148 STEAM BOILERS 



obtained from the fires in the boilers that are to be cut out. 

 This can be accomplished by running until the fires have given 

 up all of their available heat for making steam, as indicated by 

 the gradual fall in pressure when the dampers are wide open, 

 and then making the change. While the fires in one set of 

 boilers are burning low and the pressure is falling, the pressure 

 in the boilers to be cut in is gradually rising and meeting, so 

 to speak, the falling pressure of the set in operation. When 

 the difference of 5 Ib. is reached, change over. A man should 

 be stationed at each stop-valve, and while one is being opened 

 the other should be closed; the engine will continue running 

 uninterruptedly while the change is being made. 



EQUALIZING THE FEED 



When the boilers of a battery have been cut into service and 

 hence are all connected together through the steam main, 

 the regulation and equalization of the feedwater becomes an 

 important factor. Each boiler has its own check-valve and 

 feed stop- valve, and generally all the boilers are supplied from 

 one pump, which is running constantly. The quantity of 

 water admitted to each boiler is regulated by its feed stop- 

 valve. When the water gets low in any boiler, the feed stop- 

 valve should be opened wider, while at the same time the feed 

 stop-valves on one or more of the other boilers in operation 

 may be closed partly and thus divert the feedwater to the one 

 most requiring it. Some boiler plants have check-valves with 

 an adjustable lift; in that case the feed is equalized by adjust- 

 ing the lifts of the check- valves, the stop- valves being left 

 wide open while running. It will be understood from the 

 foregoing that the object in view is the maintaining of an equal 

 water level in all the boilers through the manipulation of the 

 feed stop-valves or check-valves. A boiler that is not doing 

 its legitimate share in generating steam may be known by the 

 fact that the feed stop-valve or check-valve on that boiler 

 will be nearly, if not entirely, closed most of the time. 



FIRING WITH SOLID FUEL 



General Remarks. The safe and economical operation of 

 steam boilers calls for careful and intelligent management. 

 The fires should be kept in such condition as to maintain the 



