Document 10w64MV0GDNpmN7w1NkGRKy0K

Dependency on Electricity serious cases are not as widespread as might have been It takes a hurricane such as that which swept the Northeast Seaboard on November 25 to drive home to most people their widespread dependence upon electric energy for carrying on their normal everyday pursuits. Among the diverse inconveniences and hardships result ing from partial or complete suspension of electric service were stoppage or curtailment of electric railway service, both above and under ground, ferry service where dock ing facilities were dependent on electric power, tele supposed; that other contents of the oil, notably sodium sulfate, are as responsible as vanadium pentoxide, and that trouble from plugging and hot-end corrosion is un likely if tube temperatures are kept below 1100 F. Coldend corrosion in the air heater may present a problem due to the sulfur, if the exit gas temperature is low. Here it is a matter of balancing a slight decrease in efficiency against the cost of washing and maintenance, as well as the residual oil price. phones, street, shop and home lighting, heating with oil burners or stokers, electric hot-water heating, cooking Engineering Manpower by electricity, radio and television, not to mention a One of the most important problems facing the engi multitude of other electric appliances. neering profession at the present time relates to the sup Had the storm occurred during the week, numerous ply of engineering manpower. Several factors contribute business operations would also have suffered. to the anticipated shortage of engineers. Foremost is While many of the service stoppages were due to over head distribution lines being down from fallen trees or poles, or cut off as a precautionary measure, underground distribution also suffered in some cases from inundation. the international situation as reflected in military mobili zation and defense production. But as far as continuing education of engineers is concerned, related factors are the pessimistic reports on the future need for engineers The extent and periods of outage varied, of course, with the location of the affected area, ranging from a few hours to two or more days. Meanwhile, those affected were treated to a glimpse of living during the middle of the nineteenth century. For the most part the inconveni ences were taken in their stride, as inevitable in an elec emanating from the Bureau of Labor Statistics and the fact that there are fewer persons now coming of college age because of the low birth rate during the depression of the 1030's. By implying that there will not be enough jobs for engineers and influencing school counselors to discourage high school students to enter engineering, one tric age where the annual per capita use of electricity reaches approximately 1650 kwhr. However, one mav wonder as to how many stopped to think of the heroic efforts of the utility service crews in striving, under ad government agency is aggravating the engineering man power problem at the same time that other government agencies--to say nothing of private industry--stand in need of more engineers. verse and often dangerous conditions, to restore normal services as quickly as possible. These are the men to whom major credit is due. The engineering profession through the Engineers Joint Council has been asked by the National Security Resources Board to suggest policies and methods which will insure the effective utilization of engineers for Troubles from Burning Residual Oils large-scale mobilization. An eighteen-man Engineering Manpower Commission composed of representatives of One of the best attended and most timclv sessions at six engineering societies has been appointed with the the A.S.M.E. Annual Meeting, from the operating man's responsibility of developing policies and procedures de standpoint, was that dealing with the burning of residual signed to secure the most effective use of engineering fuel oils in steam boilers. With the marked increase in skills in industry and government during any future fuel oil consumption by central stations and the influx emergency and of taking necessary steps within the of foreign oils during the past lew years, difficulties from scope of the Engineers Joint Council to bring such corrosion and plugging have beer, encountered. These policies and procedures into effect. The situation is have initiated several studies and resulted in a number complicated by the uncertainty of universal military of published papers on the subject. In general, the training and expansion of R.O.T.C. in the