Document ybVjrDKQaNNQgzMojxoK7yNad

Reprint from N BRICK & CLAY RECORD May 1961 Johns-Manville Insulating Firebrick Are Different! The combined skills of John6-Manville research, engineering and production have developed a new method of producing insulating firebrick. This article describes the entire system. JOHSS-M '**\ M IE PRODUCTS TIm xlinqxr machiiw thick lyr of mix on ilobi to form o column of cloy. Johns-Manvil It* They're made by entirely different processes--for example, brick are cut from fired slabs Insulating firehrh k at the* JohnsManville plant in Zelienople ran best be described bv two words: "They're different'. These refractorie- are dif ferent because Johns-Mam iile makes them b> entirely different processes than the standard accepted methods. Probably the biggest deviation in the process is that the brick are cut out of fired slabs. These slabs are molded, fired rapid ly through tunnel kilns and then cut into standard brick and special shapes The standard fired slab will produce five 9-inch straight brick or standard shapes. The advantages of this sys tem are many. Handling of the slabs throughout the process is easier, a more stable load is possible on the kiln cars with better spacing to permit removal of the burnout and to obtain uniform temperatures throughout the kiln cars. Finally, the use of slabs reduces labor and the trim in tile sizing operation. Many special shapes can be produced directly from slabs, which normally would have to be molded and proc essed as special items. But the difference goes beyond the method of producing from slabs. It also extends into preparation of raw materials, forming methods, and dry ing. There are no presses or extru sion machines in the factory. The en tire process, while using some stand ard components, has been developed, engineered and constructed as a joint effort by the research, engineering, and production departments. The slabs are formed in processes almost foreign to the clay products industry. The 1600, 2000 and 2.100 brick slabs are formed in a casting operation, the 2600, 2800 and 3000 brick slabs arc molded by a slinger type machine. In addition to production economies and high quality obtained, the op eration provides the flexibility and basis for giving quick shipment of standard and special shapes to its customers. Raw Materials Raw materials must be carefully selected for refractories and particu larly the amount of iron and titanium. Major ingredients for all refrac tories are fireclay, kaolin, sawdust and grog. The clays are unloaded from hopper bottom car or by scoop truck into a cross conveyor and ele vated to drop into bins. Ponderosa Pine sawdust is used because of its high bulking property, which reduces burnout problems in the kiln. Hard wood sawdust can be used, and although the hard woods increase plasticity, this property is not necessary in the processes used. The sawdust is unloaded from box cars by a pneumatic system to a hammennill. which breaks down the saw'dust to the desired particle size. The hammermill uses special type hammers which are more like blades and which have a shearing action as compared to the crushing action nor mally obtained in a hammermill. The grog is the trim obtained dur ing the sizing operations. The trim from each type is collected separate!' for use in the same type brick foimula from which it was obtained. The raw materials, except groc. are stored in large bins, which are equipped with dust collector svstems. Grog is collected, transported and stored in lnvert-a-Bins la type of metal tote box holding 88 cubic feet >. To empty them they are imertrd above a conveyor leading to the use bin. The lnvert-a-Bins provide a du>t free method of collecting, storing and discharging the fine grog. Dust col lectors are located at the finishing operations, raw material storage ami batching operations to pro' ide an ex tremely clean operation. The dry portion of the mix con tains clay, grog, sawdust. Gypsum le Firebrick Are Different! planter is also included in mixes for tlii- casting operation. The dry in gredients are weighed out in a batch <ar and dumped into a skip bucket vhiih delivers them to a paddle type mixer. This mixer provides a homo geneous mixture known as the dry