ASME B16.49

Applies to: Factory-made induction bends in high-strength pipeline steel for gas, oil, and liquid product transmission systems; API 5L Grades X42–X80; NPS 4 and larger; bend radii 3D and above.

Does NOT cover: Field cold bends; bends made from seam-welded pipe without specific qualification; fittings for process plant piping (use ASME B16.9).

• Post-bend heat treatment documented and verified to restore original toughness
• Wall thickness at extrados ≥ minimum design wall thickness
• Hardness limits after heat treatment (typically ≤248 HV10 for sour service)
• Charpy V-notch impact testing at specified design temperature
• Ovality limits at bend tangent and body
• Qualification procedure documentation for each pipe grade and heat-treatment combination

ASME B16.49 governs factory-made induction bends for onshore and offshore pipelines. The induction bending process locally heats a narrow band of pipe to 900–1100 °C and progressively forms the bend radius while moving the pipe through a fixed induction coil. The key engineering concern is restoring original yield strength and fracture toughness after this heating cycle; the standard mandates documented heat treatment procedures, hardness verification, and CVN impact testing on each heat-treated lot.

Engineering note: Unlike wrought fittings (B16.9 elbows), induction bends can achieve large-radius sweeping bends (5D, 7D, 10D) that reduce pressure drop in transmission systems. For sour-service pipelines (H₂S per NACE MR0175/ISO 15156), hardness limits are critical — all bends must be verified to avoid SSC susceptibility.