colleges. vanadium content of certain oils was believed to be Also, present policies of Selective Services have appar chiefly responsible, although its action and that of cer ently led to much confusion concerning the future of tain other constituents was not dehnitelv established. engineering students. The survey presented at this session, and reported The fundamental need is to use the limited reservoir briefly elsewhere in these pages, was most exhaustive in of engineering manpower to its best advantage. It is that it brought together the operating experiences of to be hoped that the Engineering Manpower Commission practically all the oil-burning central stations, as well will be able to set up and implement a policy which will as the refineries, supplemented by the findings of sev eral forestall the waste of engineering skills that resulted investigations. It would appear from this that the Iroin some of the induction procedures of World War II. December 1950--C OMBUSTION R8-000208 1/17/02 NUECES 43 Architect's perspective o Johnsonville plant - v> - / Johnsonville Steam Plant of the TVA A discussion of the design features and By H. J. PETERSEN* some of the reasons why certain condi tions and designs were selected. The plant is laid out for six 125,000-kw units with throttle conditions of 1450 psi, 1000 F. The first unit is scheduled for Plant will be the second largest steam-electric plant in the world and will make an important and substantial contribution to the national defense program. operation in October 1951 and the others at two-month intervals thereafter. Site Selection The site selected for the plant was chosen because of the advantages it offered in the way of fuel availability DaJjodtsuaueficmcicl3nrayopi1ttUpneei41tcrandhdd,R,aae0naipss0ts1lIfrhsNriy0i9sdoeoa4ehGenlkm8ytxohw,Vpttryrhtir1aattandeoioh,nlgcr7lgeeoqrep5Jretyuoa4wuaoyi,wmcalp0sofeyker0ioapneweyr0wroga1esso,ewkwatsurdwre1oaafsleod9rons.bm5lntdilohny0otaoa,Ammwn2tvhteadoi,ehsn0fedrsiete6grteutfmonSocedaite,rictbW0yvnxoe0uepegtoon0provufaforewinlgdkamtdwtdheeewhierincesy,suWrateitt-sneapalAateaahnwrkruortsmeoaahb.tinftnyehlIecaIpotpFtrmonTooeroriwetaowtepohiysnmenxrbeee'ersrvesaanswmsmcitynninhturxisoioddcilnslWtsusheusttsunsmreetesafineisstatevnseetclewetosawmthbrropharaneyloiredoyllslrnTrbToetbsceaaeitoasuehnrtnthgptnirnenoienesaeterenev,fsnrmsyr,iafsrds,aiaetonc6eecietnro5igetnoleog0otpootr.,tlRhnio0srhane.i0gattvgUrT0rneurra.hwaeWrc3gp.eStqak0aehhr.ut.0ledyeeliHCorf,nrtoenlooiogrtmssnareiahuatsle,dopwnnoi,cfsptsaathftsmclhnyyceroe,oeifsooNabasrslrieleiiloimitnzoeplt.agedhpne7tdeicorisw0ohlfrhiatnvtoapwhaocestlanuhteaieroleecrtirnnterdai,ttteep,hhnsaoeaeeiids,strft plant. Accordingly, funds were requested from Congress for a steam plant of three units, each having a capability of 125,000 kw. These funds were approved in Mav 1949 and construction began immediately. In March 1950 one more unit of similar capacity was authorized, and during the fall of 1950 another two units were authorized, mak ing the total installed capability 750,000 kw. The first unit is scheduled for operation in October 1951 with the remaining units following at approximately two-month intervals. When completed, the Tohnsonville Steam * Head mechanical engineer and chief of the Kieehamcil Tennessee Valley Authority, Knoxville, Teun branch the Power House An investigation was made regarding the merits of a semi-outdoor type of power house versus the conven tional fully enclosed type. After considerable study it was decided that while it is recognized that the semi-outdoor type offers some saving in first cost, this could be minimized with a cheaper type of construction, and the operating conveniences of a closed power house need not be sacrificed. Accordingly, the superstructure walls are faced with aluminum, siding, which lias a very low erec tion cost, tvith a horizontal section of brick to relieve the monotony of the solid wall for architectural appearance. 