Steam:
Its Generation and Use

 PROPERTIES OF SATURATED STEAM. Ice is liquified and becomes water at 320 F. Above this point water increases in temperature up to the steaming point, nearly at the rate of i° for each unit of heat added per pound of water. The steaming point (2120 at atmospheric press- ure), rises as the superimposed pressure in- creases, but at a decreasing ratio; as, for ex- ample, at atmospheric pressure it takes 3^° to thermometric temperature), constitutes the ‘ ‘ Total Heat.” The “total heat” being greater as the pressure increases, it will take more heat, and consequently more fuel, to make a pound of steam the higher the pressure. Saturated steam cannot be cooled except by lowering its pressure, the abstraction of heat be- ing compensated by the latent heat of a portion which is condensed. Neither can steam, in Babcock & Wilcox Boilers, at The Turner & Seymour Mfg. Co., Torrington, Ct. 100 H. P. Erected 1880-1. add a pound, while at 150 lbs. gives the same increase of pressure. For each unit of heat added above the steam- ing point, a portion of the water is converted into steam, having the same temperature and the same pressure as that at which it is evaporated. The heat so absorbed is called ‘ ‘ Latent Heat. ’ ’ The amount of heat rendered latent by each pound of water in becoming steam varies at different press- ures, decreasing as the pressure increases. This latent heat added to the sensible heat (or the contact with water, be heated above the tem- perature normal to its pressure. The density of saturated steam varies from that of air of same temperature and pressure, below that of the atmosphere, to % at 100 lbs. Its weight per cubic foot varies as the 16 root of the 17th power, and may be found by the formula : D — .003027/ -941, which is correct to within } per cent, up to 250 lbs. pressure. The following table gives the properties of steam at different pressures — from 1 lb. to 400. 48