Document zb39qe5yjz8NOqB1QX1K8mK4z

FILE NAME: Power Generation (POW) DATE: 1946 DOC#: POW008 DOCUMENT DESCRIPTION: Published Article from Trade Journal S*" iI' ' '-'"T- ?v r b R - U Eugene W . O 'Brien Managing Director SV Francis C . Smith, Editor Jk\. Hunter R. Hughes, Jr. -V.Jy. Associate Editor I- Richard L Priess Southwestern Editor W. L Coogler Production Manager tuiintu Reprotentativei E. It. ltogers, 18 Bust 48th St., Uooin 1004, New York 17, N. Y.--Phone, Plain 8-0505 William K. Horruimi, HO llowdolu 8t,, Muplewood, N. J.--Phone So. Orange 2-2484. M aynard L. D u rh a m , 67 Corlngtou Road, Buffalo 16, N. Y.-- Phone, Amherat 6882. X. E. C. Smith. 206 Auditorium Building, Cleveland 14, Ohio --Phone, Cherry 7852. P O. K. Johnson, 168 North Michigan Ave., Chicago 1, 111.--Phone, Central 4181. L. B. Chappell, Auditorium Bldg., 427 West 6th St., Dos Angeleji^Callf. -- Phone, Tucker jUehard L. Prelaa, 1841 Lib erty Bank Bldgg., Dallas, Texas.--Phone, Central 7678. Annual Subscription--*1.00 Canada--*1.60 ; Foreign *2.00 fubliihed Monthly by W. R. C . SMITH PUBLISHING C O . ' ' Mdlsbere also of: Cotton, HIccIriesi Sooth, Southern Hardware, lasthem Automotive Journal W. J. Rooke, President; B. P. smith, Executive Vice-President; J j f , McAllister, Vice-President: s W'. O'Brien, Vlee-l'resldent: A, & C. Bmlth, Vice-President: I, C. Cook, Vice-President: O. A. arpless, Treasurer; A. V. Bob 5 , Secretary. Editorial and Elocution Oiticos grant bu ild in g ATLANTA, G E O R G IA U I l'"s ,\ - VsdRa -i i'%, CONTENTS y>. v' . . ' , , . . v , .... N 0! v 1. Hof Power for Tampa, by E.J. Wiseman and E. A* Sfroborg.,. . : . . . 44 , Sound Conditioning, by Francis A. Westbrook . . . . . .V.. ., 48 lea Handling Methods, by John E. Hyler . , . . . . . . . . ............ 51 Virginia Rayon Tira Cord Plant . . . . ,-J ............... 54 * Tima Stitdy Improves Relations in Industry, by W. C. Warn*......... . 55 Crushed Cribbing, by J. P. McEvoy.............. ................................ 55 ' Metallic Corrosion, by M. F. Wulfihghoff . . . . . ,. 58 Radiant Heating, by Jama* A. Cain . . . . . . . . , . . . . . . . . 60 Mississippi Beckons to Industry........................... .....................63 . Dipt Exhaust Systems, by C. C. Hermann.. .. . ............................. . 64 . ' >fbc^stntction of Italy's War WrockadUtifitios, - by Robert A. Bell ___ ...................................... ....... 66 i Pipage fVo^BnilarWatar, by Marry M. Spring........... .......68 N # , *. i ...... I I ..; >'*' * ' * * * ' ! ***.*1 *T5 " -,r 90 "AjiPoria" Plpa Chart : /J. ; -A-t-k : . .' .*' . "x. ff iV j V ,fV; V..- f : f ' *f{ v ^ . ' ' v t j;^4)swm ch|Md K. io? - VO Dust Exhaust Systei B y C. C. Hermann This a rticle discusses the scale a t effectiven ess o f d u st c o lle c tio n s y s te m s a n d presents m eth ods for checking air velocity and resistance. THE effectiveness of a dust ex haust and separation system is not measured by the weight of sol ids removed, the weight of air handled or the efficiency of the separating equipment but by the ability of the system to reduce the dust count in the working area to an acceptable safe minimum. The safe limits for several common at mospheric dusts are set forth in Table I. The allowable amounts vary for different cities and states which accounts for the spread given in the table. It is advisable to con sult local and state codes for veri fication in every case. This is the yard stick by which the effective ness of the dust collection system must be measured. Dust Collector The effectiveness of the dust col lector lies in the amount of fine dust it fails to remove from the air. The dust loading from the productive operations may be high, 50 to 100 grains of solids per cubic foot of air, but the air discharged from the collector should not ex ceed the city and/or state codes which in some instances is speci fied but in most instances is not. While it is true that the air from the collector discharge is liberated outside, an over burden of contam inates may result as a plant nuis ance, a neighborhood nuisance or even a hazard to health. The con taminated air may short circuit back into the work rooms of the plant through open windows or doors. It is well then to bear in mind that the dust collector has a job to do. Exhaust Fan The efficiency of the exhaust fan is very well established by the design and the original system was installed with a clear knowledge of what this