mix. A major part of the clay is added In the batch as clay slip. This is made in blungers charged by a scoop truck. The slip" contains about 40% clav and is screened carefully, be fore storage in tanks below floor level.which are continuously agitated. (ilav slip is pumped from storage tanks to a rather long pug mill, where it is mixed with the dry mix and additional water. The mix is then fed from the pug mill to a slinger type machine which forms a column from w hich the slabs are cut. The slinger is a rotating machine which throw,} the mix. between the moxing side belts, onto Transite pal lets, mocing on the molding, conveyor. The slinger builds the column up to a thickness of 4 to 5 inches. The column passes under a rotary cutter, which cuts the column to the desired height. The trim from the cutter or exener. as it is called in the plant, is returned to the pug mill for remix ing. The column proceeds to another cutter which operates like a guillo tine, and cuts the column into slabs. The guillotine cutting must be timed exactly right, so that the slabs will be located in the center of the pal let. The dimensions of the slabs are approximately 26" x 10" x 3". Remove Slab9 Automatically The slabs are automatically re moved from the conveyor belt onto dryer cars, which are positioned on the lowervator principle. The dryer cars are somewhat unusual in con struction. They rest on legs after be ing moved to storage with a platform truck. They also have wheels for mov- ing them along the loading truck and through the tunnel dryers. The slinger type slabs are dried in tunnel driers, which operate con tinuously. Molding is normally on a five day week to supply the drier: and kilns for a seven day period. After the slabs are dried they are removed from the Transite pallets and loaded onto kiln cars for the firing operation. In this process the dry mix i* weighed out from an. overhead sti.rage bin on a batch basis. Clay slip and water for the batch are meas ured voluinetrically. These propor tioned materials are dropped into a paddle type mixer, and mixed for a period of about ten seconds. The mixer is then tilted and the mix pours over the side of the mixer into a large steel gang mold. This mold will make thirty slabs, approximately 25" x 10" x 3". Since the mix contains about 50% water it flows easily to fill up the mold cavities. After about fifteen minutes, the gypsum plaster in the mix has ab- Slabi ara tranifarrad from main convayor to dryar ear which au tomatically Iow an on kiln can. Flow Chart, Johni-Manvilla Zalianopla Plant. Typical Chomicjl Anolyti*--Uiuletin9 Rr* (rick Material Competition s;o: t;o. p.-o. Al-Oc*o MqO N-,0 to P,0 Al (Matal) JM-20 44.2 l.2 0 46 3S.0 IS.2 .06 .02 .27 0-16 JM-23 44.2 1.2? 0.46 31.0 IS.2 .06 .02 .27 0.16 Ne. 26 57.4 1.7 .1 3?.7 0.2 .1 .1 .1 -- -- Corrected for Al?0: oquivoioM ol Al Motat proton* No. 21 39.0 1.25 .5 59.0 _ -- .19 .06 -- -- JM-3000 294 1.0 .71 65.6 0.3 0.5 .1 .1 -- 3.6 ,S. I * . sorbed sufficient water to cause the - mix to set or harden. After the mix has set, the filled mold is picked up by a crane and moved to a strip ping machine. A kiln car is positioned at the stripping machine, which is op erated to extrude the slabs from the mold directly onto the kiln car. This loads one course of slabs on the kiln car. Two additional molds filled and stripped in the same manner are used to load the car three courses high. Charged Directly The loaded kiln car is then charged directly into a high temperature dryer. Two types of drying treatment are available. The one method is to charge directly into, a dryer operat ing between 500 and 700:. depend ing upon the schedule. This is a single tunnel dryer holding 9 kiln cars, and drying can be completed in 41 j hours, when operating at maximum sched ule. After drying, the kiln car pro ceeds to a tunnel kiln where the firt ing is carried out. < A newer dryer method, which has just been completed and is expected j. to obsolete the method described above, consists of drving above 1000 in a combination dryer and kiin. In ^ this method, the kiln car of molded slabs goes directly from the loading v' position into the combination dryer and kiln, and the slabs progress from " the drying to the firing without in terruption. This method reduces fuel, cuts down the cycle, and results in an improved control of the operation. PROPERTIES TYPE OF JOHNS-MANVILLE INSULATING FIRE IRICK lAnnn valval) JM-3000 JM-2* JM-24 JM-23 JM-20 JM-1620 Tamparrfvf* limit T1000F t2*00F t2600F 2300 2000 J2000F tl400F 65 SI SI 30 21 31 Traaavana itrangth, pii 200 I7S 140 140 105 10 CaM mulling ftrangth, pti 400 300 210 210 IS5 120 Li--ar dirinkaga, --emt *04 at 3000F 14 at 2S00F 14 at 2600F 5 04 at -- 2000F Ra--rrtli tfcarmil aipaniiaa. 