The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

character of the tests have never been surpassed. he first six tests were run by a picked crew of firemen who had experience in torpedo beat work. It was believed that these men by training and experience were particularly well fitted to operate the boiler when under severe forced draft conditions. An experience of a few weeks with this force showed that new methods in firing had to be employed in efficiently operating water-tube boilers, and that the best means of securing efficient work was to have skill and intelligence from those in charge of the fire room and implicit obedience upon the part of the subordinates. The re- -- : = i. a Perce -- eee ere ea ici <o | po Ee ' Vi Fig. 1. Longitudinal Section Hohenstein Water-Tube Boiler. maining eleven tests were thus made by firemen living in the city, not one of whom had ever before worked a boiler under forced draft conditions. 'The second set of firemen implicitly obeyed orders, and it was therefore possible for the board to have its instructions carried out. A uniform pressure of steam was main- tained, as well as a regularity in firing that was productive of good results. The data secured can be regarded as reliable, for checks and counter checks were used so that the bureau could be placed in possession of information that could be relied upon as to com- pleteness and accuracy. As this same boiler is being used to carry on the extended series of tests to determine the value of liquid fuel for naval purposes, it is proposed to duplicate every one of the coal tests with cil as a combustible. The comparative information thus obtained ought to afford valuable data as to the relative value of the two combustibles. In view of the present condition of this experimental boiler after eighteen months of use with both coal and oil as a combustible, considering the results secured, and by reason of the following report submitted by the board which conducted the series of tests, the bureau has no hesitation in regarding the boiler as the equal in efficiency and en- durance of any used in a foreign battleship. REPORT OF BOARD ON HOHENSTEIN BOILER TRIALS. BurEAU OF STEAM ENGINEERING, Navy Department, July 1, 1902. Sir:--The board appointed to conduct an extended series of tests to determine the efficiency and adaptability of the Hohen- stein marine boiler for naval purposes submits the following report: The boiler was built by the Oil City Boiler Works of Oil City, Pa., in conformity with the bureau specifications for the cruiser Denver and class. 'The limitations as to weight, height and floor space in regard to the Denver's steam generators were therefore taken into account in the construction of this boiler. The installation was affected in an air-tight steel house, the dimensions of this house approximating to one of the fire rooms of the Denver. It may be incidentally stated that the specifica- tions for the boilers of the Denver are probably as severe as those for any American war ship. The headers of the boiler are made of wrought steel, a special requirement of the bureau. While only seventeen official tests were made with coal as fuel, there was considerable experimentation between these tests, so that the series of tests represent much more observation and ex- perimentation than is apparent. A most noteworthy feature of the boiler is the arrangement of the tubes in pairs in such a way that each tube is free to expand independently of other tubes, thus effectually preventing longitudinal stresses in them. Figure 1 shows a longitudina! section of the boiler. Attention is called to the fact that the entire down flow takes place within tubes which are located in a comparatively cool place, while, on the MARINE REVIEW AND MARINE RECORD. a7 other hand, there is invariably an upward trend to the current in all tubes and headers exposed to the hot gases. It is therefore highly probable that there are no reverse currents at any part of the water circuit, and the cross-section areas of tubes and head- ers are equitably apportioned with a corresponding degree of certainty. The feed water is introduced at the top of the down- take tubes, which is obviously the best possible place as regards influence on the circulation; at the same time the head due the velocity of the feed water is conserved by means of injector noz- zles pointing in the direction of the flow. 'The following are the more important dimensions: f. Drums at water-surface level:--One front drum, 24 in. diameter (inside) ; one rear drum, 24 in. diameter; four connect- ing drums, 16 in. diameter. a One lower rear mud drum, 24 in. diameter. Tube-heating surface:--Three hundred and eighty-four 2-in. tubes, 9 ft. long; sixteen 4-in. tubes, 7 ft. long. Fifteen down-take tubes, 5 in. in diameter. Floor space occupied, 9 ft. wide, ro ft. 1114 in. deep. Height above floor line, 12 ft. 34 in. Height over all; 12 ft, 634 in. Heating surface :---2,174 sq. ft. for tests No. 1 to No. 6, inclu- sive; 2,130 sq. ft. for tests No. 7 to No. 17, inclusive. Per cent. water-heating surface, 100. Grate surface--so.14 sq. ft., 6 ft. 4 in. long, 7 ft. 11 in. 'wide. Pressure of heating surface to ~rate surface--43.4 to 1 for tests No. 1 to No. 6, inclusive; 42.5 to 1 for tests No. 7 to No. 17, inclusive. Volume of water at steaming level, 142 cu. ft. Volume of steam space, 50 cu. ft. Area of steam liberating surface, 75 sq. ft. Weight of water at steaming level and 275 lbs. pressure, 7,559 lbs. Weight of boiler and fittings, excluding up-take and smoke pipe--Without water, 46,568 lbs.; with water, 54,127 Ibs. -"With- out water per square foot of heating surface, 21.4 Ibs. for tests No. 1 to No. 6, inclusive; 21.8 lbs. for tests No. 7 to No: 17, inclu- sive. With water per square foot of heating surface, 24.9 lbs. for tests No. 1 to No. 6, inclusive; 25.4 lbs. for tests No. 7 to No. 17, inclusive. With water per square foot of grate surface, 1,080 Ibs. Height-of furnace, 2 ff. 5 ins: Volume of furnace above bars, 121.14 cu. ft. Width of air spaces between grate bars--Five-eighths inch for tests No. 1 to No. 11, inclusive; 34 in. for tests No. 12 to No. 17, inclusive. Ratio of grate area to area of air space--1l% :54=1 :0.555 for tests No. 1 to No. 11, inclusive; 114 :34=1:0.60 for tests No. 12 to No. 17, inclusive. Height of smoke pipe above grate, 70 ft. Area of smoke pipe, 8.73 sq. ft. Ratio of smoke-pipe area to grate area, 1 :5.75. Number of fire doors, 3. The boiler was erected in a steel structure built especially for these tests and having the following dimensions: Floor space, 16 ft. by 24 ft.; height, 14 ft. The structure was air tight, had : Rarsed 4) platform |, oes 2 Fig. 2. Ground Plan of the Plant. an air lock for entrance and exit during forced-draft trials, and seven windows that could be opened during natural-draft trials. Figure 2 shows. the ground plan. The auxiliary machinery, to- gether with facilities for making observations, were, so far as possible, placed in an adjoining lean-to wooden structure. The auxiliaries consisted of a Davidson suction pump, two weighing tanks, one feed tank, a Snow high-pressure feed pump, a small upright boiler with independent feed pump, and a direct-connected blowing engine and fan. The fan had an impeller 72 ins. in