This reference page provides dimension and drafting information for a Weld Neck Flange 8 Inch Class 300. Use the listed data to coordinate piping layouts, flange connections, fabrication details, and CAD work while keeping the project specification as the controlling requirement.
The flange’s tapered hub is an important identifying feature. Unlike shorter flange designs, a weld neck flange transitions from the flange body into the pipe connection through a long hub, supporting a smoother load path at the welded joint. For related terminology, compare this page with the site’s references for pipe schedules, flange types, stud bolts, and raised-face flanges.
Weld Neck Flange 8″ Class 300
Weld Neck Flange 8″ 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 8″ Class 300 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):8″
- DN Size: DN200
- Outside Diameter:381mm
- Flange Thickness:39.6mm
- Hub Diameter:260mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:269.7mm
- Weight: 36kg
- Number of Bolts:12
- Stud Bolt Size: 7/8″ UNC (or M24) x 140 Long
- Hole Diameter: 1″ (25.4mm)
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 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 8″ 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 Use These Weld Neck Flange Dimensions
The listed outside diameter, thickness, hub diameter, raised-face diameter, bolt count, bolt-hole diameter, and overall weight are useful for preliminary layout and detailing. Confirm that the selected flange matches the mating flange, gasket arrangement, pipe end preparation, and project material requirements before fabrication.
Bore and Pipe Schedule
The bore is not a single universal dimension for this flange entry. It varies with the connected pipe schedule and wall thickness, so the bore should be checked against the actual pipe specification rather than assumed from the nominal pipe size. This is particularly important when preparing a weld detail or coordinating the flange with a piping isometric.
Bolting and Mating Components
The source data identifies twelve bolt locations and lists the stud bolt designation as 7/8" UNC (or M24) x 140 Long. Treat this as a coordination reference, not as a substitute for the project bolting specification. Verify thread system, material, washer requirements, engagement, tightening procedure, and the mating flange before ordering components. The hole diameter should also be checked against the selected bolting arrangement.
Raised Face and Gasket Coordination
The raised face is the gasket-contact area shown in the dimensional data. Gasket selection and facing compatibility should be reviewed together with the mating flange and service requirements. Do not select a gasket solely from the flange size or class designation.
CAD and Drawing Workflow
The downloadable DWG can support drafting, piping layout coordination, detailing, and fabrication reference. Before using it as a final shop drawing, confirm orientation, bore condition, weld preparation, material, facing, and all project-specific requirements. Related internal references for CAD piping blocks, flange drawings, and pipe fitting dimensions can help extend the design workflow.
Reference Data at a Glance
- Size identification: NPS 8" and DN200.
- Connection type: Weld neck flange with a tapered hub.
- Facing reference: Raised face.
- Bolting reference: Twelve bolts with the listed stud and hole details.
- Key qualification: Bore selection depends on pipe schedule and wall thickness.
Use the page’s dimension list as the local reference for this size and class. Engineering review is still required for pressure-temperature service, materials, welding, gasket selection, and installation.
Frequently Asked Questions
What is a weld neck flange?
A weld neck flange has a long tapered hub and is welded directly to the pipe. Its geometry is intended to provide a gradual transition at the flange-to-pipe connection.
What pipe size does this flange fit?
This reference is for NPS 8", identified in the source data as DN200. The final bore must still be selected or confirmed from the connected pipe schedule and wall thickness.
How many bolts are listed for the flange?
The source data lists twelve bolts. Confirm the mating flange and complete bolting specification before procurement or installation.
What stud bolt information is provided?
The listed stud reference is 7/8" UNC (or M24) x 140 Long. Check the applicable project standard, material, thread system, and installation requirements before treating this as a purchase specification.
Is the CAD drawing ready for fabrication?
The DWG is provided as a drafting, layout, detailing, and fabrication reference. It should be reviewed against the project’s pipe schedule, bore, weld details, materials, gasket, bolting, and applicable requirements before release.
Why should the flange data be checked before installation?
Flange selection depends on more than nominal size. Confirm the material specification, pipe schedule, bore, gasket type, bolt length, mating flange, and pressure-temperature requirements for the actual service.