05-04 0544 0544 pmrm at 2000F at 2000F at 2000F -- -- 0544 at 2000F Ciarfailil( (Itv in. S00F 352 251 252 0.77 par -- ft par F par I000F 350 2J0 2.44 150 1.14 142 nr at --Rawing maan 1500c 3.37 346 241 157 tamparatvrat) 2000F 3.44 352 2.93 -- "tf-hr Simulttiva Sr>c Final Tattr all athin 24-hr leaking parted 21 act-ap anly. tkaek-up ff aipaaad Cannot Stand Drying Essentially the problem with the casting process is that this material cannot stand any drying of the or dinary type. If placed in an ordinary dryer and raised to say 3o0:, the cast slabs slump. In the new drying and firing meth od, the slabs must be introduced inij to a temperature of approximately 1000 F. as rapidly as possible after they have been formed. The water has to be converted almost instantly into steam with a tremendous ab sorption of heat. If the temperature is allowed to drop at any point, crack ing results. Therefore, the process has to be continued on a steadily advanc ing temperature until the firing por tion of the kiln is reached. This involved some very serious difficulties because of the enormous ivffle _ : of heat required for the evap"*: viratkm of the water. The design of the kiln includes four high temperstuze recireolation fans. These take jfcg. gases oat of the crown of the Bh od ntma -thsi-ahrough gat* sages in the side walls of the kiln to chambers located along walls which sje 'provided with a kind of checkwork of openings through which the gases are moved into the loads at high velocity. * " Excess Air -Barriers -Ae heat is made op by excess anTburners installed in the side walls I ji! [j^i r loin in'the moving stream of hot gases.. Sufficient fuel is burned `to maintain the temperstnre to the desired point of the gases entering the kiln. The capacity of the fans is glUhl^enough to recirculate the en- r. - tire volume many times per minute. An exhaust fan was installed at the - ^`entrance of the kiln to take the gases of the kiln and discharge them to the^atmosphere. This draws upon the teuton of the Idln just inside the jMjgimcngnd. . &3tSSgsjsiSJThe produtea of combustion. from i js%r: the high .itigjyrTsriire section pass down, towards Ihe '^Strsnoe of the ire picked up through ^ in th^AOMrxL.and side trails of the kiln by It high Witperature fan ^i^rjjmfing the ahilky to be ran atl65*F. . Disck^^lnto -Flues ~;'5fay-*T*~distiuu,ged into the flues 4n. the.side walls of the kiln and baagimated HsM smpMrte by die excess air burners kiln. They are '*3? then -picked up bj-tbe intake of the ;4an andCwtarndl^again after ^heated, an(^ so ra dowp to the trance, fa Ah tnqr^' ps. -of- rediculatioQ is, maintained aS * the entrance end of the Idln, so much water is formed. E' a water-gas the presence of die great of steam which aea from the body itself. In order to .successfully a ma. t .^_p_^_t_e_fs_^_ _ b" to be established. As riMBthmrf oluiad ett the t^B*tamperature recirculating dryer section. These reconsist of two 1650* two 1*50*F fans. The ex... .... rated at 1250*F. Me^lmdher example of the complexity above, there can he WO deckingrfff ' *oHh operation is the fact that each inioat or the slahs^are *pkod, o{ iu weight in dry. least on the surface, or fn more ..'*-^ 6TM. ,^`wtojMw. d j.b. .TMa b, '*** ** " * "d had^p^li.. .1 ,,-..jgSB,-ro 4 ,,J int0 all the sawdust has been burned, out . - . . _. . . ... - * ^****NkThey ore then ..SJs^jahd^ol eqmjmmt to msintsin good fired to__t_he desired'.. .... - -`toffrftingoaoditions and to collect the erabng lamneraturo jjfi- h* The cast method ^Tionplelely Automatic determined --famr'T jifT'hiortiriH for producing seven days .