STEAM BOILERS 145 



EXAMPLE. A boiler trial shows a useful expenditure of 

 186,429,030 B. T. U. and a total supply of 270,187,000 B. T. U. 

 What is the efficiency of the boiler? 



SOLUTION. Applying the formula, 



186,429,030 



= = .69 = 69% 



270,187,000 



Standard Code. For elaborate boiler trials, the standard 

 code recommended by the American Society of Mechanical 

 Engineers should be used. 



BOILER MANAGEMENT 



FILLING BOILERS 



Preparation for Filling Boiler. Before starting the flow of 

 water into the boiler, the manhole plates or handhole plates 

 that were removed preparatory to cleaning and overhauling 

 must be replaced, and the blow-off valve must be closed. 

 The gaskets, and also the surfaces with which they come in 

 contact, should be examined to see that they are in good con- 

 dition. It is customary to place a mixture of cylinder oil and 

 graphite on the outer surface of each gasket, so that it may be 

 removed without tearing. It is important that the manhole 

 plates and handhole plates be properly replaced and secured 

 in order to prevent leakage. 



Height of Water. In some cases the water can flow in and 

 fill the boiler to the required height by means of the pressure 

 that exists in the main supply pipe. In other cases, it may be 

 necessary to use a hose or to fill the boiler with a steam pump 

 or a hand pump. The boiler should be filled until the water 

 shows half way up in the gauge glass. 



Escape of Air. While filling a boiler it is necessary to make 

 provision for the escape of the contained air, since otherwise 

 the pressure caused by the compression of the air may prevent 

 the boiler from being filled to the proper height. Most boilers 

 have some valve that can be used for this purpose; a gauge- 

 cock may be left open until water issues therefrom, when it 

 may be closed. Sometimes the manhole plate, if the manhole 

 is on top, is left off while filling a boiler. 



