This reference page provides the dimensional information, connection details, and drafting resources for a Weld Neck Flange 1 1/4 Inch Class 300. Use the listed values when checking a piping layout, preparing a flange detail, or coordinating a CAD model with the pipe and gasket arrangement.
The flange size is identified by nominal pipe size and pressure class. The dimensional list below should be read together with the pipe schedule, material requirements, gasket selection, and project specifications because those items affect compatibility and installation.
Weld Neck Flange 1 1/4″ Class 300
Weld Neck Flange 1 1/4″ 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 1 1/4″ Class 300 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):1 1/4″
- DN Size: DN32
- Outside Diameter:133mm
- Flange Thickness:17.5mm
- Hub Diameter:64mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:63.5mm
- Weight: 1.8kg
- Number of Bolts:4
- Stud Bolt Size: 5/8″ UNC (or M16) x 85 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 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 1 1/4″ 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 Flange Reference
The outside diameter, thickness, hub dimensions, raised face, bolt-hole information, and weight help establish the flange envelope for layout and detailing work. These values are useful for checking clearances, matching mating flanges, and reviewing fabrication drawings.
The bore is not a single universal value in this reference. It varies with the pipe schedule and wall thickness, so the flange bore should be checked against the actual pipe selected for the project. This is especially important when preparing a weld detail or coordinating the flange with an existing piping model.
Connection and Bolt-Pattern Checks
Before using the stud bolt information for fabrication, confirm the mating flange, gasket arrangement, bolt material, thread requirements, and required tightening procedure. The bolt count and hole size describe the flange connection, but they do not replace a project-specific bolting review.
Design and Drafting Context
A weld neck flange uses a tapered hub to transition from the flange into the pipe. Its geometry is commonly reviewed where connection strength, welding detail, thermal movement, and cyclic service are design considerations. Final selection remains dependent on the applicable design code, material specification, service conditions, and engineering approval.
For related research, connect this page with internal references for pipe schedules, flange facing types, flange bolt dimensions, gasket selection, and CAD flange drawings. Those topics help readers move from a dimensional lookup to a complete piping connection check.
CAD File Use
The downloadable DWG can support preliminary drafting, piping layout coordination, detailing, and fabrication reference. Verify units, drawing orientation, bore geometry, and project-specific modifications before using the file as a manufacturing document.
Frequently Asked Questions
What does NPS 1 1/4 inch identify?
NPS 1 1/4 inch identifies the nominal pipe size associated with this flange. The corresponding DN designation shown in the reference is DN32.
Does the listed bore apply to every pipe schedule?
No. The bore varies according to the pipe schedule and wall thickness. Confirm the pipe selected for the project before finalizing the weld detail.
What should be checked before ordering the bolts?
Confirm the mating flange, gasket, bolt material, thread specification, bolt length, and installation requirements. The listed stud bolt information is a dimensional reference and should be reviewed against the project specification.
What is the purpose of the weld neck hub?
The long tapered hub provides a gradual transition between the pipe and flange. This geometry helps manage stress at the flange connection and supports the welded connection design.
Can the DWG be used directly for fabrication?
The DWG is intended as a drafting and coordination reference. Review its units, bore, mating components, material requirements, and project-specific details before fabrication.
Does Class 300 alone define allowable service pressure?
No. The applicable pressure-temperature rating depends on the relevant standard requirements, material, temperature, and project design conditions. Confirm the rating with the governing specification and engineering review.