218 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 1910. 



itself, which may be from 100 to 150 pounds per square inch, with a 

 temperature of from 300° to 350° F. When a boiler tender opens 

 the valve after putting in a new glass it is liable to explode before 

 his face like the cannon cracker which the boy celebrating the Fourth 

 of July holds too long after lighting, and the results are much the 

 same — more or less severe cuts and burns, and possible destruction 

 of his sight. Danger from this, source has been eliminated by using 

 the gauge-glass guard shown in plate 2, figures 1 and 2. This guard is 

 made of sheet steel, and can be turned in front of the glass when any- 

 one is working about it. After the Avork is done it is swung around 

 back of the glass, so as not to interfere with the view of the water. 



A number of our boiler plants have been equipped with nonreturn 

 valves, which only come into play in case of an accident. There may 

 be 10,000 horsepower of boilers connected into one piping system, 

 so that if any part of a boiler or main steam pipe fails this stored- 

 up energy will be released with terrific force at the point where the 

 break occurs, until valves can be closed or fires drawn and the boilers 

 cooled down. The nonreturn valve closes automatically in case of 

 accidents of this sort, and thus brings the system under control with- 

 out the risk which must be taken by men going in to close the valves 

 by hand. 



Three connections are necessary for each boiler — one through 

 which water to be evaporated is admitted; a connection from the 

 boiler to the main piping through which the steam is carried aA\ ; . 

 and a connection to a system of "blow-off" piping, so that the sedi- 

 ment which settles from the water can be blown out at intervals. 

 Entrance to a boiler is obtained by means of a "manhole," which 

 is just about large enough to enable an average-sized man to wrig- 

 gle through comfortably — a process which can not be accomplished 

 very quickly. Thus the workman who enters a boiler while other 

 boilers of the same plant are in use is necessarily at the mercy of the 

 men outside, as the accidental opening of a valve might result in his 

 serious scalding. There are long rows of these valves exactly alike, 

 and mistakes are liable to occur. To guard against this the valves 

 have been numbered and red warning signs marked " Danger — do 

 not move " are hung on them when anyone is in a boiler. Wherever 

 practicable it is made the duty of the man doing the work to place 

 these warning signs. 



ENGINE INSTALLATIONS. 



The power which turns the shafting and drives the machinery in 

 our mills, is furnished chiefry by large steam engines. These engines 

 have flywheels weighing from 25 to 75 tons each, running at a rim 

 speed of 5,000 or 6,000 feet per minute. The energy stored in one of 

 these wheels when operating is about equivalent to an average sized 



