This reference provides the dimensional and connection details for a 3/4 inch Class 2500 weld neck flange, including the listed flange dimensions, weight, bolt information, and CAD resource. Use the data as a drafting and identification reference, then verify the complete piping specification before fabrication or installation.
The most important selection check is the relationship between the flange bore and the pipe schedule. The flange size identifies the nominal connection, but the bore must still be matched to the actual pipe wall thickness and project requirements.
Weld Neck Flange 3/4″ Class 2500
Weld Neck Flange 3/4″ Class 2500 is widely used in piping systems that require strong, leak-resistant flange connections under extremely high-pressure service. It features a long tapered hub that provides excellent stress distribution and is commonly applied in refineries, petrochemical plants, power generation systems, and critical industrial piping where welding strength and connection reliability are essential.
This dimension data is based on ANSI / ASME B16.5-2020.
Weld Neck Flange 3/4″ Class 2500 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):3/4″
- DN Size: DN20
- Outside Diameter:140mm
- Flange Thickness:31.8mm
- Hub Diameter:51mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:42.9mm
- Weight: 3.7kg
- Number of Bolts:4
- Stud Bolt Size: 3/4″ UNC (or M20) x 125 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 3/4″ Class 2500 is commonly used for:
- Process piping systems
- Oil and gas lines
- Refinery and petrochemical piping
- Extremely 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 3/4″ Class 2500, which can be used for drafting, detailing, piping layout coordination, and fabrication reference.
Available Weld Neck Flange Class 2500 Sizes
This size is part of the Weld Neck Flange Class 2500 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 Weld Neck Flange Reference
The dimensional list identifies the flange envelope, hub geometry, facing, bolt-hole information, and connection hardware. These details support layout, preliminary modeling, drawing review, and fabrication coordination. They should be read together rather than treating the outside diameter or flange thickness as a complete fit-up specification.
Key checks before using the dimensions
- Confirm the bore: The bore varies with pipe schedule and wall thickness, so it must be checked against the pipe being connected.
- Check the bolt pattern: Confirm the listed number of bolts, hole diameter, stud size, and bolt length against the mating flange and project specification.
- Review the facing: The raised face dimension affects gasket selection, flange contact, and connection detailing.
- Coordinate the hub and weld: The tapered hub is part of the weld-neck geometry and should be considered during pipe fit-up and stress-sensitive detailing.
- Verify the material and service requirements: The dimensional reference does not replace project checks for material grade, gasket type, temperature, pressure, corrosion allowance, or applicable fabrication requirements.
Related piping references
For a complete design workflow, compare this page with the site’s references for pipe schedules, flange dimensions, stud bolt terminology, gasket selection, and piping CAD/DWG resources. These related references help connect nominal size information with the pipe, gasket, bolting, and drawing details required for a coordinated assembly.
Drafting and CAD Use
The downloadable DWG can help with piping layout, flange orientation, equipment connection coordination, and fabrication drawing preparation. Before issuing a drawing, confirm units, mating-flange compatibility, bore selection, facing details, and the project-specific revision requirements. A CAD outline should not be treated as a substitute for the governing dimensional reference or an approved fabrication drawing.
Frequently Asked Questions
What does the 3/4 inch designation mean?
It identifies the nominal pipe size, listed in the reference as NPS 3/4 inch and DN20. It is not, by itself, the measured outside diameter or the final bore.
Why does the bore depend on the pipe schedule?
Pipe wall thickness changes the inside diameter of the pipe. The flange bore therefore needs to be selected or verified against the actual pipe schedule and wall thickness used in the assembly.
What information is provided for the bolts?
The reference lists the number of bolts, stud bolt size, bolt length, and hole diameter. Confirm these details with the mating flange, gasket arrangement, material specification, and project bolting requirements.
What is the purpose of the tapered hub?
The long tapered hub provides a gradual transition between the flange and pipe. This geometry helps distribute stress and supports the weld-neck connection, particularly where pressure, temperature changes, or cyclic loading are design concerns.
Can the DWG be used directly for fabrication?
The DWG is useful for drafting and coordination, but fabrication still requires verification of the bore, material, facing, bolting, gasket, welding, and project-specific requirements.