Pipe Fabrication and Joining Flashcards

What does the term 'centerline to end' (CL-E) dimension represent in pipe fabrication?

Answer: The distance from the center of a fitting to the end of its connecting pipe or hub

CL-E (centerline to end) is the measured or calculated distance from the center of a fitting to the face or end of the pipe connection, used in pipe layout and spool fabrication.

Which type of gasket is most appropriate for a raised-face flange operating in 600-psig high-temperature steam service?

Answer: Spiral-wound metallic gasket with inner and outer rings

Spiral-wound metallic gaskets with inner and outer rings are the industry-standard choice for high-temperature, high-pressure steam on raised-face flanges due to their resilience and leak resistance.

A pipefitter is fabricating a 45-degree offset using two 45-degree elbows. The offset distance (rise) is 12 inches. What is the travel (pipe cut length between fittings)?

Answer: 16.97 inches

For a 45-degree offset, travel = offset ÷ sin(45°) = 12 ÷ 0.7071 ≈ 16.97 inches; this is the pipe length between the two elbow centers.

Which pipe joining method uses a roll-groove cut into the pipe OD and a mechanical coupling to create the joint?

Answer: Victaulic (grooved mechanical) coupling

Victaulic (grooved mechanical) couplings engage a roll groove machined or cut into the pipe OD, allowing fast assembly and some pipe deflection without welding.

When performing a butt weld on pipe in the 6G (inclined fixed) position, what is the primary challenge for the welder compared to the 1G (flat) position?

Answer: The weld must be completed in all positions simultaneously without rotating the pipe

The 6G position requires the welder to weld in all positions (flat, vertical, overhead) continuously around a fixed, inclined pipe without rotation, making it the most comprehensive test position.

A carbon steel pipe isometric shows a 90-degree elbow with a 'long radius' (LR) designation. For a 4-inch nominal pipe size, what is the centerline radius of this elbow?

Answer: 6 inches

For long-radius elbows, the centerline radius is 1.5 times the nominal pipe size; for 4-inch pipe, 1.5 × 4 = 6-inch centerline radius.

What is the correct sequence of steps when making up a bolted flange joint to ensure even gasket compression?

Answer: Tighten bolts in a cross (star) pattern through multiple torque passes

Bolts must be tightened in a cross (star) pattern through at least three incremental torque passes to achieve even gasket seating and prevent joint leakage.