1. Q: What is the typical maximum hardness limit (in Brinell) for the weld area of API 5L X65 PSL2 pipe intended for sour service?
A: For sour service, a maximum hardness of 248 HB (22 HRC) is typically specified for the weld metal, HAZ, and base metal to mitigate SSC risk. This is often a project-specific requirement beyond the base API 5L standard.
2. Q: Which ASTM standard covers welded pipe for fence structures, and what is a key mechanical property?
A: ASTM A849, specification for post and rail, welded, steel fence structures. A key property is tensile strength, with grades like 50 [345] (50 ksi min tensile) and 65 [450] (65 ksi min tensile).
3. Q: For repairing a surface defect on an API 5L X52 ERW pipe by grinding, what is the typical maximum depth allowed before weld repair is required?
A: Per standards like API 1107, grinding is generally acceptable if it does not reduce the wall thickness below the specified minimum (often 87.5% of nominal). For a defect, grinding depth is usually limited to ~0.8 mm (1/32 inch) or less; deeper defects require qualified weld repair procedures.
4. Q: What is the primary purpose of the "hydrostatic test" required by standards like ASTM A53 and API 5L?
A: The hydrostatic test verifies the pressure-containing integrity of the pipe body and its weld seam. It is a proof test that subjects the pipe to a stress level above its rated working pressure without failure.
5. Q: Why is HFIW (High Frequency Induction Welding) often preferred over ERW for higher-grade line pipes (e.g., API 5L X70 and above)?
A: HFIW provides a narrower, more precisely controlled heat-affected zone (HAZ) and produces a cleaner weld with less oxide inclusion. This results in better weld seam consistency, superior toughness, and fewer defects, which is critical for high-strength, high-performance pipes.