^mr*week^fejuit the-ad-, otraight and zactangular shapes is vantage of - L-^omjjgaly-ontomatic from the point material in process time to the freed wish., the iired -rfaht are fed into I2n -this equipment the than 24 hours. ittob sets of grinders Very careful round jgj kilns is rdqqind to : w ^desired thickness; the f-conveyed between the out of t^, neerwry j*iuai which cat the slabs to ^`-and finally pass The de^r*1 very high. "'Bring thra which produces f gang slitters, spaced the slabs into five 'dab. Adjustment' 13e machine to pro- eovery rate. ' * M J" series brick naUy _ the firing .The largest finished i jhi^equipment so that the' burning of the equipment produce standard shapes, . vantage in hdpiag to,raise >11 types of apecial perature of the -cedueas fprf usage all i oqui^ment end operations de- . In the new -method ' ay-jirrl to. produce insulat- cast type hriS^tisiljgM oni br ibe classes of 16, ..oombinadoa, considerable^ ' and experime before a successful^ 88. In addition, a ; fire brick for prodamd using tained. In additioft-'-- P4i*v plete -.the-water, and '^srt:: Mwdpatta carried out of the "*' *-3 it was necessary to move \ volumes of hot ** ' -?* iding mortars, and rates. * ** . ' frr^ - 'V''*. " - -.-a. VerSa fa/1 . . *. i-s 'V. '* ^ oW-ii if" * <--S JOHVS-M SV'VIIIE PR.ODU CTS Johns-Manville General Headquarters: 22 East 40th Street, New York 16, N. Y. Offices In All Large Cifies >l \ t I OiOiOtOiO c OSCTM! hrmmtt;tjnsaaexa)o:om<ir G ^.U O C C J OO i iW w O2 * CASTABLE REFRACTORIES Vo SppH to B"ait for Special Refractory Shapes OU^'i. WITH INDUSTRIAL plants Tbranny down >>n war production. it is important that furnace shut down- and outage hour- be kept to a minimum. At this critical time J-M Firecrele is an unfail ing guard against prolonged -hut downs. Many readers of The Power Specialist al ready are using this refractory. To others, faced with ever increasing production schedule-, a description of Firecrete and it- application mav he of help. Firecrete i- a hydraulic setting refrac tory u-ed for iurnacc dour linings, burner rings, baffle tile, header protector tile, pipe linings, furnace bottom', special shapes of all kinds and for casting small monolithic furnaces. It i- furnished dry and. when mixed with water on the job. can be placed as easily as ordinary concrete. If neces sary. shape- and small monolithic linings can be put in service within 24 hrs. after being placed. Firecrete has practically no IfonoilfAir Jininf Mr non; lurmio W*or run strutted of Light V eight hrerr+te. thi- * low heat -lurage capacity jnd high resistance to spalling nuke it an ideal insulating refractory ion. r.i. j..r lin ing door- ot all -ire- ami t"i j-tm. special shape-, furnjie Im.iiomi- ami small monolithic furnace-. The type or type- of Fireciep- i.. lo used depend upon the particular -ervoc requirement. Johns-Manyille engineers, fa miliar with such problem-, anil with a thorough knowledge of then own pnu|. ucts. are readily ayailahb- at the nearest J-M office. drying or firing shrinkage and is highly Application / Firecrele resistant to spalling. As Firecrete harden- rapnilv. water It is furnished in three t>pe-: -- should not be added until the j..l. i- ready 1. Standard Firecrele for temperatures for application of the refractory. Direc up to 2400 F. This j the most gen tions for mixing with the amount of walei erally applicable type of Firecrete. required can be obtained with the material. 2. High Temperature Firecrete for tem Firecrete may be tantpe.l ..r rammed peratures up to 2800'F. This is sim into place but where possible it i- belter ilar in properties and u-es to Stand to pour the mix into a mold a- it nuke- ard Firecrete but is composed of a more homogeneous shape-, requires |e-- higher heat-resistant base which labor, and eliminate- po--ibilip of failure make- it applicable for use against because of inadequate ramming. W hen a higher temperature. casting it is preferable to make a complete 3. Light Weight Firecrete for tempera section at one lime to prevent -tratihcation. tures up to 2200"F. This is similar If material has set. the surface -Inuild be to Standard Firecrete but much well scarified to insure proper bond with lighter in weight. It has unusually fresh refractory. The mix should be low thermal conductivity and is ap -hoveled into place immediately, and proximately four times as effective as rodded with a blunt end tool until all cor tire hrick in retarding heat flow. Its ners are filled and air pocket- eliminated. power Specialist March-April 194? `r'S/ MT6s;s*:/-p/7t.'irrc`j thk powi Lrft: i-V Intnlated water tupph ptpt under Boh Rit'er brt ieRilhi: The Bou Rtver hndpe from a more pinuretque untl* coldest winter night-. Here is where Mr. \. C. Ghent. Canadian Manager. Govern ment Service Unit of Johns-Manville at Ottawa, should continue the story. "Twenty-two vears ago last September." said Mr. Ghent, "the Department of Public Works at Ottawa sent for me. Advice on insulation was desired. 