Page:Sheet Metal Drafting.djvu/91

Sample Problem.—Two heaters are to be connected to a chimney flue by one pipe. One heater has a 7-inch, and the other a 9-inch neck. How large must a main pipe be to care for both heaters?

Formula for area,	A=	D2×.7854
Substituting,	A=	72×.7854
	A=	38.485 sq. in., area of 7" pipe
and	A=	92×.7854
	A=	63.617 sq. in., area of 9" pipe.

Since this is an exhaust system the areas must be added to get the equivalent area of the main.

Equivalent area=38.485+63.617=102.102 sq. in.

Transposing the above formula,
$\scriptstyle {D={\sqrt {A\div .7854}}}$ (Problem 8, Article 24.)

Substituting in this formula,
$\scriptstyle {D={\sqrt {102.102\div .7854}}}$

		.7854	102.1020	130
			78.54
			23.562
			23.562
	$\scriptstyle {{\sqrt {130}}=11.4''}$				11.4" Ans.

In actual practice we would make the pipe 11½" in diameter.

Problem 18A.—Two heaters are to be connected to a chimney flue by one pipe. One heater has an 8-inch, and the other a 10-inch neck. How large must the main pipe be to serve both heaters?

Problem 18B.—A battery of three steam heaters having 8½" smoke necks are to be connected to the chimney by one main pipe. (a) What will be the diameter of the main between the second and the third heaters? (b) What will be the diameter of the main between the third heater and the chimney?

Problem 18C.—Six blacksmith forges are to be connected to one smokestack. Each forge has a 6-inch neck. Give the size for the main pipe as each forge is "picked up."

Problem 18D.—In a shavings removal system a "sticker" is