This reference page provides the dimensional and connection details for a Weld Neck Flange 1 1/4 Inch Class 900. Use the listed data when checking piping layouts, flange interfaces, fabrication drawings, and related CAD work.
The flange’s tapered hub is welded to the pipe, while the flange face and bolting arrangement provide the connection interface. Because the bore depends on the pipe schedule and wall thickness, dimensional coordination should include the mating pipe specification rather than relying on nominal size alone.
Weld Neck Flange 1 1/4″ Class 900
Weld Neck Flange 1 1/4″ 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 1 1/4″ Class 900 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):1 1/4″
- DN Size: DN32
- Outside Diameter:159mm
- Flange Thickness:28.6mm
- Hub Diameter:64mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:63.5mm
- Weight: 4.1kg
- Number of Bolts:4
- Stud Bolt Size: 7/8″ UNC (or M24) x 125 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 1 1/4″ 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 1 1/4″ 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 Use This Flange Reference
The source dimensions identify the flange outside diameter, thickness, hub diameter, raised face, bolt-hole information, stud bolt size, and listed weight. These details support preliminary drafting and component identification, but the final selection should be checked against the project’s piping specification and the applicable pressure-temperature requirements.
Check the Bore Against the Pipe Schedule
A weld neck flange is intended to align with the pipe it is welded to. The bore is therefore not treated as a single universal value on this page: it varies with pipe schedule and wall thickness. For accurate detailing, compare the flange reference with the pipe dimensions, weld preparation, and internal-flow requirements used in the project.
Coordinate the Bolting and Gasket Interface
The listed bolt count, stud bolt size, and hole diameter should be reviewed together with the mating flange. Gasket selection, facing details, bolt projection, and tightening requirements also need to follow the applicable project specification. Do not use the flange dimensions alone to establish a complete assembly procedure.
Useful Related References
- Compare this page with other pipe flange dimensions when coordinating adjacent equipment or piping components.
- Review pipe schedules and wall thickness before finalizing the weld neck bore.
- Use related flange CAD and DWG references for layout, detailing, and fabrication coordination.
- Check flange terminology when distinguishing weld neck, slip-on, blind, socket weld, and threaded connections.
Using the CAD Download
The downloadable DWG can assist with drafting and layout coordination. Confirm units, drawing scale, mating-pipe dimensions, face orientation, and project revision status before incorporating the file into a production drawing.
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. The hub helps provide a gradual transition between the pipe and flange and supports stress distribution at the connection.
Why does the bore vary for this flange?
The bore depends on the connected pipe schedule and wall thickness. The nominal flange size identifies the intended pipe size category, but the internal opening must be coordinated with the selected pipe.
What bolting information is provided?
The reference lists the number of bolts, stud bolt size, and hole diameter. These details should be checked against the mating flange, gasket arrangement, and project bolting requirements before fabrication or installation.
Can the DWG file be used directly for fabrication?
The DWG is provided as a drafting and fabrication reference. Verify dimensions, units, mating components, material requirements, weld details, and the current project specification before issuing fabrication drawings.
Which requirements should be confirmed before installation?
Confirm the flange material, pipe schedule, bore, gasket type, bolt length, facing details, and applicable pressure-temperature rating. The project specification and responsible engineer should govern final approval.