1 was told that a 12" water main was to be erected to carry fresh water over the Bow River to the town f Banff. This pipe was to be hung on swing braces under the existing Bow River bridge. Temperatures in winter ran as low a 50 degrees below zero--sometimes lower. The water would have an all time flow through the pipe of one half foot per second. Could it be adequately insulated? "5es--by using the following J-M speci fication. 'Cover pipe with 2 plies of 15 lb. J-M Asbestos Felt, cement all laps, then a layer of Johns-Manville Standard Hair Felt. 1" thick, secured to the pipe with a wrapping of heavy jute twine on 2" centres, and over each layer shall be applied a layer of 15 lb. Asphalt Saturated Asbestos Felt secured in place with a wrapping of jute twine. Thi- combination of Johns-Manville Standard Hair Felt and Asphalt Saturated Asbestos Felt shall be repeated until the necessary thickness i- applied, and over the whole shall he applied a wrapping of 55-lb. Asbestos Felt secured with ring- ot copperweld wire applied on 4" centres. The laps on the horizontal pipe -hall hr placed on the side and turned downward to shed water. The whole shall be finallv coated with two coats of cold asphalt coat ing.' " "It is over a score of years since thispecification was given. 1 had altno.t for gotten it until, during a recent conversa tion with Mr. J. M. \4ardle. Director nt Surveys and Engineering. Department of Mine* and Resources at Ottawa, the sub ject of Banff was brought up. Mr. 5kardh said that twentv-three years ago he was Chief Engineer of National Park- of Canada in which Banff wa situated. Hr well remembered the installation of thr water main, and its insulation according to J-M specifications. But what wa- of greater interest to me. as a John --Mans ill-man. was to learn that Mr. 5k anile had. shortly before our merting. inspected thipipe line. He had found m> delect- in it Judging from its present appearance it seemed likely to last another dcradr oi In all the years since it- installation the pipe had had no failurr. Thr people >.t Banff had their water in all weather-, tinCanadian government had made an excellent investment, and John--Mam ill-- had another job well done" TIE POWER SPECIALIST I.T k ' ' Form* for shape* may Lt made either of wood or metal. IX ooden form- are u-ed generally in emergencies, since ihev are quickly ron-lrucied and. H nece--ar*. ran be burned awa* without damage to the refraclor>. If a number of shape- art re quired. a heavy metal form, well coated with oil. which can lie u-ed repeatedlv will prove more sati-faiP>r*. Mich moldshould be in 2 or 3 -ection- -< that tliev can he easily removed, and made ready for another casting. Firecrete harden- sufficiently in six hours to permit the removal of the formif necessary. On small tn-tallations 12 hour- curing i- de-iralde before heat is applied. It is preferable, however, to let lining- ,f Firecrete cure for 24 hours or longer before putting into service. The hardening can be accelerated by mixing Firecrete with hot water. This practice, however, is not recommended except when the shape is urgenth required a- it re duce* ultimate compre-sive strength. Because of it- inherent advantages, a monolithic furnace door lining is a dr-trable construction for both new and old equipment. By using a castable refractory material, the labor and cost of cutting and fitting brick to the door frame i- elim inated. For old door- which have become warped or distorted in operation, a mono lithic material afford- the only practical, economical method of relining. Firecrete. quickly prepared and placed the