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How to Match Class 300 Flange Bore to Pipe Schedule
In mid-pressure piping systems, the Class 300 Welding Neck Flange is favored for its high structural integrity. However, the most critical step in procurement is ensuring the "Bore" (internal diameter) of the flange perfectly matches the internal diameter of the mating pipe. This is determined by the Pipe Schedule (wall thickness).
The Importance of Precision Bore Matching
A Welding Neck (WN) flange features a tapered hub that is butt-welded to a pipe. If the flange wall is thicker or thinner than the pipe wall, it creates a "step" inside the system, leading to turbulence, erosion, and stress concentration at the weld root.
When ordering a Class 300 Welding Neck Flange, you must specify the Schedule, such as Sch 40, Sch 80, or Sch XS. At Jiangyin Zhonghai Precision Machinery Co., Ltd., we utilize high-precision CNC turning to machine the bore of our forged flanges to exact tolerances, ensuring a seamless transition for fluid flow.
Parameter Comparison: Bore Dimensions for Class 300 WN Flanges
Based on ASME B16.5 for common nominal pipe sizes (NPS):
| NPS (Inches) | External Diameter (hub) | Bore (Sch 40) | Bore (Sch 80) | Bore (Sch 160) |
| 2" | 60.3 mm | 52.5 mm | 49.3 mm | 42.9 mm |
| 4" | 114.3 mm | 102.3 mm | 97.2 mm | 87.3 mm |
| 6" | 168.3 mm | 154.1 mm | 146.3 mm | 131.7 mm |
| 8" | 219.1 mm | 202.7 mm | 193.7 mm | 174.6 mm |
| 12" | 323.9 mm | 303.2 mm | 288.9 mm | 257.2 mm |
Precision Manufacturing at Jiangyin Zhonghai
Achieving a perfect match requires strict control over the forging and machining stages. Jiangyin Zhonghai Precision Machinery Co., Ltd. provides a technical advantage through:
- Custom Bore Machining: We support fully customized, drawing-based manufacturing, allowing us to produce Class 300 flanges for non-standard pipe wall thicknesses.
- Material Integrity: Our PED/TUV/TS qualifications ensure that even after significant machining to reach a specific Schedule, the flange maintains its rated pressure strength.
- Large-Scale Capability: We can manufacture welding neck flanges up to 60" with a maximum dimension of 4 meters, suitable for heavy industrial headers and mainlines.
Frequently Asked Questions (FAQ)
1. Does Jiangyin Zhonghai Precision Machinery Co., Ltd. provide Class 300 flanges for heavy-wall pipes like Sch XXS?
Yes. Jiangyin Zhonghai Precision Machinery Co., Ltd. specializes in precision machined flanges. With our in-house CNC turning and drilling lines, we can machine the bore of any Class 300 Welding Neck flange to match heavy-wall or custom-thickness pipes, ensuring a perfect weld prep and flow path.
2. How does Jiangyin Zhonghai Precision Machinery Co., Ltd. ensure the welding end is properly beveled?
Every Welding Neck flange produced by Jiangyin Zhonghai Precision Machinery Co., Ltd. is beveled according to ASME B16.25 standards or customer-specific drawings. Our ISO 9001–certified quality system ensures that the root face and bevel angle are consistent, facilitating easier on-site welding for our global clients.
3. What is the maximum size range for Class 300 flanges at Jiangyin Zhonghai Precision Machinery Co., Ltd.?
Our production range covers 1/2'' to 60''. Thanks to our heavy-duty forging equipment and CNC infrastructure, Jiangyin Zhonghai Precision Machinery Co., Ltd. can handle single-piece weights up to 10 tons, providing reliable Class 300 solutions for both standard volume production and massive, complex machined parts.
