This reference provides the listed dimensions, weight, and fastening information for a Weld Neck Flange 20 Inch Class 300. Use it alongside related pipe schedule, flange, gasket, and piping terminology references when preparing layouts, fabrication details, or procurement documents.
The dimensional values on this page are the local reference data. Because the bore depends on the connected pipe schedule and wall thickness, dimensional coordination should include the matching pipe specification rather than relying on nominal size alone.
Weld Neck Flange 20″ Class 300
Weld Neck Flange 20″ Class 300 is widely used in piping systems that require strong, leak-resistant flange connections. It features a long tapered hub that provides excellent stress distribution and is commonly applied in process piping, utility lines, and industrial systems where welding strength and reliability are important.
This dimension data is based on ANSI / ASME B16.5-2020.
Weld Neck Flange 20″ Class 300 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):20″
- DN Size: DN500
- Outside Diameter:775mm
- Flange Thickness:62mm
- Hub Diameter:587mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:584.2mm
- Weight: 230kg
- Number of Bolts:24
- Stud Bolt Size: 1 1/4″ UNC (or M33) x 205 Long
- Hole Diameter: 1 3/8″ (34.925mm)
What Is a Weld Neck Flange?
A weld neck flange is a type of pipe flange designed with a long tapered hub that is welded directly to the pipe. This design helps reduce stress concentration at the flange base and provides better strength under pressure, temperature fluctuation, and cyclic loading.
Common Applications
Weld Neck Flange 20″ Class 300 is commonly used for:
- Process piping systems
- Oil and gas lines
- Water and utility piping
- Higher pressure service
- Pressure piping connections
- Industrial fabrication and maintenance work
CAD Drawing Download
This page includes the CAD drawing file for Weld Neck Flange 20″ Class 300, which can be used for drafting, detailing, piping layout coordination, and fabrication reference.
Available Weld Neck Flange Class 300 Sizes
This size is part of the Weld Neck Flange Class 300 series. Check other sizes in the same category to find matching dimension data and CAD files for your project.
Notes
Before fabrication or installation, always confirm the latest project requirements, flange material specification, pipe schedule, bore size, gasket type, bolt length, and applicable pressure-temperature rating.
How to Read This Weld Neck Flange Reference
The flange dimensions identify the main outside geometry, thickness, hub, raised face, bolt quantity, stud bolt requirement, and bolt-hole diameter. These fields are useful when checking clearances, preparing a piping arrangement, or coordinating the flange with a pipe and gasket assembly.
Why the Bore Requires Pipe Schedule Coordination
The listed bore is not a single fixed value because the opening must correspond to the connected pipe wall thickness. For drafting and fabrication, confirm the pipe schedule, actual wall thickness, weld-end preparation, and any project machining requirements before finalizing the detail.
Using the Bolt Information
The bolt count, stud size, length, and hole diameter support preliminary connection detailing and procurement review. Final bolt selection should also be checked against the flange material, gasket arrangement, joint design, installation method, and project specifications.
CAD and Internal Reference Workflow
The downloadable DWG can support layout coordination and drafting reference. Pair this file with the site’s related weld neck flange size pages, Class 300 flange references, pipe schedule charts, and gasket or bolting terminology pages. A CAD file should be checked against the applicable project requirements before it is used for fabrication.
Design Verification Reminder
Nominal size and class designation do not replace engineering review. Confirm the applicable pressure-temperature requirements, material specification, connected pipe details, facing and gasket arrangement, bolt requirements, and installation constraints before approving the connection.
Frequently Asked Questions
What is the listed nominal pipe size?
The reference identifies this flange as NPS 20 inches and DN500.
Why is the weld neck flange hub tapered?
The long tapered hub provides a gradual transition from the flange to the pipe. This geometry is intended to help distribute stress compared with a flange design without the same hub form.
Is the bore fixed for every 20-inch flange?
No. The source data states that the bore varies with pipe schedule and pipe wall thickness. Confirm the connected pipe details before using the dimension for fabrication.
What bolt information is provided?
The reference lists the number of bolts, stud bolt size and length, and hole diameter. These details should be coordinated with the complete joint specification and installation requirements.
Can the DWG be used directly for fabrication?
The DWG is provided as a drafting, detailing, layout, and fabrication reference. Verify the drawing against the project specification, pipe schedule, flange material, gasket arrangement, and current engineering review before release.