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ures have been plotted for floating loads and hogging conditions. Capt. Emory S. Land, naval constructor, prominently identified with the navy’s aeronautic activities presented the paper in the absence of the author. He also pointed out to the society that the problem covered in Captain Richardson’s paper was directly in the line of the naval architect. Also that the design of craft of this type in Europe was far ahead of this coun- try. 5. The Inclining Experiment, by Rear Admiral John G. Tawresey, C.C. U.S.N., retired, member. Admiral Tawresey in_ presenting this paper performed a very valuable service to the profession of naval ar- chitecture. He clarified and brought up to date an old and well known experiment. He has emphasized the practical side of the problem, detail- ing throughout what he has found from practice to be the best. Anyone faced with the responsibility of per- forming an inclining experiment will find valuable assistance in Admiral Tawresey’s excellent paper. ‘The dis- cussion following the presentation of the paper was animated and _ inter- esting. Various practical experi- ences in conducting inclining experi- ments were presented and add to the value of the paper. 6. Propeller Backing Power in Tugboats, by Alfred J. C. Robertson, member. Mr. Robertson as naval architect with the Fairbanks, Morse Co. is bringing a very useful point of view to the engine builder. His paper on the backing power in tugboats is ex- actly along this line. It is a valuable attempt to solve some of the difficult questions propounded by the customer. As the author points out, very little has been published on the backing power of the screw propeller. The experiments were carried out at the model basin, Washington. The model with which the experiments were con- ducted was taken to represent a tug- boat of 110 feet in length by 23 feet 4% inches beam and a mean draft of 6 feet 9 inches. Many interesting curves of valu- able data are published with the paper. The author comes to the con- clusion that it is apparent from the tests that it is quite impossible for a tugboat with a single screw to de- velop an efficiency going astern equal to that of going ahead, a _ require- ment, which, as he says, is not infre- quently specified. A number of fa- vorable comments and some _ discus- sion followed this paper. 7. Development of Pulverized Fuel for Marine Purposes During 1927- 1928, by Carl J. Jefferson, member; 26 Commander Joseph S. Evans, U:S.N., and Commander Joseph Broshek, U.S.N. visitors. The authors of this paper par- ticularly, Mr. Jefferson and Com- mander Evans have been intimately connected with the excellent work carried out over the past two years by the fuel conservation committee of the shipping board and the fuel testing plant at the League Island navy yard, Philadelphia. On _ the strength of their work an important paper was presented at the meeting of the society a year ago on the re- sults obtained burning pulverized coal in a standard, three furnace separate combustion chamber, scotch marine boiler. The paper deals with a brief de- scription of the pulverized coal burn- ing equipment on the S. S. MERCER. This vessel was converted to burn pulverized fuel at the Maryland Dry Dock & Shipbuilding Co., October 1927. An account is given at some length of the first voyage of the MERCER operated as a pulverized coal burner. In this account the _ eco- nomic features of comparative fuel costs and crew wages are discussed. Such questions as ash deposits and mechanical troubles developed are mentioned. An analysis is given of the sea performance of the pulverizer. Brief accounts are also given of the MERCER voyages, 2, 3, 4 and 5. After a year’s operating service of the MercER the authors are able to point to several salient points that must be taken care of to make a satisfac- tory installation of pulverized fuel in seotch marine boilers. These points are summarized as follows: A. Considerably finer pulveriza- tion of fuel is required, than that necessary with large refractory lined furnaces such as found in_ shore plants. B. High turbulence of flame is required to produce complete and rapid combustion necessary in_ the comparatively short flame travel of a scotch boiler. C. Consistently uniform distribu- tion of fuel between various furnaces of the scotch boiler is necessary for efficient performance. D. The power plant for producing pulverized fuel must be of an eco- nomical type which may be secured either by installation of efficient low water rate units or by useful em- ployment of exhaust if less efficient units be used. E. Extra precaution must be taken to secure dust tight smoke box doors and uptakes, otherwise when using soot blowers it will be impossible to maintain a satisfactory fire room con- dition. MARINE REVIEW—December, 1928 F. The velocity of coal stream throughout cycle requires special con- sideration to prevent overloading of fans and coal precipitation in pipe lines and to secure satisfactory selec- tion of superfine grind from mill and turbulence at burner. G. Personnel must be trained to give the same close supervision to velocity as is required in regard to viscosity and pressures when using fuel oil. H. The usual fire room _instru- ments, such as orsat and pyrometer, are important but of greater impor- tance are the draft gage and smoke indicators. é I. Sized coal of 100 per cent slack coal gives more uniform operating conditions than will run-of-mine; in fact, bunkering with run-of-mine will require use of crushers to produce fuel having a limited maximum size, otherwise feed to mill will be very irregular, a condition that will be reflected throughout the whole opera- tion of the boiler plant. Two other installations, those on the =.S..-S.. LINGAN “and the. 82 -s. STUARTSTAR are briefly described. It is stated that the reliability and the safety of pulverized fuel have been thoroughly demonstrated by actual sea aperation of the three seagoing installations cited, also by the per- formances of the towboat ILLINOIS which has been in operation approxi- mately 18 months on the Mississippi river. It has also been demonstrated that certain fuels which could not be used otherwise in a scotch marine boiler can be satisfactorily burned with the pulverized system. Further- more the economic possibilities have been indicated and the problem in relation to adapting pulverized fuel in marine practice has been crystal- lized. Definite progress has been ac- complished but the final standard type of installation still needs to be worked out. Conversions and new _ installa- tions now being made will further the development of the art and aid toward transforming it from an art into a fixed science having definite laws that can be employed with con- fidence by marine engineers. The paper continues giving some important facts on distribution, dif- ferent types of mills and other equip- ment of a pulverized coal burning system. Something is also said con- cerning the fineness of the coal. A brief description with illustrations is given of the new Todd system of pulverized coal burning for scotch boilers. 'The paper stated that this equipment was then under test and complete data was not available but that preliminary results had _ been very satisfactory. 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