This reference page provides dimension data and drafting guidance for a Weld Neck Flange 4 Inch Class 900. Use the original source list below for the authoritative local values, then verify the flange, pipe, gasket, and bolting details against the requirements of the project.
The most important coordination issue is the connection between the flange bore and the mating pipe. Because the bore can vary with pipe schedule and wall thickness, flange selection should be checked together with the applicable pipe schedule, weld detail, gasket arrangement, and stud bolt information.
Weld Neck Flange 4″ Class 900
Weld Neck Flange 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 4″ Class 900 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):4″
- DN Size: DN100
- Outside Diameter:292mm
- Flange Thickness:44.5mm
- Hub Diameter:159mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:157.2mm
- Weight: 24.5kg
- Number of Bolts:8
- Stud Bolt Size: 1 1/8″ UNC (or M30) x 170 Long
- Hole Diameter: 1 1/4″ (31.75mm)
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 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 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 Read This Flange Reference
A weld neck flange combines a machined flange face with a tapered hub that transitions into the pipe. The hub provides a gradual geometry change near the weld, while the butt-welded connection allows the pipe and flange assembly to be coordinated as one pressure-boundary component. Final suitability still depends on material, fabrication quality, inspection requirements, service conditions, and engineering approval.
Key dimensions to coordinate
- Outside diameter and thickness: These control the flange envelope and are important for layout, clearance, and connection detailing.
- Hub diameter: This identifies the external hub geometry used in fabrication and CAD coordination.
- Bore diameter: Do not assume a single bore for every pipe application. Confirm the bore against the selected pipe schedule and wall thickness before fabrication.
- Raised face: The raised-face dimension must be coordinated with the gasket and mating flange arrangement.
- Bolt pattern: Confirm the bolt count, hole diameter, stud size, and bolt length together. These details affect fit-up and assembly clearance.
Using the CAD file
The downloadable DWG is useful for preliminary drafting, piping layout coordination, equipment-interface review, and fabrication reference. Before issuing a drawing, compare the CAD geometry with the dimension list and project specifications. CAD geometry should not override the governing project documents or a verified fabrication detail.
Related reference topics
For broader coordination, see the site resources on flange types, pipe dimensions, pipe schedules, gasket types, and piping CAD and DWG references. These related topics help explain how the flange data connects to the pipe and bolted joint.
Frequently Asked Questions
What is a weld neck flange?
A weld neck flange is a flanged fitting with a long tapered hub that is welded directly to the pipe. Its geometry supports a gradual transition between the pipe and flange and is commonly selected where a robust welded connection is required.
Does the flange bore have one fixed dimension?
No. The bore can vary with the pipe schedule and wall thickness. Confirm the required bore before ordering, machining, or releasing fabrication drawings.
Is Class 900 by itself a working-pressure value?
No. The class designation should not be treated as a universal allowable working pressure. Pressure-temperature capability depends on the applicable standard, material, temperature, service conditions, and project requirements.
What bolt information should be checked?
Check the bolt count, hole diameter, stud size, and required length as one coordinated set. Also verify the mating flange, gasket arrangement, thread compatibility, tightening procedure, and available assembly clearance.
Can the DWG be used directly for fabrication?
The DWG can support drafting and fabrication reference, but it should be reviewed against the listed source data, the selected pipe schedule, project specifications, and approved fabrication procedures before release.