DESIGNING. 17 1 



imate an angle 6 in. x6 in. by T 7 ff inches, without considering the 

 plate of which the tank is composed. The connecting-angle is 

 sometimes placed inside and sometimes outside of the cylinder, 

 but as the pressures are from the inside, the outside angle loca- 

 tion is preferred, as the bed-plate then extends beyond the shell, 

 and the angle riveted on acts as a brace, and the plate and leg 

 of the angle give that much additional stability to the structure. 

 Some engineers prefer to flange the shell- and bed-plate, 

 making a flanged joint instead of the angle-joint as described. 

 Where it is unnecessary to extend the area of the base by the 

 use of angles and web-plates, and the simple angles are used, as 

 shown, the outer arrangement of the connecting-angle is impos- 

 sible, and the connection is necessarily made on the inside. 



Details. As has been said, the hydrostatic pressure at the 

 top of a tank being zero, the thickness and strength of a sheet 

 of paper would be sufficient to control and restrain the pres- 

 sures and water; but, in stand-pipes of any size, the thickness 

 of the top rings is usually J in., and never less than T 3 T in. 

 These thicknesses are used to provide for the weakening of the 

 plates by oxidation or rusting of the metal, and also to resist 

 the action of the wind, to successfully resist which it -is usual 

 to provide some "stiffener" at the top, usually an angle riv- 

 eted to the inner or outer circumference of the cylinder, the 

 horizontal leg being used to fasten and support an ornamental 

 cresting, generally of malleable iron, cast in segments, and 

 bolted to the angle. 



In the record of stand-pipe failures, several large structures 

 have suffered partial or total collapse during high winds, the 

 metal being rolled up at the top into a cone shape, similar to 

 the twisting of a piece of paper into a taper. This action of 

 the wind is not very well understood, and therefore the size of 

 the stiffening angle customarily placed about the top of the stand- 

 pipe is generally arbitrarily assumed. 