efficiency was. The fan efficiency will not remain con F I6 . I. FOUNDRY SAND HANDLING SYSTEM . stant since many things can hap*! pen to the fan. The belt may bi slipping resulting in a reduction in' speed and since the volume han* died by the fan and its static ca* pacity are functions of speed there will be a considerable change id volume handled. The fan blade may become bent or coated with " material from the air stream and the internal walls of the housing may become badly worn, rusted > or caked with material all of which will effect its efficiency. Duet Work The duct work connecting the t various dust points to the dust collector may acquire a heavy internal coat of solids. Solids may have precipitated out of the air stream and lay in the bottom of . the pipes. All of these things cause a change in the functioning of the system and they all show up at the points of production in the way of reduced ventilation and a subsequent increase in the dust count of the atmosphere at this point. Hood It is often possible to correct a deficiency in ventilation and keep the dust count 'down at a given production point by making a change in the hood. Take for ex ample the belt transfer point on a foundry sand handling system, as shown in Fig. 1, in which "A" is a plan view, "B'' is a side elevation and "C" is an end elevation. The delivery belt is shown at 1, the take-away belt at 2, the dust hood at 3, and the exhaust duct at 4. The belts are 24" wide and the material handled is molding sand removed from the shake-out but still of sufficient high temperature to produce a very heavy dust cloud at the point where the sand is transferred from one belt to an other by falling through the space .A F IG . 3. USE OF T H E 8TAT1C T U B E IN CH ECK IN G R ES IS T A N C E. between the two belts. After many experiments and trials it has been found that a hood such as shown provides a very ef fective means for capturing the dust. The dust particles may be as small as a fraction of a micron in size and never settle in a mov ing atmosphere. Left open to the general atmosphere the particles would contaminate the air for a considerable distance around the belt transfer point. Properly hooded the hazardous dust can be readily removed, i.e., force as much air into the hood as it is designed to take out. The proper ventilation for a 24" or 30" belt is 750 cfm and for a 36" to 42" belt 1000 cfm. The air is removed from the hood through the duct connection 4 located at the high point of the hood. The replacement air is ad mitted through the openings at 5, 6, 7, 8 and 9. The opening at 6 is a free opening while the others are restricted. A piece of leather se cured to the top edge of the open ings 7 and 8 restrict these since the leather will ride on the sand heap allowing air to enter at each side where the sand slopes away to ward the edge of the belt. The opening along the sides at 9 and around the pulley and belt at 5 are restricted as much as possible. The total openings are tabulated as fol lows: Sq. In. 5. ^ " c le a ra n c e aro u n d th e belt, 14" p u l l e y .... ............. = 81 6. 24" w ide by 12" high b e tw een b e l t s ........................... = 288 7. S and heap 8" high, each opening 36 sq i n __ ______ = 72 8. Sam e as No. 7 .................... =: 72 9. 1% " x 36" each side............ -- 108 a total of 621 sq in or 4.31 sq ft. Then 750 cfm/4.31 -- 175 fpm ve locity of the inflowing air. Where there are no strong cross drafts existing this velocity is satisfac tory, however, it is near the mini mum as any appreciable decrease in the volume handled by the ex haust system would drop the in put velocity below the desired minimum. One way to determine if such hood is performing as it should would be to make a dust check of the atmosphere in the vicinity of the hood. In the absence of a dust counting apparatus or skilled as sistance to make such count, the air volume handled by the pipe leading away from the hood can be determined and compared with the design figures. The mere tak ing of static readings at this point would be of slight value. Observa tions made with the eye would, likewise, be questionable in view of the microscopic nature of the dust. Aix Velocity A velometer or any other type of pitot tube can be used to make air velocity readings direct in a duct. The jet is connected to the (Continued on page 84) -- --------------------------TABLE 1----------------------------- Approxim ate safe lim its for atm osphere dusts Substance Silica dust Silica dust Asbestos dust Blast cleaning Foundry general Free silica content 10% o r m ore by w eight Less th a n 10% b y w eight Millions of particles per cu. ft. of air by light field, low powc counting technic. 