1. Q: What is the significance of "Schedule" in pipe sizing (e.g., Sch 40, Sch 80)?
A: Schedule defines the wall thickness for a given nominal pipe size (NPS). Higher schedule numbers mean thicker walls and higher pressure ratings.
2. Q: Which seamless pipe grade is common for steam tracing lines?
A: ASTM A106 Gr. B, Schedule 40 or 80, due to its strength and temperature resistance for low to medium pressure steam.
3. Q: What is a key quality test for seamless boiler tubes (A192)?
A: The flattening test, flange test, and hydrostatic or non-destructive electric test (EDDY current) to ensure soundness for pressure duty.
4. Q: What is the main alloying element difference between carbon steel and "Carbon-Molybdenum" pipe like ASTM A335 P1?
A: The addition of approximately 0.44-0.65% Molybdenum (Mo) in P1, which improves high-temperature strength, especially for steam service up to about 470°C (875°F).
5. Q: What is the concern with "graphitization" in carbon steel pipes at elevated temperatures?
A: Long-term exposure above 425°C (800°F) can cause carbide phases to break down into iron and graphite nodules, weakening the pipe and leading to failure.
