Q: How does "sour service" affect pipe material selection?
A: Sour service involves exposure to fluids containing hydrogen sulfide (H₂S). This can cause Sulfide Stress Cracking (SSC) in high-strength steels. Special grades with controlled hardness, chemistry, and heat treatment (e.g., API 5L PSL2 with SSC requirements) must be selected.
Q: What is a hydrostatic test and why is it performed?
A: It is a pressure test where the pipe is filled with water and pressurized to a level higher than its design pressure (e.g., 1.5 times) to verify its strength and leak tightness. It is a common requirement before a new pipe is put into service-5.
Q: What non-destructive tests (NDT) are common for checking pipe welds?
A: Common methods include Ultrasonic Testing (UT) to detect internal flaws and measure wall thickness, and Radiographic Testing (RT) using X-rays or gamma rays to inspect for internal defects in the weld-9.
Q: What is a flattening test?
A: A flattening test is a mechanical test performed on a sample of welded pipe. The sample is flattened between two parallel plates to a specified distance to assess the quality and ductility of the weld and the parent metal-5.
Q: Why is heat treatment important for some carbon steel pipes?
A: Heat treatment (like normalizing or stress relieving) is used to achieve desired mechanical properties (strength, toughness), relieve residual stresses from manufacturing, and ensure the weld zone's integrity matches the base metal-7.
