pile; and second the “pre cast” pile. Ordinarily “cast in place” piles are not reinforced while “pre cast” piles are reinforced so that they can be handled. Piles carry their load partly by friction with the earth throughout its length 83 and partly as a column supported at its lower end by being firmly driven into stable soil, or upon rock. Piles are driven by means of a pile driver or in* sandy soils are sunk by means of a water jet. The carrying capacity of piles is ordinarily determined by means of the “Engineering News Formula L = ‘ - S +c Where L = Load in pounds w= Weight of falling parts in pounds h = Drop in feet of falling parts S = Final penetration per blow in inches c= Constant whose value is 1.0 for gravity hammers and 0.1 for steam hammers. If in doubt as to the carrying capacity of the piles a test load can be applied. For ordinary conditions a maximum load of 15 tons per pile for wood piles, and 30 tons per pile for the standard “cast in place” concrete piles is recommended. In view of the widely varying soil conditions no hard and fast rule can be given. e, therefore, suggest that conference be arranged with our engineers so that we may make a report based upon a study of the conditions. Wood piles are ordinarily spaced approximately 2' 6" to 3' 0" center to center and project 6" into the cap \\ hile standard “cast in place" concrete piles are spaced 3' 0" center to center and project 3" into the cap. Illustrations of some types of pile foundations are given (page 85, Figs. 45, 46). Note that the designs of the concrete mass overlying the piles are similar to the concrete footings employed in cases where the foundations rest directly upon the soils. 84 LUXJ r I . i . j lZ, I -i-t m Wcm DJ Fig. 42 Typical designs of mass concrete foundations Z 7 1 zz u r '• 2 Z 34 e>. & Oc t W Z. Earth F.ll p Oa iz 2 ?i T\ V- i , f-r r-r~ Live Bed Rock Fig. 44 Foundations resting on solid rock Fig. 43 Unique design of a chimney foundation to resist shocks from blasting in an adjacent stone quarry. Showing con¬ fined artificial clay cushion. See next page Fig. 16 Reinforced spread built for foundations on piling Fig. 49 Designs of foundations with concrete sub-base under¬ ground. Note earth fill in center covered over with concrete floor Fig. 50 Typical design of foundation with underground flue Design of a shallow. reinforced concrete foundation for a chimney 450' x 16' 85 CHAPTER VI LIGHTNING RODS Renjamin Franklin installed the first lightning rod on his own house in 1753, after making careful researches. In the United States and France public approval was quickly given his invention. In Europe, generally speaking, the installation of lightning rods was opposed on t lie grounds that they interfered with Divine punishment of the wicked. A half century or so ago unscrupulous and unskilled men took up the business of selling and installing lightning rods. Their equipment was cheap, flimsy and unscientific. Their business methods were questionable and frequently dis¬ honest. The natural result was that lightning protection was looked upon with disfavor and suspicion, and in fact today, some of this feeling still exists. During the past few years the Insurance Companies have kept careful records of the fire losses caused by lightning. They have found that these losses average over eight million dollars yearly, also that in the case of barns, lightning rods properly installed are 99% efficient, and in the case of other structures the efficiency is but little below that point. As a result of the statistics now available, the Rureau of Standards, Washington, D. C., and many scientific bodies in the United States and Europe have endorsed the use of lightning rods. In fact educated thought throughout the world favors this protection against lightning. For a number of years the Custodis Com¬ pany has kept records of the chimneys damaged by lightning, that have come under their observation. On account of being the oldest Chimney Company in the country operating over the entire continent of North America, more cases of chimneys struck by lightning are reported to this Company than to any other firm. Our files show that we have never been called upon to repair a chimney seriously damaged by lightning that was equipped with a lightning rod properly designed and Encircling Cable >r: i i © § Detail of connec¬ tion showing cop¬ per bronze T at point of juncture with conductor cable ---p-_ /?^> Detail of Cable Clamp Elevation Showing Arrangement of Lightning Rods 86 installed. In several cases we have repaired the aerial terminals or points of lightning rods which have carried off heavy discharges and found that chimney was undamaged. The damage to some chimneys was so severe that the plant was forced to suspend operations, causing a heavy loss. The cost of adequate lightning pro¬ tection is small. It is unquestioned that it is good insurance at a low rate. The installation of such protection warrants the most serious consideration by every owner, architect and engineer. Lightning is the name given to the discharge of electrical energy from the clouds, the difference in potential being sufficient to overcome the resistance of the intervening gaps. The resistance through the air between charged clouds and tall structures is generally less than the resistance between the charged clouds and the earth. For that reason tall structures are generally damaged by the passage of the electrical discharge, unless a path in the form of a lightning rod is provided to the ground. There are usually several discharges. The first warms the air in the path of the discharge decreasing its resistance so that the remaining discharges will take place along the same path, provided the warm air column is not moved laterally by the wind. Experience has shown that this movement is extremely likely to occur. Provision is, therefore, made accordingly by installing several air terminals properly distributed on the structure to be protected. There is no exact data available regarding the electrical characteristics of lightning. There is no doubt that the currents in flashes must be reckoned in the thousands of amperes and millions of volts with a frequency in the thousands of cycles. This lack of information accounts for the difference of opinion among the scientists as to what is adequate protection. Some manufacturers of lightning rods are tempted to take advantage of this by producing weird and complicated systems that do little else than increase the cost. The Custodis Company has for many years investigated the subject and concludes as follows: The interest of its clients is served best when the lightning rod is installed as the chimney is built. The “Contour" system consisting of a network of conductors is designed upon the theory that it is better to depend upon a large number of small conductors rather than one or two large conductors as is the case of the “Point" system. Experi¬ ence has shown that the “Contour" system is not more effective in discharging electrical energy than the “Point" system and neither is it more reliable. The former is more complicated than the latter system. We recommend the “Point system. Iron conductors are slightly superior from an electrical standpoint and are cheaper in first cost: however, copper resists corrosion better and is more workable, in the field. These are the governing factors and the use of copper has become practically universal. 87 The aerial terminals or points should be heavy and substantial to maintain their vertical position. They should have sufficient cross section to prevent their fusing when carrying a heavy discharge. We recommend solid copper rods at least 3 4 inches in diameter. 6 ]