This reference covers the identifying dimensions and connection details for a Weld Neck Flange 2 1/2 Inch Class 900. Use the source data below when checking flange geometry, preparing piping drawings, or coordinating a flange connection with pipe, gasket, and bolting requirements.
The page is also useful alongside PipeSTD references for pipe schedules, flange terminology, stud bolts, gasket selection, and CAD/DWG piping details. These related references help place the flange dimensions in the context of a complete piping connection rather than treating the flange as an isolated component.
Weld Neck Flange 2 1/2″ Class 900
Weld Neck Flange 2 1/2″ Class 900 is widely used in piping systems that require strong, leak-resistant flange connections under high-pressure service. It features a long tapered hub that provides excellent stress distribution and is commonly applied in process piping, utility lines, refineries, power plants, and industrial systems where welding strength and reliability are essential.
This dimension data is based on ANSI / ASME B16.5-2020.
Weld Neck Flange 2 1/2″ Class 900 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):2 1/2″
- DN Size: DN65
- Outside Diameter:244mm
- Flange Thickness:41.1mm
- Hub Diameter:124mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:104.8mm
- Weight: 16kg
- Number of Bolts:8
- Stud Bolt Size: 1″ UNC (or M27) x 160 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 2 1/2″ Class 900 is commonly used for:
- Process piping systems
- Oil and gas lines
- Refinery and petrochemical piping
- Very high-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 900, which can be used for drafting, detailing, piping layout coordination, and fabrication reference.
Available Weld Neck Flange Class 900 Sizes
This size is part of the Weld Neck Flange Class 900 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 listed outside diameter, thickness, hub diameter, and raised face diameter describe the principal external features used for layout, detailing, and dimensional checking. The bore requires particular attention because it varies with the pipe schedule and wall thickness. The flange should therefore be coordinated with the actual pipe specification before fabrication or installation.
Bore and Pipe Compatibility
A weld neck flange is welded directly to the pipe through its tapered hub. The bore should align with the pipe inside diameter and the selected welding detail. Because the source data identifies the bore as schedule-dependent, do not assume that every pipe associated with this nominal size uses the same bore.
Bolting and Joint Assembly
The bolt count, stud bolt size, bolt length, and hole diameter are separate checks. Confirm that the selected studs, nuts, washers where required, gasket, and mating flange are compatible with the project specification. Bolt length should be checked against the combined flange thicknesses, gasket arrangement, and required thread engagement rather than selected from nominal size alone.
Using the CAD File
The downloadable DWG can support drafting, piping layout coordination, and fabrication reference. Before incorporating it into a final drawing, verify the drawing units, insertion scale, flange facing detail, bore requirement, and mating components against the project documents. A CAD block is a dimensional aid; it does not replace the applicable design review or fabrication checks.
Related PipeSTD References
- Link this page to the PipeSTD reference for pipe schedules and wall thickness when reviewing the variable bore.
- Link to the related Class 900 weld neck flange size series for comparison with adjacent nominal sizes.
- Link to the flange bolt and gasket terminology reference when checking joint assembly details.
- Link to the piping CAD and DWG resources page for drafting workflow guidance.
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, helping the connection manage stress more effectively than simpler flange profiles in demanding service.
Why does the bore vary for this flange?
The bore depends on the pipe schedule and wall thickness selected for the nominal pipe size. Confirm the actual pipe specification before ordering, machining, welding, or finalizing a drawing.
What does Class 900 identify?
Class 900 is the flange class designation used to identify the applicable dimensional and pressure-temperature requirements. It should not be treated as a standalone allowable pressure. Verify the material, temperature, service conditions, and governing project requirements before selecting the connection.
Can the listed stud bolt size be used without checking the mating flange?
No. The listed bolting information should be coordinated with the mating flange, hole diameter, gasket arrangement, flange thicknesses, nut engagement, and project bolting specification.
Is the DWG file ready for fabrication without review?
No. Use the DWG as a drafting and coordination reference, then verify its units, scale, facing configuration, bore, material requirements, and project-specific fabrication details.