This reference page provides dimensional and bolting information for a Weld Neck Flange 1 1/4 Inch Class 400, together with a downloadable CAD file for piping layout and detailing. Use the listed values as a reference for coordination, then verify the flange, pipe, gasket, and fastener requirements against the project specification before fabrication or installation.
The most important selection detail is the relationship between the flange bore and the pipe. Because the bore can vary with the pipe schedule and wall thickness, the flange size designation alone does not identify every fit-up condition.
Weld Neck Flange 1 1/4″ Class 400
Weld Neck Flange 1 1/4″ Class 400 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 1 1/4″ Class 400 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):1 1/4″
- DN Size: DN32
- Outside Diameter:133mm
- Flange Thickness:20.6mm
- Hub Diameter:64mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:63.5mm
- Weight: 2.3kg
- Number of Bolts:4
- Stud Bolt Size: 5/8″ UNC (or M16) x 95 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 1 1/4″ Class 400 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 1 1/4″ Class 400, which can be used for drafting, detailing, piping layout coordination, and fabrication reference.
Available Weld Neck Flange Class 400 Sizes
This size is part of the Weld Neck Flange Class 400 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 dimension list separates the flange’s external geometry from its connection details. Outside diameter, thickness, hub diameter, and raised face diameter describe the visible flange form. The bore is treated separately because it must match the selected pipe wall condition.
The bolt count, stud bolt size, bolt-hole diameter, and flange class should be checked together when preparing a joint detail. Do not select replacement fasteners from nominal size alone: confirm the required length, thread form, material, gasket arrangement, and project requirements before ordering or assembly.
Why the Weld Neck Hub Matters
The long tapered hub provides a gradual transition between the pipe and flange. The welded connection and tapered profile are intended to support a robust joint arrangement, particularly where the piping system may experience pressure, temperature changes, or cyclic service. Final suitability still depends on the complete design, material specification, welding procedure, and applicable engineering review.
Using the CAD Download
The downloadable DWG can support preliminary drafting, flange orientation, piping layout coordination, and fabrication reference. Before issuing drawings, compare the CAD geometry with the dimension data on this page and confirm the bore, facing arrangement, bolt-hole details, and connection requirements for the actual pipe assembly.
Related Reference Topics
For a complete piping check, pair this page with references covering pipe schedules, flange dimensions, gasket selection, stud bolts, pressure-temperature ratings, and piping isometric drafting. These topics help distinguish nominal pipe size from the dimensions needed for a real connection.
Frequently Asked Questions
What does NPS mean on this flange reference?
NPS is the nominal pipe size designation used to identify the connected pipe and flange size. It is a nominal system label, so it should not be treated as the measured outside diameter or as a complete description of the pipe bore.
Why does the bore depend on the pipe schedule?
Pipe schedule identifies a pipe wall condition. When the outside pipe size is held within the applicable nominal system, changes in wall thickness affect the inside diameter. The flange bore therefore needs to be checked against the actual pipe selected for the project.
Does Class 400 by itself determine the allowable working pressure?
No. The applicable pressure-temperature limit depends on the governing standard information, flange material, temperature, service conditions, and project requirements. Use the class designation with the complete engineering specification rather than as a standalone pressure value.
What should be verified before using the DWG for fabrication?
Confirm the flange standard, pipe schedule and bore, facing details, bolt-hole arrangement, stud bolt requirements, gasket, material, and drawing revision. The CAD file is a drafting reference and should be checked against the approved project documents before manufacture.