44 RS-000209 December 1950--C OMBUSTION 1/17/02 NUECES should be taken to eliminate as much of; the'jfly?aslip nuisance as possible. The mechanical fly-ash collecwrer'which are being installed to protect the induced-draft fans from excessive erosion will eliminate most of the fly ash. Also provision has been made in the power house design for the future installation of electrostatic pre cipitators should they prove necessary. The stacks rise 50 ft above the power house roof, which makes their height 171 ft above grade. They also are designed so that an additional 100 ft can be added at any future time, for better dispersal, if necessary. Wind direction and velocity instruments will be installed on the stacks to aid in the air pollution studies. Relation of Johnsonville to other plants of TVA Turbine-Generators The walls of the turbine room and the office wing and service area are a combination of aluminum siding and brick and glass block. By close supervision of the design, waste space in the power house was eliminated in so far as possible, thus fur ther reducing the advantage of a semi-outdoor type. The final figure of 19.6 cu ft per kilowatt for the power house proper compares favorably with other modern stations of this size. If all the shops, offices, storage rooms, etc., are included, this figure increases only to 21.2 cu ft per kilo watt. The turbines have a capability rating of 125,000 kw with a terminal pressure of 2l/2 in. Hg and the steam conditions at the throttle are 1450 psi and 1000 F. The first four generators will have a capability of 125,000 kva at 0.5 lb hydrogen pressure and 143,750 kva at 15 lb hydrogen pressure. The last two generators are designed for a capability rating of 156,250 kva at 30 lb hydrogen pressure. The first four units will be single-shaft tandemcompound double-flow units, operating at 1800 rpm with generator voltage of 13,800. The last two will be triple flow units operating at 3600 rpm with generator voltage of 18,000. At the time the first four units were purchased Ply-Ash Dispersal they were among the largest units combining these limits of capacity, temperature and pressure. By the The tremendous quantities of coal which will be burned time the last two units were purchased the major turbine at Johnsonville would result in a very large emission of builders had developed designs for 3600-rpm machines of fly ash from the stacks unless preventive measures were this size, which partially accounts for' the change in adapted. Although the location is not near any large speed. Another factor is that the 3600-rpm machines centers of population, it was recognized that some steps cost from $400,000 to $500,000 less per unit. The 1S00- COMBUSTIO N--December 1950 RS-000210 1/17/02 NUECES 45 rpm machines have higher efficiencies at lower back pressures, but the higher speed units have the better efficiencies at the higher back pressures with the change over coming at about 1 `/* in. Hg. A study of the cooling water temperatures and the load duration curve indicated that the units will operate approximately half the time on either side of iyt-m. Hg back pressure. Single-casing versus tandem-compound double-flow turbines was investigated. It was found that the savings of the double-flow unit due to its higher efficiency at the scheduled loadings would more than offset the appre ciably lower cost of the single-casing unit. This, plus the fact that no single-casing units of the required capacity had been built at the time these units were purchased led to the choice of the double-flow turbines. heat balances. Although one or two plants were being designed for 1050 F and/or a higher pressure, it was felt that these conditions, at that time, were still in the ex perimental stage and they were rejected in favor of the 1450-psi, 1000-F machines. Since that time the Author ity is contemplating the use of 1800-psi, 1000-F turbines for future units at another plant. The first four units (1800 rpm) will be equipped with moisture separators in the cross-over pipe to the lowpressure turbines. The turbine manufacturer guarantees that this device will remove 24,500 lb of moisture per hour at rated load from the steam at this point, resulting in a decrease in the turbine heat rate of 34 Btu at this load. This moisture will be drained from the separator to the lowest pressure heater, thus returning it to the heat .- j -- ; - ij' Sectional elevation o plant Two sets of pressure-temperature conditions were in vestigated; namely, 1250 psi, 950 F and 1450 psi, 1000 l'. At 1 '/2-in. Hg back pressure and rated load the gain in heat rate by going to the higher steam conditions is ap proximately 1.45 per cent for the temperature rise and approximately 1.0 per cent for the pressure rise, making a total gain of approximately 2.45 per cent. The econom ics of this gain in heat rate is verv favorable, hence, the higher pressure and temperature were adopted. Use of 1050 F and some higher pressure than 1450 psi was also investigated, but nor to the extent of running cycle. The moisture reduction at the end-point because of the extractor is approximately from 15 per cent to 10.G per cent which will eliminate much of the erosion on the last stage blades, thereby