1. Q: When is seamless pipe mandatory over welded pipe?
A: For critical services with high pressure, high temperature, severe cyclic loading, or where the inherent defect risk of a weld seam is unacceptable. Often specified by applicable code (e.g., ASME B31.3 for certain conditions).
2. Q: What is the main advantage of using Quenched & Tempered (Q&T) grades like API 5L X80?
A: Very high strength-to-weight ratio, allowing for higher pressure transmission or thinner walls (cost savings on material and welding), especially in long-distance pipelines.
3. Q: What is the purpose of bevelled ends on pipe?
A: To prepare the pipe for butt-welding. The bevel angle (typically 37.5°) allows proper penetration and fusion of the weld root.
4. Q: What is "cold drawing" in pipe manufacturing and its benefit for grades like ASTM A179?
A: Pulling a seamless tube through a die at room temperature. It improves surface finish, dimensional accuracy, and mechanical strength.
5. Q: What does "Schedule" refer to (e.g., Schedule 40, 80)?
A: It defines the wall thickness for a given NPS. Higher schedule number = thicker wall. Schedule 40 and 80 are common for carbon steel.
