This reference page provides the dimensional and connection information for a Weld Neck Flange 2 1/2 Inch Class 400. Use the listed values when reviewing flange layouts, preparing piping details, or coordinating the matching pipe, gasket, and bolting requirements.
The flange dimensions should be read together with the pipe schedule because the bore is not a single universal dimension. For related design and drafting work, link this page to the site’s pipe schedule, flange dimensions, stud bolt terminology, and CAD/DWG resources references.
Weld Neck Flange 2 1/2″ Class 400
Weld Neck Flange 2 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 2 1/2″ Class 400 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):2 1/2″
- DN Size: DN65
- Outside Diameter:190mm
- Flange Thickness:28.4mm
- Hub Diameter:100mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:104.8mm
- Weight: 6.8kg
- Number of Bolts:8
- Stud Bolt Size: 3/4″ UNC (or M20) x 120 Long
- Hole Diameter: 7/8″ (22.225mm)
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 2 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 2 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 Read This Flange Reference
The nominal pipe size identifies the intended piping size, while the outside diameter, thickness, hub diameter, raised face diameter, bolt-hole information, and weight describe the flange itself. These values support dimensional checks and drafting coordination; they do not replace verification of the complete piping specification.
The bore requires special attention. A weld neck flange is welded to the pipe, so the finished opening must correspond with the selected pipe schedule and wall thickness. Confirm the bore against the pipe data before fabrication or installation rather than assuming that the nominal size alone defines the opening.
Bolting and Facing Checks
- Check the listed number of bolts, stud size, bolt length, and hole diameter together as one bolting arrangement.
- Confirm that the mating flange, gasket, and bolt specification are compatible with the selected raised-face arrangement.
- Review material, service conditions, and project requirements before treating the listed dimensions as fabrication approval.
Using the CAD File
The downloadable DWG can help with piping layouts, flange orientation, equipment coordination, and preliminary detailing. CAD geometry should be checked against the dimensional list and the project’s current fabrication requirements before it is used for release or manufacture.
Why the Tapered Hub Matters
The long tapered hub provides a gradual transition between the pipe and flange body. This geometry is intended to support stress distribution at the welded connection, which is why weld neck flanges are often selected for demanding piping arrangements. Final selection still depends on the applicable design basis, materials, joining procedure, and service conditions.
Frequently Asked Questions
What is the bore of a 2 1/2 Inch Class 400 weld neck flange?
The bore varies with the pipe schedule and pipe wall thickness. Select and verify the bore using the actual pipe specification rather than the nominal flange size alone.
What information is included for the flange bolting?
The reference lists the number of bolts, stud bolt size and length, and hole diameter. These details should be checked against the mating flange, gasket, and project bolting requirements.
Why is a weld neck flange used instead of a flat flange type?
A weld neck flange has a long tapered hub that creates a gradual transition from the pipe to the flange. This configuration is intended to reduce stress concentration at the connection and support reliable welded construction.
Can the DWG file be used directly for fabrication?
The DWG is useful for drafting, layout coordination, and fabrication reference. Confirm its geometry against the listed dimensions, pipe schedule, material requirements, and latest project instructions before fabrication.
Does Class 400 alone confirm the flange is suitable for a piping system?
No. Flange selection also requires review of material, temperature and pressure conditions, gasket details, bolting, pipe schedule, joining requirements, and the applicable project design criteria.