reducing maintenance. Use of a moisture extractor in the 3600-rpm machines is impractical because of the temperature and pressure con ditions at this point. The reheat cycle was investigated, especially for Units 5 and 6, but it was rejected because the low price of fuel ($0.IS/MBhu) did not offer enough financial advantage to overcome anticipated extra complexities of control December 1950--C OMBUSTION NUECES Heat-rate curves and maintenance. However, with fuel costs continuing to rise and with the added experience being gained in con trol and operation, the advantages of the reheat cycle continue to increase, and it is probable that the Authority will install reheat units in some future plants. The maximum lift for the generator requires a 150-ton crane. However, two 80-ton cranes will be installed in stead of one larger one, because it is felt that the slight extra cost of this arrangement is more than compensated for by the extra flexibility and availability of the two smaller cranes. Heat Balance The diagram here reproduced shows the heat balance at rated load and l'/'j-in- Hg back pressure for the first four units. The calculated net plant heat rate of 995(> Btu per kwhr which includes 5 j>er cent station power, 2 per cent makeup, and 1 per cent of the throttle flow each for steam and water losses in the boiler, will make the Johnsonville Steam Plant one of the most efficient steam plants in the world. Inasmuch as experience at other plants indicates a makeup of less than 1 per cent, the actual net plant heat rate will be somewhat lower. The number of feedwater heaters was investigated and it was found that six heaters gave the best economy. As the diagram shows, condensate pumps will pump through two low-pressure heaters, one of which will be located in the condenser neck (two in the case of Units 5 and 6), then into the deaerating heater, from which the boiler feed pumps will force the water through three highpressure heaters to the economizer in the boiler. The deaerating heater has an effective storage capacity of 200,000 lb of condensate, which is equivalent to approxi mately twelve minutes of operation. Closed heaters were chosen over open heaters because of their simpler piping and pumping arrangement. On the first four units the three high-pressure heaters are designed with internal subcoolers to reduce the drain temperature to within 15 deg of the incoming feedwater. This was more than justified in the heat rate, and, in addition, reduces the flashing in the drain line, thereby eliminating to some extent a usually troublesome main tenance item. On the feedwater side, all closed heaters are designed for a 5 deg total temperature difference; but when Units 5 and ti were purchased, further study in dicated that a lower drain T.T.D. could be justified and COMBUSTIO N--December 1953 Heat-balance diagram RS-000212 1/17/02 NUECES a ....... ... uuiu) are oeing ae- mum output from one coal pulverizer and <will be used in signed for a drain T.T.D. of 10 deg. In addition, a sub starting up the boiler. ' cooling section is being added to the second low-pressure The economics of steam versus air soot blowers was heater. This addition was primarily to reduce the high investigated. The steam generators purchased have amount of drain flash, since the two low-pressure heaters only three soot blowers on each side of the furnace at the are located in the condenser neck, and it is impossible entrance to the superheater section. This low consump to design the cascaded drain line such as to avoid entirely tion of soot-blowing medium would not justify the in the erosion of fittings. vestment required of compressors, tanks, and piping for Steam Generators air soot blowing so a steam system was chosen. Pro vision is made in the economizer section and in the The steam generators will be of the dry-bottom type furnace for future soot blowers, if they should prove each with a continuous rating of 1,000,000 lb per hr and a necessary. All soot blowing will be by the so-called auto three-hour rating of 1,100,000 lb per hr based on using matic-sequential system where the pushing of one button West Kentucky coal. They are completely water walled automatically operates all soot blowers in their proper and steam conditions at the superheater outlet are 1475 sequence. psi and 1003 F. Because of the large capacity of these Because of the height of the boiler drum it was found units, a study was made to determine whether one or two impractical to mirror drum level to the centralized con boilers should serve each turbine-generator. The unit trol