This reference provides the dimensional data, bolt information, weight, and CAD resource for a Weld Neck Flange 8 Inch Class 400. Use the listed values for drafting and coordination, while confirming the final flange, pipe, gasket, and bolting details against the project requirements.
The most important matching detail is the pipe connection at the flange bore. Because the bore varies with pipe schedule and wall thickness, flange selection should be coordinated with the applicable pipe dimensions and schedules reference before fabrication or installation.
Weld Neck Flange 8″ Class 400
Weld Neck Flange 8″ 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 8″ Class 400 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):8″
- DN Size: DN200
- Outside Diameter:381mm
- Flange Thickness:47.8mm
- Hub Diameter:260mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:269.7mm
- Weight: 46kg
- Number of Bolts:12
- Stud Bolt Size: 1″ UNC (or M27) x 170 Long
- Hole Diameter: 1 1/8″ (28.575mm)
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 8″ 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 8″ 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 Use This Weld Neck Flange Reference
The dimensional list below is useful for piping layout, equipment connection checks, spool detailing, and preliminary material takeoff. The outside diameter, thickness, hub dimensions, raised-face dimension, bolt-hole information, and listed weight describe the flange component itself. The bore is treated separately because it must match the connected pipe configuration.
Why the Weld Neck Design Matters
A weld neck flange transfers the connection through a tapered hub and a welded pipe joint. This geometry supports a gradual transition between the pipe and flange, which is especially relevant when a piping system experiences pressure, temperature changes, or repeated loading. The weld detail, alignment, inspection requirements, and material specification still require review by the responsible engineering and fabrication teams.
Bolting and Facing Checks
Before ordering or assembling the connection, compare the listed bolt quantity, stud size, bolt-hole diameter, flange facing, gasket selection, and available thread engagement. Bolt length can be affected by gasket thickness, flange facing, washers, and the connected component. Related flange dimensions, gasket references, and pipe fitting terminology can help when coordinating the complete joint.
CAD and Drafting Workflow
The downloadable DWG is intended as a drafting and layout reference. Check its units, insertion scale, layer conventions, face orientation, and connection assumptions before incorporating it into a project drawing. CAD geometry should not replace verification of the authoritative dimensional data or the project-specific requirements.
Selection and Verification Checklist
- Confirm the nominal pipe size and DN designation.
- Match the flange bore to the actual pipe schedule and wall thickness.
- Verify the flange class, facing, material, and pressure-temperature requirements.
- Coordinate gasket dimensions and bolting with the mating flange.
- Review weld preparation, alignment, inspection, and installation requirements.
- Use the CAD file as a layout aid and confirm critical dimensions before fabrication.
Frequently Asked Questions
What does the class designation identify?
The class designation identifies the flange pressure-temperature category used for selecting and checking the component. It should not be treated as a standalone allowable pressure; the material, temperature, fluid service, and applicable design requirements must also be reviewed.
Why does the bore depend on the pipe schedule?
The outside size of the connected nominal pipe can remain consistent while its wall thickness changes. That changes the inside opening, so the flange bore must be selected to suit the actual pipe schedule and wall thickness.
Can the DWG file be used directly for fabrication?
The DWG is useful for drafting, detailing, and coordination, but it should be checked against the listed reference data, project units, material requirements, weld details, and fabrication procedure before release.
What should be checked before installation?
Confirm flange alignment, facing condition, gasket compatibility, bolt selection, thread engagement, tightening procedure, pipe fit-up, and the project pressure-testing requirements. Final acceptance should follow the responsible engineer’s and fabricator’s procedures.
Is this flange interchangeable with every eight-inch flange?
No. Interchangeability depends on the flange class, facing, bolt pattern, dimensions, bore, material, and mating component. Compare all relevant details rather than relying on nominal pipe size alone.