This reference provides the published dimensions and installation-related details for a Weld Neck Flange 3 Inch Class 900. Use the listed values when reviewing piping layouts, preparing fabrication drawings, checking flange connections, or coordinating the matching pipe and bolting.
The page also explains how to interpret the flange dimensions, why the bore must be checked against the pipe schedule, and what to verify before using the data for fabrication or installation. For related work, compare this information with the applicable pipe schedule, flange dimensions, gasket selection, and stud bolt reference pages on PipeSTD.
Weld Neck Flange 3″ Class 900
Weld Neck Flange 3″ 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 3″ Class 900 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):3″
- DN Size: DN80
- Outside Diameter:241mm
- Flange Thickness:38.1mm
- Hub Diameter:127mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:127mm
- Weight: 13kg
- Number of Bolts:8
- Stud Bolt Size: 7/8″ UNC (or M24) x 145 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″ 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 3″ 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 Weld Neck Flange Reference
The flange dimensions identify the external geometry used for layout and coordination. The outside diameter, thickness, hub diameter, raised face diameter, bolt count, and hole diameter are useful when checking clearances, matching a companion flange, or preparing a piping detail.
The bore diameter requires particular attention. Unlike several external flange dimensions, the bore is associated with the pipe’s schedule and wall thickness. Confirm the selected pipe specification before finalizing the flange bore, weld preparation, or fabrication drawing.
Nominal Size and Pipe Compatibility
NPS and DN are nominal size designations rather than a complete description of the pipe’s actual wall geometry. The flange should therefore be coordinated with the pipe outside diameter, wall thickness, material specification, and project requirements. A nominal size match alone does not replace a schedule and bore check.
Bolting and Connection Checks
The listed stud bolt information should be reviewed together with the companion flange, gasket, washer requirements, thread form, and available engagement. Confirm whether the project uses the stated inch designation or its metric counterpart before ordering or detailing hardware. Bolt length can also depend on the complete joint arrangement, including gasket and flange thicknesses.
Using the CAD Drawing
The downloadable DWG is useful for drafting, piping layout coordination, and preliminary detailing. Treat the drawing as a dimensional reference and verify the final connection against the project specification, approved material documentation, pipe schedule, gasket selection, and applicable pressure-temperature requirements.
Practical Review Checklist
- Confirm the nominal pipe size and DN designation.
- Match the bore to the selected pipe schedule and wall thickness.
- Check the flange face, gasket, and companion flange arrangement.
- Verify stud bolt size, length, thread designation, and joint assembly.
- Review material, service conditions, and project approval requirements before fabrication.
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, helping manage stress at the connection when the joint is correctly designed and installed.
What does Class 900 mean?
Class 900 is a flange pressure-temperature class designation. It should not be treated as a single allowable pressure for every service condition. Confirm the applicable rating, material, temperature, and project requirements before selecting the connection.
Why does the bore vary with pipe schedule?
The pipe schedule affects wall thickness and the internal opening of the pipe. The flange bore must be coordinated with that pipe geometry, so the schedule and wall thickness should be confirmed before fabrication.
What bolt information is provided for this flange?
The reference lists the required bolt count, stud bolt designation, bolt length, and hole diameter. Check these details against the companion flange, gasket thickness, washers, thread system, and approved joint assembly.
Can the listed weight be used for lifting or shipping?
Use the listed weight as a reference for this page’s flange data. For lifting, shipping, or equipment-support decisions, verify the actual supplied component, material, machining condition, and manufacturer documentation.
What is the DWG file used for?
The DWG file can support piping layouts, drafting, dimensional coordination, and fabrication reference. Final drawings should still be checked against the project specification and the verified flange, pipe, gasket, and bolting requirements.