room. Accordingly, this level will be brought to the system of one steam generator per turbine was finally control room by a "Utiliscope," which is wired television. adopted because of the proved reliability of steam gen Furnace flame indication will be brought into the control erators of this size, and also because of the large savings room by mirroring glass cat's-eyes which are to be installed in first cost, maintenance and operating costs of the unit in the furnace doors. system. To this end, the furnace, superheater, econo Provision has been made in the circulating parts of the mizer and all other components of the steam generating steam generator for acid cleaning. units were specified to be designed liberally with respect The superheated steam will be maintained at constant to water-cooled heat-absorbing area, heat release in the temperature (1003 F) down to one-half load. The con furnace, tube sizing and spacing, gas velocities entering trol of this temperature will be by automatic tilting of the the superheater, etc., in order that the slagging be kept burners and by desuperheating. at a minimum and the unit availability be kept as high as Regenerative-type basketed air preheaters will be used possible. The heat release in the furnace was held to and the exit gas temperature (uncorrected for leakage) 15,100 Btu per cu ft per hr and the heat available in Btu will be 307 F. Lower exit temperatures were considered, per sq ft of water-cooled flat projected furnace envelope is but were discarded because of the possibility that exists 99,200, both at rated load. The temperature of the gas of fouling the air preheater elements when the lower leaving the furnace at this load will be 1940 F which is temperatures approach the dew point of the exit gases. below' the fusion temperature of the coal. It is felt that However, provision has been made in the heaters so that with these safeguards the Authority will be able to burn additional elements may be inserted in the future, if they any coal found in this area with a minimum of slagging. prove desirable. These additional elements will lower the Firing is by pulverized coal with provision for future exit gas temperatures approximately 20 deg, gaining ap burning of gas. Four pulverizers are provided per fur proximately one-half per cent in boiler efficiency. Pro nace with any three capable of carrying rated load with vision also has been made for manually bypassing the air normal coal. There are four vertically adjustable, preheater during starting up and low-load operation to tangential coal burners, four ignitors, and one oil burning prevent slagging of the heater elements at these relatively torch at each corner of the furnace. The oil-burning low temperatures. If operation proves it necessary, this torches have a slightly greater capacity than the mini bypass can be converted to automatic control. Construction view as of late September 48 December 1950--C OMBUSTION RS-000213 1/17/02 NUECES Progress on boilers by mid-October Condensers A scale model test was performed on the main steam piping. There are no loops in this piping and our calcula The condensers are horizontal single-pass units, and each will ^condense 690,000 lb of steam per hour at 2 in. Hg with 79-F circulating water. They each have 70,000 tions indicated that the stresses were close to the allow able limit. A model test confirmed this by indicating the maximum stress to be less than 300 lb per sq in. under the sq ft of surface, are directly connected to the turbine exhaust, and are supported by springs which are an chored to the turbine foundation. A twin-element steam jet ejector will remove all non-condensable vapors. allowable limit. Thus, the use of the model test per mitted us to eliminate loops in this heavy expensive pip ing. It is estimated that the savings because of the elim ination of these loops amounts to $18,000 per unit. The use of two-pass condensers was rejected because of excessive pumping costs and also because we shall have There are no valves on the main steam line between the superheater outlet and the turbine stop valve. Venturi an unlimited supply of cooling water which is required for the single-pass design. No chlorination of condensing valves will be used in the boiler feed discharge lines. A cost analysis indicated that the extra pressure loss for this water will be provided for at present, but provision has been made for this feature in the future should it be re quired. Moreover, no reverse flow of circulating water type valve was far outweighed by the saving in first cost. All 1500-lb valves have