. A manual of marine engineering: comprising the design, construction, and working of marine machinery. ; the top lever spindle is carried through the door at oneend, and is balanced by a lever and weight. The float is always full ofwater, and the weight is adjusted to balance when one half is immersed inwater. To the weight lever another lever is attached, which actuates thethrottle valve, F, and controls the supply of steam to the pump drawingfrom the heater. When the water in the heater rises the float is raised, andthe throttle valve opened, and, when the water level is lowered, the floatf
. A manual of marine engineering: comprising the design, construction, and working of marine machinery. ; the top lever spindle is carried through the door at oneend, and is balanced by a lever and weight. The float is always full ofwater, and the weight is adjusted to balance when one half is immersed inwater. To the weight lever another lever is attached, which actuates thethrottle valve, F, and controls the supply of steam to the pump drawingfrom the heater. When the water in the heater rises the float is raised, andthe throttle valve opened, and, when the water level is lowered, the floatfollows, and the valve is closed ; the level of the water is thus kept constantin the heater, and the pumps are completely filled with water. The regulat-ing valve is a cock with a parallel key; the pressure of the steam keeps itperfectly steam-tight, although it may have worn slack in the shell : thepressure also keeps the shoulder of the key against the bottom of the stufling-box, so that the stufting gland is always kept slack. A relief valve and thenecessary gauges are also fitted to the Fig. 195.—Weirs Feed-Water Heaterand Automatic Regulating Gear. 504 MANUAL OF MARINE ENGINEERING. Evaporators.—The advantages of supplying marine boilers with purewater are great, and are so obvious as not to need specifying. Samuel Hall,the inventor of the surface condenser, was so thorough in his desire to useonly fresh water in the boilers of ships with his condenser that in 1833 hefitted evaporators to several of them made on precisely the same principlesas govern the design of our modern ones. He, however, went beyond themodern engineer by placing his apparatus in the steam chest of the boiler soas to lose no heat. The necessity of it was not, however, so severely feltuntil voyages of considerable length had been made with ships whose boilerswork at pressures of 100 lbs. and upwards. The weight of water evaporated
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