This reference provides the dimensional and connection details for a 3 inch Class 300 weld neck flange, including its outside diameter, thickness, hub, raised face, bolt arrangement, stud size, hole diameter, and listed weight. Use the data with the applicable pipe schedule and project specifications when preparing piping layouts, fabrication drawings, or material takeoffs.
The weld neck configuration is identified by its tapered hub and butt-weld connection to the pipe. That geometry makes the flange different from slip-on, socket weld, threaded, and blind flange types, so flange selection should account for the joint design, welding procedure, gasket arrangement, and service requirements.
Weld Neck Flange 3″ Class 300
Weld Neck Flange 3″ Class 300 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″ Class 300 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):3″
- DN Size: DN80
- Outside Diameter:210mm
- Flange Thickness:26.9mm
- Hub Diameter:117mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:127mm
- Weight: 7.3kg
- Number of Bolts:8
- Stud Bolt Size: 3/4″ UNC (or M20) x 110 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″ Class 300 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″ Class 300, which can be used for drafting, detailing, piping layout coordination, and fabrication reference.
Available Weld Neck Flange Class 300 Sizes
This size is part of the Weld Neck Flange Class 300 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 source dimensions identify the flange by both NPS and DN. These designations describe the nominal pipe size system; they are not a direct substitute for the pipe’s measured outside diameter or internal bore. For fabrication and CAD coordination, compare the flange data with the selected pipe schedule and the mating flange before releasing drawings.
Why the Bore Requires Pipe Schedule Confirmation
The listed bore is schedule-dependent because the pipe wall thickness changes the opening through the weld neck flange. Confirm the pipe outside diameter, wall thickness, and weld-end preparation against the project piping specification. This is especially important when coordinating the flange with pipe schedule dimensions, weld details, and internal-flow requirements.
Understanding the Bolt and Facing Details
The bolt count, stud size, bolt-hole diameter, and raised-face diameter should be checked together with the mating flange. A compatible connection also requires the correct gasket style, bolt material, tightening method, and flange-facing condition. The Class designation should not be treated as a standalone allowable pressure: material grade, temperature, service fluid, and the applicable rating basis must also be verified.
CAD and Related PipeSTD References
Use the supplied DWG file as a drafting and layout reference, then verify fabrication-critical details against the dimensional data and project documents. Useful related references include pipe schedules, flange class dimensions, flange bolt sizes, raised-face flanges, and piping CAD resources. These topics help connect the flange geometry to the pipe, gasket, bolting, and drawing workflow.
Frequently Asked Questions
What does a 3 inch Class 300 weld neck flange do?
It provides a flanged pipe connection using a tapered hub and a butt-welded pipe joint. The flange can then be bolted to a compatible mating flange with a gasket between the facing surfaces.
Why is the weld neck hub tapered?
The tapered hub provides a gradual transition between the flange body and pipe. This helps distribute stresses more smoothly than a simple flat flange-to-pipe transition, although final suitability still depends on the design and service conditions.
Does the listed bore apply to every pipe schedule?
No. The source identifies the bore as dependent on pipe schedule and wall thickness. Confirm the bore and weld-end geometry against the pipe specification selected for the project.
What should be checked before ordering this flange?
Check the nominal size, flange class, material specification, facing type, bore, bolt arrangement, stud requirements, gasket, pipe schedule, and applicable pressure-temperature rating. Also confirm whether the mating flange and installation procedure are compatible.
Can the DWG file be used for fabrication?
The DWG is provided for drafting, detailing, piping-layout coordination, and fabrication reference. Fabrication should proceed only after the drawing, dimensional data, material requirements, weld details, and project specifications have been reviewed.