Steam:
Its Generation and Use

 ÖTEV) LÖCIO ECONOMY AND SAFETY IN STEAM GENERATION. ECONOMY IN THE USE OF COAL is a 1 matter of great and growing importance. It is estimated that the annual production of coal in the world at the present time is not far from 400,000,000 tons. The report of the Royal Com- mission in England in 1870, shows the distribu- tion at that time to have been as follows : Metallurgy and Mines, - - - - - 44 per cent. Domestic purposes, including gas and water, - 26 “ . “ General Manufacturing, - - - - 25 “ “ Locomotion by sea and land, - - - - 5 “ " As a considerable part of the coal used in met- allurgy and mines, as also that for domestic water supply, is used for power, we shall not be far wrong in estimating that one-half of all the coal mined, or 200,000,000 tons annually, is used for making steam. A low estimate of the value of this coal at the place of use would be an aver- age of $2.50 per ton, which gives as the present annual expenditure for steam, a sum equal to $500,000,000; from which it will be seen how largely even a small per cent, of saving would add to the wealth of the world. It is estimated that of the steam-power at pres- ent in use in the world, 80 per cent, has been added in the last twenty-five years, so that these figures are none too large for the present time. While manufacturers and engineers have given much care to the improvement of the steam engine, whereby they might reduce the con- sumption of steam for a given amount of power, but little attention, comparatively, has been given to securing economy in its generation. In fact, the boilers in use at the present day, are sub- stantially the same as were in common use at the close of the last century, and but slight advance has been made in their economy. Of late years, however, steam users have begun to realize that there are principles and aims of equal promi- nence, and greater importance, to be considered in choosing a boiler, to the selection of a steam engine. Engineering experience and scientific investi- gation have established the following as the Requirements of a Perfect Steam Boiler. i st. The best materials sanctioned by use, simple in construction, perfect in workmanship, durable in use, and not liable to require early repairs. 2d. A mud-drum to receive all impurities de- posited from the water in a place removed from the action of the fire. 3d. A steam and water capacity sufficient to prevent any fluctuation in pressure or water level. 4th. A large water surface for the disengage- ment of the steam from the water in order to pre- vent foaming. 5th. A constant and thorough circulation of water throughout the boiler, so as to maintain all parts at one temperature. 6th. The water space divided into sections, so arranged that should any section give out, no general explosion can occur, and the destructive effects will be confined to the simple escape of the contents; with large and free passages between the different sections to equalize the water line and pressure in all. 7th. A great excess of strength over any le- gitimate strain ; so constructed as not to be liable to be strained by unequal expansion, and, if possible, no joints exposed to the direct action of the fire. Sth. A combustion chamber, so arranged that the combustion of the gases commenced in the furnace may be completed before the escape to the chimney. 9th. The heating surface as nearly as possible at right angles to the currents of heated gases, and so as to break up the currents and extract the entire available heat therefrom. 10th. All parts readily accessible for cleaning and repairs. This is a point of the greatest im- portance as regards safety and economy. nth. Proportioned for the work to be done, and capable of working to its full rated capacity with the highest economy. 12th. The very best gauges, safety valves, and other fixtures. 4 7