same aconcrete, readily adapts itself to any irreg ularities in the frame and i* read*- for ser vice after a few hour* of air curing. Firecrete is suitable for lining doors of practically any design. Doors less than 4 sq. feet in area generall* require no rein forcing to hold refraciorv m place. On larger doors anchor rod- with bent end*, or bolt with waher- and nuts are gener ally used. Here again John-Manville engi neers are available for advice on the lay out and spacing of -uch reinforcement, or on any other question on the use of Fire crete Refractorte-. SPECIALIST I7 Firecrete is handled ns ensilv ns ordtnnrv nmrrete. Be eareiut to itv the right amount of uuf-r. Above: Standpipe limnps are t/imUt poured. Belou: Specie/ thape$ are eauh roo*tructed. Arm*-Vorv "E" flag warded to Johns-Manvill* factory workers ot Vom ill*. V J. Lrli to nthi: l*tunt Mgr. John E. Begen, Claude Schollenbergtr, president of the A. F. of L. unton ot Montitle, Mi Elisabeth Mosell, and Major General Thomas E. Robins. ARMY-NAVY "E" AWARDED Workers of J-M Manville Factory Receive Coveted Honor VER 4.000 Johns-Manville workers tial part they plaved. "Not onlv do -.m O and members of their families as help make it possible for our armed fori. sembled in Manville. N. J.. on March 24ttho fight." he pointed out. "but you plj\ tu celebrate the formal raising of the a vital part in training million- more to Army-Navy "E" flag over their factory. join the more than a million and a hall Major General Thomas E. Robins, fighting men we already hae mer-oa- chief of the Construction Division. O.C.E.. Throughout the United State* llir-e muiii- together with other Army and Navy men. the flower of American manhood, air officers, represented the Government. being sheltered in building- in which sou- President Lewis H. Brown, in a short shingles. wall board and other building speech, pledged continued and unceasing materials are to be found. All tlie-i--i- effort in the production line from Johns- gether with new war product- and -ecu i Manville and its workers. u-e- of material- that cannot be imi ab-.l The war production at Manville in now--make your part in the war elbm clude- such essential item- a- asbestos tex one of which any group of men and wo tiles. packings, packing cup- and gaskets, men can well be proud." insulating materials, a-he-t..- and asphalt The flag was accepted on behalf of th- building product-. Tran-ite pipe, brake Manville factory worker- b\ John F linings and clutch facings. Begert. plant manager. Commander Aii-'in Referring directly to some products not S. Kibbee. appearing for the Na". pr-. ordinarih linked with fighting equipment. -ented the lapel in-icnia which ru-n >-ii,- Major General Robin- told of the e--en- ployee of the plant t- entitled t.. wt-ai. 1M TIE Pll af" f ' 1 **4 Fire Bride -i Modem Furnace Construction By N. ALLEN HUMPHREY District Engineer Jehns-MtnviUe NSULATION' is playing its part in speeding up I the wheels of industry as well as keeping them turning efficiently. Until recently insulation was employed for economy and to afford comfortable working conditions only. With the advent of insulating fire brick insulation can actually be used' to speed up many furnace operations. Periodic operating furnaces such as those for heating, forging and heat treating are ones in which insulating fire brick play their important role. In these furnaces losses due to heat storage within the walls become a greater factor than heat transfer through the wall. With heavy refractory walls that soak up the heat like a sponge hours of valuable time and large quan tities of fuel are required to bring the furnace up to the desired operating temperature. On the other hand light weight insulating fire brick walls heat up quickly and absorb far less heat. In fact about onefourth as much heat is required to establish equili brium conditions in an insulating fire brick wall as would be required in a fire brick wall of the same thickness. Figs. 1 and 2 illustrate the equilibrium conditions of a 9-in. fire brick wall subjected to a furnace tem perature of 2400 deg. F. Fig. 1 is for an uninsulated wall; Fig. 2 for a wall insulated with 4J4 in. of 2000 deg. F. insulating brick. Note that the 4y3 in. of insulating