pressure-sealed bonnets. for trash removal is provided because past experiences with plants on the Tennessee River have indicated that it Control Room was not needed. Racks and traveling screens are deemed sufficient to keep the condensers from clogging. Each condenser will be served by two vertical mixedflow circulating wafer pumps, each rated at .">(>,000 gpm at 21-ft head. They are located in the pumping station at the river's edge and pump through 78-iu. diameter concrete pipes to the condensers. Under emergency conditions, one pump will operate the svstem with S-VF cooling water to produce 3 in. Hg back pressure at a throttle steam flow of 1,100,000 lb per hour. At this rating one unit will pump 7-1,000 gpm at 10 tt hcad due to the reduced friction loss in the circulating svstem at this lesser flow. All necessary valves and pumps will be controlled from a central control room in the pumping station. Throughout the whole design of this plant an effort was made to reduce the number of operators required. This is especially evident in the design of the control room where all the principal mechanical and electrical control functions (except switching) are centralized in one room. For example, each unit will be provided with an SO-point temperature indicator-recorder scanning device to record the temperatures of all main turbine-generator, draft fan, boiler feed pump and pulverizer bearings. Each control room will serve two generating units. This arrangement called for some ingenuity of design be cause of the multiplicity of control piping and conduit concentrated at one point; however, it is felt that the result is worth the effort. Some investigation of a single control room for each boiler-generator combination was Piping and Valves All 1000-F main steam piping is forged and bored and conforms to the requirements of A.S.T.M. Specification A1S2-4ST, except that the chemical composition will be in accordance with A.S.T.M. Specification A2i:l-hi, made, particularly with a view toward reducing the length of the control boards. It is probable that as the development of miniature instruments becomes more ad vanced that they may be used in future plants, thus re ducing the size and length of the control boards. Symbol T-22, containing 21', per cent chromium and 1 per cent molybdenum, except that the carbon will be Auxiliaries limited to 0. H) per cent maximum. Steel is specified t ' n- No steam-driven auxiliaries will be used except the silicon killed to minimize graphiti/.aliou. steam jet air pumps for the condensers. The numerous COMBUSTIO N--December 1950 RS-000214 1/17/02 NUECES 49 incoming sources of power supply, dictated the use of The furnace ash, fly ash and pyrites will lje removed motor drives for all auxiliary equipment. by a jet system, rather than by pumping. This method Calculations indicated that fluid drives were econom of handling the ash was selected because the Authority ical for the boiler feed pumps, but not for the mechani believes it involves less maintenance and operation. cal draft fans. One of the major factors influencing fluid The fly-ash system will be controlled by an automatic drives for the pumps was that we omitted the boiler feed- sequential arrangement whereby each hopper is auto water regulating valve in the pump discharge line, thus matically unloaded in its proper sequence. eliminating pumping against the high-pressure drop Plant service air will be obtained from three 660-cfm, across the regulating valve. The speed of the pump two-stage, air compressors operating at 100 psi. Air for which regulates the feedwater flow is controlled by the the various control instruments will be obtained from a fluid drive. separate system of two single-stage compressors, each Three boiler feed pumps are provided for each boiler rated 440 cfm at 100 psi. These latter machines will have with any two capable of handling the rated load. These non-lubricated carbon rings in the cylinders to prevent pumps are barrel-casing type and are rated 1209 gpm at oil leakage past the pistons where it might reach the in 4770-ft head with 290-F water. They each have a shut struments. off head of 5505 ft, and the impellers are designed with a A completely automatic sodium-zeolite system is being rising pressure characteristic which will prevent hunting provided for treating the makeup water delivered to the with its consequent surging at the part-load operation. evaporator, and a secondary chemical system will be They operate under a net positive suction head of 6G provided for feeding sulfite, phosphate and caustic soda feet. to the