Page:Sheet Metal Drafting.djvu/92

78 to be provided for. Two hoods on the "sticker" have 5-inch necks, and two other hoods have 4-inch necks. How many square inches should be added to the area of the main pipe to care for this machine?

Problem 18E.—A forced draft heating system in a factory has a 9" diameter outlet every 20 feet. The main pipe as it leaves the fan is 20" in diameter, (a) How many 9" branch outlets will this main serve? (b) What will be the diameters of the main after each branch is taken off?

Problem 18F.—Two boilers are set side by side. Each boiler has a rectangular smoke neck measuring 14"×37". How large must the round pipe be made that is to convey the gases from these boilers to the stack?