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512 TRANSACTIONS OF TH E A.S.M.E. AUGUST, 1941 creased steam output, would call for increased heat input to the saturated furnace. In order to maintain a constant total steam temperature, this might necessitate reducing the heat input to the superheater furnace. An explanation as to just how this is accomplished without a somewhat complicated system of automatic control would be of interest. The writer would further ask what means are employed to advise the operator when the rate of firing in the superheater furnace to produce a certain steam temperature has become unduly high for that particular load and prompts him to use the radiant-superheater soot blowers to remove accumulated ash and possible clinker from these surfaces. The question of completely bare waterwall tubes or armor-clad surfaces in furnaces subjected to high heat inputs with consequent high furnace temperatures is still debatable. An increase in mean furnace temperature from 2000 F to 2500 F would increase the volume of the products of combustion in the ratio of 1 to 1.17 or 17 per cent and the velocity head approximately 0.037 in. water gage. Since complete combustion of a pulverized-coal particle depends largely upon rapid and intimate contact with oxygen, viz., turbulence, the particle size, volatile content, etc., and also temperature to a lesser extent, the increase in the time element in the furnace, which is due to even a large increase in furnace temperature would not materially affect the completeness of combustion of the particle. A u t h o r s ’ C l o s u r e Mr. Julsrud asks how the temperature of the steam, from the large boiler described in the paper is controlled. The temperature of the steam is controlled automatically by a temperature controller that operates so as to vary the loading pressure on the fuel and air controllers for the saturated and superheater furnaces in accordance with the requirements. An increase in steam output is automatically met by an increase in heat input to both furnaces. Then if the steam temperature is low the loading pressure on the fuel controller regulating the fuel to the superheater furnace is increased which increases the heat input to the superheater furnace. This will increase the steam pressure since the total heat input is now more than the demand so the master pressure controller acts to reduce the input to both furnaces. This action is maintained until the steam temperature is as required. The opposite takes place if the steam temperature is high following a change in load. Differential pressure gages are provided to indicate to the operators the extent by which the flow of fuel to one furnace exceeds that to the other furnace. At full load both furnaces are fired equally. From experience the operator knows about how much difference in differential there should be for the designed steam temperature at various loads. When the operating gages indicate too great a difference from the normal in fuel flow to the superheater furnace he has an indication that the radiant superheater needs cleaning. Another indication is obtained from the position indicators of the fuel controllers. In addition the desirability of cleaning the radiant superheater may be made by inspection. Mr. Julsrud also discusses the effect of increasing the mean temperature of the gases in the furnace from 2000 to 2500 F on burning the coal. This increase in temperature would increase the specific volume of the gases by 20 per cent and accordingly would cause the gases at the lower temperature to take 20 per cent longer to pass through the furnace, which would thus give the coal 20 per cent longer time in which to bum. He appears to infer that since the velocity pressure will be higher at the higher temperature, the turbulence will be greater. But velocity pressure unless taken as a ratio of the pressure gradient is not a measure of turbulence. Actually, since the viscosity at 2500 F is 11 per cent greater than it is at 2000 F the turbulence presumably is less at the higher temperature.
C ondenser T ubes and T h eir C orrosion By CHARLES W. E. CLARKE,1 A. E. W HITE,8 a n d C. UPTHEGROVE3 The authors present a brief review of the development of condensers for steam prime movers, a discussion of some of the problems in connection w ith them th at have been m et and overcome, and a tabulation of returns from a questionnaire. They then describe and report a series of tests with a miniature condenser with tubes made of admiralty m etal, alum inum brass, and cupronickel. Conditions were as closely as possible a duplication of those existing in a working condenser. In addition to corrosion tests, im pingem ent tests were made. The authors present and discuss the results of these tests and grade the tubes tested in order of resistance to corrosion. Full information on th e tubes tested is presented, w ith the results of metallographic examination of the materials of which the tubes were made. The conclusions arrived at as a result of a study of the tests are summarized at the end of the paper. THIS paper has to do mainly with condenser tubes and their life as related to the material of which they are made. However, a brief review of the development of condensers, particularly as applied to stationary power-plant practices, and a discussion of some of the problems that have been met and overcome may be of interest. The use of condensers to extend the heat range of steam-power units is old. In fact, Savery and others in the seventeenth century used the condensation of steam in a closed vessel to perform work. Surface condensers began to come into use along with steam navigation but there was little or no development until the advent of the steam turbine as an important prime mover. Prior to that development, high- or low-head jet condensers were the principal means of providing vacuum for engine-driven power units in land practice. The original surface condenser consisted of a shell containing as many tubes as could be crowded in. Vacuum requirements were not severe, as these early installations were made in conjunction with reciprocating engines. One of the principal land uses originally was in connection with pumping engines