890 Transactions of the American Institute. 



Globe valves are not worn out, but destroj'ed by hard screwing, 

 which is unnecessary with our valves. 



When worn out the valve-seat is changed by unscrewing, with a 

 flat piece of metal pressed against the lugs ( b b ) the valve is changed 

 by unscrewing the nut on the spindle. 



To shut the valve turn both wheels. 



To keep the valve tight, needs only to rub it to a joint when dirt 

 intervenes between the valve and its seat ; this is accomplished by 

 turning the crank wheel (which revolves the valve, C), two or three 

 times around, after placing the valve so as to just touch the seat. 



Comjmrison. — It cannot be denied that all the slide valves wear 

 unequal on their surfaces by sliding, the bottom of the valve face and 

 the top valve seat wears fastest ; also, the current passing through 

 the valve deposits dirt in the valve chamber, and cuts (wears) the 

 valve seat, and when partially closed cuts both the valve and the 

 Beat ; also, the backlash required to tighten the valves causes the 

 current to toss the valve up and prevents graduating the flow. 

 Again, when the valve seats are leaky, they must be put in the lathe 

 and milled (faced) over again. The slide valve has a straight current 

 or flow, but this is compensated for in the perpetual valve by having 

 a large port, and the current wears the valve and seat equal all around. 



Durahility. — The valve is made durable by simply changing such 

 parts as are worn (witliout unscrewing the pipe), and also by their 

 being made of a material the least afl'ected by hot or cold grease^ 

 super-heated steam, chemical ingredients in the water, oil works, 

 sugar house, petroleum and alcohol distilleries, &c., for which purpose, 

 this bronze metal has proved the best, all softer materials forming 

 receptacles for grit, &c., to roughen the joint and make it leak. 



When the duplicate valve and seat ring is destroyed others can be 

 bought instead of buying the whole shell, wheel, &c., which will last 

 much longer than the pipes, and saves taking down pipes to repair 

 the valve. 



Covering for Steam Boilers. 

 Mr. F. H. Snyder, of New York city, exhibited specimens of his 

 improved covering for steam boilers, consisting of three hn^ers of 

 materials. The flrst layer is made of flre-clay ; the second is com- 

 posed of rye flour, saw -dust and charcoal, sometimes alum is added; 

 the third laj'er is the same substantially as the flrst. The whole is 

 coated with paint. An inch thick of this coating will stand the heat 



