308 APPLIED SCIENCE 



formula for determining the thickness of boiler plate: 

 _PXRXFS 

 TSX% 



Where T = thickness of the boiler plate in inches. 



P = boiler pressure in pounds per square inch. 



R = radius (f/2 diam. of boiler) in inches. 



FS = factor of safety. 



TS = tensile strength of the metal in pounds per 



square inch. 

 % = strength of the joint. 



The efficiency or strength of a joint is the percentage of the 

 strength of the solid plate that is retained in the joint. It 

 depends upon the kind of joint and method of construction. 

 If the thickness of the plate is more than J^ inch, the joint 

 should always be of the double-bolt type. 



EXAMPLE. What thickness of plate should be used when making 

 a 40-in. diameter boiler to carry 125 Ibs. pressure, if the strength of 

 the plate is 60,000 Ibs. per square inch, using a factor of safety of 6, 

 and 50% as the strength of joint? 



125 X 20 X 



T = - = % in. sheet 



60,000 X .50 



To find the safe working pressure use the following formula, where 

 the letters have the same significance as in the previous formula : 



TS X % X T 



R XFS 

 EXAMPLE. Find the safe working pressure of the same boiler. 



60,000 X .50 X .5 

 P = i- - = 125 Ibs. 



20 X 6 



