This reference page provides dimensional and drafting information for a Weld Neck Flange 3 1/2″ Class 400. It brings together the flange dimensions, weight, bolt details, CAD file, and selection notes needed when coordinating piping layouts, fabrication drawings, and flange connections.
Use the listed values as the page’s local reference data, then verify the flange, pipe, gasket, and bolting requirements against the project specification before fabrication or installation. The bore is schedule-dependent, so it should be checked against the pipe wall thickness rather than assumed from the nominal pipe size alone.
Weld Neck Flange 3 1/2″ Class 400
Weld Neck Flange 3 1/2″ 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 3 1/2″ Class 400 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):3 1/2″
- DN Size: DN90
- Outside Diameter:229mm
- Flange Thickness:35.1mm
- Hub Diameter:133mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:139.7mm
- Weight: 13.2kg
- Number of Bolts:8
- 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 3 1/2″ 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 3 1/2″ 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 nominal pipe size identifies the piping connection category, while the flange dimensions describe the outside geometry used for layout and detailing. The listed outside diameter, flange thickness, hub diameter, and raised face diameter can help with CAD coordination, clearance checks, and fabrication drawings.
A weld neck flange is attached by welding the pipe to its tapered hub. The hub provides a gradual transition from the flange body to the pipe, which is why weld neck designs are commonly selected where connection strength, alignment, and resistance to service-related stress are important. The welding procedure, material specification, and inspection requirements still need to come from the applicable project documents.
Bore and Pipe Schedule Coordination
The bore diameter is not a single fixed value in this reference because it varies with the pipe schedule and wall thickness. Before using the CAD file for a final detail, match the flange bore to the actual pipe specification. This check is especially important when coordinating flange drawings with pipe dimensions, fittings, valves, and isometric layouts.
Bolting and Face Details
The source data identifies the bolt count, stud bolt size, bolt length, and hole diameter for this flange. Confirm that the selected studs, nuts, washers, gasket, and facing arrangement are compatible with the mating flange and the project installation requirements. Do not use the nominal Class designation by itself to determine allowable service conditions; pressure-temperature limits and material requirements must be verified for the complete flange assembly.
CAD and Related Reference Work
The downloadable DWG can support preliminary piping layout, equipment coordination, detailing, and fabrication reference. For a complete connection review, compare this flange with related resources for pipe schedules, flange dimensions, gasket selection, stud bolts, and mating fittings. Those cross-checks help prevent bore, bolt-hole, face, and clearance mismatches during drafting.
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 provides a gradual transition between the pipe and flange, supporting connection strength and stress management when properly selected and installed.
What are the key dimensions listed for this flange?
The reference lists the outside diameter, flange thickness, hub diameter, bore guidance, raised face diameter, weight, bolt count, stud bolt size, bolt length, and hole diameter. Use the source dimension list for the authoritative local values.
Why does the bore depend on the pipe schedule?
The bore must accommodate the actual pipe inside diameter, which changes with pipe wall thickness. Therefore, the correct bore should be checked against the selected pipe schedule before fabrication or final CAD detailing.
Does Class 400 alone establish the allowable service pressure?
No. The applicable pressure-temperature rating depends on the relevant material, temperature, flange specification, and project requirements. Confirm the complete rating basis before approving a piping connection.
What should be checked before installation?
Confirm the mating flange, face and gasket arrangement, pipe bore, material specification, stud and nut compatibility, bolt length, alignment, and applicable project requirements. Fabrication and installation should follow the approved engineering documents.