Pipefitting Math and Calculations Flashcards

A pipe system requires a 45° offset. If the travel distance is 14.14 inches, what is the set (run) distance?

Answer: 10 inches

For a 45° offset, the set equals the travel divided by 1.414 (√2), so 14.14 ÷ 1.414 ≈ 10 inches.

What is the internal cross-sectional area of a 6-inch nominal pipe with an inside diameter of 6.065 inches?

Answer: 28.89 sq in

Area = π × r² = 3.1416 × (3.0325)² ≈ 28.89 square inches.

A pipe is being cut to fit between two flanges. The pipe must be 36 inches face-to-face. Each flange has a 1.5-inch raised face and gasket compression of 0.125 inches. What is the cut length of pipe?

Answer: 33.25 inches

Cut length = 36 − 2(1.5) − 2(0.125) = 36 − 3 − 0.25 = 32.75; with both flanges each reducing 1.375, cut = 33.25 inches.

A pipefitter needs to calculate the weight of a 20-foot section of 4-inch Schedule 40 steel pipe (weight = 10.79 lb/ft). What is the total weight?

Answer: 215.8 lbs

Total weight = 10.79 lb/ft × 20 ft = 215.8 lbs.

Using the rolling offset formula, if the set is 9 inches and the roll is 12 inches, what is the true offset?

Answer: 15 inches

True offset = √(set² + roll²) = √(81 + 144) = √225 = 15 inches.

What is the developed length of a 90° elbow with a centerline radius of 12 inches?

Answer: 18.85 inches

Developed length = (angle/360) × 2π × radius = (90/360) × 2 × 3.1416 × 12 ≈ 18.85 inches.

A pressure gauge reads 145 psig. What is the absolute pressure in psia at sea level (atmospheric pressure = 14.7 psia)?

Answer: 159.7 psia

Absolute pressure = gauge pressure + atmospheric pressure = 145 + 14.7 = 159.7 psia.