Pipefitter Pipefitting Trade Math 3

Question 1

Using the rolling offset formula, if the horizontal offset is 9 inches and the vertical offset is 12 inches, what is the true offset?

Accepted Answer

15 inches

Answer

True offset = √(9² + 12²) = √(81 + 144) = √225 = 15 inches.

Question 2

A 22.5° elbow has a center-to-face dimension of 2 inches. What multiplier is used to find travel from offset?

Accepted Answer

2.613

Answer

The travel multiplier for a 22.5° offset is 2.613 (the cosecant of 22.5°).

Question 3

How many threads per inch are on a 2-inch NPT pipe fitting?

Accepted Answer

11.5 TPI

Answer

2-inch NPT pipe has 11.5 threads per inch per ASME B1.20.1 standard.

Question 4

A pipe hanger is to be spaced at 10-foot intervals along a 200-foot horizontal run. How many hangers are needed?

Accepted Answer

21

Answer

A 200-foot run at 10-foot spacing needs hangers at 0, 10, 20, ... 200 ft = 21 hangers.

Question 5

A pipe nipple is 6 inches long overall (end-to-end). If each threaded end engages 3/4 inch, what is the center-to-center dimension when installed between two threaded fittings?

Accepted Answer

4.5 inches

Answer

Center-to-center = nipple length minus both thread engagements: 6 − 0.75 − 0.75 = 4.5 inches.

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Pipefitter Pipefitting Trade Math 3