brick reduce the heat transfer by 1852 -- 473 = 1379 B.t.u. per square foot per hour. With the equipment operating continuously for approxi mately 8000 hours per year, being fired with oil at 3 cents per gallon, there would be an annual sav ing by the use of the insulation of approximately $4 per square foot of wall area per year. The installed costs of the 4yi in. of insulating brick would not be over $1 per square foot. Therefore, for equipment operating continuously the use of insulation in back of fire brick is most desirable. On the other hand a vast majority of heating, reheating, forging and heat treating furnace* artoperated intermittently. With intermittent opera tions the heat storage within the walls becomes a more important factor than the heat transfer through the walls. In many instances the equi librium conditions of heat storage and heat transfer are not obtained before the iurnace is shut off tor the night. In Fig. 2 the heat storage of 54.910 B.t.u. per square foot of wall area is equivalent to 9 gal lons of fuel oil; compare this with a similar wall constructed of 9 in. of insulating fire brick with 1 in. of high temperature block insulation as shown in Fig. 3. In this wall the heat storage is reduced to approximately one-fourth of the amount stored in the insulated fire brick wall. Unfortunately inis comparison does not tell the whole story, or may not even serve to guide us in our choice of materials for furnace wall construc tion. What we should know is how much heat must be applied to the respective walls during a normal t*eo V Reprinted from Blast Finuua An Sm Plajtt rm Dmtn, 1941 A-' Printed in US.A. cycle of operation. As a guide in this direction we have constructed Schmidt Graphs* and obtained the data given in Fig. 4. This figure is the composite data obtained bv construction of a series of the Schmidt Graphs on heating as illustrated by Fig. 6 and on cooling as illustrated by Fig. 7. Insulating fire brick walls come up to the operat ing temperature in much less time than regular fire brick under the same firing conditions. This is illus trated by the Schmidt Graphs; compare Figs. 4 and 5-A. Only about one hour is required to bring the insulating fire brick wall face temperature up to the 2400 deg. F. operating temperature, while many hours are required to heat the inner face of the fire brick wall. This has to be compensated for by allowing more time in which to reach the full 'Industrial Furnaces. Volume 1, Third Edition by W. Trinks. Appendix 2. John Wiley & Sons, Inc., 1934. .kMWlM'mr 1 rm tzj l! 1 r/y/nm 'XSSf/Mi sXSSM/IK SXSJMtU operating temperature or by harder firing As a result much time and a considerable quamirv of fuel would be saved, each time the insulating fire brick furnace is heated. No attempt has been made to estimate this saving except as a factor in com paring the losses in cooling because of the greater heat storage in the fire brick wall. The advantage of this difference in time required to heat up is one of the chief reasons for the use of insulating fire brick in combustion chambers o: domestic oil burners. Better combustion condi tions and reduced heat losses often result in fuel saving of 10 per cent or more. See Measuring Losses from On-Off Firing by F. K. Ovetz and J. G. Nellis, Fuel Oil Journal. November 1938. In constructing these graphs we assumed that the furnace would not be tightly sealed during the shutdown period and that the natural draft would cool the interior at the rate indicated in Fig. S. Curves "A". In the case of a tightly sealed iurnace the loss would be from the outside due to heat transfer through the wall only. This condition sel dom exists except in electric furnaces which do not have flues. As the insulating fire brick heat up more quickly than fire brick we have assumed that the cooling will also be more rapid on the interior face. To select the most economic furnace wall con struction a Performance Cost Study can be made from tfie data obtained by the construction of the Schmidt Graphs in much the same manner that comparisons are made on various thicknesses and kinds of insulation to determine the most economic kind and thickness of insulation to be employed. In order to make the analysis more complete we have also compiled similar data on 9-in. fire brickwall only, as shown in Fig. 9, and on a 9-in. insulat ing fire brick wall only as shown in Fig. 10. The tabulation shown in Table I is a Performance Cost Study comparing the data obtained above M|. 