5 to 10 30 to 100 5 10 30 SOUTHERN POWER & INDUSTRY for APRIL, 1946 65 Dust Systems (Continued from page 65) indicator and a hole large enough to receive the staff is made in the side wall of the duct. The staff is inserted to the centerline of the pipe, the staff being marked off in inches and fractions for conven ience in locating the jet. Read ings, taken for each inch of radius of the pipe are added and divided by the number of readings to ob tain an average velocity. Table II shows velocities in fpm corresponding velocity pressure and the volume of air carried by pipes of different diameters. Sup pose the average of our readings was 3,750 fpm and the diameter of the air duct was, by measurement 6". Going down the column of figures below the 3,750 fpm head ing to the 6" dia. pipe line we find that the volume handled is 736 cfm. This is within 14 cfm of the design. But suppose the velocity read only 3,000 fpm--under the 3000 fpm heading we find 589 cfm as the volume flowing in a 6" pipe. Dividing this by 4.31 sq ft as found to be the hood opening above, we have an inlet velocity of 136 fpm or a reduction of 22%% and to return the inlet velocity to the original design amount of 175 fpm we must close off at opening No. 6 to 1.4 sq ft. The alternative would be to go through the system and determine the cause of the re duction in velocity and correct the trouble at its source. This latter course is the logical one since other vent points must be affected in a similar manner. Resistance Check When dealing with a system which has been in service for a considerable period of time and trouble of this character is dis covered the next logical step would be to take a resistance test across.1 the dust collector. The resistance | of dust collectors varies in differ->3 ent makes. The resistance of the'? dry type collector varies from to 3" water gauge, and in a w et| type collector the resistance from a inlet to outlet is approximately 3" water gauge. The standard resist ance for a given type and make collector should be obtained from the manufacturer. To measure the resistance across the collector, regardless of type and make, static readings should be made at point 1 on the dirty air side of the unit as shown in Fig. 3 and at 2 on the clean air side of the unit. There may be a slight. difference in the velocity at the respective points but for the pres ent purpose this may be ignored. Subtract the pressure reading at 1 from the pressure reading at 2 if the fan is beyond 2 or on the clean air side. The difference in total F IG . 4. EXH AUST FAN D R IVE INSTALLATION. Courtesy American Foundry Equip. Co. pressure thus obtained is the ap proximate resistance of the unit. If a pitot tube is being used take the RP at the two points and make the subtraction to obtain the re sistance of the unit. If the fan is on the dirty air side of the collector and is blowing through use the static tube as shown in Fig. 3 and subtract reading NO. 2 from NO. 1 i to obtain the resistance of the unit. Compare this with the manufac turer's standard and if it is high it indicates that a plug is forming, or has formed in some part of the collector. Perhaps it merely needs cleaning. Filter type collectors will increase in resistance when used without periodic shaking but will reduce in resistance when worn out or contain damaged cloth or bags. Exhaust Fan Drives Exhaust fan drives give consid erable trouble from slipping par ticularly when the motor is mount,ed wrong and the pull of the belt is on the top stands instead of the bottom for wide center drives. Fig. 4 is an excellent drive design. One improvement could have been made by lowering the motor some what as the angle drive has some desirable features. The motor is on the discharge side of the fan and the bottom strand of belt is ' 84 SOUTHERN POWER & INDUSTRY for APRIL, 1946 TABLE II A ir V olum e in Piped a t S p e c ific V e lo c itie s and V> P . V P = (V /4006)2 Dia., inch* 2 3 4 5 Ara. sq ft .0218 .0491 .0873 .1364 3000' V 0.56 VP 65 147 262 409 3500' V 0.76 VP 76 172 306 477 3750' V 0.88 VP 82 184 327 512 4000' V 0.997 VP 87 196 349 546 4500' V 1.26 VP 98 221 393 614 5000' V 1.56 VP 109 246 437 682 6 .1964 7 .2673 ! 