Pipefitter Pipe Fabrication Methods 2

Question 1

When making a 90-degree offset using two 45-degree elbows, what is the travel distance if the offset is 18 inches?

Accepted Answer

25.46 inches

Answer

The travel distance for a 45-degree offset equals the offset multiplied by the constant 1.414 (square root of 2). For an 18-inch offset: 18 x 1.414 = 25.45 inches.

Question 2

What is the correct process for post-weld heat treatment (PWHT) of a carbon steel weld to reduce residual stress?

Accepted Answer

Heat the weldment uniformly to 1100 to 1200 degrees F (593 to 649 C) and hold for a specified time, then cool slowly

Answer

PWHT for carbon steel requires heating the weld zone to 1100 to 1200 degrees F, holding at temperature for approximately 1 hour per inch of wall thickness, then cooling slowly in still air to relieve residual stresses.

Question 3

What is the minimum preheat temperature required by ASME B31.3 for welding carbon steel pipe with a wall thickness greater than 1 inch?

Accepted Answer

175 degrees F (79 C)

Answer

ASME B31.3 Table 330.1.1 requires a minimum preheat of 175 degrees F (79 C) for carbon steel (P-Number 1) with base metal thickness greater than 1 inch, to slow cooling and prevent hydrogen cracking.

Question 4

What is the purpose of back-purging with argon gas when TIG welding stainless steel pipe?

Accepted Answer

To prevent oxidation (sugaring) on the pipe ID weld root, maintaining corrosion resistance

Answer

Back-purging displaces oxygen from the pipe interior so the weld root is shielded from oxidation. Without purging, stainless steel forms a porous, chromium-depleted 'sugared' root bead that severely reduces corrosion resistance.

Question 5

When using a pipe wrap-around to mark a cutline on a pipe, what is the tool ensuring?

Accepted Answer

The cut line is perfectly perpendicular (square) to the pipe axis

Answer

A pipe wrap-around or scribe marker ensures the cutline is exactly 90 degrees to the pipe axis (square cut), preventing angled cuts that would create gap variations and poor weld fit-up.

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Certified Pipefitter Practice Test

Pipefitter Pipe Fabrication Methods 2