This reference page provides the dimensional and connection data for a 3 1/2 inch Class 150 weld neck flange. Use the listed values when checking piping layouts, flange interfaces, fabrication drawings, and related CAD details.
Because weld neck flanges are welded directly to the pipe, the flange bore must be coordinated with the pipe outside diameter and wall thickness. The source data identifies the bore as schedule-dependent, so confirm the applicable pipe schedule before using the flange in a detailed design.
Weld Neck Flange 3 1/2″ Class 150
Weld Neck Flange 3 1/2″ Class 150 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 3 1/2″ Class 150 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):3 1/2″
- DN Size: DN90
- Outside Diameter:216mm
- Flange Thickness:22.4mm
- Hub Diameter:122mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:139.7mm
- Weight: 5.9kg
- Number of Bolts:8
- Stud Bolt Size: 5/8″ UNC (or M16) x 90 Long
- Hole Diameter: 3/4″ (19.05mm)
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 3 1/2″ Class 150 is commonly used for:
- Process piping systems
- Oil and gas lines
- Water and utility piping
- High-temperature service
- Pressure piping connections
- Industrial fabrication and maintenance work
CAD Drawing Download
This page includes the CAD drawing file for Weld Neck Flange 3 1/2″ Class 150, which can be used for drafting, detailing, piping layout coordination, and fabrication reference.
Available Weld Neck Flange Class 150 Sizes
This size is part of the Weld Neck Flange Class 150 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 outside diameter, flange thickness, hub diameter, and raised face diameter describe the principal geometry needed for layout and flange-face coordination. The bolt count, stud bolt specification, and hole diameter define the bolting interface with the mating flange.
The listed 5/8 inch UNC (or M16) stud bolt size should be checked against the project bolting specification and the mating flange. Do not assume that an imperial and metric designation are interchangeable for every procurement or assembly requirement; verify the selected hardware, thread form, grip length, and project requirements before ordering.
Bore and Pipe Schedule Coordination
A weld neck flange is normally selected with a bore that matches the connected pipe. Since the source data does not assign one fixed bore diameter, the final bore selection depends on the pipe schedule and wall thickness. This is an important cross-check when using the page with a pipe schedule reference or a pipe dimensions guide.
Bolting and Mating-Flange Checks
Before fabrication, compare the bolt-hole pattern, hole diameter, raised-face geometry, and stud length with the mating flange. The listed weight is useful for handling and material estimates, but lifting arrangements and installation procedures should be established from the complete assembly and site requirements.
Using the CAD Drawing
The downloadable DWG can support drafting, piping-layout coordination, and fabrication reference. Treat the drawing as a dimensional aid rather than a substitute for checking the applicable flange standard, pipe schedule, gasket selection, material specification, and project design documents. A related flange dimensions reference and piping CAD resource can help compare this item with other flange types and sizes.
Selection and Installation Review
- Confirm the nominal pipe size and DN designation against the connected piping.
- Verify the bore against the actual pipe schedule and wall thickness.
- Check the mating flange, gasket, bolt-hole pattern, and bolting specification.
- Confirm material, service conditions, pressure-temperature requirements, and project specifications.
- Use the latest approved project documents before fabrication or 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. The hub provides a gradual transition between the pipe and flange and is intended to improve stress distribution at the connection.
What are the published dimensions for this flange?
The source data lists the flange outside diameter, thickness, hub diameter, raised face diameter, weight, bolt count, stud bolt size, and hole diameter. Refer to the dimension list on this page for the authoritative local values.
Why is the bore not given as one fixed dimension?
The bore varies with the pipe schedule and pipe wall thickness. Select or verify the bore only after identifying the pipe that will be welded to the flange.
Can the supplied DWG be used for fabrication?
The DWG is provided as a drafting, layout, and fabrication reference. Final fabrication should also use the approved standard, material requirements, pipe schedule, gasket and bolting specifications, and project drawings.
Does Class 150 alone determine the complete design?
No. The flange class is only one part of the selection process. Material, service conditions, temperature, gasket, bolting, mating flange, and applicable project requirements must also be reviewed by the responsible engineer or designer.