This reference provides the dimensional data, bolt information, weight, and CAD resource for a weld neck flange in NPS 18, Class 300 service. Use the listed values for drawing review and preliminary layout coordination, then verify the flange, pipe, gasket, and bolting details against the governing project documents.
The flange type is especially relevant when a welded, tapered-hub connection is preferred for demanding piping service. The page also identifies an important design consideration: the bore must be matched to the connected pipe schedule and wall thickness rather than assumed from the nominal pipe size alone.
Weld Neck Flange 18″ Class 300
Weld Neck Flange 18″ 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 18″ Class 300 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):18″
- DN Size: DN450
- Outside Diameter:711mm
- Flange Thickness:58.7mm
- Hub Diameter:533mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:533.4mm
- Weight: 181kg
- Number of Bolts:24
- Stud Bolt Size: 1 1/4″ UNC (or M33) x 195 Long
- Hole Diameter: 1 3/8″ (34.925mm)
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 18″ 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 18″ 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 source dimensions are useful for checking flange clearances, bolt-circle coordination, face alignment, and the space required around a piping connection. They can also support preliminary CAD layouts before the final material, facing, gasket, and pressure-temperature requirements are confirmed.
For drafting work, compare the flange data with the connected pipe schedule, pipe outside diameter, and selected bore. A nominal pipe size identifies the general connection size, but it does not by itself define the internal opening of a weld neck flange. This is why the bore should be checked against the actual pipe wall thickness and project specification.
Connection and Assembly Checks
- Confirm that the flange class matches the piping specification and service conditions.
- Check the bolt quantity, stud dimensions, hole diameter, and available wrench or tool clearance.
- Coordinate the raised face with the selected gasket and the mating flange.
- Verify that the weld-end geometry is compatible with the connected pipe and welding procedure.
- Review the listed weight when planning handling, supports, and installation access.
For broader design work, this page can be paired with a pipe dimensions and schedules reference, a flange types guide, and a gasket and bolting reference. Those related resources help connect the flange dimensions to the complete piping joint rather than treating the flange as an isolated component.
CAD and Fabrication Reference
The downloadable DWG is intended to assist with drafting, piping layout coordination, detailing, and fabrication reference. Treat the drawing as a dimensional aid, not as a substitute for project-approved fabrication drawings or engineering review. Before release, confirm the selected bore, flange facing, material specification, tolerances, and mating components.
Frequently Asked Questions
What does the Class 300 designation indicate?
Class 300 is the flange pressure-class designation used for selecting compatible flanges within the applicable piping system. It should not be interpreted as a universal allowable pressure; pressure-temperature limits depend on material, temperature, applicable standard requirements, and project specification.
Why can the weld neck flange bore vary?
The bore is coordinated with the connected pipe schedule and wall thickness. Confirm the actual pipe dimensions before fabrication, especially when the flange will be welded directly to the pipe.
What should be checked before ordering the flange?
Check the nominal size, class, material, facing, bore, bolt and stud details, gasket requirements, and the applicable project piping specification. Also confirm that the mating flange uses compatible dimensional and facing requirements.
Can the DWG be used as a final fabrication drawing?
The DWG is useful for layout and drafting reference. Final fabrication should rely on approved project drawings, verified dimensions, material documentation, welding requirements, and engineering review.
Where can related flange information be found?
Use the site’s related references for pipe schedules, flange types, bolt dimensions, gaskets, and CAD or DWG resources. Linking these topics helps users verify the complete connection assembly.