Safety Apparaius Jor Steam Boats o 



321 



Fig. 1, represents an I'lg- 1- 



oblique view of part of 

 a boiler with the safety 

 apparatus attached. An 

 unfavorable case, as to 

 the space occupied by 

 thB apparatus, is taken, 

 namely, that of a high 

 pressure boiler required 

 to work with steam of 

 150 lbs. bursting pres- 

 sure, (ten atmospheres,) 

 rendering it necessary 

 to load the valve with rather more than 150 pounds. 



Fig. 2, gives more in detail the method of arranging the fusible 

 plate, &;c. being a section of the apparatus. The area of the aper- 

 ture closed by the plate is taken at 3 square inches, which is one 

 half more than the area of the safety valve commonly used in a high 

 pressure boiler of 3 feet in 

 diameter by 10 feet in length. 

 A, B, Fig. 2. is the aperture 

 closed by thS plate, C, D, of 

 fusible metal, covered by a 

 piece of wire gauze to pre- 

 vent the plate from yielding 

 as the temperature approaches 

 its point of fusion. The plate 

 is surrounded by a cylinder, 

 E, F, G, H, of a greater diameter than the plate, terminated, above, 

 by the valve seat E, F. Should the fusible plate, in giving vent to 

 the steam, be thrown upwards, as an expression used by Arago in 

 relation to it, gives reason to suppose, the valve should not be in the 

 cylinder, E, F, G, H, but in one at right angles to it, so that the 

 valve seat should not be vertically over the fusible plate. The valve. 

 I, K, is represented of the usual form, though it may be questioned, 

 v^^hether this is the best which can be given : it is drawn in the posi- 

 tion which it should habitually have, that is, so far raised from the 

 seat as to give an opening for the escape of steam, equal in area to 

 the valve. . "^ 



