This reference page provides the dimensional data, bolt information, weight, and CAD resource for a Weld Neck Flange 20 Inch Class 900. Use the listed values for piping layout, preliminary drafting, flange identification, and fabrication coordination, while treating the project specification and approved engineering documents as controlling.
The page is especially useful when coordinating a flange with the related pipe schedule, stud bolt selection, gasket requirements, and piping isometric. The bore is not a single universal value because it must correspond to the pipe wall thickness and schedule selected for the connection.
Weld Neck Flange 20″ Class 900
Weld Neck Flange 20″ 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 20″ Class 900 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):20″
- DN Size: DN500
- Outside Diameter:857mm
- Flange Thickness:108mm
- Hub Diameter:622mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:584.2mm
- Weight: 463kg
- Number of Bolts:20
- Stud Bolt Size: 2″ UNC (or M52) x 350 Long
- Hole Diameter: 2 1/8″ (53.975mm)
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 20″ 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 20″ 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
The dimension list identifies the flange envelope and connection features used in layout and detailing. Outside diameter and flange thickness help establish the overall space occupied by the component. Hub diameter describes the tapered transition around the welded pipe connection, while the raised face diameter identifies the gasket-facing area used for bolted joint coordination.
The bore requires particular attention. Unlike the outside flange dimensions, the bore is associated with the mating pipe and can vary with pipe schedule or wall thickness. Confirm the bore against the selected pipe before releasing fabrication drawings, purchase documents, or spool details. A nominal pipe size identifies the connection family; it does not by itself confirm the finished bore.
Bolt and Hole Coordination
Do not treat the stud bolt size and bolt-hole diameter as interchangeable descriptions. The stud bolt identifies the fastener specification, while the hole diameter describes the clearance opening through the flange. Confirm the complete bolting arrangement, including thread form, length, material, washers where specified, tightening procedure, and project requirements.
Using the CAD File
The downloadable DWG can support drafting, equipment and piping layout coordination, and fabrication reference. Before using the drawing for a final deliverable, check units, insertion scale, layer conventions, face orientation, weld-end details, and the selected pipe bore. The CAD geometry should be compared with the dimension list and the approved project documents rather than used as a substitute for design verification.
For related research, connect this page with internal references for pipe schedules, flange types, raised face flanges, stud bolt dimensions, ASME B16.5 flange dimensions, and piping CAD blocks. These topics help readers interpret the flange data in the context of a complete piping connection.
Frequently Asked Questions
What does a weld neck flange do?
A weld neck flange connects to the pipe through a welded tapered hub. Its geometry is intended to provide a gradual transition between the pipe and flange and to support demanding piping connections when properly selected and installed.
Why can the bore vary for this flange?
The bore must match the pipe inside diameter associated with the selected pipe schedule or wall thickness. Confirm the mating pipe and finished bore before fabrication or installation.
Is the Class 900 designation enough to select the flange?
No. Selection also requires confirmation of the applicable standard, material specification, temperature and pressure conditions, pipe details, gasket, bolting, facing, and project requirements. The class designation should not be used as a standalone design approval.
What is the difference between the bolt size and hole diameter?
The bolt or stud size identifies the fastener used in the joint. The hole diameter identifies the opening in the flange. Both must be coordinated with the flange pattern and the approved bolting requirements.
Can the DWG file be used directly for fabrication?
The DWG is intended as a drafting and reference resource. Check its units, geometry, bore, mating pipe, facing, and project-specific requirements before using it in fabrication documentation.