CATALOG OF THE MECHANICAL COLLECTIONS 125 



tion of the fuel with only 12 to 14 percent of the air in excess of 

 that theoretically required for complete combustion. 



This burner has eight burner tubes and consists of three principal 

 parts, the refractory block in which the tubes are formed, the gas 

 manifold, and the air damper. The gas manifold is a rectangular 

 box that fits against the back of the tube block and has cylindrical 

 openings in line with the tubes. In each tube opening in the mani- 

 fold are cast the four jets through which gas is supplied to the tube.. 

 The damper is a hinged door that fits over the back of the gas mani- 

 fold and controls the flow of air into the air tubes. 



This burner, which is 11 inches square, burns 1,500 cubic feet of 

 natural gas an hour at 3-ounce gas pressure, or 2,400 cubic feet at 

 10-ounce pressure. 



BOILER FEED-WATER PUMPS AND INJECTORS 



The problem of putting water into a steam boiler against the 

 pressure of the steam within the boiler was not a serious one when 

 the pressures used were only slightly above atmospheric pressure. 

 The first boiler feed-water pumps were small pump pistons attached 

 to the walking beams of the early engines which pumped water to 

 elevated reservoirs from which the water flowed into the boilers by its 

 own weight. Later these pumps were designed to pump water di- 

 rectly into the boilers as it was needed. So long as the boiler was 

 considered a part of the steam engine it was reasonable and practical 

 to operate the boiler feed pump directly from the engine and this 

 arrangement continued to the middle of the nineteenth century. In 

 the meantime the steamboat and the steam locomotive had been suc- 

 cessfully introduced, and it was found that running a steamboat 

 while made fast to a landing and idling a locomotive up and down 

 a terminal track, for no purpose other than to replenish the water 

 in their boilers, were awkward procedures, and separate steam op- 

 erated pumps soon came into use on boats and locomotives. Finally 

 engines and boilers came to be considered as entirely independent 

 units, and in stationary land plants boilers were located in separate 

 parts of the buildings under the direction of individual boiler op- 

 erators, and practical arrangement required that boiler feed pumps 

 be designed as boiler accessories independent of any connection with 

 the main plant engines. Boiler feed pumps have taken many forms, 

 including the most popular direct-connected "simplex" and "duplex" 

 reciprocating pumps and the recent steam and electric, multistage, 

 centrifugal pumps. Several forms of reciprocating feed-water 

 pumps are described below under the section "Steam Pumps" (p. 133). 



Apart from the development of the feed-water pump was the 

 perfection of the boiler feed-water injector, a device that emi^loys 

 steam from the boiler, acting directly upon the water to force the 