5-A Fie. 5-B L The 9-in. insulating tire brick and 1-in. block insula tion wall shows very good economy and affords the best construction. The 9-in. insulating fire brick only shows slightly better economy. However, the insulating block offers broken joint construction which is conducive to good tight furnace wall con struction and is therefore the standard recom mendation. This study is, of course, based on a rather com plete cooling of the furnace walls during the over night shutdown. The design of the furnace would to a large degree govern the cooling rate. The rates chosen for these studies may be excessive for the better type of construction. With some experience records to serve as a guide studies should be made in the above manner in order to arrive at the most economic furnace wall design. As an illustration we have supplemented the above study with another cooling cycle for the wall constructed of 9 in. of insulating fire brick backed up with 1 in. of block insulation. See Cooling Curve "B" for insulating fire brick Fig. 8 and Fig. 5-B for the composite data on heating and cooling. The performance cost study clearly indicates that with Fig. 7 Table I--Pwf Coat Study--Xaaulatiac Brick i Fin Brick Furnace wall eonitruction 9* fire brick onI 9* fire brick 9* insulating 9' Insulating fire brick 4H* insulation fire brick on`y and 1* insulating block 1-- Heat transfer equilibrium. B.tu./aq. ft-/hr....... 2-- Heat storage equilibrium. B.t.u./q. ft............. 3--Assured heating and cooling cycle............. ...... 4-- Heat transfer. 10 hours heating and operation.. 5-- Heat loss transfer--14 hours cooling.............. 6-- Heat loss to interior--14 hours cooling........... 7-- Total heat loss--14 bours cooling (5 + 01....... 8-- Total average heat loss per. 24-hr. day (4 4-7). 9-- Total heat loss million B.tu./sq. ft./year*..... 10-- Approximate cost of furnace wall per sq. ft11-- Normal fixed chargeit--25 per cent............... 12-- Total yearly cost (9 -l. H)............................... 1852 31300 A 10080 8135 22365 30500 40580 10.22 $ .90 $ .22 110 44 473 52200 A 1750 3315 40935 44250 46000 11.44 S 1.67 S .417 $11.85 537 9975 A 2290 3395 5870 9265 11555 2.88 $2.16 $ .54 $1.42 392 12480 A jJ45S 2795 7535 10390 11785 2.94 $2.36 S .59 $1.51 392 12480 B 1655 3370 5650 9020 10675 2 67 S2.J6 S .59 $.1 26 Assumed Conditions 2400 deg. F. normal operating temperature. * Eight hours per day operation--250 days per year--2000 hours per year. Fuel oil. 3 cents per sallon--150.000 B.t.u. per gallon. 40 per cent efficiency = 50 cents per million B.t.u. available heat. Fire brick cost $60 per M--Labor laying $20 per U. 260Q deg. F. insulating refractory brick--$145 per M-- Labor laying $20 per M. 2000 deg. F. insulating refractory brick--$100 per M-- Labor laying $20 per M. 1900 deg. F. diatomaceous earth block insulation--15 cents per sq. ft., 1 in. thick--Labor installing 5 cents per sq. ft. tNormal fixed charges--Amortized in approximately 5 years with interest = Approximately 25 per cent per year less complete cooling during the shutdown period the insulating block in back of the insulating fire brick affords a good return on the investment. The same is true in the case of furnaces used for annealing where the cycle of operation extends over a longer period of time. Insulating fire brick will replace ordinary fire brick as the lining for periodically operated furnaces as fast as the trade becomes aware of the improved economy and greater flexibility in heating and cool ing that is obtainable by their use. The insulating fire brick must possess the refractory qualities of the better grade of fire brick. Even with a some what foreshortened life the economy of using the light weight insulating fire brick is apparent. Theo retical studies such as the above will guide us and actual performance will prove that insulating fire brick are a big contribution to modern furnace design. Reprmtti fnm Burnt Fuxxacx ana Stbl Puur raa Dusmub, 1941