SPECIFICATIONS. 381 



where d approximate distance between angles, in feet; 

 / thickness <>| tank plates, in inches; 

 D = diameter of tank, in fn-t. 



34. The top of the tank will generally be covered with a conical roof of thin plates; and the 

 pitch shall be I to 6. For tanks up to 22 ft. in diameter, the roof elates will be assumeti to be 

 s< 1! supporting. If the diameter of the tank exceeds 22 ft., angle rafters shall be used to support 

 the roof plates, which are generally i in. thick. 



1 Mates of the following thicknesses will be assumed to be self-supporting for various diameters: 

 fj in. plate, up to a diameter of 18 ft. 

 \ in. plate, up to a diameter of 20 ft. 

 tV in. plate, up to a diameter of 22 ft. 



Rivets in the roof plates shall be from J to -fg in. in diameter, and shall be driven cold. These 

 mvts iuvd not be headed with a button set. 



35. A trap-door, 2 ft. square, shall be provided in the roof plate. Near the top of the higher 

 tanks, there shall be a platform with a railing, for the safety of the men operating the trap-door. 



36. There shall be an ornamental finial at the top of the roof. 



37. There shall be a ladder, I ft. 3 in. wide, extending from a point about 8 ft. above the 

 foundation to the top of the tank, and also one on the inside of the tank. Each ladder shal' be 

 made of two 2\ by f in. bars with \ in. round rungs I ft. apart. On large, high tanks, 30 fi. or 

 more in diameter, a walk shall be provided from the column nearest *the ladder to the expansion 

 joint on the riser or inlet pipe. 



38. In designing a tank, a height of 6 in. shall be added to the required height of the tank 

 if an overflow pipe is not specified by the owner. 



39. Each elevated tank shall be furnished with a riser or inlet pipe, the size of which shall be 

 determined by the rate at which the tank must be filled. The size of the riser pipe will be speci- 

 fied by the owner. The outlet pipe, in most cases, is not required, as the riser or inlet pipe will 

 serve the same purpose, but it shall be furnished if demanded by the owner. 



40. AH pipes entering the tank shall have cast-iron expansion joints with rubber packing, and 

 facilities for tightening such joints. The expansion joint, generally, shall be fastened to the 

 bottom of the tank with bolts having lead washers. The tank plates shall be reinforced where the 

 pipes enter the tank. 



41. All pipes entering the tank shall be thoroughly braced laterally with adjustable diagonal 

 bracing at the panel points of the tower. 



42. The diagonal bracing in the tower shall preferably be adjustable, and shall be calculated 

 for an initial stress of 3,000 Ib. in addition to wind stresses, etc. 



43. The size and number of the anchor-bolts in the tower shall be determined by the maxi- 

 mum uplift when the tank is empty. The anchor-bolts in the tower, where the maximum uplift 

 is greater than 10,000 Ib., shall be fastened directly to the columns with bent plates or similar 

 details. In all other cases it will be sufficient to connect the anchor-bolts directly to the base- 

 plates. 



The tension in anchor-bolts shall not exceed 15,000 Ib. per sq. in. of net area. The minimum 

 section shall be limited to a diameter of ij in. The details shall be made so that the anchor- 

 bolts will develop their full strength, and, at the lower end, they shall be furnished with an anchor- 

 plate, not less than \ in. thick, to assure good anchorage to the foundation without depending on 

 the adhesion between the concrete and the steel. 



44. The concrete foundation shall be assumed to have a weight of 140 Ib. per cu. ft., and 

 shall be sufficient in quantity to take the uplift, with a factor of safety of l^. 



45. Three-ply frost-proof casing shall be provided, if necessary, around the pipes leading to 

 and from the tank. This casing shall be composed of two layers of f by 2j in. dressed lumber, 

 and each layer shall be covered with tar paper or tarred felt, and one outside layer of f by 2\ in. 

 dressed and matched flooring. The lumber shall be in lengths of about 12 ft. There shall be a 

 I in. air space between the layers of lumber, and wooden rings or separators shall be nailed to 

 them every 3 ft. (In very cold climates it is good practice to fill the space between the pipes and 

 the first layer of lumber with hay or similar material.) The frost casing may be square or cylin- 

 drical; it shall be braced to the tower with adjustable diagonal bracing, as described for pipes in 

 Section 41. 



46. All detailed drawings shall be subject to the owner's approval before work is commenced. 



47. For materials, workmanship, inspection, painting, and testing, see Part III; for founda- 

 tions, see Part IV. 



PART II. DESIGN OF STAND-PIPES. 



Definition. I. A stand-pipe is a tank, generally cylindrical, used for the storage of water, 

 oil, etc. Its height, in most cases, is considerably greater than its diameter; it has a flat bottom, 

 and rests directly on its foundation. 



