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An ASME B16.5 Class 600 Weld Neck Flange is easily identified by its long, tapered hub that transitions gradually into the pipe wall thickness. This specific geometry provides excellent reinforcement, making it highly resistant to dishing and bending.
The Class 600 designation represents the pressure-temperature rating of the flange as defined by the American Society of Mechanical Engineers (ASME). At ambient temperatures, a Class 600 carbon steel flange can handle working pressures up to approximately 1480 psi (102.1 bar), though this rating scales down as operating temperatures rise.
Key Benefits of the WN Configuration
Stress Distribution: The tapered hub transfers stress from the flange to the pipe, reducing high stress concentrations at the base.
Radiographic Testing: The butt-weld joint between the flange neck and the pipe allows for seamless X-ray inspection.
Erosion Resistance: The smooth transition inside the bore minimizes turbulence and erosion within the piping system.
Dimensional Breakdown of Class 600 WN Flanges
ASME B16.5 covers flange sizes from NPS 1/2 to NPS 24. For sizes larger than 24 inches, engineers must reference ASME B16.47 Series A or B.
When specifying a Class 600 Weld Neck flange, several critical parameters must match your piping schedule:
- Outside Diameter (O): The total width of the flange disk.
- Minimum Thickness (C): The thickness of the flange mating flange face (excluding the 7mm/0.25" raised face).
- Diameter of Hub (X): The width of the tapered hub where it meets the flange body.
- Length Through Hub (Y): The overall height of the flange from the weld bevel to the bottom face.
- Bore (B): The internal diameter, which must be specified by the buyer to match the schedule of the matching pipe (e.g., Schedule 40, 80, 160, or XXS).
Facing Options for Class 600 Flanges
While the Raised Face (RF) is the most common option for Class 600 applications, high-pressure or high-temperature environments often dictate alternative sealing surfaces:
- Ring Type Joint (RTJ): For critical applications, Class 600 WN flanges are frequently ordered with an RTJ face. A metallic oval or octagonal ring gasket rests inside a machined groove on the flange face. This creates a highly secure, metal-to-metal seal ideal for upstream oil production.
- Flat Face (FF): Rarely used in Class 600 ratings unless connecting to heavy-duty cast iron valves or machinery bodies where uneven bolt torque could crack the equipment casing.
ASME B16.5 Class 600 Weld Neck Flange Dimension
