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

ea ae MARINE REVIEW. | 19 Howden Hot Draft in 26 Lake Steamers. Some time ago there was presented data and letters to show the effi- ciency of the Howden hot draft system, which had been applied to the boilers of several steamers by the Detroit Dry Dock Company. 'This was at a time when the profits in the lake carrying trade were at the minimum. Although many owners were convinced of the economical advantages of the system, the expense of fitting it to their vessels caused them to delay. Notwithstanding this condition sixteen of the better class of steamers on the lakes have been equipped, and ten more will come out next spring with PIONEER, FITTED WITH HOWDEN HOT DRAFT. distributing box through which the air under pressure passes into the furnace and over the surface of the fuel. The outer or air-tight door is not exposed to the heat of the furnace, and simply retains the air under pressure entering from the upper valve. The air from this valve, besides filling the space between the doors and passing into the furnace through the inner door, also fills the spaces above the dead-plate around the furnace door, and passes into fixed air-distributing boxes covering the whole sur- face inside the furnace. In this manner the furnace front castings are preserved from the injurious effects of the great heat of the furnace, while the air entering under pressure is highly heated before being distributed in small jets or streams over the surface of the burning fuel so as to effect complete combustion with the smallest admission of air practicable. By means of the balance of air pressure above and below the fires all tendency for the fire to blow out at the furnace door, however high the rate of combustion, is entirely removed. By regulating the admission of the air by the valves above and below the fires the highest rate of combustion possible by the air pressure used can be effected, and in same manner the rate of combustion can be reduced to far below that of natural draft, while complete and economical com- bustion at all rates is secured. : In usual working at sea, in most recent practice, only one ash pit valve is opened and shut unless the very highest power is required. The upper valve for the air admission over the fires is adjusted at the beginning of the trip to suitthe character of the fuel used, and does not require to be afterwards moved during the trip unless the engines are stopped. ; If the combustion is required to be suspended, as in the event of the engines being suddenly stopped when working at full power, all that is necessary is to shut the air admission valves, the upper one being very slightly open to maintain a limited circulation of air through the boxes. Blowing off steam is thus prevented, and the boilers may be kept for hours in this state with the combustion suspended and the steam sustained al- most without loss or pressure. a PENOBSCOT, FITTED WITH HOWDEN HOT DRAFT. it. The sixteen already equipped are the Virginia, Pioneer, W. B. Ket- cham, H. H. Brown, Madagascar, Nicaragua, Argo, Arrow, Rappahannock, Sacramento, Schoolcraft, Pleasure, Penobscot, the City of Alpena, the City of Mackinac and the Chicora. This system of draft is being fitted to the new C. & B. line passenger steamer, two steamers building at Chester, Pa., for the New York and New London trade, the two new steamers building for the Wolverine Steamship Co., and for C. R. Jones & Co. Two of the Rockefeller steamers will have this draft and a comparison with the others of this new fleet willbe interesting. T'wo of the Davidson steamers will also be equipped. He has had experience with it in four other steamers, and is the last man on the lakes who would spend money or adopt a new thing un. less it made dollarsfor him. Ownersof the Fayette Brown, S. R. Kirby, R. P. Ranney and A. McVittie have ordered these steamers equipped. There is but very little doubt that the expense of equipping a steamer will be equalled by the saving of coalin two seasons, and then goon making from 33% to 50 per cent. each season thereafter. The saving is made in two ways. First it is very plain that heating the air that goes into the furnace by the gases that go up the stack saves, and then the draft enables a cheaper quality of coal to be used. Fair profits were made last season and it would be financial wisdom or good horse sense to appropriate some of these profits to securing a coal saving device that will put older steamers on an equal footing in this regard with the steamers coming out next spring. The Howden system supplies hot air to closed ash pits, resulting in the production of maximum power together with the highest efficiency and economy of fuel. The means by which these objects are attained is by first placing an air-tight reservoir or chamber on the front end of the boi.er and surrounding the furnaces. This reservoir, which projects from 8 to 10 inches from the end of the boiler, receives the air under pressure, which is passed by the valves into the ash pits and over the fires in propor- tions exactly suited to the kind of fuel used and the rate of combustion re- quired. The air used above the fires is admitted by its valve toa space between the outer and inner furnace doors, which swing on one hinge, the inner being the proper door of the furnace, having perforations and an air- CITY OF BUFFAI,O, FITTED WITH HOWDEN HOT DRAFT. This system of draft can be very effectively and economically worked with cold air in consequence of the controlled admissions described rend- ering the temperature and quantity of the waste gases less than in other modes of working for equal weights of fuel consumed. The most im- portant feature, however, in securing both the highest efficiency and econ- omy is the combination of the heating of the air of cumbustion by the waste gases with the controlled and regulated admission of air to the furnaces. This arrangement is effected most conveniently by passing the hot fire-gases after they leave the boiler through stacks of vertical tubes enclosed in the up-take, their lower ends being immediately above the smoke-box doors.