which always provided a cooling-water flow many times the actual needs for steam condensation, so that what might be called the “surface efficiency” was not important. The original shell full of tubes has given way to tube layouts which provide proper steam access to all of the cooling surface. This has permitted a great reduction in the surface requirement per pound of steam condensed. Pressure drops across the condenser have been reduced from about one half inch of mercury in the older designs to a tenth of an inch in present-day installations. This is no small item, especially for turbine operation where exhaust pressures of one inch of mercury absolute or less are the order of the day instead of the 2*/« to 3 in. of days gone by. An interesting example of the early steps in the improvement 1 Consulting Engineer, United Engineers & Constructors Inc., Philadelphia, Pa. Fellow A.S.M.E. 1 Director, Department of Engineering Research, University of Michigan, Ann Arbor, Mich. Mem. A.S.M.E. 8 Professor of Metallurgical Engineering, University of Michigan. Contributed by the Power Division and presented at the Annual Meeting, New York, N. Y., Dec. 2-6, 1940, of T h e A m e r i c a n S o c i e t y o f M e c h a n i c a l E n g i n e e r s . N o t e : Statements and opinions advanced in papers are to be understood as individual expressions of their authors, and not those of the Society. of condenser performance occurred in 1908 at the Port Morris Station of the New York Central Railroad. The condensers consisted of a shell packed as full as possible with 4000 tubes. About 25 per cent of the tubes were removed in such a way as to leave three tapering steam lanes leading into the body of the tube bank and a fairly wide lane along the top. This change resulted in an increase of about one inch in vacuum. Vacuum pumps were of the wet-vacuum type, usually driven from the shaft of the main prime mover. Later, separately driven dry-vacuum pumps were developed, to be superseded in presentday practice by steam-jet air pumps. In order to secure some authentic information as to the detailed history of surface-condenser development, questionnaires were sent to several of the largest manufacturers of condensers and tubes. The answers to these questions are shown in Tables 1 and 2. In the development of surface condensers, one of the main difficulties has been corrosion of tubes. The location of many of our large public utilities and industrial power plants is such that the condensing-water supply is contaminated by industrial waste and sewage, resulting in water which is corrosive. In many cases the water contains gases which are liberated in passing through the condenser, which add to the corrosive difficulties. The liberation of corrosive gases within the condenser tubes owing to the increase in temperature and reduction of pressure is a principal cause of tube deterioration. Various methods have been tried to remove part of these gases before they can act on the cooling surfaces. One simple method consists of suitable pipe connections from the top of the inlet water boxes to the drop leg of the circulating system. The vacuum produced by the drop-leg siphon draws off a mixture of water and such gases as may be free at this point. However, this will not remove the dissolved gases which are occluded owing to the temperature rise and pressure drop within the tube itself. Much has been written regarding these matters in the past. However, each location or water quality presents a different problem and results in actual service have more often than not been contradictory. Collection of debris at the tube entrances (leaves, etc.) has always been a problem in surface-condenser operation. Highpressure water jets from nozzles which operate through ball-andsocket joints in the water-box cover plates have been effective in many cases. Divided water boxes, which allow tube replacement and cleaning of half the condenser while the unit operates, are common. Hot-well temperatures in old-type condensers were often five degrees lower than the temperatures due to vacuum. Proper tube laning in modern condensers allows steam to come in contact with the condensate going to the hot well. This secures temperatures substantially the same as those due to vacuum and at the same time causes more complete deaeration of the condensate which is so important in modern high-pressure-boiler practice. Tube end leakage was formerly a serious problem. Methods of packing have been gradually improved from the old corset lace to fiber, metallic, and finally to the expanding of tubes into the tube plates without the use of any packing material. In most of the older designs the tube ends protruded beyond the face of the tube sheet. This resulted in serious wear and deterioration of the tube at the inlet end. To correct this condition.
Page 1 and 2: Transactions of the Significance of
Page 3 and 4: Significance of Coal-A sh Fusing T
Page 5 and 6: BAILEY, ELY—COAL-ASH FUSING TEM P
Page 7 and 8: BAILEY, ELY—COALrASH FUSING TEMPE
Page 9 and 10: BAILEY, ELY— COAL-ASH FUSING TEM
Page 15 and 16: BAILEY, ELY—COAL-ASH FUSING TEMPE
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Page 27 and 28: L ubrication of G eneral E lectric
Page 29 and 30: DANTSIZEN—LUBRICATION OF GENERAL
Page 35 and 36: Stress and Deflection in R eciproca
Page 37 and 38: BOYER, KUTVINEN—STRESS AND D EFLE
Page 39 and 40: BOYER, KUIVINEN—STRESS AND DEFLEC
Page 41 and 42: Some P articu lars of Design and O
Page 43 and 44: BLIZARD, FOSTER—SOME PARTICULARS
Page 45 and 46: BLIZARD, FOSTER—SOME PARTICULARS
Page 47: BLIZARD, FOSTER—SOME PARTICULARS
Page 51 and 52: CLARKE, WHITE, UPTHEGROVE—CONDENS
Page 53 and 54: CLARKE, W HITE, UPTHEGROVE—CONDEN
Page 55 and 56: CLARKE, W HITE, UPTHEGROVE— CONDE
Page 61 and 62: CLARKE, W H ITE, UPTHEGROVE—CONDE
Page 67 and 68: Therm om etric Time Lag T h e p urp
Page 69 and 70: ate of change will be n = T J L . I
Page 71 and 72: Bulb temperature B ath ✓---------
Page 73 and 74: The Bureau of Standards paper2 give
Page 75 and 76: Discussion M. F. Behar.4 This paper
Page 77 and 78: The differential equations for the
Page 79 and 80: Filling it with mercury reduces the
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