This reference provides the dimensional and identification data for a Weld Neck Flange 12 Inch Class 400, including flange geometry, bolt information, weight, and the related CAD file. Use the dimension list as a drafting and specification aid, then verify the final selection against the piping design, material requirements, pipe schedule, gasket arrangement, and project specifications.
The page is also useful when coordinating flange details with pipe dimensions and schedules, flange specifications, piping fittings, and CAD or DWG reference resources. The bore is not a universal flange dimension because it must correspond to the connected pipe and its wall thickness.
Weld Neck Flange 12″ Class 400
Weld Neck Flange 12″ Class 400 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 12″ Class 400 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):12″
- DN Size: DN300
- Outside Diameter:521mm
- Flange Thickness:57.2mm
- Hub Diameter:375mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:381mm
- Weight: 102kg
- Number of Bolts:16
- 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 12″ Class 400 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 12″ Class 400, which can be used for drafting, detailing, piping layout coordination, and fabrication reference.
Available Weld Neck Flange Class 400 Sizes
This size is part of the Weld Neck Flange Class 400 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 the Weld Neck Flange Dimensions
The listed outside diameter and flange thickness describe the main flange body, while the hub diameter identifies the tapered welding hub that transitions into the pipe. These dimensions are important for checking clearances, mating connections, fabrication drawings, and interference with adjacent piping components.
Pay particular attention to the bore description. A weld neck flange is welded to the pipe, so the finished bore must be coordinated with the selected pipe schedule or wall thickness. The flange outside geometry alone does not determine the correct internal opening.
Bolting and Facing Considerations
The number of bolts, stud bolt designation, bolt length, and hole diameter should be reviewed together. Bolting must match the mating flange and the project requirements, while bolt length also depends on the flange arrangement, gasket, washers, and any additional components in the joint.
The raised face diameter identifies the sealing-face area used with the specified flange arrangement. Confirm the gasket type, facing condition, alignment, and tightening procedure before fabrication or installation. A CAD model is helpful for layout and detailing, but it should not replace dimensional verification against the approved engineering documents.
Using the CAD Reference
The downloadable DWG can support piping layout, shop detailing, equipment coordination, and fabrication reference work. Before using it in a production drawing, compare the drawing geometry with the dimension list and confirm units, bore requirements, flange facing, material specification, and revision control.
Related Pipe and Flange References
For a complete connection check, pair this page with the relevant pipe schedule reference, flange class dimension guide, gasket reference, and stud bolt reference. These related resources help connect nominal size and flange geometry with the actual pipe, sealing, and bolting details required for a finished joint.
Frequently Asked Questions
What does the bore depend on for this weld neck flange?
The bore depends on the connected pipe schedule and wall thickness. Confirm the required internal opening from the pipe specification before ordering or fabricating the flange.
Why is the tapered hub important?
The tapered hub provides a gradual transition between the flange and pipe. This supports stress distribution at the welded connection and is one reason weld neck flanges are selected for demanding piping service.
Can the listed stud bolts be used for every installation?
Not automatically. Check the mating flange, gasket, washers, joint thickness, material requirements, and project bolting specification before confirming bolt size and length.
Is the DWG file suitable for final fabrication?
The DWG is a useful drafting and coordination reference. Final fabrication should use approved project documents and verified dimensions, including the required bore, facing, material, and applicable inspection requirements.
What should be checked before installation?
Verify flange alignment, facing condition, gasket compatibility, bore matching, bolt selection, tightening requirements, and the applicable pressure-temperature and material requirements for the piping system.