This reference page provides the dimensional and connection information for a Weld Neck Flange 2 1/2 Inch Class 150. Use the values in the existing reference sections when checking flange fit-up, preparing piping drawings, or coordinating a flange connection with the selected pipe and gasket.
The page also explains why weld neck construction is used, how the flange data relates to pipe schedules, and what should be confirmed before fabrication. For related work, compare this information with the applicable pipe schedule, flange dimensions, bolt pattern, and CAD/DWG reference for the rest of the piping assembly.
Weld Neck Flange 2 1/2″ Class 150
Weld Neck Flange 2 1/2″ Class 150 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 150 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):2 1/2″
- DN Size: DN65
- Outside Diameter:178mm
- Flange Thickness:20.6mm
- Hub Diameter:90mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:104.8mm
- Weight: 3.2kg
- Number of Bolts:4
- Stud Bolt Size: 5/8″ UNC (or M16) x 90 Long
- Hole Diameter: 3/4″ (19.05mm)
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 150 is commonly used for:
- Process piping systems
- Oil and gas lines
- Water and utility piping
- High-temperature 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 150, which can be used for drafting, detailing, piping layout coordination, and fabrication reference.
Available Weld Neck Flange Class 150 Sizes
This size is part of the Weld Neck Flange Class 150 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 Flange Reference
The dimension list identifies the principal outside, thickness, hub, raised-face, bolt-hole, and bolting information for this flange size and pressure class. These values are useful for drafting and coordination, but they should be read together with the project pipe specification and connection requirements.
The bore is not presented as a single fixed value because the pipe schedule and wall thickness affect the opening through the flange. This is an important distinction when matching a weld neck flange to pipe: the outside flange geometry may be selected by nominal size and class, while the bore must be checked against the actual pipe and welding detail.
Weld Neck Flange Fit-Up Considerations
- Confirm the pipe match: Check the nominal size, pipe schedule, wall thickness, and required bore before ordering or detailing the flange.
- Check the facing arrangement: The raised face must coordinate with the mating flange, gasket selection, and the project’s bolting and assembly requirements.
- Review the bolt connection: Confirm the listed bolt count, stud size, hole diameter, bolt length, nuts, washers, and clearance against the mating flange.
- Coordinate the weld: The tapered hub is welded to the pipe, so the welding procedure, material specification, inspection requirements, and fabrication details must be reviewed separately.
- Use the CAD file carefully: The downloadable DWG is useful for layout and drafting reference, but the dimensional list and approved project documents should control fabrication.
Why the Pipe Schedule Matters
A nominal pipe size does not by itself define the internal opening of a weld neck flange. Because the source data identifies the bore as schedule-dependent, the flange should not be selected from nominal size alone when internal alignment or flow passage is important. Match the flange bore to the pipe specification and verify the completed connection before fabrication.
Class, Material, and Service Checks
The Class 150 designation identifies the flange series used by the reference, but final service suitability also depends on material, temperature, pressure, gasket, bolting, corrosion requirements, and the governing project specification. The notes on this page should therefore be treated as a dimensional reference rather than a substitute for engineering approval or a pressure-temperature review.
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 is intended to provide a gradual transition between the pipe and flange and to support applications where welding strength and stress control are important.
Why does the bore depend on the pipe schedule?
The bore must align with the inside of the connected pipe. Since pipe wall thickness varies by schedule, the flange opening should be checked against the actual pipe specification rather than assumed from nominal size alone.
What should be checked before using the listed bolt size?
Verify the mating flange, hole diameter, gasket, required grip, nuts, washers, and project bolting specification. The listed stud information is a reference for this flange entry and should be checked against the complete connection assembly.
Can the DWG file be used for fabrication?
The DWG file can support drafting, layout coordination, and detailing. Before fabrication, confirm the drawing against the authoritative dimensional data, approved material specification, pipe schedule, welding requirements, and project revisions.
Does Class 150 alone confirm pressure capability?
No. Final pressure-temperature suitability depends on the applicable standard requirements, flange material, service conditions, gasket, bolting, and project design basis. Confirm the complete pressure-temperature rating before installation.
What other references are useful with this page?
Related references include pipe dimensions and schedules, flange facing details, flange bolt patterns, gasket selection guidance, piping terminology, and CAD resources for connected fittings and valves.