1. What Is a Long Neck Flange?
Enhanced stress distribution in high-pressure or high-temperature applications.
Improved resistance to bending and thermal expansion due to its extended taper.
A smoother transition between the flange and pipe, reducing turbulence and corrosion risks.
2. What Is a Weld Neck Flange?
A seamless, tapered design that matches the pipe's shape, minimizing flow disruption.
A raised face (RF) or other sealing surfaces to connect with mating flanges.
Compliance with pressure ratings (e.g., Class 150 to Class 2500) for industrial piping systems.
3. Why Use a Weld Neck Flange?
Strength and Durability: The butt weld connection creates a strong, leak-resistant joint, suitable for high-pressure, high-temperature, or hazardous fluid systems.
Stress Reduction: The tapered neck distributes mechanical and thermal stresses, preventing flange distortion or pipe failure.
Flow Efficiency: The smooth internal profile reduces turbulence, making it ideal for critical flow applications (e.g., refineries, chemical plants).
Code Compliance: They meet strict industry standards for safety and reliability in pressurized systems.
4. What is the ASME Code for weld neck flanges?
Dimensions, pressure-temperature ratings, and materials (e.g., carbon steel, stainless steel).
Design requirements for the neck taper, face types (e.g., RF, RTJ), and bolt patterns.
Testing and inspection protocols to ensure compliance with safety regulations.
Additionally, ASME B31.3 (Process Piping) and B31.1 (Power Piping) dictate application-specific installation guidelines.
5. How Are Long Weld Neck Flanges Made?
Material Selection: High-grade steel (e.g., ASTM A105 for carbon steel, A316 for stainless steel) is chosen based on pressure and temperature requirements.
Forming the Neck:
Forging or casting: The flange body and extended neck are shaped using hot forging (for strength) or casting (for complex designs).
Machining: The neck is tapered to match the pipe's OD, with precise dimensions per ASME B16.5.
Face and Bolt Hole Machining:
The sealing face (e.g., raised face) is machined to specified roughness (e.g., 125 microinches).
Bolt holes are drilled and tapped to align with mating flanges.
Heat Treatment: If required (e.g., for high-strength alloys), the flange undergoes annealing or quenching to improve mechanical properties.
Inspection and Testing:
Dimensional checks against ASME standards.
Non-destructive testing (NDT) like ultrasonic or magnetic particle inspection for welds (if applicable).
Pressure testing to ensure leak-tightness.
Finishing: Surface coating (e.g., galvanizing, paint) is applied for corrosion resistance, followed by marking with material grade, pressure class, and manufacturer details.
