Pipefitter Pipefitting Trade Math 3 — Questions and Answers
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?
- 13 inches
- 15 inches (Correct answer)
- 17 inches
- 21 inches
Correct answer: 15 inches
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?
- 1.082
- 1.414
- 2.613 (Correct answer)
- 3.864
Correct answer: 2.613
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?
- 8 TPI
- 11.5 TPI (Correct answer)
- 14 TPI
- 18 TPI
Correct answer: 11.5 TPI
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?
- 19
- 20
- 21 (Correct answer)
- 22
Correct answer: 21
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?
- 4.5 inches (Correct answer)
- 6 inches
- 7.5 inches
- 9 inches
Correct answer: 4.5 inches
Center-to-center = nipple length minus both thread engagements: 6 − 0.75 − 0.75 = 4.5 inches.
Question 6: If a pipe has a pitch of 1/8 inch per foot (fall), how much does a 48-foot run drop in elevation?
- 4 inches
- 6 inches (Correct answer)
- 8 inches
- 12 inches
Correct answer: 6 inches
Total drop = 48 ft × 1/8 in/ft = 6 inches.
Question 7: A pipe flange bolt circle has a diameter of 11.75 inches and requires 8 equally spaced bolts. What is the arc length between bolt holes?
- 3.46 in
- 4.62 in (Correct answer)
- 5.78 in
- 6.94 in
Correct answer: 4.62 in
Arc length = (π × D) / n = (3.1416 × 11.75) / 8 ≈ 4.62 inches.
Pipefitter Pipefitting Trade Math 3
Using the rolling offset formula, if the horizontal offset is 9 inches and the vertical offset is 12 inches, what is the true offset?