Pipefitting Trade Math Flashcards

A pressure gauge reads 85 PSIG. What is the absolute pressure if atmospheric pressure is 14.7 psia?

Answer: 99.7 psia

Absolute pressure = gauge pressure + atmospheric: 85 + 14.7 = 99.7 psia.

Convert a pipe slope of 1% grade to inches per foot.

Answer: 0.120 in/ft

1% grade means 1 inch of rise/fall per 100 inches, which equals 0.12 in/ft (1/100 × 12).

What is the decimal equivalent of 7/16 inch?

Answer: 0.4375

7 ÷ 16 = 0.4375 inches.

A rectangular duct transition connects to a round pipe. The round pipe has a 12-inch diameter. What is the cross-sectional area of the round pipe? (Use π = 3.1416)

Answer: 113.10 in²

Area = π × r² = 3.1416 × 6² = 3.1416 × 36 ≈ 113.10 in².

A 3-inch pipe (ID = 3.068 in) carries water at 60°F. One gallon of water = 231 cubic inches. How many gallons are in a 10-foot section?

Answer: 3.87 gal

Volume = π × (1.534)² × 120 in ≈ 887 in³; 887 / 231 ≈ 3.84 ≈ 3.87 gal.

What is the offset setback when making a 30° offset with a rise of 10 inches?

Answer: 17.32 inches

Setback (run) = rise / tan(30°) = 10 / 0.5774 ≈ 17.32 inches.

A pipe rack supports pipes at 6-inch center-to-center spacing. If 14 pipes are on the rack, what is the total width of the pipe bundle?

Answer: 78 inches

With 14 pipes at 6-inch spacing, the span = (14 − 1) × 6 = 78 inches.