Length of flue, 18 feet; diameter of flue, 14 inches; thickness of material, 31. 195lbs., pressure allowable. For every foot or fraction thereof over 18 feet, deduct three pounds per square inch from the pressure allowable on a flue 18 feet in length or add of an inch to the thickness of material required for a flue 18 feet in length for every 3 feet or fraction thereof over 18 feet. To determine the thickness of material for any required pressure, multiply the pressure in pounds by the radius of the diameter of the flues. in inches, and divide the product by the constant 44; the quotient will be the thickness required. Required the thickness of material for a flue 18 feet in length and 14 inches in diameter, requiring a working pressure of 195 pounds to the square inch. The thickness of lap-welded flues shall not be less than the product of the constant 2.20 multiplied by the diameter of the flues in inches, which will express the thickness in hundredths of an inch. Formula: CXD=T, minimum thickness. EXAMPLE. Required the least thickness allowable for a lap-welded flue 14 inches in diameter: 2.20 X 14 = 30.80 100' least thickness allowable. Lap-welded flues 7 inches and not over 16 inches in diameter, over 5 feet and not over 10 feet in length, shall be re-enforced by one wrought-iron ring attached externally at the centre of the flue. Lap-welded flues over 10 feet, and not over 15 feet in length shall have two wrought-iron rings attached to the flue externally, equidistant between the ends of the flue, and there shall be attached one additional ring for every 5 feet or fraction thereof over 15 feet in length. All such rings shall be good and substantially made, and properly and securely attached to the flues, and shall have a thickness of material of not less than the thickness of the material of the flues, and a width of not less than 21⁄2 inches: Provided, however, Where such flues are made. in lengths of not over 5 feet, and fitted one into the other, and substantially riveted, the wroughtiron rings may be dispensed with. Lap-welded flues seven inches in diameter and less, shall be in accordance with the following table of thicknesses : 10. For cylindrical boiler flues over 16 and less than 40 inches in diameter, the following formulas shall be used in determining the pressure allowable: Τ A, constant. thickness of flue, in decimals of an inch. P = pressure of steam allowable, in pounds. 1760 D = = F, a factor. .31 C, a constant. = Formula: FXT EXAMPLE. Given a flue twenty (20) inches in diameter and thirty-seven one hundredths (.37) of an inch CORRUGATED FURNACE-FLUES. SEC. 10. The strength of corrugated flues, when used for furnaces or steam-chimneys (corrugation not less than 11⁄2 inches deep), and provided that the plain parts at the ends do not exceed 6 inches in length, and the plates are not less than thick, when new corrugated and practicably true circles, to be calculated from the following formula: Given a corrugated flue 40 inches mean diameter, 1⁄2 inch thick; required the pressure allowed II. The formulas for cylindrical lap-welded and riveted flues in boilers to be used as furnaces, which shall be used by inspectors in determining the pressure to be allowed, shall be as follows, viz: Let D= diameter of flue in inches. T-thickness of flue in decimais of an inch. Given, a flue forty (40) inches in diameter, seven (7) feet in length, and five (5) tenths of an inch in thickness; required working pressure to be allowed: Substituting values in the formula, and performing the operation indicated, we have— Р _89600 XT2 89600 X.25_22400-80 lbs. pressure. 7 X 40 280 Provided, That if rings of wrought-iron are fitted and riveted properly on, around, and to the flues, in such manner that the tensile strain on the rivets shall not exceed 6,000 pounds per square inch of section, the distance between the rings shall be taken as the length of the flue in the formula. EXAMPLE. Given, a flue forty (40) inches in diameter, eight (8) feet long, and five (5) tenths of an inch in thickness, having one ring at the middle of |