Pipefitter Pipefitting Math and Calculations 5

Question 1

A pipe drops 3 inches over a 10-foot horizontal run. What is the slope expressed as inches per foot?

Accepted Answer

0.30 in/ft

Answer

Slope = 3 inches ÷ 10 feet = 0.30 inches per foot.

Question 2

How many threads per inch (TPI) are on a 2-inch NPT pipe thread?

Accepted Answer

11.5 TPI

Answer

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

Question 3

What is the circumference of a pipe with an outside diameter of 10.75 inches (10-inch nominal)?

Accepted Answer

33.77 inches

Answer

Circumference = π × OD = 3.1416 × 10.75 ≈ 33.77 inches.

Question 4

A 5-piece equal-spread 45° offset uses 4 fittings and covers a 24-inch set. What is the spread between each fitting center?

Accepted Answer

6 inches

Answer

In a 5-piece equal-spread offset with 4 fittings, each fitting covers 24 ÷ 4 = 6 inches of set.

Question 5

A hydrostatic test requires pressurizing a system to 1.5 times the design pressure of 400 psig. What is the test pressure?

Accepted Answer

600 psig

Answer

Test pressure = 1.5 × 400 psig = 600 psig, which is the standard hydrostatic test multiplier.

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