8 .3491 9 . .4418 10 .5454 589 802 1047 1325 1636 687 936 1222 1546 1909 736 1002 1309 1652 2046 786 1069 1396 1767 2182 884 1203 1571 1988 2454 982 1337 1746 2209 2727 11 .6600 12 .7854 13 .9218 14 1.0690 15 1.2272 1980 2356 2765 3207 3682 2310 2749 3226 3742 4295 2475 2946 3507 4009 4602 2640 3142 3687 4276 4909 2970 3534 4148 4811 5522 3300 3927 4609 5345 6136 16 1.3963 17 1.5763 18 1.7671 19 1.9690 20 2.1817 4189 4729 5301 5907 6545 4887 5517 6185 6892 7636 5236 5911 6627 7384 8182 5585 6305 7068 7876 8727 6383 7093 7952 8861 9818 6982 7882 8838 9845 10908 21 9.4008 93 9.6398 23 2.8852 24 3.1416 25 3.4088 7316 7919 8656 9425 10226 8419 9239 10098 10996 11931 9090 9889 10820 11781 12783 9831 10559 11541 12566 13635 10825 11879 12983 14137 15340 19037 13199 14426 15708 17044 26 3.6870 11061 12905 13827 14748 16592 18435 27 3.9761 11928 13916 14910 15904 17892 19880 28 4.2761 12828 14966 16035 17104 19242 21381 29 4.5869 13761 16054 17151 18348 20641 22935 30 4.9087 14726 17180 18408 19635 22089 24544 under tension when power is on while the top strand may lay down thus increasing the angle of con tact. The drive is nearly a ratio 1:1 and is protected by a heavy sheet metal shield. The motor is provided with a take-up base. A desired feature of belt guards is an opening opposite the shaft ends so that shaft speeds may be taken without the necessity for removal of the guard. Knowing the design speed for the fan and having the name plate speed of the motor it is a simple matter to check the slip page by aid of a revolution counter. Reconstruction of Italy's Utilities (Continued from page 67) In Sicily, Sardinia, and Southern Italy, the Germans did compara tively little damage to the power systems. There was little heavy industry in this part of Italy, hence they did not see the necessity of demolishing power facilities, and the war was moving so rapidly that they had no time to plan ex tensive demolition. Then, too, they thought that they would soon be back and would need this equip ment. However, things could hardly be said to have been left undisturbed. In order to obtain conductors to repair a 70,000 v trunk line in Sicily, it was necessary to recover and use much of the overhead trolley-wire of the street-car sys tem of wrecked Messena. A group of Hydro-electric plants in Calabria (the part of Southern Italy so well known to the readers of Norman Douglas) with a capaci ty of 170,000 kw was left practical ly undamaged. This capacity soon in operation and supplkf Naples, Toronto, Bari, and Fogg Before the transmission line fflUthese plants to Naples was put ia service, the city was supplied wi, power from submarines in the har bor. Naples' own steam pla^,: (normally a standby), which ww considerably damaged, was t*t paired by the Royal Navy, and it? three 15,000 kw units went In' operation in May, August, and No*\ vember of 1944. Central Italy Conditions were quite different in central Italy. By this time the fighting was moving forward slow ly, the Germans were angry with the Italians for quitting, and they began to see that there was little likelihood of th eir regaining much lost territory. With these thing in mind, the Germans did a thor ough job of demolition, destroying 93% of all power generating ca pacity between Naples and Flor ence. The effective generating ca pacity in this area had amounted to about one million kw, but after the permans left, only 57,000 kw were in operating condition. Of this, 30,000 kw were in two old standby steam plants in Home. The Electrical Division and other Allied Military Units went to work immediately and within six months had increased the plant capacity to 170,000 kw and then added an other 170,000 in the following year. This was accomplished primarily by rebuilding wrecked machinery without the import of new parts. Construction materials, as well as food, were in the black market, and in 1943-44 it took six months to receive an order from the states. Major overhaul jobs were under taken and completed in the field that would have been considered impossible under most favorable peace-time conditions. For exam ple, the main casting for a 12,000 kw, 3000 rpm steam turbine was. cast, machined, and assembled without blueprints (the factory in Northern Italy being in German hands) and with only the broken and scattered pieces of the demol ished casting to use as a pattern. Sheet mica for insulating com mutator bars and generator coils 86 SOUTHERN POWER & INDUSTRY for APRIL 1940-