This reference provides dimension and drafting information for a Weld Neck Flange 12 Inch Class 900. Use the source data below to check the flange envelope, hub details, bolt-hole arrangement, weight, and stud-bolt information during piping layout or fabrication review.
The listed flange dimensions should be read together with the applicable pipe schedule, material specification, gasket selection, and project requirements. The bore is schedule-dependent, so it should not be selected from the flange outside dimensions alone.
Weld Neck Flange 12″ Class 900
Weld Neck Flange 12″ 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 12″ Class 900 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):12″
- DN Size: DN300
- Outside Diameter:610mm
- Flange Thickness:79.2mm
- Hub Diameter:419mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:381mm
- Weight: 189kg
- Number of Bolts:20
- Stud Bolt Size: 1 3/8″ UNC (or M36) x 255 Long
- Hole Diameter: 1 1/2″ (38.1mm)
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 12″ 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 12″ 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 Read This Weld Neck Flange Reference
A weld neck flange has a tapered hub that is welded directly to the pipe. The hub provides a gradual transition from the flange to the pipe and helps manage stress at the connection. This makes the flange geometry especially important when reviewing high-pressure piping, temperature changes, or cyclic service.
Key Dimensions to Check
- Outside diameter and thickness: These define the main flange envelope and affect clearance, mating-flange coordination, and installation space.
- Hub diameter: This identifies the tapered welded hub geometry and should be coordinated with the flange drawing and pipe connection.
- Bore diameter: The bore varies with pipe schedule and wall thickness. Confirm the selected bore against the actual pipe before fabrication or procurement.
- Raised face: The raised-face dimension affects gasket seating and the mating flange interface. Confirm facing details as part of the complete joint specification.
- Bolt information: The bolt count, hole diameter, stud-bolt size, and bolt length should be checked together with the mating flange, gasket, washers, and available thread engagement.
Class, NPS, and DN Terminology
NPS identifies the nominal pipe size used in U.S. customary piping terminology, while DN is the corresponding metric designation shown in the source data. Class 900 is a flange pressure-class designation; it is not, by itself, a single allowable working pressure for every material and temperature. Pressure-temperature limits must be verified against the applicable material and project requirements.
Using the CAD File
The downloadable DWG can support piping layout, equipment-area coordination, detail drafting, and fabrication reference. Treat the drawing as a geometry aid and verify the source dimensions, flange facing, bore selection, orientation, and mating components before issuing fabrication or construction documents.
Related Pipe and Flange References
For broader coordination, link this page with related pipe schedule and wall-thickness references, flange dimension pages, gasket references, stud-bolt guides, and other Class 900 weld neck flange sizes. These related resources help users compare connection geometry without confusing nominal size, bore selection, and pressure class.
Frequently Asked Questions
What does the bore depend on?
The bore depends on the pipe schedule and pipe wall thickness selected for the connection. Confirm the bore against the actual pipe specification before ordering or machining.
Is Class 900 the same as a fixed pressure rating?
No. Class 900 identifies the flange pressure class. The allowable pressure-temperature limit depends on the applicable material, temperature, code requirements, and project specification.
Why is a weld neck flange used instead of a flat flange?
The long tapered hub provides a gradual transition to the pipe and is intended to improve the connection’s behavior under pressure, temperature changes, and cyclic loading. Final selection requires engineering review.
Can the listed stud bolts be used for every installation?
Not automatically. Confirm the mating flange, gasket thickness, washer arrangement, material requirements, thread engagement, and project bolt specification before installation.
Can the DWG be used for fabrication?
The DWG may be used as a drafting and coordination reference. Fabrication should proceed only after the drawing, bore, facing, material, tolerances, and project requirements have been verified.