feedwater as required. The test block requirements of the forced-draft fans All engineering and construction work on this plant is are 160,000 cu ft of air per minute against 12.5 in. water under the direction of C. E. Blee, chief engineer; R. A. pressure and of the induced-draft fans are 250,000 cfm of Monroe, chief design engineer; G. K. Leonard, chief gas against 14.75 in. water pressure. There are two of construction engineer; and J. S. Bowman, chief water each per boiler, and the ratings established are such that control planning engineer. All mechanical design is a continuous output of approximately 600,000 lb per hr under the supervision of the writer. may be obtained from the boiler with only one forceddraft and one induced-draft fan operating. Speeds were limited to 900 rpm for the forced-draft fans and 600 rpm for the induced-draft fans. All fans are direct-connected and volume regulation is by means of inlet vanes and inlet dampers. The general scheme of ventilation is for the incoming air to be blown in at the lower levels in both the boiler JOHNSONVILLE STEAM PLANT--PRINCIPAL EQUIPMENT FOR SIX GENERATING UNITS Items Turbine-generators (Units 1, 2, 3 and 4) Turbine-generators (Units 5 and 6) Steam generators Contractors Ceneral Electric Co. Westinghousc Electric Corp. Combustion Engineering-Super heater, Inc. room and the turbine room. Additional outside air will be blown in at the heater area level to make these hot spots more comfortable. The floor areas and gratings Soot blowers Condensers Feedwater heaters Deaerating heaters Diamond Power Specialty Corp. Ingersoll-Rand Co. The Lummus Co. Elliott Co. are designed to make the inlet air for the forced-draft fans pass from the lower power house levels to the fan floor up along the walls of the boiler. In this way the air will pick up a good deal of heat from the radiation from the boiler thereby increasing its temperature before it Evaporators Boiler feedwater pumps Condenser circulating water pumps Combustion controls and con trol boards Foster Wheeler Corp. Worthington Pump and Mach it. cry Corp. Ingersoll-Rand Co. Bailey Meter Co. reaches the forced-draft fan inlet. Since each 3S deg rise in this air increases the clliciencv of the boiler ap proximately one per cent, the advantage of this arrange ment becomes obvious. The whole power house is under a slight positive pressure from the supplv fans, which helps prevent infiltration of dust and dirt. All the main auxiliaries which will have a direct in fluence on the plant output, such as draft fans, feedwater pumps, condensate pumps, condenser circulating water pumps and pulverizers, were investigated as to their capacities during times of reduced frequency and or voltage. It was found that each generating unit will be able to maintain an output of 125,000 kw with frequency reduced to 55.2 cycles at 100 per cent voltage, or with a frequency of 56.3 cycles at 83 per cent voltage. The capacity of the coal bunkers was fixed at 2201) tons per unit. This capacity was decided upon because it is enough coal to run the units at rated capacity ewer a Piping contract National Valve and Mfg. Co Ash-handling system United Conveyor Corp Draft Fans American Blower Corp. Fly-ash collectors Western Precipitation Corp. Boiler room coal scales Richardson Scale Co. Coal valves Columbus Conveyor Co. Zeolite softeners Hungerford and Terry, Ine. Secondary chemical feed equip Proportioueers, Inc. ment Station service air compressors Pennsylvania Pump and Cot pressor Co. Control air compressors Bury Compressor Co. Valves--high pressure Chapman Valve Mfg. Co. Safety valves Foster Engineering Co. Butterfly valves Henry Pratt Co. Condenser water conduits (78- Lock-Joint Pipe Co iu. diameter) Turbine room cranes Judson Pacific Murphy Corp. Traveling water screens Chain Belt Co. Coal-handling equipment Link-Belt Co. Powerhouse structural steel Ingalls Iron Works Stacks Birmingham Tank Co. Aluminum siding and steel roof H. H. Robertson Co decking Main Transformers Westinghousc Electric Cor week end, thus eliminating any coal handling activi ties over that period. The coal yard has sufficient area to store 1,000,000 tons ol coal, because ut the large s:"e of the storage area, mobile coal-handling equipment wp! be Main switchboard Auxiliary switchboard Auxiliary switchboard Station service transformers ' Ml circuit-breakers and General Electric Co. Allis-Chalmers Mfg. Co. Westinghousc Electric Corp 1 T.E Circuit Breaker Co. Westinghousc Electric Co: and General Electric Co. Westinghousc Electric Corp 50 December 1950--C OMBUSTIO RS-000216 1/17/02 NUECES